Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

9 files changed, 7546 insertions, 0 deletions

diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/README.md b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/README.md
new file mode 100644
index 0000000000..91372fd31c
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/README.md
@@ -0,0 +1 @@
+This directory is where files generated by Uniffi will be created.
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustArithmetic.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustArithmetic.sys.mjs
new file mode 100644
index 0000000000..1790f0effa
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustArithmetic.sys.mjs
@@ -0,0 +1,492 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterU64 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isSafeInteger(value)) {
+            throw new UniFFITypeError(`${value} exceeds the safe integer bounds`);
+        }
+        if (value < 0) {
+            throw new UniFFITypeError(`${value} exceeds the U64 bounds`);
+        }
+    }
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readUint64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterBool extends FfiConverter {
+    static computeSize() {
+        return 1;
+    }
+    static lift(value) {
+        return value == 1;
+    }
+    static lower(value) {
+        if (value) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint8(this.lower(value))
+    }
+    static read(dataStream) {
+        return this.lift(dataStream.readUint8())
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+
+
+
+export class ArithmeticError extends Error {}
+
+
+export class IntegerOverflow extends ArithmeticError {
+
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+    toString() {
+        return `IntegerOverflow: ${super.toString()}`
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeArithmeticError extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return new IntegerOverflow(FfiConverterString.read(dataStream));
+            default:
+                throw new Error("Unknown ArithmeticError variant");
+        }
+    }
+    static computeSize(value) {
+        // Size of the Int indicating the variant
+        let totalSize = 4;
+        if (value instanceof IntegerOverflow) {
+            return totalSize;
+        }
+        throw new Error("Unknown ArithmeticError variant");
+    }
+    static write(dataStream, value) {
+        if (value instanceof IntegerOverflow) {
+            dataStream.writeInt32(1);
+            return;
+        }
+        throw new Error("Unknown ArithmeticError variant");
+    }
+
+    static errorClass = ArithmeticError;
+}
+
+
+
+
+
+export function add(a,b) {
+
+        const liftResult = (result) => FfiConverterU64.lift(result);
+        const liftError = (data) => FfiConverterTypeArithmeticError.lift(data);
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(a)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("a");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterU64.checkType(b)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("b");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                35, // arithmetic:uniffi_arithmetical_fn_func_add
+                FfiConverterU64.lower(a),
+                FfiConverterU64.lower(b),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function div(dividend,divisor) {
+
+        const liftResult = (result) => FfiConverterU64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(dividend)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("dividend");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterU64.checkType(divisor)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("divisor");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                36, // arithmetic:uniffi_arithmetical_fn_func_div
+                FfiConverterU64.lower(dividend),
+                FfiConverterU64.lower(divisor),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function equal(a,b) {
+
+        const liftResult = (result) => FfiConverterBool.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(a)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("a");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterU64.checkType(b)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("b");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                37, // arithmetic:uniffi_arithmetical_fn_func_equal
+                FfiConverterU64.lower(a),
+                FfiConverterU64.lower(b),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function sub(a,b) {
+
+        const liftResult = (result) => FfiConverterU64.lift(result);
+        const liftError = (data) => FfiConverterTypeArithmeticError.lift(data);
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(a)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("a");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterU64.checkType(b)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("b");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                38, // arithmetic:uniffi_arithmetical_fn_func_sub
+                FfiConverterU64.lower(a),
+                FfiConverterU64.lower(b),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustCustomTypes.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustCustomTypes.sys.mjs
new file mode 100644
index 0000000000..286c046fa6
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustCustomTypes.sys.mjs
@@ -0,0 +1,467 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterI64 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isSafeInteger(value)) {
+            throw new UniFFITypeError(`${value} exceeds the safe integer bounds`);
+        }
+    }
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeInt64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readInt64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+export class CustomTypesDemo {
+    constructor({ url, handle } = {}) {
+        try {
+            FfiConverterTypeUrl.checkType(url)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("url");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterTypeHandle.checkType(handle)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("handle");
+            }
+            throw e;
+        }
+        this.url = url;
+        this.handle = handle;
+    }
+    equals(other) {
+        return (
+            this.url == other.url &&
+            this.handle == other.handle
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeCustomTypesDemo extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new CustomTypesDemo({
+            url: FfiConverterTypeUrl.read(dataStream),
+            handle: FfiConverterTypeHandle.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterTypeUrl.write(dataStream, value.url);
+        FfiConverterTypeHandle.write(dataStream, value.handle);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterTypeUrl.computeSize(value.url);
+        totalSize += FfiConverterTypeHandle.computeSize(value.handle);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof CustomTypesDemo)) {
+            throw new TypeError(`Expected 'CustomTypesDemo', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterTypeUrl.checkType(value.url);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".url");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterTypeHandle.checkType(value.handle);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".handle");
+            }
+            throw e;
+        }
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypeCustomTypesDemo extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypeCustomTypesDemo.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypeCustomTypesDemo.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypeCustomTypesDemo.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypeCustomTypesDemo.computeSize(value)
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeHandle extends FfiConverter {
+    static lift(buf) {
+        return FfiConverterI64.lift(buf);    
+    }
+    
+    static lower(buf) {
+        return FfiConverterI64.lower(buf);
+    }
+    
+    static write(dataStream, value) {
+        FfiConverterI64.write(dataStream, value);
+    } 
+    
+    static read(buf) {
+        return FfiConverterI64.read(buf);
+    }
+    
+    static computeSize(value) {
+        return FfiConverterI64.computeSize(value);
+    }
+}
+// TODO: We should also allow JS to customize the type eventually.
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeUrl extends FfiConverter {
+    static lift(buf) {
+        return FfiConverterString.lift(buf);    
+    }
+    
+    static lower(buf) {
+        return FfiConverterString.lower(buf);
+    }
+    
+    static write(dataStream, value) {
+        FfiConverterString.write(dataStream, value);
+    } 
+    
+    static read(buf) {
+        return FfiConverterString.read(buf);
+    }
+    
+    static computeSize(value) {
+        return FfiConverterString.computeSize(value);
+    }
+}
+// TODO: We should also allow JS to customize the type eventually.
+
+
+
+
+
+export function getCustomTypesDemo(demo) {
+
+        const liftResult = (result) => FfiConverterTypeCustomTypesDemo.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterOptionalTypeCustomTypesDemo.checkType(demo)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("demo");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                39, // custom_types:uniffi_uniffi_custom_types_fn_func_get_custom_types_demo
+                FfiConverterOptionalTypeCustomTypesDemo.lower(demo),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustExternalTypes.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustExternalTypes.sys.mjs
new file mode 100644
index 0000000000..c01b1a58b3
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustExternalTypes.sys.mjs
@@ -0,0 +1,427 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterF64 extends FfiConverter {
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypeLine extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypeLine.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypeLine.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypeLine.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypeLine.computeSize(value)
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypePoint extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypePoint.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypePoint.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypePoint.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypePoint.computeSize(value)
+    }
+}
+
+import {
+  FfiConverterTypeLine,
+  Line,
+} from "resource://gre/modules/RustGeometry.sys.mjs";
+
+// Export the FFIConverter object to make external types work.
+export { FfiConverterTypeLine, Line };
+
+import {
+  FfiConverterTypePoint,
+  Point,
+} from "resource://gre/modules/RustGeometry.sys.mjs";
+
+// Export the FFIConverter object to make external types work.
+export { FfiConverterTypePoint, Point };
+
+
+
+
+
+export function gradient(value) {
+
+        const liftResult = (result) => FfiConverterF64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterOptionalTypeLine.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                40, // external_types:uniffi_uniffi_fixture_external_types_fn_func_gradient
+                FfiConverterOptionalTypeLine.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function intersection(ln1,ln2) {
+
+        const liftResult = (result) => FfiConverterOptionalTypePoint.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeLine.checkType(ln1)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("ln1");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterTypeLine.checkType(ln2)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("ln2");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                41, // external_types:uniffi_uniffi_fixture_external_types_fn_func_intersection
+                FfiConverterTypeLine.lower(ln1),
+                FfiConverterTypeLine.lower(ln2),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustFixtureCallbacks.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustFixtureCallbacks.sys.mjs
new file mode 100644
index 0000000000..75fe81a458
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustFixtureCallbacks.sys.mjs
@@ -0,0 +1,639 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+
+/**
+ * Handler for a single UniFFI CallbackInterface
+ *
+ * This class stores objects that implement a callback interface in a handle
+ * map, allowing them to be referenced by the Rust code using an integer
+ * handle.
+ *
+ * While the callback object is stored in the map, it allows the Rust code to
+ * call methods on the object using the callback object handle, a method id,
+ * and an ArrayBuffer packed with the method arguments.
