Adding upstream version 124.0.1.upstream/124.0.1

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

19 files changed, 1383 insertions, 0 deletions

diff --git a/third_party/rust/diplomat/.cargo-checksum.json b/third_party/rust/diplomat/.cargo-checksum.json
new file mode 100644
index 0000000000..e68087c073
--- /dev/null
+++ b/third_party/rust/diplomat/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"Cargo.toml":"42a489a0e146bba3fe0d2c1e9abc24f8f24164404b88c687a53c575864ac7a7e","LICENSE-APACHE":"639c20c7f14fb122750d5ad1a6cfb116d9bf8d103e709ee40949e5a12a731666","LICENSE-MIT":"3337fe6e4a3830ad87c23cb9d6d750f9a1e5c45efc08de9c76c1a207fc6966c4","src/enum_convert.rs":"c0068cb8b563043030186cd9a0be6a4eac1a5f1761fe3646a99528e6d3dc5f54","src/lib.rs":"e05eb7285e68c64ee6936868cb3b39bfac041ee722bb4ecd6fb892fdf8bcff06","src/snapshots/diplomat__tests__cfgd_struct.snap":"2874497e83ba3f43541d90869bfa428973c5b23df7fec2826e187d530f1a620b","src/snapshots/diplomat__tests__cfged_method-2.snap":"b2ff2801b5f1e08bf660c63a5b8763cf99326e0b9d13cdcc9ae82532825727b2","src/snapshots/diplomat__tests__cfged_method.snap":"b478d2d14e01209b45032b092bf91a2068f08f704b2395bc3ebd2ada21141077","src/snapshots/diplomat__tests__method_taking_mutable_slice.snap":"eafa335a999e416a044d32106e096ef57b7f41fb2f74b03d4adce13e7179b03d","src/snapshots/diplomat__tests__method_taking_mutable_str.snap":"e4c65337861a78b3c9762545fcdbccc1169bab9183ff750fc467a5367dba9c56","src/snapshots/diplomat__tests__method_taking_slice.snap":"eb2d7d00381ddef71411c170ce27d2490acfe9322bc3de397fe1cedcedeeee7b","src/snapshots/diplomat__tests__method_taking_str.snap":"92aa38d8618f0d52d5bc967a8d67a87f4b9cdc4f8651c624a9cc7b73033dbaa4","src/snapshots/diplomat__tests__mod_with_enum.snap":"fc225e910aa1afe496eb8d4da4342894f7786c53e12725b2f70018cf5230dddc","src/snapshots/diplomat__tests__mod_with_rust_result.snap":"48e30564d2cf0477db7062c58842b264d0cfec1d635e7dbaf12c12a2e9f1ab31","src/snapshots/diplomat__tests__mod_with_writeable_result.snap":"6ddbc34dbf7d362366cddda70c87a2f25d7ba0821ccbab90b5a79748f1064593","src/snapshots/diplomat__tests__multilevel_borrows.snap":"708fb54c2c3b8498aac83c20af891e12212874b94691fd734fd57f500ce54666","src/snapshots/diplomat__tests__self_params.snap":"1f6652799973e4afa751afebd6306e71ea439640cc1cae9848c5757d060bf699","src/transparent_convert.rs":"dde901986a6709a21f359596e85bc4fd009bb645c79b698d5af8e2a603996ac4"},"package":"a31672b3ebc3c7866c3c98726f7a9a5ac8f13962e77d3c8225f6be49a7b8c5f2"}
\ No newline at end of file
diff --git a/third_party/rust/diplomat/Cargo.toml b/third_party/rust/diplomat/Cargo.toml
new file mode 100644
index 0000000000..af5ef28fa6
--- /dev/null
+++ b/third_party/rust/diplomat/Cargo.toml
@@ -0,0 +1,55 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "diplomat"
+version = "0.7.0"
+authors = [
+    "Shadaj Laddad <shadaj@users.noreply.github.com>",
+    "Manish Goregaokar <manishsmail@gmail.com>",
+    "Quinn Okabayashi <QnnOkabayashi@users.noreply.github.com>",
+]
+description = "The diplomat FFI generation macro"
+documentation = "https://docs.rs/diplomat_core/"
+keywords = [
+    "ffi",
+    "codegen",
+]
+categories = ["development-tools"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-diplomat/diplomat"
+
+[lib]
+path = "src/lib.rs"
+proc-macro = true
+
+[dependencies.diplomat_core]
+version = "0.7.0"
+
+[dependencies.proc-macro2]
+version = "1.0.27"
+
+[dependencies.quote]
+version = "1.0"
+
+[dependencies.syn]
+version = "2.0"
+features = [
+    "full",
+    "extra-traits",
+]
+
+[dev-dependencies.insta]
+version = "1.7.1"
+
+[dev-dependencies.tempfile]
+version = "3.2.0"
diff --git a/third_party/rust/diplomat/LICENSE-APACHE b/third_party/rust/diplomat/LICENSE-APACHE
new file mode 100644
index 0000000000..05fcffa855
--- /dev/null
+++ b/third_party/rust/diplomat/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
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+   "Licensor" shall mean the copyright owner or entity authorized by
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+   "Legal Entity" shall mean the union of the acting entity and all
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+   You may add Your own copyright statement to Your modifications and
+   may provide additional or different license terms and conditions
+   for use, reproduction, or distribution of Your modifications, or
+   for any such Derivative Works as a whole, provided Your use,
+   reproduction, and distribution of the Work otherwise complies with
+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
+   except as required for reasonable and customary use in describing the
+   origin of the Work and reproducing the content of the NOTICE file.
