Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

10 files changed, 1761 insertions, 0 deletions

diff --git a/third_party/rust/wasm-encoder/src/component/aliases.rs b/third_party/rust/wasm-encoder/src/component/aliases.rs
new file mode 100644
index 0000000000..1e317fb0e2
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/aliases.rs
@@ -0,0 +1,160 @@
+use super::{COMPONENT_SORT, CORE_MODULE_SORT, CORE_SORT, CORE_TYPE_SORT, TYPE_SORT};
+use crate::{
+    encode_section, ComponentExportKind, ComponentSection, ComponentSectionId, Encode, ExportKind,
+};
+
+/// Represents the kinds of outer aliasable items in a component.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ComponentOuterAliasKind {
+    /// The alias is to a core module.
+    CoreModule,
+    /// The alias is to a core type.
+    CoreType,
+    /// The alias is to a type.
+    Type,
+    /// The alias is to a component.
+    Component,
+}
+
+impl Encode for ComponentOuterAliasKind {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::CoreModule => {
+                sink.push(CORE_SORT);
+                sink.push(CORE_MODULE_SORT);
+            }
+            Self::CoreType => {
+                sink.push(CORE_SORT);
+                sink.push(CORE_TYPE_SORT);
+            }
+            Self::Type => sink.push(TYPE_SORT),
+            Self::Component => sink.push(COMPONENT_SORT),
+        }
+    }
+}
+
+/// An encoder for the alias section of WebAssembly component.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, Alias, ComponentAliasSection, ComponentExportKind, ComponentOuterAliasKind};
+///
+/// let mut aliases = ComponentAliasSection::new();
+/// aliases.alias(Alias::InstanceExport { instance: 0, kind: ComponentExportKind::Func, name: "f" });
+/// aliases.alias(Alias::Outer { count: 0, kind: ComponentOuterAliasKind::Type, index: 1 });
+///
+/// let mut component = Component::new();
+/// component.section(&aliases);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentAliasSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+/// Different forms of aliases that can be inserted into a
+/// [`ComponentAliasSection`].
+#[derive(Copy, Clone, Debug)]
+pub enum Alias<'a> {
+    /// An alias of a component instance export.
+    InstanceExport {
+        /// The index of the component instance that's being aliased from.
+        instance: u32,
+        /// The kind of item that's being extracted from the component
+        /// instance.
+        kind: ComponentExportKind,
+        /// The name of the export that's being aliased.
+        name: &'a str,
+    },
+    /// Same as `InstanceExport`, but for core instances.
+    #[allow(missing_docs)]
+    CoreInstanceExport {
+        instance: u32,
+        kind: ExportKind,
+        name: &'a str,
+    },
+    /// Aliasing an item from an outer component.
+    Outer {
+        /// The kind of item being aliased, either a type or a component.
+        kind: ComponentOuterAliasKind,
+        /// Number of levels "up" to go to lookup the index within. Level 0 is
+        /// the current scope and level 1 is the enclosing scope, and so on.
+        count: u32,
+        /// The index of the item to alias within the scope referenced by
+        /// `count`.
+        index: u32,
+    },
+}
+
+impl ComponentAliasSection {
+    /// Create a new alias section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of aliases in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an alias to a component instance's export.
+    pub fn alias(&mut self, alias: Alias<'_>) -> &mut Self {
+        alias.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentAliasSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentAliasSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Alias.into()
+    }
+}
+
+impl Encode for Alias<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Alias::InstanceExport {
+                instance,
+                kind,
+                name,
+            } => {
+                kind.encode(sink);
+                sink.push(0x00);
+                instance.encode(sink);
+                name.encode(sink);
+            }
+            Alias::CoreInstanceExport {
+                instance,
+                kind,
+                name,
+            } => {
+                sink.push(CORE_SORT);
+                kind.encode(sink);
+                sink.push(0x01);
+                instance.encode(sink);
+                name.encode(sink);
+            }
+            Alias::Outer { kind, count, index } => {
+                kind.encode(sink);
+                sink.push(0x02);
+                count.encode(sink);
+                index.encode(sink);
+            }
+        }
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/canonicals.rs b/third_party/rust/wasm-encoder/src/component/canonicals.rs
new file mode 100644
index 0000000000..e81819c44e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/canonicals.rs
@@ -0,0 +1,133 @@
+use crate::{encode_section, ComponentSection, ComponentSectionId, Encode};
+
+/// Represents options for canonical function definitions.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CanonicalOption {
+    /// The string types in the function signature are UTF-8 encoded.
+    UTF8,
+    /// The string types in the function signature are UTF-16 encoded.
+    UTF16,
+    /// The string types in the function signature are compact UTF-16 encoded.
+    CompactUTF16,
+    /// The memory to use if the lifting or lowering of a function requires memory access.
+    ///
+    /// The value is an index to a core memory.
+    Memory(u32),
+    /// The realloc function to use if the lifting or lowering of a function requires memory
+    /// allocation.
+    ///
+    /// The value is an index to a core function of type `(func (param i32 i32 i32 i32) (result i32))`.
+    Realloc(u32),
+    /// The post-return function to use if the lifting of a function requires
+    /// cleanup after the function returns.
