18 files changed, 4307 insertions, 0 deletions

diff --git a/crates/proc_macro_srv/Cargo.toml b/crates/proc_macro_srv/Cargo.toml
new file mode 100644
index 000000000..7171f0808
--- /dev/null
+++ b/crates/proc_macro_srv/Cargo.toml
@@ -0,0 +1,27 @@
+[package]
+name = "proc_macro_srv"
+version = "0.0.0"
+license = "MIT OR Apache-2.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[lib]
+doctest = false
+
+[dependencies]
+goblin = "0.2.1"
+libloading = "0.6.0"
+memmap = "0.7"
+
+tt = { path = "../tt" }
+mbe = { path = "../mbe" }
+proc_macro_api = { path = "../proc_macro_api" }
+test_utils = { path = "../test_utils" }
+
+[dev-dependencies]
+cargo_metadata = "0.11.1"
+difference = "2.0.0"
+# used as proc macro test target
+serde_derive = "1.0.106"
+
+toolchain = { path = "../toolchain" }
diff --git a/crates/proc_macro_srv/src/cli.rs b/crates/proc_macro_srv/src/cli.rs
new file mode 100644
index 000000000..d428b9567
--- /dev/null
+++ b/crates/proc_macro_srv/src/cli.rs
@@ -0,0 +1,39 @@
+//! Driver for proc macro server
+
+use crate::ProcMacroSrv;
+use proc_macro_api::msg::{self, Message};
+use std::io;
+
+pub fn run() -> io::Result<()> {
+    let mut srv = ProcMacroSrv::default();
+
+    while let Some(req) = read_request()? {
+        let res = match req {
+            msg::Request::ListMacro(task) => srv.list_macros(&task).map(msg::Response::ListMacro),
+            msg::Request::ExpansionMacro(task) => {
+                srv.expand(&task).map(msg::Response::ExpansionMacro)
+            }
+        };
+
+        let msg = res.unwrap_or_else(|err| {
+            msg::Response::Error(msg::ResponseError {
+                code: msg::ErrorCode::ExpansionError,
+                message: err,
+            })
+        });
+
+        if let Err(err) = write_response(msg) {
+            eprintln!("Write message error: {}", err);
+        }
+    }
+
+    Ok(())
+}
+
+fn read_request() -> io::Result<Option<msg::Request>> {
+    msg::Request::read(&mut io::stdin().lock())
+}
+
+fn write_response(msg: msg::Response) -> io::Result<()> {
+    msg.write(&mut io::stdout().lock())
+}
diff --git a/crates/proc_macro_srv/src/dylib.rs b/crates/proc_macro_srv/src/dylib.rs
new file mode 100644
index 000000000..f8f705da8
--- /dev/null
+++ b/crates/proc_macro_srv/src/dylib.rs
@@ -0,0 +1,224 @@
+//! Handles dynamic library loading for proc macro
+
+use crate::{proc_macro::bridge, rustc_server::TokenStream};
+use std::fs::File;
+use std::path::{Path, PathBuf};
+
+use goblin::{mach::Mach, Object};
+use libloading::Library;
+use memmap::Mmap;
+use proc_macro_api::ProcMacroKind;
+use std::io;
+
+const NEW_REGISTRAR_SYMBOL: &str = "_rustc_proc_macro_decls_";
+
+fn invalid_data_err(e: impl Into<Box<dyn std::error::Error + Send + Sync>>) -> io::Error {
+    io::Error::new(io::ErrorKind::InvalidData, e)
+}
+
+fn is_derive_registrar_symbol(symbol: &str) -> bool {
+    symbol.contains(NEW_REGISTRAR_SYMBOL)
+}
+
+fn find_registrar_symbol(file: &Path) -> io::Result<Option<String>> {
+    let file = File::open(file)?;
+    let buffer = unsafe { Mmap::map(&file)? };
+    let object = Object::parse(&buffer).map_err(invalid_data_err)?;
+
+    let name = match object {
+        Object::Elf(elf) => {
+            let symbols = elf.dynstrtab.to_vec().map_err(invalid_data_err)?;
+            symbols.into_iter().find(|s| is_derive_registrar_symbol(s)).map(&str::to_owned)
+        }
+        Object::PE(pe) => pe
+            .exports
+            .iter()
+            .flat_map(|s| s.name)
+            .find(|s| is_derive_registrar_symbol(s))
+            .map(&str::to_owned),
+        Object::Mach(Mach::Binary(binary)) => {
+            let exports = binary.exports().map_err(invalid_data_err)?;
+            exports
+                .iter()
+                .map(|s| {
+                    // In macos doc:
+                    // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/dlsym.3.html
+                    // Unlike other dyld API's, the symbol name passed to dlsym() must NOT be
+                    // prepended with an underscore.
+                    if s.name.starts_with('_') {
+                        &s.name[1..]
+                    } else {
+                        &s.name
+                    }
+                })
+                .find(|s| is_derive_registrar_symbol(s))
+                .map(&str::to_owned)
+        }
+        _ => return Ok(None),
+    };
+    return Ok(name);
+}
+
+/// Loads dynamic library in platform dependent manner.
+///
+/// For unix, you have to use RTLD_DEEPBIND flag to escape problems described
+/// [here](https://github.com/fedochet/rust-proc-macro-panic-inside-panic-expample)
+/// and [here](https://github.com/rust-lang/rust/issues/60593).
+///
+/// Usage of RTLD_DEEPBIND
+/// [here](https://github.com/fedochet/rust-proc-macro-panic-inside-panic-expample/issues/1)
+///
+/// It seems that on Windows that behaviour is default, so we do nothing in that case.