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+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
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+   other commercial damages or losses), even if such Contributor
+   has been advised of the possibility of such damages.
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+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
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+   License. However, in accepting such obligations, You may act only
+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
+   replaced with your own identifying information. (Don't include
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+Copyright 2022 The Diplomat Developers
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/third_party/rust/diplomat/LICENSE-MIT b/third_party/rust/diplomat/LICENSE-MIT
new file mode 100644
index 0000000000..cf62c31bc7
--- /dev/null
+++ b/third_party/rust/diplomat/LICENSE-MIT
@@ -0,0 +1,27 @@
+MIT License
+
+Copyright (c) 2022 The Diplomat Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/third_party/rust/diplomat/src/enum_convert.rs b/third_party/rust/diplomat/src/enum_convert.rs
new file mode 100644
index 0000000000..0244f320e6
--- /dev/null
+++ b/third_party/rust/diplomat/src/enum_convert.rs
@@ -0,0 +1,85 @@
+use quote::{quote, ToTokens};
+use syn::parse::{Parse, ParseStream};
+use syn::*;
+
+// An attribute that is a list of idents
+pub struct EnumConvertAttribute {
+    path: Path,
+
+    needs_wildcard: bool,
+}
+
+impl Parse for EnumConvertAttribute {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let paths = input.parse_terminated(Path::parse, Token![,])?;
+        if paths.is_empty() {
+            return Err(input.error("#[diplomat::enum_convert] needs a path argument"));
+        }
+        let needs_wildcard = if paths.len() == 2 {
+            if let Some(ident) = paths[1].get_ident() {
+                if ident == "needs_wildcard" {
+                    true
+                } else {
+                    return Err(input.error(
+                        "#[diplomat::enum_convert] only recognizes needs_wildcard keyword",
+                    ));
+                }
+            } else {
+                return Err(
+                    input.error("#[diplomat::enum_convert] only recognizes needs_wildcard keyword")
+                );
+            }
+        } else if paths.len() > 1 {
+            return Err(input.error("#[diplomat::enum_convert] only supports up to two arguments"));
+        } else {
+            // no needs_wildcard marker
+            false
+        };
+        Ok(EnumConvertAttribute {
+            path: paths[0].clone(),
+            needs_wildcard,
+        })
+    }
+}
+
+pub fn gen_enum_convert(attr: EnumConvertAttribute, input: ItemEnum) -> proc_macro2::TokenStream {
+    let mut from_arms = vec![];
+    let mut into_arms = vec![];
+
+    let this_name = &input.ident;
+    let other_name = &attr.path;
+    for variant in &input.variants {
+        if variant.fields != Fields::Unit {
+            return Error::new(variant.ident.span(), "variant may not have fields")
+                .to_compile_error();
+        }
+
+        let variant_name = &variant.ident;
+        from_arms.push(quote!(#other_name::#variant_name => Self::#variant_name));
+        into_arms.push(quote!(#this_name::#variant_name => Self::#variant_name));
+    }
+
+    if attr.needs_wildcard {
+        let error = format!(
+            "Encountered unknown field for {}",
+            other_name.to_token_stream()
+        );
+        from_arms.push(quote!(_ => unreachable!(#error)))
+    }
+    quote! {
+        impl From<#other_name> for #this_name {
+            fn from(other: #other_name) -> Self {
+                match other {
+                    #(#from_arms,)*
+                }
+            }
+        }
+        impl From<#this_name> for #other_name {
+            fn from(this: #this_name) -> Self {
+                match this {
+                    #(#into_arms,)*
+                }
+            }
+        }
+    }
+}
diff --git a/third_party/rust/diplomat/src/lib.rs b/third_party/rust/diplomat/src/lib.rs
new file mode 100644
index 0000000000..dad44bff62
--- /dev/null
+++ b/third_party/rust/diplomat/src/lib.rs
@@ -0,0 +1,691 @@
+use proc_macro2::Span;
+use quote::{quote, ToTokens};
+use syn::*;
+
+use diplomat_core::ast;
+
+mod enum_convert;
+mod transparent_convert;
+
+fn cfgs_to_stream(attrs: &[Attribute]) -> proc_macro2::TokenStream {
+    attrs
+        .iter()
+        .fold(quote!(), |prev, attr| quote!(#prev #attr))
+}
+
+fn gen_params_at_boundary(param: &ast::Param, expanded_params: &mut Vec<FnArg>) {
+    match &param.ty {
+        ast::TypeName::StrReference(_) | ast::TypeName::PrimitiveSlice(..) => {