+ *
+ * When the Rust code drops its reference, it sends a call with the methodId=0,
+ * which causes callback object to be removed from the map.
+ */
+class UniFFICallbackHandler {
+    #name;
+    #interfaceId;
+    #handleCounter;
+    #handleMap;
+    #methodHandlers;
+    #allowNewCallbacks
+
+    /**
+     * Create a UniFFICallbackHandler
+     * @param {string} name - Human-friendly name for this callback interface
+     * @param {int} interfaceId - Interface ID for this CallbackInterface.
+     * @param {UniFFICallbackMethodHandler[]} methodHandlers -- UniFFICallbackHandler for each method, in the same order as the UDL file
+     */
+     constructor(name, interfaceId, methodHandlers) {
+        this.#name = name;
+        this.#interfaceId = interfaceId;
+        this.#handleCounter = 0;
+        this.#handleMap = new Map();
+        this.#methodHandlers = methodHandlers;
+        this.#allowNewCallbacks = true;
+
+        UniFFIScaffolding.registerCallbackHandler(this.#interfaceId, this.invokeCallback.bind(this));
+        Services.obs.addObserver(this, "xpcom-shutdown");
+     }
+
+    /**
+     * Store a callback object in the handle map and return the handle
+     *
+     * @param {obj} callbackObj - Object that implements the callback interface
+     * @returns {int} - Handle for this callback object, this is what gets passed back to Rust.
+     */
+    storeCallbackObj(callbackObj) {
+        if (!this.#allowNewCallbacks) {
+            throw new UniFFIError(`No new callbacks allowed for ${this.#name}`);
+        }
+        const handle = this.#handleCounter;
+        this.#handleCounter += 1;
+        this.#handleMap.set(handle, new UniFFICallbackHandleMapEntry(callbackObj, Components.stack.caller.formattedStack.trim()));
+        return handle;
+    }
+
+    /**
+     * Get a previously stored callback object
+     *
+     * @param {int} handle - Callback object handle, returned from `storeCallbackObj()`
+     * @returns {obj} - Callback object
+     */
+    getCallbackObj(handle) {
+        return this.#handleMap.get(handle).callbackObj;
+    }
+
+    /**
+     * Set if new callbacks are allowed for this handler
+     *
+     * This is called with false during shutdown to ensure the callback maps don't
+     * prevent JS objects from being GCed.
+     */
+    setAllowNewCallbacks(allow) {
+        this.#allowNewCallbacks = allow
+    }
+
+    /**
+     * Check that no callbacks are currently registered
+     *
+     * If there are callbacks registered a UniFFIError will be thrown.  This is
+     * called during shutdown to generate an alert if there are leaked callback
+     * interfaces.
+     */
+    assertNoRegisteredCallbacks() {
+        if (this.#handleMap.size > 0) {
+            const entry = this.#handleMap.values().next().value;
+            throw new UniFFIError(`UniFFI interface ${this.#name} has ${this.#handleMap.size} registered callbacks at xpcom-shutdown. This likely indicates a UniFFI callback leak.\nStack trace for the first leaked callback:\n${entry.stackTrace}.`);
+        }
+    }
+
+    /**
+     * Invoke a method on a stored callback object
+     * @param {int} handle - Object handle
+     * @param {int} methodId - Method identifier.  This the 1-based index of
+     *   the method from the UDL file.  0 is the special drop method, which
+     *   removes the callback object from the handle map.
+     * @param {ArrayBuffer} argsArrayBuffer - Arguments to pass to the method, packed in an ArrayBuffer
+     */
+    invokeCallback(handle, methodId, argsArrayBuffer) {
+        try {
+            this.#invokeCallbackInner(handle, methodId, argsArrayBuffer);
+        } catch (e) {
+            console.error(`internal error invoking callback: ${e}`)
+        }
+    }
+
+    #invokeCallbackInner(handle, methodId, argsArrayBuffer) {
+        const callbackObj = this.getCallbackObj(handle);
+        if (callbackObj === undefined) {
+            throw new UniFFIError(`${this.#name}: invalid callback handle id: ${handle}`);
+        }
+
+        // Special-cased drop method, remove the object from the handle map and
+        // return an empty array buffer
+        if (methodId == 0) {
+            this.#handleMap.delete(handle);
+            return;
+        }
+
+        // Get the method data, converting from 1-based indexing
+        const methodHandler = this.#methodHandlers[methodId - 1];
+        if (methodHandler === undefined) {
+            throw new UniFFIError(`${this.#name}: invalid method id: ${methodId}`)
+        }
+
+        methodHandler.call(callbackObj, argsArrayBuffer);
+    }
+
+    /**
+     * xpcom-shutdown observer method
+     *
+     * This handles:
+     *  - Deregistering ourselves as the UniFFI callback handler
+     *  - Checks for any leftover stored callbacks which indicate memory leaks
+     */
+    observe(aSubject, aTopic, aData) {
+        if (aTopic == "xpcom-shutdown") {
+            try {
+                this.setAllowNewCallbacks(false);
+                this.assertNoRegisteredCallbacks();
+                UniFFIScaffolding.deregisterCallbackHandler(this.#interfaceId);
+            } catch (ex) {
+                console.error(`UniFFI Callback interface error during xpcom-shutdown: ${ex}`);
+                Cc["@mozilla.org/xpcom/debug;1"]
+                    .getService(Ci.nsIDebug2)
+                    .abort(ex.filename, ex.lineNumber);
+            }
+         }
+    }
+}
+
+/**
+ * Handles calling a single method for a callback interface
+ */
+class UniFFICallbackMethodHandler {
+    #name;
+    #argsConverters;
+
+    /**
+     * Create a UniFFICallbackMethodHandler
+
+     * @param {string} name -- Name of the method to call on the callback object
+     * @param {FfiConverter[]} argsConverters - FfiConverter for each argument type
+     */
+    constructor(name, argsConverters) {
+        this.#name = name;
+        this.#argsConverters = argsConverters;
+    }
+
+    /**
+     * Invoke the method
+     *
+     * @param {obj} callbackObj -- Object implementing the callback interface for this method
+     * @param {ArrayBuffer} argsArrayBuffer -- Arguments for the method, packed in an ArrayBuffer
+     */
+     call(callbackObj, argsArrayBuffer) {
+        const argsStream = new ArrayBufferDataStream(argsArrayBuffer);
+        const args = this.#argsConverters.map(converter => converter.read(argsStream));
+        callbackObj[this.#name](...args);
+    }
+}
+
+/**
+ * UniFFICallbackHandler.handleMap entry
+ *
+ * @property callbackObj - Callback object, this must implement the callback interface.
+ * @property {string} stackTrace - Stack trace from when the callback object was registered.  This is used to proved extra context when debugging leaked callback objects.
+ */
+class UniFFICallbackHandleMapEntry {
+    constructor(callbackObj, stackTrace) {
+        this.callbackObj = callbackObj;
+        this.stackTrace = stackTrace
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterI32 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < -2147483648 || value > 2147483647) {
+            throw new UniFFITypeError(`${value} exceeds the I32 bounds`);
+        }
+    }
+    static computeSize() {
+        return 4;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeInt32(value)
+    }
+    static read(dataStream) {
+        return dataStream.readInt32()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeLogger extends FfiConverter {
+    static lower(callbackObj) {
+        return callbackHandlerLogger.storeCallbackObj(callbackObj)
+    }
+
+    static lift(handleId) {
+        return callbackHandlerLogger.getCallbackObj(handleId)
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readInt64())
+    }
+
+    static write(dataStream, callbackObj) {
+        dataStream.writeInt64(this.lower(callbackObj))
+    }
+
+    static computeSize(callbackObj) {
+        return 8;
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterSequencei32 extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterI32.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterI32.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterI32.computeSize(innerValue);
+        }
+        return size;
+    }
+
+    static checkType(value) {
+        if (!Array.isArray(value)) {
+            throw new UniFFITypeError(`${value} is not an array`);
+        }
+        value.forEach((innerValue, idx) => {
+            try {
+                FfiConverterI32.checkType(innerValue);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart(`[${idx}]`);
+                }
+                throw e;
+            }
+        })
+    }
+}
+
+
+// Define callback interface handlers, this must come after the type loop since they reference the FfiConverters defined above.