+#[cfg(windows)]
+fn load_library(file: &Path) -> Result<Library, libloading::Error> {
+    Library::new(file)
+}
+
+#[cfg(unix)]
+fn load_library(file: &Path) -> Result<Library, libloading::Error> {
+    use libloading::os::unix::Library as UnixLibrary;
+    use std::os::raw::c_int;
+
+    const RTLD_NOW: c_int = 0x00002;
+    const RTLD_DEEPBIND: c_int = 0x00008;
+
+    UnixLibrary::open(Some(file), RTLD_NOW | RTLD_DEEPBIND).map(|lib| lib.into())
+}
+
+struct ProcMacroLibraryLibloading {
+    // Hold the dylib to prevent it from unloading
+    _lib: Library,
+    exported_macros: Vec<bridge::client::ProcMacro>,
+}
+
+impl ProcMacroLibraryLibloading {
+    fn open(file: &Path) -> io::Result<Self> {
+        let symbol_name = find_registrar_symbol(file)?.ok_or_else(|| {
+            invalid_data_err(format!("Cannot find registrar symbol in file {}", file.display()))
+        })?;
+
+        let lib = load_library(file).map_err(invalid_data_err)?;
+        let exported_macros = {
+            let macros: libloading::Symbol<&&[bridge::client::ProcMacro]> =
+                unsafe { lib.get(symbol_name.as_bytes()) }.map_err(invalid_data_err)?;
+            macros.to_vec()
+        };
+
+        Ok(ProcMacroLibraryLibloading { _lib: lib, exported_macros })
+    }
+}
+
+pub struct Expander {
+    inner: ProcMacroLibraryLibloading,
+}
+
+impl Expander {
+    pub fn new(lib: &Path) -> io::Result<Expander> {
+        // Some libraries for dynamic loading require canonicalized path even when it is
+        // already absolute
+        let lib = lib.canonicalize()?;
+
+        let lib = ensure_file_with_lock_free_access(&lib)?;
+
+        let library = ProcMacroLibraryLibloading::open(&lib)?;
+
+        Ok(Expander { inner: library })
+    }
+
+    pub fn expand(
+        &self,
+        macro_name: &str,
+        macro_body: &tt::Subtree,
+        attributes: Option<&tt::Subtree>,
+    ) -> Result<tt::Subtree, bridge::PanicMessage> {
+        let parsed_body = TokenStream::with_subtree(macro_body.clone());
+
+        let parsed_attributes = attributes
+            .map_or(crate::rustc_server::TokenStream::new(), |attr| {
+                TokenStream::with_subtree(attr.clone())
+            });
+
+        for proc_macro in &self.inner.exported_macros {
+            match proc_macro {
+                bridge::client::ProcMacro::CustomDerive { trait_name, client, .. }
+                    if *trait_name == macro_name =>
+                {
+                    let res = client.run(
+                        &crate::proc_macro::bridge::server::SameThread,
+                        crate::rustc_server::Rustc::default(),
+                        parsed_body,
+                    );
+                    return res.map(|it| it.subtree);
+                }
+                bridge::client::ProcMacro::Bang { name, client } if *name == macro_name => {
+                    let res = client.run(
+                        &crate::proc_macro::bridge::server::SameThread,
+                        crate::rustc_server::Rustc::default(),
+                        parsed_body,
+                    );
+                    return res.map(|it| it.subtree);
+                }
+                bridge::client::ProcMacro::Attr { name, client } if *name == macro_name => {
+                    let res = client.run(
+                        &crate::proc_macro::bridge::server::SameThread,
+                        crate::rustc_server::Rustc::default(),
+                        parsed_attributes,
+                        parsed_body,
+                    );
+                    return res.map(|it| it.subtree);
+                }
+                _ => continue,
+            }
+        }
+
+        Err(bridge::PanicMessage::String("Nothing to expand".to_string()))
+    }
+
+    pub fn list_macros(&self) -> Vec<(String, ProcMacroKind)> {
+        self.inner
+            .exported_macros
+            .iter()
+            .map(|proc_macro| match proc_macro {
+                bridge::client::ProcMacro::CustomDerive { trait_name, .. } => {
+                    (trait_name.to_string(), ProcMacroKind::CustomDerive)
+                }
+                bridge::client::ProcMacro::Bang { name, .. } => {
+                    (name.to_string(), ProcMacroKind::FuncLike)
+                }
+                bridge::client::ProcMacro::Attr { name, .. } => {
+                    (name.to_string(), ProcMacroKind::Attr)
+                }
+            })
+            .collect()
+    }
+}
+
+/// Copy the dylib to temp directory to prevent locking in Windows
+#[cfg(windows)]
+fn ensure_file_with_lock_free_access(path: &Path) -> io::Result<PathBuf> {
+    use std::{ffi::OsString, time::SystemTime};
+
+    let mut to = std::env::temp_dir();
+
+    let file_name = path.file_name().ok_or_else(|| {
+        io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!("File path is invalid: {}", path.display()),
+        )
+    })?;
+
+    // generate a time deps unique number
+    let t = SystemTime::now().duration_since(std::time::UNIX_EPOCH).expect("Time went backwards");
+
+    let mut unique_name = OsString::from(t.as_millis().to_string());
+    unique_name.push(file_name);
+
+    to.push(unique_name);
+    std::fs::copy(path, &to).unwrap();
+    Ok(to)
+}
+
+#[cfg(unix)]
+fn ensure_file_with_lock_free_access(path: &Path) -> io::Result<PathBuf> {
+    Ok(path.to_path_buf())
+}
diff --git a/crates/proc_macro_srv/src/lib.rs b/crates/proc_macro_srv/src/lib.rs
new file mode 100644
index 000000000..7e4e4ad50
--- /dev/null
+++ b/crates/proc_macro_srv/src/lib.rs
@@ -0,0 +1,69 @@
+//! RA Proc Macro Server
+//!
+//! This library is able to call compiled Rust custom derive dynamic libraries on arbitrary code.
+//! The general idea here is based on https://github.com/fedochet/rust-proc-macro-expander.
+//!
+//! But we adapt it to better fit RA needs:
+//!
+//! * We use `tt` for proc-macro `TokenStream` server, it is easier to manipulate and interact with
+//!   RA than `proc-macro2` token stream.