+            let data_type = if let ast::TypeName::PrimitiveSlice(.., prim) = &param.ty {
+                ast::TypeName::Primitive(*prim).to_syn().to_token_stream()
+            } else {
+                quote! { u8 }
+            };
+            expanded_params.push(FnArg::Typed(PatType {
+                attrs: vec![],
+                pat: Box::new(Pat::Ident(PatIdent {
+                    attrs: vec![],
+                    by_ref: None,
+                    mutability: None,
+                    ident: Ident::new(&format!("{}_diplomat_data", param.name), Span::call_site()),
+                    subpat: None,
+                })),
+                colon_token: syn::token::Colon(Span::call_site()),
+                ty: Box::new(
+                    parse2({
+                        if let ast::TypeName::PrimitiveSlice(_, ast::Mutability::Mutable, _) =
+                            &param.ty
+                        {
+                            quote! { *mut #data_type }
+                        } else {
+                            quote! { *const #data_type }
+                        }
+                    })
+                    .unwrap(),
+                ),
+            }));
+
+            expanded_params.push(FnArg::Typed(PatType {
+                attrs: vec![],
+                pat: Box::new(Pat::Ident(PatIdent {
+                    attrs: vec![],
+                    by_ref: None,
+                    mutability: None,
+                    ident: Ident::new(&format!("{}_diplomat_len", param.name), Span::call_site()),
+                    subpat: None,
+                })),
+                colon_token: syn::token::Colon(Span::call_site()),
+                ty: Box::new(
+                    parse2(quote! {
+                        usize
+                    })
+                    .unwrap(),
+                ),
+            }));
+        }
+        o => {
+            expanded_params.push(FnArg::Typed(PatType {
+                attrs: vec![],
+                pat: Box::new(Pat::Ident(PatIdent {
+                    attrs: vec![],
+                    by_ref: None,
+                    mutability: None,
+                    ident: Ident::new(param.name.as_str(), Span::call_site()),
+                    subpat: None,
+                })),
+                colon_token: syn::token::Colon(Span::call_site()),
+                ty: Box::new(o.to_syn()),
+            }));
+        }
+    }
+}
+
+fn gen_params_invocation(param: &ast::Param, expanded_params: &mut Vec<Expr>) {
+    match &param.ty {
+        ast::TypeName::StrReference(_) | ast::TypeName::PrimitiveSlice(..) => {
+            let data_ident =
+                Ident::new(&format!("{}_diplomat_data", param.name), Span::call_site());
+            let len_ident = Ident::new(&format!("{}_diplomat_len", param.name), Span::call_site());
+
+            let tokens = if let ast::TypeName::PrimitiveSlice(_, mutability, _) = &param.ty {
+                match mutability {
+                    ast::Mutability::Mutable => quote! {
+                        unsafe { core::slice::from_raw_parts_mut(#data_ident, #len_ident) }
+                    },
+                    ast::Mutability::Immutable => quote! {
+                        unsafe { core::slice::from_raw_parts(#data_ident, #len_ident) }
+                    },
+                }
+            } else {
+                // TODO(#57): don't just unwrap? or should we assume that the other side gives us a good value?
+                quote! {
+                    unsafe {
+                        core::str::from_utf8(core::slice::from_raw_parts(#data_ident, #len_ident)).unwrap()
+                    }
+                }
+            };
+            expanded_params.push(parse2(tokens).unwrap());
+        }
+        ast::TypeName::Result(_, _, _) => {
+            let param = &param.name;
+            expanded_params.push(parse2(quote!(#param.into())).unwrap());
+        }
+        _ => {
+            expanded_params.push(Expr::Path(ExprPath {
+                attrs: vec![],
+                qself: None,
+                path: Ident::new(param.name.as_str(), Span::call_site()).into(),
+            }));
+        }
+    }
+}
+
+fn gen_custom_type_method(strct: &ast::CustomType, m: &ast::Method) -> Item {
+    let self_ident = Ident::new(strct.name().as_str(), Span::call_site());
+    let method_ident = Ident::new(m.name.as_str(), Span::call_site());
+    let extern_ident = Ident::new(m.full_path_name.as_str(), Span::call_site());
+
+    let mut all_params = vec![];
+    m.params.iter().for_each(|p| {
+        gen_params_at_boundary(p, &mut all_params);
+    });
+
+    let mut all_params_invocation = vec![];
+    m.params.iter().for_each(|p| {
+        gen_params_invocation(p, &mut all_params_invocation);
+    });
+
+    let this_ident = Pat::Ident(PatIdent {
+        attrs: vec![],