+
+const callbackHandlerLogger = new UniFFICallbackHandler(
+    "fixture_callbacks:Logger",
+    0,
+    [
+        new UniFFICallbackMethodHandler(
+            "log",
+            [
+                FfiConverterString,
+            ],
+        ),
+        new UniFFICallbackMethodHandler(
+            "finished",
+            [
+            ],
+        ),
+    ]
+);
+
+// Allow the shutdown-related functionality to be tested in the unit tests
+UnitTestObjs.callbackHandlerLogger = callbackHandlerLogger;
+
+
+
+
+
+export function logEvenNumbers(logger,items) {
+
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeLogger.checkType(logger)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("logger");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterSequencei32.checkType(items)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("items");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                42, // fixture_callbacks:uniffi_uniffi_fixture_callbacks_fn_func_log_even_numbers
+                FfiConverterTypeLogger.lower(logger),
+                FfiConverterSequencei32.lower(items),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function logEvenNumbersMainThread(logger,items) {
+
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeLogger.checkType(logger)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("logger");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterSequencei32.checkType(items)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("items");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callSync(
+                43, // fixture_callbacks:uniffi_uniffi_fixture_callbacks_fn_func_log_even_numbers_main_thread
+                FfiConverterTypeLogger.lower(logger),
+                FfiConverterSequencei32.lower(items),
+            )
+        }
+        return handleRustResult(functionCall(), liftResult, liftError);
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustGeometry.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustGeometry.sys.mjs
new file mode 100644
index 0000000000..1a7ebb287a
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustGeometry.sys.mjs
@@ -0,0 +1,520 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterF64 extends FfiConverter {
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+export class Line {
+    constructor({ start, end } = {}) {
+        try {
+            FfiConverterTypePoint.checkType(start)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("start");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterTypePoint.checkType(end)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("end");
+            }
+            throw e;
+        }
+        this.start = start;
+        this.end = end;
+    }
+    equals(other) {
+        return (
+            this.start.equals(other.start) &&
+            this.end.equals(other.end)
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeLine extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new Line({
+            start: FfiConverterTypePoint.read(dataStream),
+            end: FfiConverterTypePoint.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterTypePoint.write(dataStream, value.start);
+        FfiConverterTypePoint.write(dataStream, value.end);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterTypePoint.computeSize(value.start);
+        totalSize += FfiConverterTypePoint.computeSize(value.end);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof Line)) {
+            throw new TypeError(`Expected 'Line', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterTypePoint.checkType(value.start);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".start");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterTypePoint.checkType(value.end);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".end");
+            }
+            throw e;
+        }
+    }
+}
+
+export class Point {
+    constructor({ coordX, coordY } = {}) {
+        try {
+            FfiConverterF64.checkType(coordX)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("coordX");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(coordY)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("coordY");
+            }
+            throw e;
+        }
+        this.coordX = coordX;
+        this.coordY = coordY;
+    }
+    equals(other) {
+        return (
+            this.coordX == other.coordX &&
+            this.coordY == other.coordY
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypePoint extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new Point({
+            coordX: FfiConverterF64.read(dataStream),
+            coordY: FfiConverterF64.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterF64.write(dataStream, value.coordX);
+        FfiConverterF64.write(dataStream, value.coordY);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterF64.computeSize(value.coordX);
+        totalSize += FfiConverterF64.computeSize(value.coordY);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof Point)) {
+            throw new TypeError(`Expected 'Point', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterF64.checkType(value.coordX);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".coordX");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(value.coordY);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".coordY");
+            }
+            throw e;
+        }
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypePoint extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypePoint.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypePoint.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypePoint.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypePoint.computeSize(value)
+    }
+}
+
+
+
+
+
+export function gradient(ln) {
+
+        const liftResult = (result) => FfiConverterF64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeLine.checkType(ln)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("ln");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                44, // geometry:uniffi_uniffi_geometry_fn_func_gradient
+                FfiConverterTypeLine.lower(ln),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function intersection(ln1,ln2) {
+
+        const liftResult = (result) => FfiConverterOptionalTypePoint.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeLine.checkType(ln1)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("ln1");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterTypeLine.checkType(ln2)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("ln2");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                45, // geometry:uniffi_uniffi_geometry_fn_func_intersection
+                FfiConverterTypeLine.lower(ln1),
+                FfiConverterTypeLine.lower(ln2),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustRondpoint.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustRondpoint.sys.mjs
new file mode 100644
index 0000000000..1edb7ec608
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustRondpoint.sys.mjs
@@ -0,0 +1,3384 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+
+    // Reads a Optionneur pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerOptionneur() {
+        const pointerId = 5; // rondpoint:Optionneur
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a Optionneur pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerOptionneur(value) {
+        const pointerId = 5; // rondpoint:Optionneur
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+
+    // Reads a Retourneur pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerRetourneur() {
+        const pointerId = 6; // rondpoint:Retourneur
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a Retourneur pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerRetourneur(value) {
+        const pointerId = 6; // rondpoint:Retourneur
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+
+    // Reads a Stringifier pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerStringifier() {
+        const pointerId = 7; // rondpoint:Stringifier
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a Stringifier pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerStringifier(value) {
+        const pointerId = 7; // rondpoint:Stringifier
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterU8 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < 0 || value > 256) {
+            throw new UniFFITypeError(`${value} exceeds the U8 bounds`);
+        }
+    }
+    static computeSize() {
+        return 1;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint8(value)
+    }
+    static read(dataStream) {
+        return dataStream.readUint8()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterI8 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < -128 || value > 127) {
+            throw new UniFFITypeError(`${value} exceeds the I8 bounds`);
+        }
+    }
+    static computeSize() {
+        return 1;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeInt8(value)
+    }
+    static read(dataStream) {
+        return dataStream.readInt8()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterU16 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < 0 || value > 65535) {
+            throw new UniFFITypeError(`${value} exceeds the U16 bounds`);
+        }
+    }
+    static computeSize() {
+        return 2;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint16(value)
+    }
+    static read(dataStream) {
+        return dataStream.readUint16()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterI16 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < -32768 || value > 32767) {
+            throw new UniFFITypeError(`${value} exceeds the I16 bounds`);
+        }
+    }
+    static computeSize() {
+        return 2;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeInt16(value)
+    }
+    static read(dataStream) {
+        return dataStream.readInt16()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterU32 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < 0 || value > 4294967295) {
+            throw new UniFFITypeError(`${value} exceeds the U32 bounds`);
+        }
+    }
+    static computeSize() {
+        return 4;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint32(value)
+    }
+    static read(dataStream) {
+        return dataStream.readUint32()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterI32 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isInteger(value)) {
+            throw new UniFFITypeError(`${value} is not an integer`);
+        }
+        if (value < -2147483648 || value > 2147483647) {
+            throw new UniFFITypeError(`${value} exceeds the I32 bounds`);
+        }
+    }
+    static computeSize() {
+        return 4;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeInt32(value)
+    }
+    static read(dataStream) {
+        return dataStream.readInt32()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterU64 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isSafeInteger(value)) {
+            throw new UniFFITypeError(`${value} exceeds the safe integer bounds`);
+        }
+        if (value < 0) {
+            throw new UniFFITypeError(`${value} exceeds the U64 bounds`);
+        }
+    }
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readUint64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterI64 extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (!Number.isSafeInteger(value)) {
+            throw new UniFFITypeError(`${value} exceeds the safe integer bounds`);
+        }
+    }
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeInt64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readInt64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterF32 extends FfiConverter {
+    static computeSize() {
+        return 4;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat32(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat32()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterF64 extends FfiConverter {
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterBool extends FfiConverter {
+    static computeSize() {
+        return 1;
+    }
+    static lift(value) {
+        return value == 1;
+    }
+    static lower(value) {
+        if (value) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint8(this.lower(value))
+    }
+    static read(dataStream) {
+        return this.lift(dataStream.readUint8())
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+export class Optionneur {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for Optionneur.