+    PostReturn(u32),
+}
+
+impl Encode for CanonicalOption {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::UTF8 => sink.push(0x00),
+            Self::UTF16 => sink.push(0x01),
+            Self::CompactUTF16 => sink.push(0x02),
+            Self::Memory(idx) => {
+                sink.push(0x03);
+                idx.encode(sink);
+            }
+            Self::Realloc(idx) => {
+                sink.push(0x04);
+                idx.encode(sink);
+            }
+            Self::PostReturn(idx) => {
+                sink.push(0x05);
+                idx.encode(sink);
+            }
+        }
+    }
+}
+
+/// An encoder for the canonical function section of WebAssembly components.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Component, CanonicalFunctionSection, CanonicalOption};
+///
+/// let mut functions = CanonicalFunctionSection::new();
+/// functions.lift(0, 0, [CanonicalOption::UTF8]);
+///
+/// let mut component = Component::new();
+/// component.section(&functions);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct CanonicalFunctionSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl CanonicalFunctionSection {
+    /// Construct a new component function section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of functions in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a function that will lift a core WebAssembly function to the canonical ABI.
+    pub fn lift<O>(&mut self, core_func_index: u32, type_index: u32, options: O) -> &mut Self
+    where
+        O: IntoIterator<Item = CanonicalOption>,
+        O::IntoIter: ExactSizeIterator,
+    {
+        let options = options.into_iter();
+        self.bytes.push(0x00);
+        self.bytes.push(0x00);
+        core_func_index.encode(&mut self.bytes);
+        options.len().encode(&mut self.bytes);
+        for option in options {
+            option.encode(&mut self.bytes);
+        }
+        type_index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a function that will lower a canonical ABI function to a core WebAssembly function.
+    pub fn lower<O>(&mut self, func_index: u32, options: O) -> &mut Self
+    where
+        O: IntoIterator<Item = CanonicalOption>,
+        O::IntoIter: ExactSizeIterator,
+    {
+        let options = options.into_iter();
+        self.bytes.push(0x01);
+        self.bytes.push(0x00);
+        func_index.encode(&mut self.bytes);
+        options.len().encode(&mut self.bytes);
+        for option in options {
+            option.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for CanonicalFunctionSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for CanonicalFunctionSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CanonicalFunction.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/components.rs b/third_party/rust/wasm-encoder/src/component/components.rs
new file mode 100644
index 0000000000..c08645e3b9
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/components.rs
@@ -0,0 +1,29 @@
+use crate::{Component, ComponentSection, ComponentSectionId, Encode};
+
+/// An encoder for the component section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, NestedComponentSection};
+///
+/// let mut nested = Component::new();
+/// let mut component = Component::new();
+/// component.section(&NestedComponentSection(&nested));
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct NestedComponentSection<'a>(pub &'a Component);
+
+impl Encode for NestedComponentSection<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.0.bytes.encode(sink);
+    }
+}
+
+impl ComponentSection for NestedComponentSection<'_> {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Component.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/exports.rs b/third_party/rust/wasm-encoder/src/component/exports.rs
new file mode 100644
index 0000000000..9720d51b02
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/exports.rs
@@ -0,0 +1,125 @@
+use super::{
+    COMPONENT_SORT, CORE_MODULE_SORT, CORE_SORT, FUNCTION_SORT, INSTANCE_SORT, TYPE_SORT,
+    VALUE_SORT,
+};
+use crate::{encode_section, ComponentSection, ComponentSectionId, ComponentTypeRef, Encode};
+
+/// Represents the kind of an export from a WebAssembly component.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ComponentExportKind {
+    /// The export is a core module.
+    Module,
+    /// The export is a function.
+    Func,
+    /// The export is a value.
+    Value,
+    /// The export is a type.
+    Type,
+    /// The export is an instance.
+    Instance,
+    /// The export is a component.
+    Component,
+}
+
+impl Encode for ComponentExportKind {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Module => {
+                sink.push(CORE_SORT);
+                sink.push(CORE_MODULE_SORT);
+            }
+            Self::Func => {
+                sink.push(FUNCTION_SORT);
+            }
+            Self::Value => {
+                sink.push(VALUE_SORT);
+            }
+            Self::Type => {
+                sink.push(TYPE_SORT);
+            }
+            Self::Instance => {
+                sink.push(INSTANCE_SORT);
+            }
+            Self::Component => {
+                sink.push(COMPONENT_SORT);
+            }
+        }
+    }
+}
+
+/// An encoder for the export section of WebAssembly component.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentExportSection, ComponentExportKind};
+///
+/// // This exports a function named "foo"
+/// let mut exports = ComponentExportSection::new();
+/// exports.export("foo", "", ComponentExportKind::Func, 0, None);
+///
+/// let mut component = Component::new();
+/// component.section(&exports);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentExportSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentExportSection {
+    /// Create a new component export section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of exports in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an export in the export section.