+        by_ref: None,
+        mutability: None,
+        ident: Ident::new("this", Span::call_site()),
+        subpat: None,
+    });
+
+    if let Some(self_param) = &m.self_param {
+        all_params.insert(
+            0,
+            FnArg::Typed(PatType {
+                attrs: vec![],
+                pat: Box::new(this_ident.clone()),
+                colon_token: syn::token::Colon(Span::call_site()),
+                ty: Box::new(self_param.to_typename().to_syn()),
+            }),
+        );
+    }
+
+    let lifetimes = {
+        let lifetime_env = &m.lifetime_env;
+        if lifetime_env.is_empty() {
+            quote! {}
+        } else {
+            quote! { <#lifetime_env> }
+        }
+    };
+
+    let method_invocation = if m.self_param.is_some() {
+        quote! { #this_ident.#method_ident }
+    } else {
+        quote! { #self_ident::#method_ident }
+    };
+
+    let (return_tokens, maybe_into) = if let Some(return_type) = &m.return_type {
+        if let ast::TypeName::Result(ok, err, true) = return_type {
+            let ok = ok.to_syn();
+            let err = err.to_syn();
+            (
+                quote! { -> diplomat_runtime::DiplomatResult<#ok, #err> },
+                quote! { .into() },
+            )
+        } else {
+            let return_type_syn = return_type.to_syn();
+            (quote! { -> #return_type_syn }, quote! {})
+        }
+    } else {
+        (quote! {}, quote! {})
+    };
+
+    let writeable_flushes = m
+        .params
+        .iter()
+        .filter(|p| p.is_writeable())
+        .map(|p| {
+            let p = &p.name;
+            quote! { #p.flush(); }
+        })
+        .collect::<Vec<_>>();
+
+    let cfg = cfgs_to_stream(&m.attrs.cfg);
+
+    if writeable_flushes.is_empty() {
+        Item::Fn(syn::parse_quote! {
+            #[no_mangle]
+            #cfg
+            extern "C" fn #extern_ident#lifetimes(#(#all_params),*) #return_tokens {
+                #method_invocation(#(#all_params_invocation),*) #maybe_into
+            }
+        })
+    } else {
+        Item::Fn(syn::parse_quote! {
+            #[no_mangle]
+            #cfg
+            extern "C" fn #extern_ident#lifetimes(#(#all_params),*) #return_tokens {
+                let ret = #method_invocation(#(#all_params_invocation),*);
+                #(#writeable_flushes)*
+                ret #maybe_into
+            }
+        })
+    }
+}
+
+struct AttributeInfo {
+    repr: bool,
+    opaque: bool,
+}
+
+impl AttributeInfo {
+    fn extract(attrs: &mut Vec<Attribute>) -> Self {
+        let mut repr = false;
+        let mut opaque = false;
+        attrs.retain(|attr| {
+            let ident = &attr.path().segments.iter().next().unwrap().ident;
+            if ident == "repr" {
+                repr = true;
+                // don't actually extract repr attrs, just detect them
+                return true;
+            } else if ident == "diplomat" {
+                if attr.path().segments.len() == 2 {
+                    let seg = &attr.path().segments.iter().nth(1).unwrap().ident;
+                    if seg == "opaque" {
+                        opaque = true;
+                        return false;
+                    } else if seg == "rust_link" || seg == "out" || seg == "attr" {
+                        // diplomat-tool reads these, not diplomat::bridge.
+                        // throw them away so rustc doesn't complain about unknown attributes
+                        return false;
+                    } else if seg == "enum_convert" || seg == "transparent_convert" {
+                        // diplomat::bridge doesn't read this, but it's handled separately
+                        // as an attribute
+                        return true;
+                    } else {
+                        panic!("Only #[diplomat::opaque] and #[diplomat::rust_link] are supported")
+                    }
+                } else {
+                    panic!("#[diplomat::foo] attrs have a single-segment path name")
+                }
+            }
+            true
+        });
+
+        Self { repr, opaque }
+    }
+}
+
+fn gen_bridge(input: ItemMod) -> ItemMod {
+    let module = ast::Module::from_syn(&input, true);
+    let (brace, mut new_contents) = input.content.unwrap();
+
+    new_contents.iter_mut().for_each(|c| match c {
+        Item::Struct(s) => {
+            let info = AttributeInfo::extract(&mut s.attrs);
+            if info.opaque || !info.repr {
+                let repr = if info.opaque {
+                    // Normal opaque types don't need repr(transparent) because the inner type is
+                    // never referenced. #[diplomat::transparent_convert] handles adding repr(transparent)
+                    // on its own
+                    quote!()