+//! * By **copying** the whole rustc `lib_proc_macro` code, we are able to build this with `stable`
+//!   rustc rather than `unstable`. (Although in general ABI compatibility is still an issue)…
+
+#[allow(dead_code)]
+#[doc(hidden)]
+mod proc_macro;
+
+#[doc(hidden)]
+mod rustc_server;
+
+mod dylib;
+
+use proc_macro::bridge::client::TokenStream;
+use proc_macro_api::{ExpansionResult, ExpansionTask, ListMacrosResult, ListMacrosTask};
+use std::{
+    collections::{hash_map::Entry, HashMap},
+    fs,
+    path::{Path, PathBuf},
+    time::SystemTime,
+};
+
+#[derive(Default)]
+pub(crate) struct ProcMacroSrv {
+    expanders: HashMap<(PathBuf, SystemTime), dylib::Expander>,
+}
+
+impl ProcMacroSrv {
+    pub fn expand(&mut self, task: &ExpansionTask) -> Result<ExpansionResult, String> {
+        let expander = self.expander(&task.lib)?;
+        match expander.expand(&task.macro_name, &task.macro_body, task.attributes.as_ref()) {
+            Ok(expansion) => Ok(ExpansionResult { expansion }),
+            Err(msg) => {
+                Err(format!("Cannot perform expansion for {}: error {:?}", &task.macro_name, msg))
+            }
+        }
+    }
+
+    pub fn list_macros(&mut self, task: &ListMacrosTask) -> Result<ListMacrosResult, String> {
+        let expander = self.expander(&task.lib)?;
+        Ok(ListMacrosResult { macros: expander.list_macros() })
+    }
+
+    fn expander(&mut self, path: &Path) -> Result<&dylib::Expander, String> {
+        let time = fs::metadata(path).and_then(|it| it.modified()).map_err(|err| {
+            format!("Failed to get file metadata for {}: {:?}", path.display(), err)
+        })?;
+
+        Ok(match self.expanders.entry((path.to_path_buf(), time)) {
+            Entry::Vacant(v) => v.insert(dylib::Expander::new(path).map_err(|err| {
+                format!("Cannot create expander for {}: {:?}", path.display(), err)
+            })?),
+            Entry::Occupied(e) => e.into_mut(),
+        })
+    }
+}
+
+pub mod cli;
+
+#[cfg(test)]
+mod tests;
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/buffer.rs b/crates/proc_macro_srv/src/proc_macro/bridge/buffer.rs
new file mode 100644
index 000000000..dae6ff1d1
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/buffer.rs
@@ -0,0 +1,149 @@
+//! lib-proc-macro Buffer management for same-process client<->server communication.
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/buffer.rs
+//! augmented with removing unstable features
+
+use std::io::{self, Write};
+use std::mem;
+use std::ops::{Deref, DerefMut};
+use std::slice;
+
+#[repr(C)]
+struct Slice<'a, T> {
+    data: &'a [T; 0],
+    len: usize,
+}
+
+unsafe impl<'a, T: Sync> Sync for Slice<'a, T> {}
+unsafe impl<'a, T: Sync> Send for Slice<'a, T> {}
+
+impl<'a, T> Copy for Slice<'a, T> {}
+impl<'a, T> Clone for Slice<'a, T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<'a, T> From<&'a [T]> for Slice<'a, T> {
+    fn from(xs: &'a [T]) -> Self {
+        Slice { data: unsafe { &*(xs.as_ptr() as *const [T; 0]) }, len: xs.len() }
+    }
+}
+
+impl<'a, T> Deref for Slice<'a, T> {
+    type Target = [T];
+    fn deref(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.data.as_ptr(), self.len) }
+    }
+}
+
+#[repr(C)]
+pub struct Buffer<T: Copy> {
+    data: *mut T,
+    len: usize,
+    capacity: usize,
+    extend_from_slice: extern "C" fn(Buffer<T>, Slice<'_, T>) -> Buffer<T>,
+    drop: extern "C" fn(Buffer<T>),
+}
+
+unsafe impl<T: Copy + Sync> Sync for Buffer<T> {}
+unsafe impl<T: Copy + Send> Send for Buffer<T> {}
+
+impl<T: Copy> Default for Buffer<T> {
+    fn default() -> Self {
+        Self::from(vec![])
+    }
+}
+
+impl<T: Copy> Deref for Buffer<T> {
+    type Target = [T];
+    fn deref(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.data as *const T, self.len) }
+    }
+}
+
+impl<T: Copy> DerefMut for Buffer<T> {
+    fn deref_mut(&mut self) -> &mut [T] {
+        unsafe { slice::from_raw_parts_mut(self.data, self.len) }
+    }
+}
+
+impl<T: Copy> Buffer<T> {
+    pub(super) fn new() -> Self {
+        Self::default()
+    }
+
+    pub(super) fn clear(&mut self) {
+        self.len = 0;
+    }
+
+    pub(super) fn take(&mut self) -> Self {
+        mem::take(self)
+    }
+
+    pub(super) fn extend_from_slice(&mut self, xs: &[T]) {
+        // Fast path to avoid going through an FFI call.
+        if let Some(final_len) = self.len.checked_add(xs.len()) {
+            if final_len <= self.capacity {
+                let dst = unsafe { slice::from_raw_parts_mut(self.data, self.capacity) };
+                dst[self.len..][..xs.len()].copy_from_slice(xs);
+                self.len = final_len;
+                return;
+            }
+        }
+        let b = self.take();
+        *self = (b.extend_from_slice)(b, Slice::from(xs));
+    }
+}
+
+impl Write for Buffer<u8> {
+    fn write(&mut self, xs: &[u8]) -> io::Result<usize> {
+        self.extend_from_slice(xs);
+        Ok(xs.len())
+    }
+
+    fn write_all(&mut self, xs: &[u8]) -> io::Result<()> {
+        self.extend_from_slice(xs);
+        Ok(())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl<T: Copy> Drop for Buffer<T> {
+    fn drop(&mut self) {
+        let b = self.take();
+        (b.drop)(b);
+    }
+}
+
+impl<T: Copy> From<Vec<T>> for Buffer<T> {
+    fn from(mut v: Vec<T>) -> Self {
+        let (data, len, capacity) = (v.as_mut_ptr(), v.len(), v.capacity());
+        mem::forget(v);
+
+        // This utility function is nested in here because it can *only*
+        // be safely called on `Buffer`s created by *this* `proc_macro`.