+    pub fn export(
+        &mut self,
+        name: &str,
+        url: &str,
+        kind: ComponentExportKind,
+        index: u32,
+        ty: Option<ComponentTypeRef>,
+    ) -> &mut Self {
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        kind.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        match ty {
+            Some(ty) => {
+                self.bytes.push(0x01);
+                ty.encode(&mut self.bytes);
+            }
+            None => {
+                self.bytes.push(0x00);
+            }
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentExportSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentExportSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Export.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/imports.rs b/third_party/rust/wasm-encoder/src/component/imports.rs
new file mode 100644
index 0000000000..8d843407f3
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/imports.rs
@@ -0,0 +1,151 @@
+use crate::{
+    encode_section, ComponentExportKind, ComponentSection, ComponentSectionId, ComponentValType,
+    Encode,
+};
+
+/// Represents the possible type bounds for type references.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub enum TypeBounds {
+    /// The type is bounded by equality.
+    Eq,
+}
+
+impl Encode for TypeBounds {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Eq => sink.push(0x00),
+        }
+    }
+}
+
+/// Represents a reference to a type.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub enum ComponentTypeRef {
+    /// The reference is to a core module type.
+    ///
+    /// The index is expected to be core type index to a core module type.
+    Module(u32),
+    /// The reference is to a function type.
+    ///
+    /// The index is expected to be a type index to a function type.
+    Func(u32),
+    /// The reference is to a value type.
+    Value(ComponentValType),
+    /// The reference is to a bounded type.
+    ///
+    /// The index is expected to be a type index.
+    Type(TypeBounds, u32),
+    /// The reference is to an instance type.
+    ///
+    /// The index is expected to be a type index to an instance type.
+    Instance(u32),
+    /// The reference is to a component type.
+    ///
+    /// The index is expected to be a type index to a component type.
+    Component(u32),
+}
+
+impl ComponentTypeRef {
+    /// Gets the export kind of the reference.
+    pub fn kind(&self) -> ComponentExportKind {
+        match self {
+            Self::Module(_) => ComponentExportKind::Module,
+            Self::Func(_) => ComponentExportKind::Func,
+            Self::Value(_) => ComponentExportKind::Value,
+            Self::Type(..) => ComponentExportKind::Type,
+            Self::Instance(_) => ComponentExportKind::Instance,
+            Self::Component(_) => ComponentExportKind::Component,
+        }
+    }
+}
+
+impl Encode for ComponentTypeRef {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.kind().encode(sink);
+
+        match self {
+            Self::Module(idx) | Self::Func(idx) | Self::Instance(idx) | Self::Component(idx) => {
+                idx.encode(sink);
+            }
+            Self::Value(ty) => ty.encode(sink),
+            Self::Type(bounds, idx) => {
+                bounds.encode(sink);
+                idx.encode(sink);
+            }
+        }
+    }
+}
+
+/// An encoder for the import section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentTypeSection, PrimitiveValType, ComponentImportSection, ComponentTypeRef};
+///
+/// let mut types = ComponentTypeSection::new();
+///
+/// // Define a function type of `[string, string] -> string`.
+/// types
+///   .function()
+///   .params(
+///     [
+///       ("a", PrimitiveValType::String),
+///       ("b", PrimitiveValType::String)
+///     ]
+///   )
+///   .result(PrimitiveValType::String);
+///
+/// // This imports a function named `f` with the type defined above
+/// let mut imports = ComponentImportSection::new();
+/// imports.import("f", "", ComponentTypeRef::Func(0));
+///
+/// let mut component = Component::new();
+/// component.section(&types);
+/// component.section(&imports);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentImportSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentImportSection {
+    /// Create a new component import section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of imports in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an import in the component import section.
+    pub fn import(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentImportSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentImportSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Import.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/instances.rs b/third_party/rust/wasm-encoder/src/component/instances.rs
new file mode 100644
index 0000000000..5f2c97dec3
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/instances.rs
@@ -0,0 +1,199 @@
+use super::CORE_INSTANCE_SORT;
+use crate::{
+    encode_section, ComponentExportKind, ComponentSection, ComponentSectionId, Encode, ExportKind,
+};
+
+/// Represents an argument to a module instantiation.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ModuleArg {
+    /// The argument is an instance.
+    Instance(u32),
+}
+
+impl Encode for ModuleArg {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let (sort, idx) = match self {
+            Self::Instance(idx) => (CORE_INSTANCE_SORT, *idx),
+        };
+        sink.push(sort);
+        idx.encode(sink);
+    }
+}
+
+/// An encoder for the core instance section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, InstanceSection, ExportKind, ModuleArg};
+///
+/// let mut instances = InstanceSection::new();
+/// instances.export_items([("foo", ExportKind::Func, 0)]);
+/// instances.instantiate(1, [("foo", ModuleArg::Instance(0))]);
+///
+/// let mut component = Component::new();
+/// component.section(&instances);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct InstanceSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl InstanceSection {
+    /// Create a new core instance section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of instances in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an instance by instantiating a core module.
+    pub fn instantiate<A, S>(&mut self, module_index: u32, args: A) -> &mut Self
+    where
+        A: IntoIterator<Item = (S, ModuleArg)>,
+        A::IntoIter: ExactSizeIterator,
+        S: AsRef<str>,
+    {
+        let args = args.into_iter();
+        self.bytes.push(0x00);
+        module_index.encode(&mut self.bytes);
+        args.len().encode(&mut self.bytes);
+        for (name, arg) in args {
+            name.as_ref().encode(&mut self.bytes);
+            arg.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    /// Define an instance by exporting core WebAssembly items.