+     * 
+     * @returns {Promise<Optionneur>}: A promise that resolves
+     *      to a newly constructed Optionneur
+     */
+    static init() {
+        const liftResult = (result) => FfiConverterTypeOptionneur.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                46, // rondpoint:uniffi_uniffi_rondpoint_fn_constructor_optionneur_new
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }}
+
+    sinonBoolean(value = false) {
+        const liftResult = (result) => FfiConverterBool.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterBool.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                47, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_boolean
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterBool.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonEnum(value = Enumeration.TROIS) {
+        const liftResult = (result) => FfiConverterTypeEnumeration.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeEnumeration.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                48, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_enum
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterTypeEnumeration.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonF32(value = 42.0) {
+        const liftResult = (result) => FfiConverterF32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterF32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                49, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_f32
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterF32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonF64(value = 42.1) {
+        const liftResult = (result) => FfiConverterF64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterF64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                50, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_f64
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterF64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI16Dec(value = 42) {
+        const liftResult = (result) => FfiConverterI16.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                51, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i16_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI16Hex(value = 0x7f) {
+        const liftResult = (result) => FfiConverterI16.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                52, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i16_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI32Dec(value = 42) {
+        const liftResult = (result) => FfiConverterI32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                53, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i32_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI32Hex(value = 0x7fffffff) {
+        const liftResult = (result) => FfiConverterI32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                54, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i32_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI64Dec(value = 42) {
+        const liftResult = (result) => FfiConverterI64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                55, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i64_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI64Hex(value = 0x7fffffffffffffff) {
+        const liftResult = (result) => FfiConverterI64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                56, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i64_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI8Dec(value = -42) {
+        const liftResult = (result) => FfiConverterI8.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                57, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i8_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonI8Hex(value = -127) {
+        const liftResult = (result) => FfiConverterI8.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                58, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_i8_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterI8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonNull(value = null) {
+        const liftResult = (result) => FfiConverterOptionalstring.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterOptionalstring.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                59, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_null
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterOptionalstring.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonSequence(value = []) {
+        const liftResult = (result) => FfiConverterSequencestring.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterSequencestring.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                60, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_sequence
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterSequencestring.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonString(value = "default") {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterString.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                61, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_string
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterString.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU16Dec(value = 42) {
+        const liftResult = (result) => FfiConverterU16.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                62, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u16_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU16Hex(value = 0xffff) {
+        const liftResult = (result) => FfiConverterU16.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                63, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u16_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU32Dec(value = 42) {
+        const liftResult = (result) => FfiConverterU32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                64, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u32_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU32Hex(value = 0xffffffff) {
+        const liftResult = (result) => FfiConverterU32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                65, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u32_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU32Oct(value = 0o755) {
+        const liftResult = (result) => FfiConverterU32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                66, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u32_oct
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU64Dec(value = 42) {
+        const liftResult = (result) => FfiConverterU64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                67, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u64_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU64Hex(value = 0xffffffffffffffff) {
+        const liftResult = (result) => FfiConverterU64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                68, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u64_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU8Dec(value = 42) {
+        const liftResult = (result) => FfiConverterU8.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                69, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u8_dec
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonU8Hex(value = 0xff) {
+        const liftResult = (result) => FfiConverterU8.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                70, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_u8_hex
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterU8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    sinonZero(value = 0) {
+        const liftResult = (result) => FfiConverterOptionali32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterOptionali32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                71, // rondpoint:uniffi_uniffi_rondpoint_fn_method_optionneur_sinon_zero
+                FfiConverterTypeOptionneur.lower(this),
+                FfiConverterOptionali32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeOptionneur extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new Optionneur(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerOptionneur());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerOptionneur(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+export class Retourneur {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for Retourneur.
+     * 
+     * @returns {Promise<Retourneur>}: A promise that resolves
+     *      to a newly constructed Retourneur
+     */
+    static init() {
+        const liftResult = (result) => FfiConverterTypeRetourneur.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                72, // rondpoint:uniffi_uniffi_rondpoint_fn_constructor_retourneur_new
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }}
+
+    identiqueBoolean(value) {
+        const liftResult = (result) => FfiConverterBool.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterBool.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                73, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_boolean
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterBool.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueDouble(value) {
+        const liftResult = (result) => FfiConverterF64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterF64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                74, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_double
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterF64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueFloat(value) {
+        const liftResult = (result) => FfiConverterF32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterF32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                75, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_float
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterF32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueI16(value) {
+        const liftResult = (result) => FfiConverterI16.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                76, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_i16
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterI16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueI32(value) {
+        const liftResult = (result) => FfiConverterI32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                77, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_i32
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterI32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueI64(value) {
+        const liftResult = (result) => FfiConverterI64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                78, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_i64
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterI64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueI8(value) {
+        const liftResult = (result) => FfiConverterI8.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                79, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_i8
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterI8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueNombres(value) {
+        const liftResult = (result) => FfiConverterTypeDictionnaireNombres.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeDictionnaireNombres.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                80, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_nombres
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterTypeDictionnaireNombres.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueNombresSignes(value) {
+        const liftResult = (result) => FfiConverterTypeDictionnaireNombresSignes.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeDictionnaireNombresSignes.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                81, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_nombres_signes
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterTypeDictionnaireNombresSignes.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueOptionneurDictionnaire(value) {
+        const liftResult = (result) => FfiConverterTypeOptionneurDictionnaire.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeOptionneurDictionnaire.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                82, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_optionneur_dictionnaire
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterTypeOptionneurDictionnaire.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueString(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterString.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                83, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_string
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterString.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueU16(value) {
+        const liftResult = (result) => FfiConverterU16.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                84, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_u16
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterU16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueU32(value) {
+        const liftResult = (result) => FfiConverterU32.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                85, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_u32
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterU32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueU64(value) {
+        const liftResult = (result) => FfiConverterU64.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                86, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_u64
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterU64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    identiqueU8(value) {
+        const liftResult = (result) => FfiConverterU8.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                87, // rondpoint:uniffi_uniffi_rondpoint_fn_method_retourneur_identique_u8
+                FfiConverterTypeRetourneur.lower(this),
+                FfiConverterU8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeRetourneur extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new Retourneur(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerRetourneur());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerRetourneur(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+export class Stringifier {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for Stringifier.
+     * 
+     * @returns {Promise<Stringifier>}: A promise that resolves
+     *      to a newly constructed Stringifier
+     */
+    static init() {
+        const liftResult = (result) => FfiConverterTypeStringifier.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                88, // rondpoint:uniffi_uniffi_rondpoint_fn_constructor_stringifier_new
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }}
+
+    toStringBoolean(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterBool.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                89, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_boolean
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterBool.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringDouble(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterF64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                90, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_double
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterF64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringFloat(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterF32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                91, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_float
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterF32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringI16(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                92, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_i16
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterI16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringI32(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                93, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_i32
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterI32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringI64(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                94, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_i64