+        fn to_vec<T: Copy>(b: Buffer<T>) -> Vec<T> {
+            unsafe {
+                let Buffer { data, len, capacity, .. } = b;
+                mem::forget(b);
+                Vec::from_raw_parts(data, len, capacity)
+            }
+        }
+
+        extern "C" fn extend_from_slice<T: Copy>(b: Buffer<T>, xs: Slice<'_, T>) -> Buffer<T> {
+            let mut v = to_vec(b);
+            v.extend_from_slice(&xs);
+            Buffer::from(v)
+        }
+
+        extern "C" fn drop<T: Copy>(b: Buffer<T>) {
+            mem::drop(to_vec(b));
+        }
+
+        Buffer { data, len, capacity, extend_from_slice, drop }
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/client.rs b/crates/proc_macro_srv/src/proc_macro/bridge/client.rs
new file mode 100644
index 000000000..cb4b3bdb0
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/client.rs
@@ -0,0 +1,478 @@
+//! lib-proc-macro Client-side types.
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/client.rs
+//! augmented with removing unstable features
+
+use super::*;
+
+macro_rules! define_handles {
+    (
+        'owned: $($oty:ident,)*
+        'interned: $($ity:ident,)*
+    ) => {
+        #[repr(C)]
+        #[allow(non_snake_case)]
+        pub struct HandleCounters {
+            $($oty: AtomicUsize,)*
+            $($ity: AtomicUsize,)*
+        }
+
+        impl HandleCounters {
+            // FIXME(eddyb) use a reference to the `static COUNTERS`, instead of
+            // a wrapper `fn` pointer, once `const fn` can reference `static`s.
+            extern "C" fn get() -> &'static Self {
+                static COUNTERS: HandleCounters = HandleCounters {
+                    $($oty: AtomicUsize::new(1),)*
+                    $($ity: AtomicUsize::new(1),)*
+                };
+                &COUNTERS
+            }
+        }
+
+        // FIXME(eddyb) generate the definition of `HandleStore` in `server.rs`.
+        #[repr(C)]
+        #[allow(non_snake_case)]
+        pub(super) struct HandleStore<S: server::Types> {
+            $($oty: handle::OwnedStore<S::$oty>,)*
+            $($ity: handle::InternedStore<S::$ity>,)*
+        }
+
+        impl<S: server::Types> HandleStore<S> {
+            pub(super) fn new(handle_counters: &'static HandleCounters) -> Self {
+                HandleStore {
+                    $($oty: handle::OwnedStore::new(&handle_counters.$oty),)*
+                    $($ity: handle::InternedStore::new(&handle_counters.$ity),)*
+                }
+            }
+        }
+
+        $(
+            #[repr(C)]
+            pub struct $oty(pub(crate) handle::Handle);
+            // impl !Send for $oty {}
+            // impl !Sync for $oty {}
+
+            // Forward `Drop::drop` to the inherent `drop` method.
+            impl Drop for $oty {
+                fn drop(&mut self) {
+                    $oty(self.0).drop();
+                }
+            }
+
+            impl<S> Encode<S> for $oty {
+                fn encode(self, w: &mut Writer, s: &mut S) {
+                    let handle = self.0;
+                    mem::forget(self);
+                    handle.encode(w, s);
+                }
+            }
+
+            impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
+                for Marked<S::$oty, $oty>
+            {
+                fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
+                    s.$oty.take(handle::Handle::decode(r, &mut ()))
+                }
+            }
+
+            impl<S> Encode<S> for &$oty {
+                fn encode(self, w: &mut Writer, s: &mut S) {
+                    self.0.encode(w, s);
+                }
+            }
+
+            impl<'s, S: server::Types,> Decode<'_, 's, HandleStore<server::MarkedTypes<S>>>
+                for &'s Marked<S::$oty, $oty>
+            {
+                fn decode(r: &mut Reader<'_>, s: &'s HandleStore<server::MarkedTypes<S>>) -> Self {
+                    &s.$oty[handle::Handle::decode(r, &mut ())]
+                }
+            }
+
+            impl<S> Encode<S> for &mut $oty {
+                fn encode(self, w: &mut Writer, s: &mut S) {
+                    self.0.encode(w, s);
+                }
+            }
+
+            impl<'s, S: server::Types> DecodeMut<'_, 's, HandleStore<server::MarkedTypes<S>>>
+                for &'s mut Marked<S::$oty, $oty>
+            {
+                fn decode(
+                    r: &mut Reader<'_>,
+                    s: &'s mut HandleStore<server::MarkedTypes<S>>
+                ) -> Self {
+                    &mut s.$oty[handle::Handle::decode(r, &mut ())]
+                }
+            }
+
+            impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
+                for Marked<S::$oty, $oty>
+            {
+                fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
+                    s.$oty.alloc(self).encode(w, s);
+                }
+            }
+
+            impl<S> DecodeMut<'_, '_, S> for $oty {
+                fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+                    $oty(handle::Handle::decode(r, s))
+                }
+            }
+        )*
+
+        $(
+            #[repr(C)]
+            #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+            pub(crate) struct $ity(handle::Handle);
+            // impl !Send for $ity {}
+            // impl !Sync for $ity {}
+
+            impl<S> Encode<S> for $ity {
+                fn encode(self, w: &mut Writer, s: &mut S) {
+                    self.0.encode(w, s);
+                }
+            }
+
+            impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
+                for Marked<S::$ity, $ity>
+            {
+                fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
+                    s.$ity.copy(handle::Handle::decode(r, &mut ()))
+                }
+            }
+
+            impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
+                for Marked<S::$ity, $ity>
+            {
+                fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
+                    s.$ity.alloc(self).encode(w, s);
+                }
+            }
+
+            impl<S> DecodeMut<'_, '_, S> for $ity {
+                fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+                    $ity(handle::Handle::decode(r, s))
+                }
+            }
+        )*
+    }
+}
+define_handles! {
+    'owned:
+    TokenStream,
+    TokenStreamBuilder,
+    TokenStreamIter,
+    Group,
+    Literal,
+    SourceFile,
+    MultiSpan,
+    Diagnostic,
+
+    'interned:
+    Punct,
+    Ident,
+    Span,
+}
+
+// FIXME(eddyb) generate these impls by pattern-matching on the
+// names of methods - also could use the presence of `fn drop`
+// to distinguish between 'owned and 'interned, above.