+    pub fn export_items<E, S>(&mut self, exports: E) -> &mut Self
+    where
+        E: IntoIterator<Item = (S, ExportKind, u32)>,
+        E::IntoIter: ExactSizeIterator,
+        S: AsRef<str>,
+    {
+        let exports = exports.into_iter();
+        self.bytes.push(0x01);
+        exports.len().encode(&mut self.bytes);
+        for (name, kind, index) in exports {
+            name.as_ref().encode(&mut self.bytes);
+            kind.encode(&mut self.bytes);
+            index.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for InstanceSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for InstanceSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreInstance.into()
+    }
+}
+
+/// An encoder for the instance section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentInstanceSection, ComponentExportKind};
+///
+/// let mut instances = ComponentInstanceSection::new();
+/// instances.export_items([("foo", ComponentExportKind::Func, 0)]);
+/// instances.instantiate(1, [("foo", ComponentExportKind::Instance, 0)]);
+///
+/// let mut component = Component::new();
+/// component.section(&instances);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentInstanceSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentInstanceSection {
+    /// Create a new instance section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of instances in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an instance by instantiating a component.
+    pub fn instantiate<A, S>(&mut self, component_index: u32, args: A) -> &mut Self
+    where
+        A: IntoIterator<Item = (S, ComponentExportKind, u32)>,
+        A::IntoIter: ExactSizeIterator,
+        S: AsRef<str>,
+    {
+        let args = args.into_iter();
+        self.bytes.push(0x00);
+        component_index.encode(&mut self.bytes);
+        args.len().encode(&mut self.bytes);
+        for (name, kind, index) in args {
+            name.as_ref().encode(&mut self.bytes);
+            kind.encode(&mut self.bytes);
+            index.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    /// Define an instance by exporting items.
+    pub fn export_items<'a, E>(&mut self, exports: E) -> &mut Self
+    where
+        E: IntoIterator<Item = (&'a str, ComponentExportKind, u32)>,
+        E::IntoIter: ExactSizeIterator,
+    {
+        let exports = exports.into_iter();
+        self.bytes.push(0x01);
+        exports.len().encode(&mut self.bytes);
+        for (name, kind, index) in exports {
+            name.encode(&mut self.bytes);
+            kind.encode(&mut self.bytes);
+            index.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentInstanceSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentInstanceSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Instance.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/modules.rs b/third_party/rust/wasm-encoder/src/component/modules.rs
new file mode 100644
index 0000000000..437cd353af
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/modules.rs
@@ -0,0 +1,29 @@
+use crate::{ComponentSection, ComponentSectionId, Encode, Module};
+
+/// An encoder for the module section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Module, Component, ModuleSection};
+///
+/// let mut module = Module::new();
+/// let mut component = Component::new();
+/// component.section(&ModuleSection(&module));
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct ModuleSection<'a>(pub &'a Module);
+
+impl Encode for ModuleSection<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.0.bytes.encode(sink);
+    }
+}
+
+impl ComponentSection for ModuleSection<'_> {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreModule.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/names.rs b/third_party/rust/wasm-encoder/src/component/names.rs
new file mode 100644
index 0000000000..0e3b02dc2e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/names.rs
@@ -0,0 +1,147 @@
+use super::*;
+use crate::{encoding_size, CustomSection, Encode, ExportKind, NameMap, SectionId};
+
+/// Encoding for the `component-name` custom section which assigns
+/// human-readable names to items within a component.
+#[derive(Clone, Debug, Default)]
+pub struct ComponentNameSection {
+    bytes: Vec<u8>,
+}
+
+enum Subsection {
+    Component,
+    Decls,
+}
+
+impl ComponentNameSection {
+    /// Creates a new blank `name` custom section.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Appends a component name subsection to this section.
+    ///
+    /// This will indicate that the name of the entire component should be the
+    /// `name` specified. Note that this should be encoded first before other
+    /// subsections.
+    pub fn component(&mut self, name: &str) {
+        let len = encoding_size(u32::try_from(name.len()).unwrap());
+        self.subsection_header(Subsection::Component, len + name.len());
+        name.encode(&mut self.bytes);
+    }
+
+    /// Appends a decls name subsection to name core functions within the
+    /// component.
+    pub fn core_funcs(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Func as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core tables within the
+    /// component.
+    pub fn core_tables(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Table as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core memories within the
+    /// component.
+    pub fn core_memories(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Memory as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core globals within the
+    /// component.
+    pub fn core_globals(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Global as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core types within the
+    /// component.
+    pub fn core_types(&mut self, names: &NameMap) {
+        self.core_decls(CORE_TYPE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name core modules within the
+    /// component.
+    pub fn core_modules(&mut self, names: &NameMap) {
+        self.core_decls(CORE_MODULE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name core instances within the
+    /// component.
+    pub fn core_instances(&mut self, names: &NameMap) {
+        self.core_decls(CORE_INSTANCE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component functions within the
+    /// component.
+    pub fn funcs(&mut self, names: &NameMap) {
+        self.component_decls(FUNCTION_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component values within the
+    /// component.