+                } else {
+                    quote!(#[repr(C)])
+                };
+                *s = syn::parse_quote! {
+                    #repr
+                    #s
+                }
+            }
+        }
+
+        Item::Enum(e) => {
+            let info = AttributeInfo::extract(&mut e.attrs);
+            if info.opaque {
+                panic!("#[diplomat::opaque] not allowed on enums")
+            }
+            for v in &mut e.variants {
+                let info = AttributeInfo::extract(&mut v.attrs);
+                if info.opaque {
+                    panic!("#[diplomat::opaque] not allowed on enum variants");
+                }
+            }
+            *e = syn::parse_quote! {
+                #[repr(C)]
+                #e
+            };
+        }
+
+        Item::Impl(i) => {
+            for item in &mut i.items {
+                if let syn::ImplItem::Fn(ref mut m) = *item {
+                    let info = AttributeInfo::extract(&mut m.attrs);
+                    if info.opaque {
+                        panic!("#[diplomat::opaque] not allowed on methods")
+                    }
+                }
+            }
+        }
+        _ => (),
+    });
+
+    for custom_type in module.declared_types.values() {
+        custom_type.methods().iter().for_each(|m| {
+            new_contents.push(gen_custom_type_method(custom_type, m));
+        });
+
+        let destroy_ident = Ident::new(
+            format!("{}_destroy", custom_type.name()).as_str(),
+            Span::call_site(),
+        );
+
+        let type_ident = custom_type.name().to_syn();
+
+        let (lifetime_defs, lifetimes) = if let Some(lifetime_env) = custom_type.lifetimes() {
+            (
+                quote! { <#lifetime_env> },
+                lifetime_env.lifetimes_to_tokens(),
+            )
+        } else {
+            (quote! {}, quote! {})
+        };
+
+        let cfg = cfgs_to_stream(&custom_type.attrs().cfg);
+
+        // for now, body is empty since all we need to do is drop the box
+        // TODO(#13): change to take a `*mut` and handle DST boxes appropriately
+        new_contents.push(Item::Fn(syn::parse_quote! {
+            #[no_mangle]
+            #cfg
+            extern "C" fn #destroy_ident#lifetime_defs(this: Box<#type_ident#lifetimes>) {}
+        }));
+    }
+
+    ItemMod {
+        attrs: input.attrs,
+        vis: input.vis,
+        mod_token: input.mod_token,
+        ident: input.ident,
+        content: Some((brace, new_contents)),
+        semi: input.semi,
+        unsafety: None,
+    }
+}
+
+/// Mark a module to be exposed through Diplomat-generated FFI.
+#[proc_macro_attribute]
+pub fn bridge(
+    _attr: proc_macro::TokenStream,
+    input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    let expanded = gen_bridge(parse_macro_input!(input));
+    proc_macro::TokenStream::from(expanded.to_token_stream())
+}
+
+/// Generate From and Into implementations for a Diplomat enum
+///
+/// This is invoked as `#[diplomat::enum_convert(OtherEnumName)]`
+/// on a Diplomat enum. It will assume the other enum has exactly the same variants
+/// and generate From and Into implementations using those. In case that enum is `#[non_exhaustive]`,
+/// you may use `#[diplomat::enum_convert(OtherEnumName, needs_wildcard)]` to generate a panicky wildcard
+/// branch. It is up to the library author to ensure the enums are kept in sync. You may use the `#[non_exhaustive_omitted_patterns]`
+/// lint to enforce this.
+#[proc_macro_attribute]
+pub fn enum_convert(
+    attr: proc_macro::TokenStream,
+    input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    // proc macros handle compile errors by using special error tokens.
+    // In case of an error, we don't want the original code to go away too
+    // (otherwise that will cause more errors) so we hold on to it and we tack it in
+    // with no modifications below
+    let input_cached: proc_macro2::TokenStream = input.clone().into();
+    let expanded =
+        enum_convert::gen_enum_convert(parse_macro_input!(attr), parse_macro_input!(input));
+
+    let full = quote! {
+        #expanded
+        #input_cached
+    };
+    proc_macro::TokenStream::from(full.to_token_stream())
+}
+
+/// Generate conversions from inner types for opaque Diplomat types with a single field
+///
+/// This is invoked as `#[diplomat::transparent_convert]`
+/// on an opaque Diplomat type. It will add `#[repr(transparent)]` and implement `pub(crate) fn transparent_convert()`
+/// which allows constructing an `&Self` from a reference to the inner field.
+#[proc_macro_attribute]
+pub fn transparent_convert(
+    _attr: proc_macro::TokenStream,
+    input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    // proc macros handle compile errors by using special error tokens.