+// Alternatively, special 'modes" could be listed of types in with_api
+// instead of pattern matching on methods, here and in server decl.
+
+impl Clone for TokenStream {
+    fn clone(&self) -> Self {
+        self.clone()
+    }
+}
+
+impl Clone for TokenStreamIter {
+    fn clone(&self) -> Self {
+        self.clone()
+    }
+}
+
+impl Clone for Group {
+    fn clone(&self) -> Self {
+        self.clone()
+    }
+}
+
+impl Clone for Literal {
+    fn clone(&self) -> Self {
+        self.clone()
+    }
+}
+
+impl fmt::Debug for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Literal")
+            // format the kind without quotes, as in `kind: Float`
+            // .field("kind", &format_args!("{}", &self.debug_kind()))
+            .field("symbol", &self.symbol())
+            // format `Some("...")` on one line even in {:#?} mode
+            // .field("suffix", &format_args!("{:?}", &self.suffix()))
+            .field("span", &self.span())
+            .finish()
+    }
+}
+
+impl Clone for SourceFile {
+    fn clone(&self) -> Self {
+        self.clone()
+    }
+}
+
+impl fmt::Debug for Span {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.debug())
+    }
+}
+
+macro_rules! define_client_side {
+    ($($name:ident {
+        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)*;)*
+    }),* $(,)?) => {
+        $(impl $name {
+            #[allow(unused)]
+            $(pub(crate) fn $method($($arg: $arg_ty),*) $(-> $ret_ty)* {
+                panic!("hello");
+                // Bridge::with(|bridge| {
+                //     let mut b = bridge.cached_buffer.take();
+
+                //     b.clear();
+                //     api_tags::Method::$name(api_tags::$name::$method).encode(&mut b, &mut ());
+                //     reverse_encode!(b; $($arg),*);
+
+                //     b = bridge.dispatch.call(b);
+
+                //     let r = Result::<_, PanicMessage>::decode(&mut &b[..], &mut ());
+
+                //     bridge.cached_buffer = b;
+
+                //     r.unwrap_or_else(|e| panic::resume_unwind(e.into()))
+                // })
+            })*
+        })*
+    }
+}
+with_api!(self, self, define_client_side);
+
+enum BridgeState<'a> {
+    /// No server is currently connected to this client.
+    NotConnected,
+
+    /// A server is connected and available for requests.
+    Connected(Bridge<'a>),
+
+    /// Access to the bridge is being exclusively acquired
+    /// (e.g., during `BridgeState::with`).
+    InUse,
+}
+
+enum BridgeStateL {}
+
+impl<'a> scoped_cell::ApplyL<'a> for BridgeStateL {
+    type Out = BridgeState<'a>;
+}
+
+thread_local! {
+    static BRIDGE_STATE: scoped_cell::ScopedCell<BridgeStateL> =
+        scoped_cell::ScopedCell::new(BridgeState::NotConnected);
+}
+
+impl BridgeState<'_> {
+    /// Take exclusive control of the thread-local
+    /// `BridgeState`, and pass it to `f`, mutably.
+    /// The state will be restored after `f` exits, even
+    /// by panic, including modifications made to it by `f`.
+    ///
+    /// N.B., while `f` is running, the thread-local state
+    /// is `BridgeState::InUse`.
+    fn with<R>(f: impl FnOnce(&mut BridgeState<'_>) -> R) -> R {
+        BRIDGE_STATE.with(|state| {
+            state.replace(BridgeState::InUse, |mut state| {
+                // FIXME(#52812) pass `f` directly to `replace` when `RefMutL` is gone
+                f(&mut *state)
+            })
+        })
+    }
+}
+
+impl Bridge<'_> {
+    fn enter<R>(self, f: impl FnOnce() -> R) -> R {
+        // Hide the default panic output within `proc_macro` expansions.
+        // NB. the server can't do this because it may use a different libstd.
+        static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
+        HIDE_PANICS_DURING_EXPANSION.call_once(|| {
+            let prev = panic::take_hook();
+            panic::set_hook(Box::new(move |info| {
+                let hide = BridgeState::with(|state| match state {
+                    BridgeState::NotConnected => false,
+                    BridgeState::Connected(_) | BridgeState::InUse => true,
+                });
+                if !hide {
+                    prev(info)
+                }
+            }));
+        });
+
+        BRIDGE_STATE.with(|state| state.set(BridgeState::Connected(self), f))
+    }
+
+    fn with<R>(f: impl FnOnce(&mut Bridge<'_>) -> R) -> R {
+        BridgeState::with(|state| match state {
+            BridgeState::NotConnected => {
+                panic!("procedural macro API is used outside of a procedural macro");
+            }
+            BridgeState::InUse => {
+                panic!("procedural macro API is used while it's already in use");
+            }
+            BridgeState::Connected(bridge) => f(bridge),
+        })
+    }
+}
+
+/// A client-side "global object" (usually a function pointer),
+/// which may be using a different `proc_macro` from the one
+/// used by the server, but can be interacted with compatibly.
+///
+/// N.B., `F` must have FFI-friendly memory layout (e.g., a pointer).
+/// The call ABI of function pointers used for `F` doesn't
+/// need to match between server and client, since it's only
+/// passed between them and (eventually) called by the client.
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct Client<F> {
+    // FIXME(eddyb) use a reference to the `static COUNTERS`, instead of
+    // a wrapper `fn` pointer, once `const fn` can reference `static`s.