+    pub fn values(&mut self, names: &NameMap) {
+        self.component_decls(VALUE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component type within the
+    /// component.
+    pub fn types(&mut self, names: &NameMap) {
+        self.component_decls(TYPE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name components within the
+    /// component.
+    pub fn components(&mut self, names: &NameMap) {
+        self.component_decls(COMPONENT_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component instances within the
+    /// component.
+    pub fn instances(&mut self, names: &NameMap) {
+        self.component_decls(INSTANCE_SORT, names)
+    }
+
+    fn component_decls(&mut self, kind: u8, names: &NameMap) {
+        self.subsection_header(Subsection::Decls, 1 + names.size());
+        self.bytes.push(kind);
+        names.encode(&mut self.bytes);
+    }
+
+    fn core_decls(&mut self, kind: u8, names: &NameMap) {
+        self.subsection_header(Subsection::Decls, 2 + names.size());
+        self.bytes.push(CORE_SORT);
+        self.bytes.push(kind);
+        names.encode(&mut self.bytes);
+    }
+
+    fn subsection_header(&mut self, id: Subsection, len: usize) {
+        self.bytes.push(id as u8);
+        len.encode(&mut self.bytes);
+    }
+
+    /// Returns whether this section is empty, or nothing has been encoded.
+    pub fn is_empty(&self) -> bool {
+        self.bytes.is_empty()
+    }
+
+    /// View the encoded section as a CustomSection.
+    pub fn as_custom<'a>(&'a self) -> CustomSection<'a> {
+        CustomSection {
+            name: "component-name",
+            data: &self.bytes,
+        }
+    }
+}
+
+impl Encode for ComponentNameSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.as_custom().encode(sink);
+    }
+}
+
+impl ComponentSection for ComponentNameSection {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/start.rs b/third_party/rust/wasm-encoder/src/component/start.rs
new file mode 100644
index 0000000000..d4b60e1dfc
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/start.rs
@@ -0,0 +1,52 @@
+use crate::{ComponentSection, ComponentSectionId, Encode};
+
+/// An encoder for the start section of WebAssembly components.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Component, ComponentStartSection};
+///
+/// let start = ComponentStartSection { function_index: 0, args: [0, 1], results: 1 };
+///
+/// let mut component = Component::new();
+/// component.section(&start);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct ComponentStartSection<A> {
+    /// The index to the start function.
+    pub function_index: u32,
+    /// The arguments to pass to the start function.
+    ///
+    /// An argument is an index to a value.
+    pub args: A,
+    /// The number of expected results for the start function.
+    ///
+    /// This should match the number of results for the type of
+    /// the function referenced by `function_index`.
+    pub results: u32,
+}
+
+impl<A> Encode for ComponentStartSection<A>
+where
+    A: AsRef<[u32]>,
+{
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let mut bytes = Vec::new();
+        self.function_index.encode(&mut bytes);
+        self.args.as_ref().encode(&mut bytes);
+        self.results.encode(&mut bytes);
+        bytes.encode(sink);
+    }
+}
+
+impl<A> ComponentSection for ComponentStartSection<A>
+where
+    A: AsRef<[u32]>,
+{
+    fn id(&self) -> u8 {
+        ComponentSectionId::Start.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/types.rs b/third_party/rust/wasm-encoder/src/component/types.rs
new file mode 100644
index 0000000000..930467d57a
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/types.rs
@@ -0,0 +1,736 @@
+use super::CORE_TYPE_SORT;
+use crate::{
+    encode_section, Alias, ComponentExportKind, ComponentOuterAliasKind, ComponentSection,
+    ComponentSectionId, ComponentTypeRef, Encode, EntityType, ValType,
+};
+
+/// Represents the type of a core module.
+#[derive(Debug, Clone, Default)]
+pub struct ModuleType {
+    bytes: Vec<u8>,
+    num_added: u32,
+    types_added: u32,
+}
+
+impl ModuleType {
+    /// Creates a new core module type.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Defines an import in this module type.
+    pub fn import(&mut self, module: &str, name: &str, ty: EntityType) -> &mut Self {
+        self.bytes.push(0x00);
+        module.encode(&mut self.bytes);
+        name.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a type in this module type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> CoreTypeEncoder {
+        self.bytes.push(0x01);
+        self.num_added += 1;
+        self.types_added += 1;
+        CoreTypeEncoder(&mut self.bytes)
+    }
+
+    /// Defines an outer core type alias in this module type.
+    pub fn alias_outer_core_type(&mut self, count: u32, index: u32) -> &mut Self {
+        self.bytes.push(0x02);
+        self.bytes.push(CORE_TYPE_SORT);
+        self.bytes.push(0x01); // outer
+        count.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self.types_added += 1;
+        self
+    }
+
+    /// Defines an export in this module type.
+    pub fn export(&mut self, name: &str, ty: EntityType) -> &mut Self {
+        self.bytes.push(0x03);
+        name.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Gets the number of types that have been added to this module type.
+    pub fn type_count(&self) -> u32 {
+        self.types_added
+    }
+}
+
+impl Encode for ModuleType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(0x50);
+        self.num_added.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
+
+/// Used to encode core types.