+    // In case of an error, we don't want the original code to go away too
+    // (otherwise that will cause more errors) so we hold on to it and we tack it in
+    // with no modifications below
+    let input_cached: proc_macro2::TokenStream = input.clone().into();
+    let expanded = transparent_convert::gen_transparent_convert(parse_macro_input!(input));
+
+    let full = quote! {
+        #expanded
+        #input_cached
+    };
+    proc_macro::TokenStream::from(full.to_token_stream())
+}
+
+#[cfg(test)]
+mod tests {
+    use std::fs::File;
+    use std::io::{Read, Write};
+    use std::process::Command;
+
+    use quote::ToTokens;
+    use syn::parse_quote;
+    use tempfile::tempdir;
+
+    use super::gen_bridge;
+
+    fn rustfmt_code(code: &str) -> String {
+        let dir = tempdir().unwrap();
+        let file_path = dir.path().join("temp.rs");
+        let mut file = File::create(file_path.clone()).unwrap();
+
+        writeln!(file, "{code}").unwrap();
+        drop(file);
+
+        Command::new("rustfmt")
+            .arg(file_path.to_str().unwrap())
+            .spawn()
+            .unwrap()
+            .wait()
+            .unwrap();
+
+        let mut file = File::open(file_path).unwrap();
+        let mut data = String::new();
+        file.read_to_string(&mut data).unwrap();
+        drop(file);
+        dir.close().unwrap();
+        data
+    }
+
+    #[test]
+    fn method_taking_str() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    impl Foo {
+                        pub fn from_str(s: &str) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn method_taking_slice() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    impl Foo {
+                        pub fn from_slice(s: &[f64]) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn method_taking_mutable_slice() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    impl Foo {
+                        pub fn fill_slice(s: &mut [f64]) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn mod_with_enum() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    enum Abc {
+                        A,
+                        B = 123,
+                    }
+
+                    impl Abc {
+                        pub fn do_something(&self) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn mod_with_writeable_result() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    impl Foo {
+                        pub fn to_string(&self, to: &mut DiplomatWriteable) -> Result<(), ()> {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn mod_with_rust_result() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    impl Foo {
+                        pub fn bar(&self) -> Result<(), ()> {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn multilevel_borrows() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    #[diplomat::opaque]
+                    struct Foo<'a>(&'a str);
+
+                    #[diplomat::opaque]
+                    struct Bar<'b, 'a: 'b>(&'b Foo<'a>);
+
+                    struct Baz<'x, 'y> {
+                        foo: &'y Foo<'x>,
+                    }
+
+                    impl<'a> Foo<'a> {
+                        pub fn new(x: &'a str) -> Box<Foo<'a>> {
+                            unimplemented!()
+                        }
+
+                        pub fn get_bar<'b>(&'b self) -> Box<Bar<'b, 'a>> {
+                            unimplemented!()
+                        }
+
+                        pub fn get_baz<'b>(&'b self) -> Baz<'b, 'a> {
+                            Bax { foo: self }
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn self_params() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    #[diplomat::opaque]
+                    struct RefList<'a> {
+                        data: &'a i32,
+                        next: Option<Box<Self>>,
+                    }
+
+                    impl<'b> RefList<'b> {
+                        pub fn extend(&mut self, other: &Self) -> Self {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn cfged_method() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    impl Foo {
+                        #[cfg(feature = "foo")]
+                        pub fn bar(s: u8) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    struct Foo {}
+
+                    #[cfg(feature = "bar")]
+                    impl Foo {
+                        #[cfg(feature = "foo")]
+                        pub fn bar(s: u8) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+
+    #[test]
+    fn cfgd_struct() {
+        insta::assert_display_snapshot!(rustfmt_code(
+            &gen_bridge(parse_quote! {
+                mod ffi {
+                    #[diplomat::opaque]
+                    #[cfg(feature = "foo")]
+                    struct Foo {}
+                    #[cfg(feature = "foo")]
+                    impl Foo {
+                        pub fn bar(s: u8) {
+                            unimplemented!()
+                        }
+                    }
+                }
+            })
+            .to_token_stream()
+            .to_string()
+        ));
+    }
+}
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfgd_struct.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfgd_struct.snap
new file mode 100644
index 0000000000..4328309170
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfgd_struct.snap
@@ -0,0 +1,23 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                #[diplomat :: opaque] #[cfg(feature = \"foo\")] struct Foo {}\n                                #[cfg(feature = \"foo\")] impl Foo\n                                { pub fn bar(s : u8) { unimplemented! () } }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[cfg(feature = "foo")]
+    struct Foo {}
+    #[cfg(feature = "foo")]
+    impl Foo {
+        pub fn bar(s: u8) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    #[cfg(feature = "foo")]
+    extern "C" fn Foo_bar(s: u8) {
+        Foo::bar(s)
+    }
+    #[no_mangle]
+    #[cfg(feature = "foo")]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfged_method-2.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfged_method-2.snap
new file mode 100644
index 0000000000..b026704b8d