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterI64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringI8(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterI8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                95, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_i8
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterI8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringU16(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU16.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                96, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_u16
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterU16.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringU32(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU32.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                97, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_u32
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterU32.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringU64(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU64.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                98, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_u64
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterU64.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    toStringU8(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterU8.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                99, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_to_string_u8
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterU8.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    wellKnownString(value) {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterString.checkType(value)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("value");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                100, // rondpoint:uniffi_uniffi_rondpoint_fn_method_stringifier_well_known_string
+                FfiConverterTypeStringifier.lower(this),
+                FfiConverterString.lower(value),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeStringifier extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new Stringifier(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerStringifier());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerStringifier(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+export class Dictionnaire {
+    constructor({ un, deux, petitNombre, grosNombre } = {}) {
+        try {
+            FfiConverterTypeEnumeration.checkType(un)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("un");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterBool.checkType(deux)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("deux");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU8.checkType(petitNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("petitNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU64.checkType(grosNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("grosNombre");
+            }
+            throw e;
+        }
+        this.un = un;
+        this.deux = deux;
+        this.petitNombre = petitNombre;
+        this.grosNombre = grosNombre;
+    }
+    equals(other) {
+        return (
+            this.un == other.un &&
+            this.deux == other.deux &&
+            this.petitNombre == other.petitNombre &&
+            this.grosNombre == other.grosNombre
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeDictionnaire extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new Dictionnaire({
+            un: FfiConverterTypeEnumeration.read(dataStream),
+            deux: FfiConverterBool.read(dataStream),
+            petitNombre: FfiConverterU8.read(dataStream),
+            grosNombre: FfiConverterU64.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterTypeEnumeration.write(dataStream, value.un);
+        FfiConverterBool.write(dataStream, value.deux);
+        FfiConverterU8.write(dataStream, value.petitNombre);
+        FfiConverterU64.write(dataStream, value.grosNombre);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterTypeEnumeration.computeSize(value.un);
+        totalSize += FfiConverterBool.computeSize(value.deux);
+        totalSize += FfiConverterU8.computeSize(value.petitNombre);
+        totalSize += FfiConverterU64.computeSize(value.grosNombre);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof Dictionnaire)) {
+            throw new TypeError(`Expected 'Dictionnaire', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterTypeEnumeration.checkType(value.un);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".un");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterBool.checkType(value.deux);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".deux");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU8.checkType(value.petitNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".petitNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU64.checkType(value.grosNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".grosNombre");
+            }
+            throw e;
+        }
+    }
+}
+
+export class DictionnaireNombres {
+    constructor({ petitNombre, courtNombre, nombreSimple, grosNombre } = {}) {
+        try {
+            FfiConverterU8.checkType(petitNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("petitNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU16.checkType(courtNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("courtNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU32.checkType(nombreSimple)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("nombreSimple");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU64.checkType(grosNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("grosNombre");
+            }
+            throw e;
+        }
+        this.petitNombre = petitNombre;
+        this.courtNombre = courtNombre;
+        this.nombreSimple = nombreSimple;
+        this.grosNombre = grosNombre;
+    }
+    equals(other) {
+        return (
+            this.petitNombre == other.petitNombre &&
+            this.courtNombre == other.courtNombre &&
+            this.nombreSimple == other.nombreSimple &&
+            this.grosNombre == other.grosNombre
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeDictionnaireNombres extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new DictionnaireNombres({
+            petitNombre: FfiConverterU8.read(dataStream),
+            courtNombre: FfiConverterU16.read(dataStream),
+            nombreSimple: FfiConverterU32.read(dataStream),
+            grosNombre: FfiConverterU64.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterU8.write(dataStream, value.petitNombre);
+        FfiConverterU16.write(dataStream, value.courtNombre);
+        FfiConverterU32.write(dataStream, value.nombreSimple);
+        FfiConverterU64.write(dataStream, value.grosNombre);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterU8.computeSize(value.petitNombre);
+        totalSize += FfiConverterU16.computeSize(value.courtNombre);
+        totalSize += FfiConverterU32.computeSize(value.nombreSimple);
+        totalSize += FfiConverterU64.computeSize(value.grosNombre);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof DictionnaireNombres)) {
+            throw new TypeError(`Expected 'DictionnaireNombres', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterU8.checkType(value.petitNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".petitNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU16.checkType(value.courtNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".courtNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU32.checkType(value.nombreSimple);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".nombreSimple");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU64.checkType(value.grosNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".grosNombre");
+            }
+            throw e;
+        }
+    }
+}
+
+export class DictionnaireNombresSignes {
+    constructor({ petitNombre, courtNombre, nombreSimple, grosNombre } = {}) {
+        try {
+            FfiConverterI8.checkType(petitNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("petitNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI16.checkType(courtNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("courtNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI32.checkType(nombreSimple)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("nombreSimple");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI64.checkType(grosNombre)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("grosNombre");
+            }
+            throw e;
+        }
+        this.petitNombre = petitNombre;
+        this.courtNombre = courtNombre;
+        this.nombreSimple = nombreSimple;
+        this.grosNombre = grosNombre;
+    }
+    equals(other) {
+        return (
+            this.petitNombre == other.petitNombre &&
+            this.courtNombre == other.courtNombre &&
+            this.nombreSimple == other.nombreSimple &&
+            this.grosNombre == other.grosNombre
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeDictionnaireNombresSignes extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new DictionnaireNombresSignes({
+            petitNombre: FfiConverterI8.read(dataStream),
+            courtNombre: FfiConverterI16.read(dataStream),
+            nombreSimple: FfiConverterI32.read(dataStream),
+            grosNombre: FfiConverterI64.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterI8.write(dataStream, value.petitNombre);
+        FfiConverterI16.write(dataStream, value.courtNombre);
+        FfiConverterI32.write(dataStream, value.nombreSimple);
+        FfiConverterI64.write(dataStream, value.grosNombre);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterI8.computeSize(value.petitNombre);
+        totalSize += FfiConverterI16.computeSize(value.courtNombre);
+        totalSize += FfiConverterI32.computeSize(value.nombreSimple);
+        totalSize += FfiConverterI64.computeSize(value.grosNombre);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof DictionnaireNombresSignes)) {
+            throw new TypeError(`Expected 'DictionnaireNombresSignes', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterI8.checkType(value.petitNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".petitNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI16.checkType(value.courtNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".courtNombre");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI32.checkType(value.nombreSimple);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".nombreSimple");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI64.checkType(value.grosNombre);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".grosNombre");
+            }
+            throw e;
+        }
+    }
+}
+
+export class OptionneurDictionnaire {
+    constructor({ i8Var = -8, u8Var = 8, i16Var = -16, u16Var = 0x10, i32Var = -32, u32Var = 32, i64Var = -64, u64Var = 64, floatVar = 4.0, doubleVar = 8.0, booleanVar = true, stringVar = "default", listVar = [], enumerationVar = Enumeration.DEUX, dictionnaireVar = null } = {}) {
+        try {
+            FfiConverterI8.checkType(i8Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("i8Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU8.checkType(u8Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("u8Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI16.checkType(i16Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("i16Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU16.checkType(u16Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("u16Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI32.checkType(i32Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("i32Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU32.checkType(u32Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("u32Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI64.checkType(i64Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("i64Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU64.checkType(u64Var)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("u64Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF32.checkType(floatVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("floatVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(doubleVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("doubleVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterBool.checkType(booleanVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("booleanVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterString.checkType(stringVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("stringVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterSequencestring.checkType(listVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("listVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterTypeEnumeration.checkType(enumerationVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("enumerationVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterOptionalTypeminusculeMajusculeEnum.checkType(dictionnaireVar)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("dictionnaireVar");
+            }
+            throw e;
+        }
+        this.i8Var = i8Var;
+        this.u8Var = u8Var;
+        this.i16Var = i16Var;
+        this.u16Var = u16Var;
+        this.i32Var = i32Var;
+        this.u32Var = u32Var;
+        this.i64Var = i64Var;
+        this.u64Var = u64Var;
+        this.floatVar = floatVar;
+        this.doubleVar = doubleVar;
+        this.booleanVar = booleanVar;
+        this.stringVar = stringVar;
+        this.listVar = listVar;
+        this.enumerationVar = enumerationVar;
+        this.dictionnaireVar = dictionnaireVar;
+    }
+    equals(other) {
+        return (
+            this.i8Var == other.i8Var &&
+            this.u8Var == other.u8Var &&
+            this.i16Var == other.i16Var &&
+            this.u16Var == other.u16Var &&
+            this.i32Var == other.i32Var &&
+            this.u32Var == other.u32Var &&
+            this.i64Var == other.i64Var &&
+            this.u64Var == other.u64Var &&
+            this.floatVar == other.floatVar &&
+            this.doubleVar == other.doubleVar &&
+            this.booleanVar == other.booleanVar &&
+            this.stringVar == other.stringVar &&
+            this.listVar == other.listVar &&
+            this.enumerationVar == other.enumerationVar &&
+            this.dictionnaireVar == other.dictionnaireVar
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeOptionneurDictionnaire extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new OptionneurDictionnaire({
+            i8Var: FfiConverterI8.read(dataStream),
+            u8Var: FfiConverterU8.read(dataStream),
+            i16Var: FfiConverterI16.read(dataStream),
+            u16Var: FfiConverterU16.read(dataStream),
+            i32Var: FfiConverterI32.read(dataStream),
+            u32Var: FfiConverterU32.read(dataStream),
+            i64Var: FfiConverterI64.read(dataStream),
+            u64Var: FfiConverterU64.read(dataStream),
+            floatVar: FfiConverterF32.read(dataStream),
+            doubleVar: FfiConverterF64.read(dataStream),
+            booleanVar: FfiConverterBool.read(dataStream),
+            stringVar: FfiConverterString.read(dataStream),
+            listVar: FfiConverterSequencestring.read(dataStream),
+            enumerationVar: FfiConverterTypeEnumeration.read(dataStream),
+            dictionnaireVar: FfiConverterOptionalTypeminusculeMajusculeEnum.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterI8.write(dataStream, value.i8Var);
+        FfiConverterU8.write(dataStream, value.u8Var);
+        FfiConverterI16.write(dataStream, value.i16Var);
+        FfiConverterU16.write(dataStream, value.u16Var);
+        FfiConverterI32.write(dataStream, value.i32Var);
+        FfiConverterU32.write(dataStream, value.u32Var);
+        FfiConverterI64.write(dataStream, value.i64Var);
+        FfiConverterU64.write(dataStream, value.u64Var);
+        FfiConverterF32.write(dataStream, value.floatVar);
+        FfiConverterF64.write(dataStream, value.doubleVar);
+        FfiConverterBool.write(dataStream, value.booleanVar);
+        FfiConverterString.write(dataStream, value.stringVar);
+        FfiConverterSequencestring.write(dataStream, value.listVar);
+        FfiConverterTypeEnumeration.write(dataStream, value.enumerationVar);
+        FfiConverterOptionalTypeminusculeMajusculeEnum.write(dataStream, value.dictionnaireVar);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterI8.computeSize(value.i8Var);
+        totalSize += FfiConverterU8.computeSize(value.u8Var);
+        totalSize += FfiConverterI16.computeSize(value.i16Var);
+        totalSize += FfiConverterU16.computeSize(value.u16Var);
+        totalSize += FfiConverterI32.computeSize(value.i32Var);