+#[derive(Debug)]
+pub struct CoreTypeEncoder<'a>(pub(crate) &'a mut Vec<u8>);
+
+impl<'a> CoreTypeEncoder<'a> {
+    /// Define a function type.
+    pub fn function<P, R>(self, params: P, results: R)
+    where
+        P: IntoIterator<Item = ValType>,
+        P::IntoIter: ExactSizeIterator,
+        R: IntoIterator<Item = ValType>,
+        R::IntoIter: ExactSizeIterator,
+    {
+        let params = params.into_iter();
+        let results = results.into_iter();
+
+        self.0.push(0x60);
+        params.len().encode(self.0);
+        params.for_each(|p| p.encode(self.0));
+        results.len().encode(self.0);
+        results.for_each(|p| p.encode(self.0));
+    }
+
+    /// Define a module type.
+    pub fn module(self, ty: &ModuleType) {
+        ty.encode(self.0);
+    }
+}
+
+/// An encoder for the core type section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, CoreTypeSection, ModuleType};
+///
+/// let mut types = CoreTypeSection::new();
+///
+/// types.module(&ModuleType::new());
+///
+/// let mut component = Component::new();
+/// component.section(&types);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct CoreTypeSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl CoreTypeSection {
+    /// Create a new core type section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of types in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Encode a type into this section.
+    ///
+    /// The returned encoder must be finished before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> CoreTypeEncoder<'_> {
+        self.num_added += 1;
+        CoreTypeEncoder(&mut self.bytes)
+    }
+
+    /// Define a function type in this type section.
+    pub fn function<P, R>(&mut self, params: P, results: R) -> &mut Self
+    where
+        P: IntoIterator<Item = ValType>,
+        P::IntoIter: ExactSizeIterator,
+        R: IntoIterator<Item = ValType>,
+        R::IntoIter: ExactSizeIterator,
+    {
+        self.ty().function(params, results);
+        self
+    }
+
+    /// Define a module type in this type section.
+    ///
+    /// Currently this is only used for core type sections in components.
+    pub fn module(&mut self, ty: &ModuleType) -> &mut Self {
+        self.ty().module(ty);
+        self
+    }
+}
+
+impl Encode for CoreTypeSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for CoreTypeSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreType.into()
+    }
+}
+
+/// Represents a component type.
+#[derive(Debug, Clone, Default)]
+pub struct ComponentType {
+    bytes: Vec<u8>,
+    num_added: u32,
+    core_types_added: u32,
+    types_added: u32,
+}
+
+impl ComponentType {
+    /// Creates a new component type.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Define a core type in this component type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn core_type(&mut self) -> CoreTypeEncoder {
+        self.bytes.push(0x00);
+        self.num_added += 1;
+        self.core_types_added += 1;
+        CoreTypeEncoder(&mut self.bytes)
+    }
+
+    /// Define a type in this component type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> ComponentTypeEncoder {
+        self.bytes.push(0x01);
+        self.num_added += 1;
+        self.types_added += 1;
+        ComponentTypeEncoder(&mut self.bytes)
+    }
+
+    /// Defines an alias for an exported item of a prior instance or an
+    /// outer type.
+    pub fn alias(&mut self, alias: Alias<'_>) -> &mut Self {
+        self.bytes.push(0x02);
+        alias.encode(&mut self.bytes);
+        self.num_added += 1;
+        match &alias {
+            Alias::InstanceExport {
+                kind: ComponentExportKind::Type,
+                ..
+            }
+            | Alias::Outer {
+                kind: ComponentOuterAliasKind::Type,
+                ..
+            } => self.types_added += 1,
+            Alias::Outer {
+                kind: ComponentOuterAliasKind::CoreType,
+                ..
+            } => self.core_types_added += 1,
+            _ => {}
+        }
+        self
+    }
+
+    /// Defines an import in this component type.
+    pub fn import(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        self.bytes.push(0x03);
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        match ty {
+            ComponentTypeRef::Type(..) => self.types_added += 1,
+            _ => {}
+        }
+        self
+    }
+
+    /// Defines an export in this component type.
+    pub fn export(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        self.bytes.push(0x04);
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        match ty {
+            ComponentTypeRef::Type(..) => self.types_added += 1,
+            _ => {}
+        }
+        self
+    }
+
+    /// Gets the number of core types that have been added to this component type.
+    pub fn core_type_count(&self) -> u32 {
+        self.core_types_added
+    }
+
+    /// Gets the number of types that have been added or aliased in this component type.
+    pub fn type_count(&self) -> u32 {
+        self.types_added
+    }
+}
+
+impl Encode for ComponentType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(0x41);
+        self.num_added.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
+
+/// Represents an instance type.
+#[derive(Debug, Clone, Default)]
+pub struct InstanceType(ComponentType);
+
+impl InstanceType {
+    /// Creates a new instance type.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Define a core type in this instance type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn core_type(&mut self) -> CoreTypeEncoder {
+        self.0.core_type()
+    }
+
+    /// Define a type in this instance type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> ComponentTypeEncoder {
+        self.0.ty()
+    }
+
+    /// Defines an outer core type alias in this component type.
+    pub fn alias(&mut self, alias: Alias<'_>) -> &mut Self {
+        self.0.alias(alias);
+        self
+    }
+
+    /// Defines an export in this instance type.