+    pub(super) get_handle_counters: extern "C" fn() -> &'static HandleCounters,
+    pub(super) run: extern "C" fn(Bridge<'_>, F) -> Buffer<u8>,
+    pub(super) f: F,
+}
+
+/// Client-side helper for handling client panics, entering the bridge,
+/// deserializing input and serializing output.
+// FIXME(eddyb) maybe replace `Bridge::enter` with this?
+fn run_client<A: for<'a, 's> DecodeMut<'a, 's, ()>, R: Encode<()>>(
+    mut bridge: Bridge<'_>,
+    f: impl FnOnce(A) -> R,
+) -> Buffer<u8> {
+    // The initial `cached_buffer` contains the input.
+    let mut b = bridge.cached_buffer.take();
+
+    panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        bridge.enter(|| {
+            let reader = &mut &b[..];
+            let input = A::decode(reader, &mut ());
+
+            // Put the `cached_buffer` back in the `Bridge`, for requests.
+            Bridge::with(|bridge| bridge.cached_buffer = b.take());
+
+            let output = f(input);
+
+            // Take the `cached_buffer` back out, for the output value.
+            b = Bridge::with(|bridge| bridge.cached_buffer.take());
+
+            // HACK(eddyb) Separate encoding a success value (`Ok(output)`)
+            // from encoding a panic (`Err(e: PanicMessage)`) to avoid
+            // having handles outside the `bridge.enter(|| ...)` scope, and
+            // to catch panics that could happen while encoding the success.
+            //
+            // Note that panics should be impossible beyond this point, but
+            // this is defensively trying to avoid any accidental panicking
+            // reaching the `extern "C"` (which should `abort` but may not
+            // at the moment, so this is also potentially preventing UB).
+            b.clear();
+            Ok::<_, ()>(output).encode(&mut b, &mut ());
+        })
+    }))
+    .map_err(PanicMessage::from)
+    .unwrap_or_else(|e| {
+        b.clear();
+        Err::<(), _>(e).encode(&mut b, &mut ());
+    });
+    b
+}
+
+impl Client<fn(crate::TokenStream) -> crate::TokenStream> {
+    pub fn expand1(f: fn(crate::TokenStream) -> crate::TokenStream) -> Self {
+        extern "C" fn run(
+            bridge: Bridge<'_>,
+            f: impl FnOnce(crate::TokenStream) -> crate::TokenStream,
+        ) -> Buffer<u8> {
+            run_client(bridge, |input| f(crate::TokenStream(input)).0)
+        }
+        Client { get_handle_counters: HandleCounters::get, run, f }
+    }
+}
+
+impl Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream> {
+    pub fn expand2(f: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream) -> Self {
+        extern "C" fn run(
+            bridge: Bridge<'_>,
+            f: impl FnOnce(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
+        ) -> Buffer<u8> {
+            run_client(bridge, |(input, input2)| {
+                f(crate::TokenStream(input), crate::TokenStream(input2)).0
+            })
+        }
+        Client { get_handle_counters: HandleCounters::get, run, f }
+    }
+}
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub enum ProcMacro {
+    CustomDerive {
+        trait_name: &'static str,
+        attributes: &'static [&'static str],
+        client: Client<fn(crate::TokenStream) -> crate::TokenStream>,
+    },
+
+    Attr {
+        name: &'static str,
+        client: Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream>,
+    },
+
+    Bang {
+        name: &'static str,
+        client: Client<fn(crate::TokenStream) -> crate::TokenStream>,
+    },
+}
+
+impl std::fmt::Debug for ProcMacro {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "ProcMacro {{ name: {} }}", self.name())
+    }
+}
+
+impl ProcMacro {
+    pub fn name(&self) -> &'static str {
+        match self {
+            ProcMacro::CustomDerive { trait_name, .. } => trait_name,
+            ProcMacro::Attr { name, .. } => name,
+            ProcMacro::Bang { name, .. } => name,
+        }
+    }
+
+    pub fn custom_derive(
+        trait_name: &'static str,
+        attributes: &'static [&'static str],
+        expand: fn(crate::TokenStream) -> crate::TokenStream,
+    ) -> Self {
+        ProcMacro::CustomDerive { trait_name, attributes, client: Client::expand1(expand) }
+    }
+
+    pub fn attr(
+        name: &'static str,
+        expand: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
+    ) -> Self {
+        ProcMacro::Attr { name, client: Client::expand2(expand) }
+    }
+
+    pub fn bang(name: &'static str, expand: fn(crate::TokenStream) -> crate::TokenStream) -> Self {
+        ProcMacro::Bang { name, client: Client::expand1(expand) }
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/closure.rs b/crates/proc_macro_srv/src/proc_macro/bridge/closure.rs
new file mode 100644
index 000000000..273a97715
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/closure.rs
@@ -0,0 +1,30 @@
+//! lib-proc-macro Closure type (equivalent to `&mut dyn FnMut(A) -> R`) that's `repr(C)`.
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/closure.rs#
+//! augmented with removing unstable features
+
+#[repr(C)]
+pub struct Closure<'a, A, R> {
+    call: unsafe extern "C" fn(&mut Env, A) -> R,
+    env: &'a mut Env,
+}
+
+struct Env;
+
+// impl<'a, A, R> !Sync for Closure<'a, A, R> {}
+// impl<'a, A, R> !Send for Closure<'a, A, R> {}
+
+impl<'a, A, R, F: FnMut(A) -> R> From<&'a mut F> for Closure<'a, A, R> {
+    fn from(f: &'a mut F) -> Self {
+        unsafe extern "C" fn call<A, R, F: FnMut(A) -> R>(env: &mut Env, arg: A) -> R {
+            (*(env as *mut _ as *mut F))(arg)
+        }
+        Closure { call: call::<A, R, F>, env: unsafe { &mut *(f as *mut _ as *mut Env) } }
+    }
+}
+
+impl<'a, A, R> Closure<'a, A, R> {
+    pub fn call(&mut self, arg: A) -> R {
+        unsafe { (self.call)(self.env, arg) }
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/handle.rs b/crates/proc_macro_srv/src/proc_macro/bridge/handle.rs
new file mode 100644
index 000000000..a2f77b5ac
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/handle.rs
@@ -0,0 +1,73 @@
+//! lib-proc-macro Server-side handles and storage for per-handle data.