+        totalSize += FfiConverterU32.computeSize(value.u32Var);
+        totalSize += FfiConverterI64.computeSize(value.i64Var);
+        totalSize += FfiConverterU64.computeSize(value.u64Var);
+        totalSize += FfiConverterF32.computeSize(value.floatVar);
+        totalSize += FfiConverterF64.computeSize(value.doubleVar);
+        totalSize += FfiConverterBool.computeSize(value.booleanVar);
+        totalSize += FfiConverterString.computeSize(value.stringVar);
+        totalSize += FfiConverterSequencestring.computeSize(value.listVar);
+        totalSize += FfiConverterTypeEnumeration.computeSize(value.enumerationVar);
+        totalSize += FfiConverterOptionalTypeminusculeMajusculeEnum.computeSize(value.dictionnaireVar);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof OptionneurDictionnaire)) {
+            throw new TypeError(`Expected 'OptionneurDictionnaire', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterI8.checkType(value.i8Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".i8Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU8.checkType(value.u8Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".u8Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI16.checkType(value.i16Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".i16Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU16.checkType(value.u16Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".u16Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI32.checkType(value.i32Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".i32Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU32.checkType(value.u32Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".u32Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterI64.checkType(value.i64Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".i64Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterU64.checkType(value.u64Var);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".u64Var");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF32.checkType(value.floatVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".floatVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(value.doubleVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".doubleVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterBool.checkType(value.booleanVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".booleanVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterString.checkType(value.stringVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".stringVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterSequencestring.checkType(value.listVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".listVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterTypeEnumeration.checkType(value.enumerationVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".enumerationVar");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterOptionalTypeminusculeMajusculeEnum.checkType(value.dictionnaireVar);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".dictionnaireVar");
+            }
+            throw e;
+        }
+    }
+}
+
+export class MinusculeMajusculeDict {
+    constructor({ minusculeMajusculeField } = {}) {
+        try {
+            FfiConverterBool.checkType(minusculeMajusculeField)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("minusculeMajusculeField");
+            }
+            throw e;
+        }
+        this.minusculeMajusculeField = minusculeMajusculeField;
+    }
+    equals(other) {
+        return (
+            this.minusculeMajusculeField == other.minusculeMajusculeField
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeminusculeMajusculeDict extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new MinusculeMajusculeDict({
+            minusculeMajusculeField: FfiConverterBool.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterBool.write(dataStream, value.minusculeMajusculeField);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterBool.computeSize(value.minusculeMajusculeField);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof MinusculeMajusculeDict)) {
+            throw new TypeError(`Expected 'MinusculeMajusculeDict', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterBool.checkType(value.minusculeMajusculeField);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".minusculeMajusculeField");
+            }
+            throw e;
+        }
+    }
+}
+
+
+export const Enumeration = {
+    UN: 1,
+    DEUX: 2,
+    TROIS: 3,
+};
+
+Object.freeze(Enumeration);
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeEnumeration extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return Enumeration.UN
+            case 2:
+                return Enumeration.DEUX
+            case 3:
+                return Enumeration.TROIS
+            default:
+                return new Error("Unknown Enumeration variant");
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === Enumeration.UN) {
+            dataStream.writeInt32(1);
+            return;
+        }
+        if (value === Enumeration.DEUX) {
+            dataStream.writeInt32(2);
+            return;
+        }
+        if (value === Enumeration.TROIS) {
+            dataStream.writeInt32(3);
+            return;
+        }
+        return new Error("Unknown Enumeration variant");
+    }
+
+    static computeSize(value) {
+        return 4;
+    }
+
+    static checkType(value) {
+      if (!Number.isInteger(value) || value < 1 || value > 3) {
+          throw new UniFFITypeError(`${value} is not a valid value for Enumeration`);
+      }
+    }
+}
+
+
+
+export class EnumerationAvecDonnees {}
+EnumerationAvecDonnees.Zero = class extends EnumerationAvecDonnees{
+    constructor(
+        ) {
+            super();
+        }
+}
+EnumerationAvecDonnees.Un = class extends EnumerationAvecDonnees{
+    constructor(
+        premier
+        ) {
+            super();
+            this.premier = premier;
+        }
+}
+EnumerationAvecDonnees.Deux = class extends EnumerationAvecDonnees{
+    constructor(
+        premier,
+        second
+        ) {
+            super();
+            this.premier = premier;
+            this.second = second;
+        }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeEnumerationAvecDonnees extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return new EnumerationAvecDonnees.Zero(
+                    );
+            case 2:
+                return new EnumerationAvecDonnees.Un(
+                    FfiConverterU32.read(dataStream)
+                    );
+            case 3:
+                return new EnumerationAvecDonnees.Deux(
+                    FfiConverterU32.read(dataStream),
+                    FfiConverterString.read(dataStream)
+                    );
+            default:
+                return new Error("Unknown EnumerationAvecDonnees variant");
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value instanceof EnumerationAvecDonnees.Zero) {
+            dataStream.writeInt32(1);
+            return;
+        }
+        if (value instanceof EnumerationAvecDonnees.Un) {
+            dataStream.writeInt32(2);
+            FfiConverterU32.write(dataStream, value.premier);
+            return;
+        }
+        if (value instanceof EnumerationAvecDonnees.Deux) {
+            dataStream.writeInt32(3);
+            FfiConverterU32.write(dataStream, value.premier);
+            FfiConverterString.write(dataStream, value.second);
+            return;
+        }
+        return new Error("Unknown EnumerationAvecDonnees variant");
+    }
+
+    static computeSize(value) {
+        // Size of the Int indicating the variant
+        let totalSize = 4;
+        if (value instanceof EnumerationAvecDonnees.Zero) {
+            return totalSize;
+        }
+        if (value instanceof EnumerationAvecDonnees.Un) {
+            totalSize += FfiConverterU32.computeSize(value.premier);
+            return totalSize;
+        }
+        if (value instanceof EnumerationAvecDonnees.Deux) {
+            totalSize += FfiConverterU32.computeSize(value.premier);
+            totalSize += FfiConverterString.computeSize(value.second);
+            return totalSize;
+        }
+        return new Error("Unknown EnumerationAvecDonnees variant");
+    }
+
+    static checkType(value) {
+      if (!(value instanceof EnumerationAvecDonnees)) {
+        throw new UniFFITypeError(`${value} is not a subclass instance of EnumerationAvecDonnees`);
+      }
+    }
+}
+
+
+
+export const MinusculeMajusculeEnum = {
+    MINUSCULE_MAJUSCULE_VARIANT: 1,
+};
+
+Object.freeze(MinusculeMajusculeEnum);
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeminusculeMajusculeEnum extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return MinusculeMajusculeEnum.MINUSCULE_MAJUSCULE_VARIANT
+            default:
+                return new Error("Unknown MinusculeMajusculeEnum variant");
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === MinusculeMajusculeEnum.MINUSCULE_MAJUSCULE_VARIANT) {
+            dataStream.writeInt32(1);
+            return;
+        }
+        return new Error("Unknown MinusculeMajusculeEnum variant");
+    }
+
+    static computeSize(value) {
+        return 4;
+    }
+
+    static checkType(value) {
+      if (!Number.isInteger(value) || value < 1 || value > 1) {
+          throw new UniFFITypeError(`${value} is not a valid value for MinusculeMajusculeEnum`);
+      }
+    }
+}
+
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionali32 extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterI32.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterI32.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterI32.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterI32.computeSize(value)
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalstring extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterString.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterString.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterString.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterString.computeSize(value)
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypeminusculeMajusculeEnum extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypeminusculeMajusculeEnum.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypeminusculeMajusculeEnum.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypeminusculeMajusculeEnum.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypeminusculeMajusculeEnum.computeSize(value)
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterSequencestring extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterString.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterString.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterString.computeSize(innerValue);
+        }
+        return size;
+    }
+
+    static checkType(value) {
+        if (!Array.isArray(value)) {
+            throw new UniFFITypeError(`${value} is not an array`);
+        }
+        value.forEach((innerValue, idx) => {
+            try {
+                FfiConverterString.checkType(innerValue);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart(`[${idx}]`);
+                }
+                throw e;
+            }
+        })
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterSequenceTypeEnumeration extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterTypeEnumeration.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterTypeEnumeration.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterTypeEnumeration.computeSize(innerValue);
+        }
+        return size;
+    }
+
+    static checkType(value) {
+        if (!Array.isArray(value)) {
+            throw new UniFFITypeError(`${value} is not an array`);
+        }
+        value.forEach((innerValue, idx) => {
+            try {
+                FfiConverterTypeEnumeration.checkType(innerValue);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart(`[${idx}]`);
+                }
+                throw e;
+            }
+        })
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterMapStringTypeEnumerationAvecDonnees extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const map = {};
+        for (let i = 0; i < len; i++) {
+            const key = FfiConverterString.read(dataStream);
+            const value = FfiConverterTypeEnumerationAvecDonnees.read(dataStream);
+            map[key] = value;
+        }
+
+        return map;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(Object.keys(value).length);
+        for (const key in value) {
+            FfiConverterString.write(dataStream, key);
+            FfiConverterTypeEnumerationAvecDonnees.write(dataStream, value[key]);
+        }
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const key in value) {
+            size += FfiConverterString.computeSize(key);
+            size += FfiConverterTypeEnumerationAvecDonnees.computeSize(value[key]);
+        }
+        return size;
+    }
+
+    static checkType(value) {
+        for (const key in value) {
+            try {
+                FfiConverterString.checkType(key);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("(key)");
+                }
+                throw e;
+            }
+
+            try {
+                FfiConverterTypeEnumerationAvecDonnees.checkType(value[key]);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart(`[${key}]`);
+                }
+                throw e;
+            }
+        }
+    }
+}
+
+
+
+
+
+export function copieCarte(c) {
+
+        const liftResult = (result) => FfiConverterMapStringTypeEnumerationAvecDonnees.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterMapStringTypeEnumerationAvecDonnees.checkType(c)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("c");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                101, // rondpoint:uniffi_uniffi_rondpoint_fn_func_copie_carte
+                FfiConverterMapStringTypeEnumerationAvecDonnees.lower(c),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function copieDictionnaire(d) {
+
+        const liftResult = (result) => FfiConverterTypeDictionnaire.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeDictionnaire.checkType(d)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("d");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                102, // rondpoint:uniffi_uniffi_rondpoint_fn_func_copie_dictionnaire
+                FfiConverterTypeDictionnaire.lower(d),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function copieEnumeration(e) {
+
+        const liftResult = (result) => FfiConverterTypeEnumeration.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeEnumeration.checkType(e)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("e");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                103, // rondpoint:uniffi_uniffi_rondpoint_fn_func_copie_enumeration
+                FfiConverterTypeEnumeration.lower(e),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function copieEnumerations(e) {
+
+        const liftResult = (result) => FfiConverterSequenceTypeEnumeration.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterSequenceTypeEnumeration.checkType(e)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("e");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                104, // rondpoint:uniffi_uniffi_rondpoint_fn_func_copie_enumerations
+                FfiConverterSequenceTypeEnumeration.lower(e),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function switcheroo(b) {
+
+        const liftResult = (result) => FfiConverterBool.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterBool.checkType(b)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("b");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                105, // rondpoint:uniffi_uniffi_rondpoint_fn_func_switcheroo
+                FfiConverterBool.lower(b),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustSprites.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustSprites.sys.mjs
new file mode 100644
index 0000000000..b404af06b1
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustSprites.sys.mjs
@@ -0,0 +1,687 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+
+    // Reads a Sprite pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerSprite() {
+        const pointerId = 8; // sprites:Sprite
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a Sprite pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerSprite(value) {
+        const pointerId = 8; // sprites:Sprite
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterF64 extends FfiConverter {
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat64()
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+export class Sprite {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for Sprite.