+    pub fn export(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        self.0.export(name, url, ty);
+        self
+    }
+
+    /// Gets the number of core types that have been added to this instance type.
+    pub fn core_type_count(&self) -> u32 {
+        self.0.core_types_added
+    }
+
+    /// Gets the number of types that have been added or aliased in this instance type.
+    pub fn type_count(&self) -> u32 {
+        self.0.types_added
+    }
+
+    /// Returns whether or not this instance type is empty.
+    pub fn is_empty(&self) -> bool {
+        self.0.num_added == 0
+    }
+
+    /// Returns the number of entries added to this instance types.
+    pub fn len(&self) -> u32 {
+        self.0.num_added
+    }
+}
+
+impl Encode for InstanceType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(0x42);
+        self.0.num_added.encode(sink);
+        sink.extend(&self.0.bytes);
+    }
+}
+
+/// Used to encode component function types.
+#[derive(Debug)]
+pub struct ComponentFuncTypeEncoder<'a>(&'a mut Vec<u8>);
+
+impl<'a> ComponentFuncTypeEncoder<'a> {
+    fn new(sink: &'a mut Vec<u8>) -> Self {
+        sink.push(0x40);
+        Self(sink)
+    }
+
+    /// Defines named parameters.
+    ///
+    /// Parameters must be defined before defining results.
+    pub fn params<'b, P, T>(&mut self, params: P) -> &mut Self
+    where
+        P: IntoIterator<Item = (&'b str, T)>,
+        P::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let params = params.into_iter();
+        params.len().encode(self.0);
+        for (name, ty) in params {
+            name.encode(self.0);
+            ty.into().encode(self.0);
+        }
+        self
+    }
+
+    /// Defines a single unnamed result.
+    ///
+    /// This method cannot be used with `results`.
+    pub fn result(&mut self, ty: impl Into<ComponentValType>) -> &mut Self {
+        self.0.push(0x00);
+        ty.into().encode(self.0);
+        self
+    }
+
+    /// Defines named results.
+    ///
+    /// This method cannot be used with `result`.
+    pub fn results<'b, R, T>(&mut self, results: R) -> &mut Self
+    where
+        R: IntoIterator<Item = (&'b str, T)>,
+        R::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        self.0.push(0x01);
+        let results = results.into_iter();
+        results.len().encode(self.0);
+        for (name, ty) in results {
+            name.encode(self.0);
+            ty.into().encode(self.0);
+        }
+        self
+    }
+}
+
+/// Used to encode component and instance types.
+#[derive(Debug)]
+pub struct ComponentTypeEncoder<'a>(&'a mut Vec<u8>);
+
+impl<'a> ComponentTypeEncoder<'a> {
+    /// Define a component type.
+    pub fn component(self, ty: &ComponentType) {
+        ty.encode(self.0);
+    }
+
+    /// Define an instance type.
+    pub fn instance(self, ty: &InstanceType) {
+        ty.encode(self.0);
+    }
+
+    /// Define a function type.
+    pub fn function(self) -> ComponentFuncTypeEncoder<'a> {
+        ComponentFuncTypeEncoder::new(self.0)
+    }
+
+    /// Define a defined component type.
+    ///
+    /// The returned encoder must be used before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn defined_type(self) -> ComponentDefinedTypeEncoder<'a> {
+        ComponentDefinedTypeEncoder(self.0)
+    }
+}
+
+/// Represents a primitive component value type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum PrimitiveValType {
+    /// The type is a boolean.
+    Bool,
+    /// The type is a signed 8-bit integer.
+    S8,
+    /// The type is an unsigned 8-bit integer.
+    U8,
+    /// The type is a signed 16-bit integer.
+    S16,
+    /// The type is an unsigned 16-bit integer.
+    U16,
+    /// The type is a signed 32-bit integer.
+    S32,
+    /// The type is an unsigned 32-bit integer.
+    U32,
+    /// The type is a signed 64-bit integer.
+    S64,
+    /// The type is an unsigned 64-bit integer.
+    U64,
+    /// The type is a 32-bit floating point number.
+    Float32,
+    /// The type is a 64-bit floating point number.
+    Float64,
+    /// The type is a Unicode character.
+    Char,
+    /// The type is a string.
+    String,
+}
+
+impl Encode for PrimitiveValType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(match self {
+            Self::Bool => 0x7f,
+            Self::S8 => 0x7e,
+            Self::U8 => 0x7d,
+            Self::S16 => 0x7c,
+            Self::U16 => 0x7b,
+            Self::S32 => 0x7a,
+            Self::U32 => 0x79,
+            Self::S64 => 0x78,
+            Self::U64 => 0x77,
+            Self::Float32 => 0x76,
+            Self::Float64 => 0x75,
+            Self::Char => 0x74,
+            Self::String => 0x73,
+        });
+    }
+}
+
+/// Represents a component value type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ComponentValType {
+    /// The value is a primitive type.
+    Primitive(PrimitiveValType),
+    /// The value is to a defined value type.
+    ///
+    /// The type index must be to a value type.