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/handle.rs
+//! augmented with removing unstable features
+
+use std::collections::{BTreeMap, HashMap};
+use std::hash::Hash;
+use std::num::NonZeroU32;
+use std::ops::{Index, IndexMut};
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+pub(super) type Handle = NonZeroU32;
+
+pub(super) struct OwnedStore<T: 'static> {
+    counter: &'static AtomicUsize,
+    data: BTreeMap<Handle, T>,
+}
+
+impl<T> OwnedStore<T> {
+    pub(super) fn new(counter: &'static AtomicUsize) -> Self {
+        // Ensure the handle counter isn't 0, which would panic later,
+        // when `NonZeroU32::new` (aka `Handle::new`) is called in `alloc`.
+        assert_ne!(counter.load(Ordering::SeqCst), 0);
+
+        OwnedStore { counter, data: BTreeMap::new() }
+    }
+}
+
+impl<T> OwnedStore<T> {
+    pub(super) fn alloc(&mut self, x: T) -> Handle {
+        let counter = self.counter.fetch_add(1, Ordering::SeqCst);
+        let handle = Handle::new(counter as u32).expect("`proc_macro` handle counter overflowed");
+        assert!(self.data.insert(handle, x).is_none());
+        handle
+    }
+
+    pub(super) fn take(&mut self, h: Handle) -> T {
+        self.data.remove(&h).expect("use-after-free in `proc_macro` handle")
+    }
+}
+
+impl<T> Index<Handle> for OwnedStore<T> {
+    type Output = T;
+    fn index(&self, h: Handle) -> &T {
+        self.data.get(&h).expect("use-after-free in `proc_macro` handle")
+    }
+}
+
+impl<T> IndexMut<Handle> for OwnedStore<T> {
+    fn index_mut(&mut self, h: Handle) -> &mut T {
+        self.data.get_mut(&h).expect("use-after-free in `proc_macro` handle")
+    }
+}
+
+pub(super) struct InternedStore<T: 'static> {
+    owned: OwnedStore<T>,
+    interner: HashMap<T, Handle>,
+}
+
+impl<T: Copy + Eq + Hash> InternedStore<T> {
+    pub(super) fn new(counter: &'static AtomicUsize) -> Self {
+        InternedStore { owned: OwnedStore::new(counter), interner: HashMap::new() }
+    }
+
+    pub(super) fn alloc(&mut self, x: T) -> Handle {
+        let owned = &mut self.owned;
+        *self.interner.entry(x).or_insert_with(|| owned.alloc(x))
+    }
+
+    pub(super) fn copy(&mut self, h: Handle) -> T {
+        self.owned[h]
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/mod.rs b/crates/proc_macro_srv/src/proc_macro/bridge/mod.rs
new file mode 100644
index 000000000..aeb05aad4
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/mod.rs
@@ -0,0 +1,408 @@
+//! lib-proc-macro Internal interface for communicating between a `proc_macro` client
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/mod.rs
+//! augmented with removing unstable features
+//!
+//! Internal interface for communicating between a `proc_macro` client
+//! (a proc macro crate) and a `proc_macro` server (a compiler front-end).
+//!
+//! Serialization (with C ABI buffers) and unique integer handles are employed
+//! to allow safely interfacing between two copies of `proc_macro` built
+//! (from the same source) by different compilers with potentially mismatching
+//! Rust ABIs (e.g., stage0/bin/rustc vs stage1/bin/rustc during bootstrap).
+
+#![deny(unsafe_code)]
+
+pub use crate::proc_macro::{Delimiter, Level, LineColumn, Spacing};
+use std::fmt;
+use std::hash::Hash;
+use std::marker;
+use std::mem;
+use std::ops::Bound;
+use std::panic;
+use std::sync::atomic::AtomicUsize;
+use std::sync::Once;
+use std::thread;
+
+/// Higher-order macro describing the server RPC API, allowing automatic
+/// generation of type-safe Rust APIs, both client-side and server-side.
+///
+/// `with_api!(MySelf, my_self, my_macro)` expands to:
+/// ```rust,ignore (pseudo-code)
+/// my_macro! {
+///     // ...
+///     Literal {
+///         // ...
+///         fn character(ch: char) -> MySelf::Literal;
+///         // ...
+///         fn span(my_self: &MySelf::Literal) -> MySelf::Span;
+///         fn set_span(my_self: &mut MySelf::Literal, span: MySelf::Span);
+///     },
+///     // ...
+/// }
+/// ```
+///
+/// The first two arguments serve to customize the arguments names
+/// and argument/return types, to enable several different usecases:
+///
+/// If `my_self` is just `self`, then each `fn` signature can be used
+/// as-is for a method. If it's anything else (`self_` in practice),
+/// then the signatures don't have a special `self` argument, and
+/// can, therefore, have a different one introduced.
+///
+/// If `MySelf` is just `Self`, then the types are only valid inside
+/// a trait or a trait impl, where the trait has associated types
+/// for each of the API types. If non-associated types are desired,
+/// a module name (`self` in practice) can be used instead of `Self`.