+     * 
+     * @returns {Promise<Sprite>}: A promise that resolves
+     *      to a newly constructed Sprite
+     */
+    static init(initialPosition) {
+        const liftResult = (result) => FfiConverterTypeSprite.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterOptionalTypePoint.checkType(initialPosition)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("initialPosition");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                106, // sprites:uniffi_uniffi_sprites_fn_constructor_sprite_new
+                FfiConverterOptionalTypePoint.lower(initialPosition),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }}
+    /**
+     * An async constructor for Sprite.
+     * 
+     * @returns {Promise<Sprite>}: A promise that resolves
+     *      to a newly constructed Sprite
+     */
+    static newRelativeTo(reference,direction) {
+        const liftResult = (result) => FfiConverterTypeSprite.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypePoint.checkType(reference)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("reference");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterTypeVector.checkType(direction)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("direction");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                107, // sprites:uniffi_uniffi_sprites_fn_constructor_sprite_new_relative_to
+                FfiConverterTypePoint.lower(reference),
+                FfiConverterTypeVector.lower(direction),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }}
+
+    getPosition() {
+        const liftResult = (result) => FfiConverterTypePoint.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                108, // sprites:uniffi_uniffi_sprites_fn_method_sprite_get_position
+                FfiConverterTypeSprite.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    moveBy(direction) {
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeVector.checkType(direction)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("direction");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                109, // sprites:uniffi_uniffi_sprites_fn_method_sprite_move_by
+                FfiConverterTypeSprite.lower(this),
+                FfiConverterTypeVector.lower(direction),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    moveTo(position) {
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypePoint.checkType(position)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("position");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                110, // sprites:uniffi_uniffi_sprites_fn_method_sprite_move_to
+                FfiConverterTypeSprite.lower(this),
+                FfiConverterTypePoint.lower(position),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeSprite extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new Sprite(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerSprite());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerSprite(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+export class Point {
+    constructor({ x, y } = {}) {
+        try {
+            FfiConverterF64.checkType(x)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("x");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(y)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("y");
+            }
+            throw e;
+        }
+        this.x = x;
+        this.y = y;
+    }
+    equals(other) {
+        return (
+            this.x == other.x &&
+            this.y == other.y
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypePoint extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new Point({
+            x: FfiConverterF64.read(dataStream),
+            y: FfiConverterF64.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterF64.write(dataStream, value.x);
+        FfiConverterF64.write(dataStream, value.y);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterF64.computeSize(value.x);
+        totalSize += FfiConverterF64.computeSize(value.y);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof Point)) {
+            throw new TypeError(`Expected 'Point', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterF64.checkType(value.x);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".x");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(value.y);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".y");
+            }
+            throw e;
+        }
+    }
+}
+
+export class Vector {
+    constructor({ dx, dy } = {}) {
+        try {
+            FfiConverterF64.checkType(dx)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("dx");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(dy)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("dy");
+            }
+            throw e;
+        }
+        this.dx = dx;
+        this.dy = dy;
+    }
+    equals(other) {
+        return (
+            this.dx == other.dx &&
+            this.dy == other.dy
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeVector extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new Vector({
+            dx: FfiConverterF64.read(dataStream),
+            dy: FfiConverterF64.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterF64.write(dataStream, value.dx);
+        FfiConverterF64.write(dataStream, value.dy);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterF64.computeSize(value.dx);
+        totalSize += FfiConverterF64.computeSize(value.dy);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof Vector)) {
+            throw new TypeError(`Expected 'Vector', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterF64.checkType(value.dx);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".dx");
+            }
+            throw e;
+        }
+        try {
+            FfiConverterF64.checkType(value.dy);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".dy");
+            }
+            throw e;
+        }
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypePoint extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypePoint.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypePoint.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypePoint.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypePoint.computeSize(value)
+    }
+}
+
+
+
+
+
+export function translate(position,direction) {
+
+        const liftResult = (result) => FfiConverterTypePoint.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypePoint.checkType(position)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("position");
+                }
+                throw e;
+            }
+            try {
+                FfiConverterTypeVector.checkType(direction)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("direction");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                111, // sprites:uniffi_uniffi_sprites_fn_func_translate
+                FfiConverterTypePoint.lower(position),
+                FfiConverterTypeVector.lower(direction),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
diff --git a/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustTodolist.sys.mjs b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustTodolist.sys.mjs
new file mode 100644
index 0000000000..59996b78fa
--- /dev/null
+++ b/toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/RustTodolist.sys.mjs
@@ -0,0 +1,929 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+import { UniFFITypeError } from "resource://gre/modules/UniFFI.sys.mjs";
+
+
+
+// Objects intended to be used in the unit tests
+export var UnitTestObjs = {};
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+
+    // Reads a TodoList pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerTodoList() {
+        const pointerId = 9; // todolist:TodoList
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a TodoList pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerTodoList(value) {
+        const pointerId = 9; // todolist:TodoList
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+
+    toString() {
+        return `UniFFIError: ${this.message}`
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    // throw `UniFFITypeError` if a value to be converted has an invalid type
+    static checkType(value) {
+        if (value === undefined ) {
+            throw new UniFFITypeError(`undefined`);
+        }
+        if (value === null ) {
+            throw new UniFFITypeError(`null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+UnitTestObjs.uniffiObjectPtr = uniffiObjectPtr;
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterString extends FfiConverter {
+    static checkType(value) {
+        super.checkType(value);
+        if (typeof value !== "string") {
+            throw new UniFFITypeError(`${value} is not a string`);
+        }
+    }
+
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+export class TodoList {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for TodoList.