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfged_method-2.snap
@@ -0,0 +1,24 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} #[cfg(feature = \"bar\")] impl Foo\n                                {\n                                    #[cfg(feature = \"foo\")] pub fn bar(s : u8)\n                                    { unimplemented! () }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    #[cfg(feature = "bar")]
+    impl Foo {
+        #[cfg(feature = "foo")]
+        pub fn bar(s: u8) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    #[cfg(feature = "foo")]
+    #[cfg(feature = "bar")]
+    extern "C" fn Foo_bar(s: u8) {
+        Foo::bar(s)
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfged_method.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfged_method.snap
new file mode 100644
index 0000000000..bc4adbb73f
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__cfged_method.snap
@@ -0,0 +1,22 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                {\n                                    #[cfg(feature = \"foo\")] pub fn bar(s : u8)\n                                    { unimplemented! () }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        #[cfg(feature = "foo")]
+        pub fn bar(s: u8) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    #[cfg(feature = "foo")]
+    extern "C" fn Foo_bar(s: u8) {
+        Foo::bar(s)
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_mutable_slice.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_mutable_slice.snap
new file mode 100644
index 0000000000..01fea65c2e
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_mutable_slice.snap
@@ -0,0 +1,20 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                { pub fn fill_slice(s : & mut [f64]) { unimplemented! () } }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        pub fn fill_slice(s: &mut [f64]) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Foo_fill_slice(s_diplomat_data: *mut f64, s_diplomat_len: usize) {
+        Foo::fill_slice(unsafe { core::slice::from_raw_parts_mut(s_diplomat_data, s_diplomat_len) })
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_mutable_str.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_mutable_str.snap
new file mode 100644
index 0000000000..bebbcf8455
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_mutable_str.snap
@@ -0,0 +1,26 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                {\n                                    pub fn make_uppercase(s : & mut str) { unimplemented! () }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        pub fn make_uppercase(s: &mut str) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Foo_make_uppercase(s_diplomat_data: *mut u8, s_diplomat_len: usize) {
+        Foo::make_uppercase(unsafe {
+            core::str::from_utf8_mut(core::slice::from_raw_parts_mut(
+                s_diplomat_data,
+                s_diplomat_len,
+            ))
+            .unwrap()
+        })
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_slice.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_slice.snap
new file mode 100644
index 0000000000..94daec2af5
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_slice.snap
@@ -0,0 +1,20 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                { pub fn from_slice(s : & [f64]) { unimplemented! () } }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        pub fn from_slice(s: &[f64]) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Foo_from_slice(s_diplomat_data: *const f64, s_diplomat_len: usize) {
+        Foo::from_slice(unsafe { core::slice::from_raw_parts(s_diplomat_data, s_diplomat_len) })
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_str.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_str.snap
new file mode 100644
index 0000000000..7e736e5599
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__method_taking_str.snap
@@ -0,0 +1,23 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                { pub fn from_str(s : & str) { unimplemented! () } }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        pub fn from_str(s: &str) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Foo_from_str(s_diplomat_data: *const u8, s_diplomat_len: usize) {
+        Foo::from_str(unsafe {
+            core::str::from_utf8(core::slice::from_raw_parts(s_diplomat_data, s_diplomat_len))
+                .unwrap()
+        })
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_enum.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_enum.snap
new file mode 100644
index 0000000000..723e17d786
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_enum.snap
@@ -0,0 +1,23 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                enum Abc { A, B = 123, } impl Abc\n                                { pub fn do_something(& self) { unimplemented! () } }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    enum Abc {
+        A,
+        B = 123,
+    }
+    impl Abc {
+        pub fn do_something(&self) {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Abc_do_something(this: &Abc) {
+        this.do_something()
+    }
+    #[no_mangle]
+    extern "C" fn Abc_destroy(this: Box<Abc>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_rust_result.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_rust_result.snap
new file mode 100644
index 0000000000..1eeb28808a
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_rust_result.snap
@@ -0,0 +1,20 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                {\n                                    pub fn bar(& self) -> Result < (), () >\n                                    { unimplemented! () }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        pub fn bar(&self) -> Result<(), ()> {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Foo_bar(this: &Foo) -> diplomat_runtime::DiplomatResult<(), ()> {
+        this.bar().into()
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_writeable_result.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_writeable_result.snap
new file mode 100644
index 0000000000..870193052f
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__mod_with_writeable_result.snap