+    Type(u32),
+}
+
+impl Encode for ComponentValType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Primitive(ty) => ty.encode(sink),
+            Self::Type(index) => (*index as i64).encode(sink),
+        }
+    }
+}
+
+impl From<PrimitiveValType> for ComponentValType {
+    fn from(ty: PrimitiveValType) -> Self {
+        Self::Primitive(ty)
+    }
+}
+
+/// Used for encoding component defined types.
+#[derive(Debug)]
+pub struct ComponentDefinedTypeEncoder<'a>(&'a mut Vec<u8>);
+
+impl ComponentDefinedTypeEncoder<'_> {
+    /// Define a primitive value type.
+    pub fn primitive(self, ty: PrimitiveValType) {
+        ty.encode(self.0);
+    }
+
+    /// Define a record type.
+    pub fn record<'a, F, T>(self, fields: F)
+    where
+        F: IntoIterator<Item = (&'a str, T)>,
+        F::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let fields = fields.into_iter();
+        self.0.push(0x72);
+        fields.len().encode(self.0);
+        for (name, ty) in fields {
+            name.encode(self.0);
+            ty.into().encode(self.0);
+        }
+    }
+
+    /// Define a variant type.
+    pub fn variant<'a, C>(self, cases: C)
+    where
+        C: IntoIterator<Item = (&'a str, Option<ComponentValType>, Option<u32>)>,
+        C::IntoIter: ExactSizeIterator,
+    {
+        let cases = cases.into_iter();
+        self.0.push(0x71);
+        cases.len().encode(self.0);
+        for (name, ty, refines) in cases {
+            name.encode(self.0);
+            ty.encode(self.0);
+            refines.encode(self.0);
+        }
+    }
+
+    /// Define a list type.
+    pub fn list(self, ty: impl Into<ComponentValType>) {
+        self.0.push(0x70);
+        ty.into().encode(self.0);
+    }
+
+    /// Define a tuple type.
+    pub fn tuple<I, T>(self, types: I)
+    where
+        I: IntoIterator<Item = T>,
+        I::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let types = types.into_iter();
+        self.0.push(0x6F);
+        types.len().encode(self.0);
+        for ty in types {
+            ty.into().encode(self.0);
+        }
+    }
+
+    /// Define a flags type.
+    pub fn flags<'a, I>(self, names: I)
+    where
+        I: IntoIterator<Item = &'a str>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        let names = names.into_iter();
+        self.0.push(0x6E);
+        names.len().encode(self.0);
+        for name in names {
+            name.encode(self.0);
+        }
+    }
+
+    /// Define an enum type.
+    pub fn enum_type<'a, I>(self, tags: I)
+    where
+        I: IntoIterator<Item = &'a str>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        let tags = tags.into_iter();
+        self.0.push(0x6D);
+        tags.len().encode(self.0);
+        for tag in tags {
+            tag.encode(self.0);
+        }
+    }
+
+    /// Define a union type.
+    pub fn union<I, T>(self, types: I)
+    where
+        I: IntoIterator<Item = T>,
+        I::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let types = types.into_iter();
+        self.0.push(0x6C);
+        types.len().encode(self.0);
+        for ty in types {
+            ty.into().encode(self.0);
+        }
+    }
+
+    /// Define an option type.
+    pub fn option(self, ty: impl Into<ComponentValType>) {
+        self.0.push(0x6B);
+        ty.into().encode(self.0);
+    }
+
+    /// Define a result type.
+    pub fn result(self, ok: Option<ComponentValType>, err: Option<ComponentValType>) {
+        self.0.push(0x6A);
+        ok.encode(self.0);
+        err.encode(self.0);
+    }
+}
+
+/// An encoder for the type section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentTypeSection, PrimitiveValType};
+///
+/// let mut types = ComponentTypeSection::new();
+///
+/// // Define a function type of `[string, string] -> string`.
+/// types
+///   .function()
+///   .params(
+///     [
+///       ("a", PrimitiveValType::String),
+///       ("b", PrimitiveValType::String)
+///     ]
+///   )
+///   .result(PrimitiveValType::String);
+///
+/// let mut component = Component::new();
+/// component.section(&types);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentTypeSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentTypeSection {
+    /// Create a new component type section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of types in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Encode a type into this section.
+    ///
+    /// The returned encoder must be finished before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> ComponentTypeEncoder<'_> {
+        self.num_added += 1;
+        ComponentTypeEncoder(&mut self.bytes)
+    }
+
+    /// Define a component type in this type section.
+    pub fn component(&mut self, ty: &ComponentType) -> &mut Self {
+        self.ty().component(ty);
+        self
+    }
+
+    /// Define an instance type in this type section.
+    pub fn instance(&mut self, ty: &InstanceType) -> &mut Self {
+        self.ty().instance(ty);
+        self
+    }
+
+    /// Define a function type in this type section.
+    pub fn function(&mut self) -> ComponentFuncTypeEncoder<'_> {
+        self.ty().function()
+    }
+
+    /// Add a component defined type to this type section.
+    ///
+    /// The returned encoder must be used before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn defined_type(&mut self) -> ComponentDefinedTypeEncoder<'_> {
+        self.ty().defined_type()
+    }
+}
+
+impl Encode for ComponentTypeSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentTypeSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Type.into()
+    }
+}