+     * 
+     * @returns {Promise<TodoList>}: A promise that resolves
+     *      to a newly constructed TodoList
+     */
+    static init() {
+        const liftResult = (result) => FfiConverterTypeTodoList.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                112, // todolist:uniffi_uniffi_todolist_fn_constructor_todolist_new
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }}
+
+    addEntries(entries) {
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterSequenceTypeTodoEntry.checkType(entries)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("entries");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                113, // todolist:uniffi_uniffi_todolist_fn_method_todolist_add_entries
+                FfiConverterTypeTodoList.lower(this),
+                FfiConverterSequenceTypeTodoEntry.lower(entries),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    addEntry(entry) {
+        const liftResult = (result) => undefined;
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            try {
+                FfiConverterTypeTodoEntry.checkType(entry)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("entry");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                114, // todolist:uniffi_uniffi_todolist_fn_method_todolist_add_entry
+                FfiConverterTypeTodoList.lower(this),
+                FfiConverterTypeTodoEntry.lower(entry),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    addItem(todo) {
+        const liftResult = (result) => undefined;
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            try {
+                FfiConverterString.checkType(todo)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("todo");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                115, // todolist:uniffi_uniffi_todolist_fn_method_todolist_add_item
+                FfiConverterTypeTodoList.lower(this),
+                FfiConverterString.lower(todo),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    addItems(items) {
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterSequencestring.checkType(items)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("items");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                116, // todolist:uniffi_uniffi_todolist_fn_method_todolist_add_items
+                FfiConverterTypeTodoList.lower(this),
+                FfiConverterSequencestring.lower(items),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    clearItem(todo) {
+        const liftResult = (result) => undefined;
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            try {
+                FfiConverterString.checkType(todo)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("todo");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                117, // todolist:uniffi_uniffi_todolist_fn_method_todolist_clear_item
+                FfiConverterTypeTodoList.lower(this),
+                FfiConverterString.lower(todo),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    getEntries() {
+        const liftResult = (result) => FfiConverterSequenceTypeTodoEntry.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                118, // todolist:uniffi_uniffi_todolist_fn_method_todolist_get_entries
+                FfiConverterTypeTodoList.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    getFirst() {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                119, // todolist:uniffi_uniffi_todolist_fn_method_todolist_get_first
+                FfiConverterTypeTodoList.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    getItems() {
+        const liftResult = (result) => FfiConverterSequencestring.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                120, // todolist:uniffi_uniffi_todolist_fn_method_todolist_get_items
+                FfiConverterTypeTodoList.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    getLast() {
+        const liftResult = (result) => FfiConverterString.lift(result);
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                121, // todolist:uniffi_uniffi_todolist_fn_method_todolist_get_last
+                FfiConverterTypeTodoList.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    getLastEntry() {
+        const liftResult = (result) => FfiConverterTypeTodoEntry.lift(result);
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                122, // todolist:uniffi_uniffi_todolist_fn_method_todolist_get_last_entry
+                FfiConverterTypeTodoList.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+    makeDefault() {
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                123, // todolist:uniffi_uniffi_todolist_fn_method_todolist_make_default
+                FfiConverterTypeTodoList.lower(this),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+    }
+
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeTodoList extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new TodoList(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerTodoList());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerTodoList(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+export class TodoEntry {
+    constructor({ text } = {}) {
+        try {
+            FfiConverterString.checkType(text)
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart("text");
+            }
+            throw e;
+        }
+        this.text = text;
+    }
+    equals(other) {
+        return (
+            this.text == other.text
+        )
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeTodoEntry extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        return new TodoEntry({
+            text: FfiConverterString.read(dataStream),
+        });
+    }
+    static write(dataStream, value) {
+        FfiConverterString.write(dataStream, value.text);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterString.computeSize(value.text);
+        return totalSize
+    }
+
+    static checkType(value) {
+        super.checkType(value);
+        if (!(value instanceof TodoEntry)) {
+            throw new TypeError(`Expected 'TodoEntry', found '${typeof value}'`);
+        }
+        try {
+            FfiConverterString.checkType(value.text);
+        } catch (e) {
+            if (e instanceof UniFFITypeError) {
+                e.addItemDescriptionPart(".text");
+            }
+            throw e;
+        }
+    }
+}
+
+
+
+
+export class TodoError extends Error {}
+
+
+export class TodoDoesNotExist extends TodoError {
+
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+    toString() {
+        return `TodoDoesNotExist: ${super.toString()}`
+    }
+}
+
+export class EmptyTodoList extends TodoError {
+
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+    toString() {
+        return `EmptyTodoList: ${super.toString()}`
+    }
+}
+
+export class DuplicateTodo extends TodoError {
+
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+    toString() {
+        return `DuplicateTodo: ${super.toString()}`
+    }
+}
+
+export class EmptyString extends TodoError {
+
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+    toString() {
+        return `EmptyString: ${super.toString()}`
+    }
+}
+
+export class DeligatedError extends TodoError {
+
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+    toString() {
+        return `DeligatedError: ${super.toString()}`
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterTypeTodoError extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return new TodoDoesNotExist(FfiConverterString.read(dataStream));
+            case 2:
+                return new EmptyTodoList(FfiConverterString.read(dataStream));
+            case 3:
+                return new DuplicateTodo(FfiConverterString.read(dataStream));
+            case 4:
+                return new EmptyString(FfiConverterString.read(dataStream));
+            case 5:
+                return new DeligatedError(FfiConverterString.read(dataStream));
+            default:
+                throw new Error("Unknown TodoError variant");
+        }
+    }
+    static computeSize(value) {
+        // Size of the Int indicating the variant
+        let totalSize = 4;
+        if (value instanceof TodoDoesNotExist) {
+            return totalSize;
+        }
+        if (value instanceof EmptyTodoList) {
+            return totalSize;
+        }
+        if (value instanceof DuplicateTodo) {
+            return totalSize;
+        }
+        if (value instanceof EmptyString) {
+            return totalSize;
+        }
+        if (value instanceof DeligatedError) {
+            return totalSize;
+        }
+        throw new Error("Unknown TodoError variant");
+    }
+    static write(dataStream, value) {
+        if (value instanceof TodoDoesNotExist) {
+            dataStream.writeInt32(1);
+            return;
+        }
+        if (value instanceof EmptyTodoList) {
+            dataStream.writeInt32(2);
+            return;
+        }
+        if (value instanceof DuplicateTodo) {
+            dataStream.writeInt32(3);
+            return;
+        }
+        if (value instanceof EmptyString) {
+            dataStream.writeInt32(4);
+            return;
+        }
+        if (value instanceof DeligatedError) {
+            dataStream.writeInt32(5);
+            return;
+        }
+        throw new Error("Unknown TodoError variant");
+    }
+
+    static errorClass = TodoError;
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterOptionalTypeTodoList extends FfiConverterArrayBuffer {
+    static checkType(value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypeTodoList.checkType(value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypeTodoList.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypeTodoList.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypeTodoList.computeSize(value)
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterSequencestring extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterString.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterString.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterString.computeSize(innerValue);
+        }
+        return size;
+    }
+
+    static checkType(value) {
+        if (!Array.isArray(value)) {
+            throw new UniFFITypeError(`${value} is not an array`);
+        }
+        value.forEach((innerValue, idx) => {
+            try {
+                FfiConverterString.checkType(innerValue);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart(`[${idx}]`);
+                }
+                throw e;
+            }
+        })
+    }
+}
+
+// Export the FFIConverter object to make external types work.
+export class FfiConverterSequenceTypeTodoEntry extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterTypeTodoEntry.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterTypeTodoEntry.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterTypeTodoEntry.computeSize(innerValue);
+        }
+        return size;
+    }
+
+    static checkType(value) {
+        if (!Array.isArray(value)) {
+            throw new UniFFITypeError(`${value} is not an array`);
+        }
+        value.forEach((innerValue, idx) => {
+            try {
+                FfiConverterTypeTodoEntry.checkType(innerValue);
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart(`[${idx}]`);
+                }
+                throw e;
+            }
+        })
+    }
+}
+
+
+
+
+
+export function createEntryWith(todo) {
+
+        const liftResult = (result) => FfiConverterTypeTodoEntry.lift(result);
+        const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+        const functionCall = () => {
+            try {
+                FfiConverterString.checkType(todo)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("todo");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                124, // todolist:uniffi_uniffi_todolist_fn_func_create_entry_with
+                FfiConverterString.lower(todo),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function getDefaultList() {
+
+        const liftResult = (result) => FfiConverterOptionalTypeTodoList.lift(result);
+        const liftError = null;
+        const functionCall = () => {
+            return UniFFIScaffolding.callAsync(
+                125, // todolist:uniffi_uniffi_todolist_fn_func_get_default_list
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}
+
+export function setDefaultList(list) {
+
+        const liftResult = (result) => undefined;
+        const liftError = null;
+        const functionCall = () => {
+            try {
+                FfiConverterTypeTodoList.checkType(list)
+            } catch (e) {
+                if (e instanceof UniFFITypeError) {
+                    e.addItemDescriptionPart("list");
+                }
+                throw e;
+            }
+            return UniFFIScaffolding.callAsync(
+                126, // todolist:uniffi_uniffi_todolist_fn_func_set_default_list
+                FfiConverterTypeTodoList.lower(list),
+            )
+        }
+        try {
+            return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+        }  catch (error) {
+            return Promise.reject(error)
+        }
+}