@@ -0,0 +1,25 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                struct Foo {} impl Foo\n                                {\n                                    pub fn to_string(& self, to : & mut DiplomatWriteable) ->\n                                    Result < (), () > { unimplemented! () }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    #[repr(C)]
+    struct Foo {}
+    impl Foo {
+        pub fn to_string(&self, to: &mut DiplomatWriteable) -> Result<(), ()> {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Foo_to_string(
+        this: &Foo,
+        to: &mut diplomat_runtime::DiplomatWriteable,
+    ) -> diplomat_runtime::DiplomatResult<(), ()> {
+        let ret = this.to_string(to);
+        to.flush();
+        ret.into()
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy(this: Box<Foo>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__multilevel_borrows.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__multilevel_borrows.snap
new file mode 100644
index 0000000000..f662608096
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__multilevel_borrows.snap
@@ -0,0 +1,45 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                #[diplomat :: opaque] struct Foo < 'a > (& 'a str) ;\n                                #[diplomat :: opaque] struct Bar < 'b, 'a : 'b >\n                                (& 'b Foo < 'a >) ; struct Baz < 'x, 'y >\n                                { foo : & 'y Foo < 'x >, } impl < 'a > Foo < 'a >\n                                {\n                                    pub fn new(x : & 'a str) -> Box < Foo < 'a >>\n                                    { unimplemented! () } pub fn get_bar < 'b > (& 'b self) ->\n                                    Box < Bar < 'b, 'a >> { unimplemented! () } pub fn get_baz <\n                                    'b > (& 'b self) -> Baz < 'b, 'a > { Bax { foo : self } }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    struct Foo<'a>(&'a str);
+    struct Bar<'b, 'a: 'b>(&'b Foo<'a>);
+    #[repr(C)]
+    struct Baz<'x, 'y> {
+        foo: &'y Foo<'x>,
+    }
+    impl<'a> Foo<'a> {
+        pub fn new(x: &'a str) -> Box<Foo<'a>> {
+            unimplemented!()
+        }
+        pub fn get_bar<'b>(&'b self) -> Box<Bar<'b, 'a>> {
+            unimplemented!()
+        }
+        pub fn get_baz<'b>(&'b self) -> Baz<'b, 'a> {
+            Bax { foo: self }
+        }
+    }
+    #[no_mangle]
+    extern "C" fn Bar_destroy<'b, 'a: 'b>(this: Box<Bar<'b, 'a>>) {}
+    #[no_mangle]
+    extern "C" fn Baz_destroy<'x: 'y, 'y>(this: Box<Baz<'x, 'y>>) {}
+    #[no_mangle]
+    extern "C" fn Foo_new<'a>(x_diplomat_data: *const u8, x_diplomat_len: usize) -> Box<Foo<'a>> {
+        Foo::new(unsafe {
+            core::str::from_utf8(core::slice::from_raw_parts(x_diplomat_data, x_diplomat_len))
+                .unwrap()
+        })
+    }
+    #[no_mangle]
+    extern "C" fn Foo_get_bar<'a: 'b, 'b>(this: &'b Foo<'a>) -> Box<Bar<'b, 'a>> {
+        this.get_bar()
+    }
+    #[no_mangle]
+    extern "C" fn Foo_get_baz<'a: 'b, 'b>(this: &'b Foo<'a>) -> Baz<'b, 'a> {
+        this.get_baz()
+    }
+    #[no_mangle]
+    extern "C" fn Foo_destroy<'a>(this: Box<Foo<'a>>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/snapshots/diplomat__tests__self_params.snap b/third_party/rust/diplomat/src/snapshots/diplomat__tests__self_params.snap
new file mode 100644
index 0000000000..6b931197ab
--- /dev/null
+++ b/third_party/rust/diplomat/src/snapshots/diplomat__tests__self_params.snap
@@ -0,0 +1,22 @@
+---
+source: macro/src/lib.rs
+expression: "rustfmt_code(&gen_bridge(parse_quote! {\n                            mod ffi\n                            {\n                                #[diplomat :: opaque] struct RefList < 'a >\n                                { data : & 'a i32, next : Option < Box < Self >>, } impl <\n                                'b > RefList < 'b >\n                                {\n                                    pub fn extend(& mut self, other : & Self) -> Self\n                                    { unimplemented! () }\n                                }\n                            }\n                        }).to_token_stream().to_string())"
+---
+mod ffi {
+    struct RefList<'a> {
+        data: &'a i32,
+        next: Option<Box<Self>>,
+    }
+    impl<'b> RefList<'b> {
+        pub fn extend(&mut self, other: &Self) -> Self {
+            unimplemented!()
+        }
+    }
+    #[no_mangle]
+    extern "C" fn RefList_extend<'b>(this: &mut RefList<'b>, other: &RefList<'b>) -> RefList<'b> {
+        this.extend(other)
+    }
+    #[no_mangle]
+    extern "C" fn RefList_destroy<'a>(this: Box<RefList<'a>>) {}
+}
+
diff --git a/third_party/rust/diplomat/src/transparent_convert.rs b/third_party/rust/diplomat/src/transparent_convert.rs
new file mode 100644
index 0000000000..9ac8bf64e7
--- /dev/null
+++ b/third_party/rust/diplomat/src/transparent_convert.rs
@@ -0,0 +1,30 @@
+use quote::quote;
+use syn::*;
+
+pub fn gen_transparent_convert(s: ItemStruct) -> proc_macro2::TokenStream {
+    let mut fields = s.fields.iter();
+    let field1 = if let Some(field1) = fields.next() {
+        &field1.ty
+    } else {
+        panic!("#[diplomat::transparent_convert] only allowed on structs with a single field")
+    };
+
+    if fields.next().is_some() {
+        panic!("#[diplomat::transparent_convert] only allowed on structs with a single field")
+    }
+    let struct_name = &s.ident;
+    let (impl_generics, ty_generics, _) = s.generics.split_for_impl();
+    let mut impl_generics: Generics = parse_quote!(#impl_generics);
+    let custom_lifetime: GenericParam = parse_quote!('transparent_convert_outer);
+    impl_generics.params.push(custom_lifetime);
+    quote! {
+        impl #impl_generics #struct_name #ty_generics {
+            // can potentially add transparent_convert_owned, _mut later
+            pub(crate) fn transparent_convert(from: &'transparent_convert_outer #field1) -> &'transparent_convert_outer Self {
+                unsafe {
+                    &*(from as *const #field1 as *const Self)
+                }
+            }
+        }
+    }
+}