+macro_rules! with_api {
+    ($S:ident, $self:ident, $m:ident) => {
+        $m! {
+            TokenStream {
+                fn drop($self: $S::TokenStream);
+                fn clone($self: &$S::TokenStream) -> $S::TokenStream;
+                fn new() -> $S::TokenStream;
+                fn is_empty($self: &$S::TokenStream) -> bool;
+                fn from_str(src: &str) -> $S::TokenStream;
+                fn to_string($self: &$S::TokenStream) -> String;
+                fn from_token_tree(
+                    tree: TokenTree<$S::Group, $S::Punct, $S::Ident, $S::Literal>,
+                ) -> $S::TokenStream;
+                fn into_iter($self: $S::TokenStream) -> $S::TokenStreamIter;
+            },
+            TokenStreamBuilder {
+                fn drop($self: $S::TokenStreamBuilder);
+                fn new() -> $S::TokenStreamBuilder;
+                fn push($self: &mut $S::TokenStreamBuilder, stream: $S::TokenStream);
+                fn build($self: $S::TokenStreamBuilder) -> $S::TokenStream;
+            },
+            TokenStreamIter {
+                fn drop($self: $S::TokenStreamIter);
+                fn clone($self: &$S::TokenStreamIter) -> $S::TokenStreamIter;
+                fn next(
+                    $self: &mut $S::TokenStreamIter,
+                ) -> Option<TokenTree<$S::Group, $S::Punct, $S::Ident, $S::Literal>>;
+            },
+            Group {
+                fn drop($self: $S::Group);
+                fn clone($self: &$S::Group) -> $S::Group;
+                fn new(delimiter: Delimiter, stream: $S::TokenStream) -> $S::Group;
+                fn delimiter($self: &$S::Group) -> Delimiter;
+                fn stream($self: &$S::Group) -> $S::TokenStream;
+                fn span($self: &$S::Group) -> $S::Span;
+                fn span_open($self: &$S::Group) -> $S::Span;
+                fn span_close($self: &$S::Group) -> $S::Span;
+                fn set_span($self: &mut $S::Group, span: $S::Span);
+            },
+            Punct {
+                fn new(ch: char, spacing: Spacing) -> $S::Punct;
+                fn as_char($self: $S::Punct) -> char;
+                fn spacing($self: $S::Punct) -> Spacing;
+                fn span($self: $S::Punct) -> $S::Span;
+                fn with_span($self: $S::Punct, span: $S::Span) -> $S::Punct;
+            },
+            Ident {
+                fn new(string: &str, span: $S::Span, is_raw: bool) -> $S::Ident;
+                fn span($self: $S::Ident) -> $S::Span;
+                fn with_span($self: $S::Ident, span: $S::Span) -> $S::Ident;
+            },
+            Literal {
+                fn drop($self: $S::Literal);
+                fn clone($self: &$S::Literal) -> $S::Literal;
+                fn debug_kind($self: &$S::Literal) -> String;
+                fn symbol($self: &$S::Literal) -> String;
+                fn suffix($self: &$S::Literal) -> Option<String>;
+                fn integer(n: &str) -> $S::Literal;
+                fn typed_integer(n: &str, kind: &str) -> $S::Literal;
+                fn float(n: &str) -> $S::Literal;
+                fn f32(n: &str) -> $S::Literal;
+                fn f64(n: &str) -> $S::Literal;
+                fn string(string: &str) -> $S::Literal;
+                fn character(ch: char) -> $S::Literal;
+                fn byte_string(bytes: &[u8]) -> $S::Literal;
+                fn span($self: &$S::Literal) -> $S::Span;
+                fn set_span($self: &mut $S::Literal, span: $S::Span);
+                fn subspan(
+                    $self: &$S::Literal,
+                    start: Bound<usize>,
+                    end: Bound<usize>,
+                ) -> Option<$S::Span>;
+            },
+            SourceFile {
+                fn drop($self: $S::SourceFile);
+                fn clone($self: &$S::SourceFile) -> $S::SourceFile;
+                fn eq($self: &$S::SourceFile, other: &$S::SourceFile) -> bool;
+                fn path($self: &$S::SourceFile) -> String;
+                fn is_real($self: &$S::SourceFile) -> bool;
+            },
+            MultiSpan {
+                fn drop($self: $S::MultiSpan);
+                fn new() -> $S::MultiSpan;
+                fn push($self: &mut $S::MultiSpan, span: $S::Span);
+            },
+            Diagnostic {
+                fn drop($self: $S::Diagnostic);
+                fn new(level: Level, msg: &str, span: $S::MultiSpan) -> $S::Diagnostic;
+                fn sub(
+                    $self: &mut $S::Diagnostic,
+                    level: Level,
+                    msg: &str,
+                    span: $S::MultiSpan,
+                );
+                fn emit($self: $S::Diagnostic);
+            },
+            Span {
+                fn debug($self: $S::Span) -> String;
+                fn def_site() -> $S::Span;
+                fn call_site() -> $S::Span;
+                fn mixed_site() -> $S::Span;
+                fn source_file($self: $S::Span) -> $S::SourceFile;
+                fn parent($self: $S::Span) -> Option<$S::Span>;
+                fn source($self: $S::Span) -> $S::Span;
+                fn start($self: $S::Span) -> LineColumn;
+                fn end($self: $S::Span) -> LineColumn;
+                fn join($self: $S::Span, other: $S::Span) -> Option<$S::Span>;
+                fn resolved_at($self: $S::Span, at: $S::Span) -> $S::Span;
+                fn source_text($self: $S::Span) -> Option<String>;
+            },
+        }
+    };
+}
+
+// FIXME(eddyb) this calls `encode` for each argument, but in reverse,
+// to avoid borrow conflicts from borrows started by `&mut` arguments.
+macro_rules! reverse_encode {
+    ($writer:ident;) => {};
+    ($writer:ident; $first:ident $(, $rest:ident)*) => {
+        reverse_encode!($writer; $($rest),*);
+        $first.encode(&mut $writer, &mut ());
+    }
+}
+
+// FIXME(eddyb) this calls `decode` for each argument, but in reverse,
+// to avoid borrow conflicts from borrows started by `&mut` arguments.
+macro_rules! reverse_decode {
+    ($reader:ident, $s:ident;) => {};
+    ($reader:ident, $s:ident; $first:ident: $first_ty:ty $(, $rest:ident: $rest_ty:ty)*) => {
+        reverse_decode!($reader, $s; $($rest: $rest_ty),*);
+        let $first = <$first_ty>::decode(&mut $reader, $s);
+    }
+}
+
+#[allow(unsafe_code)]
+mod buffer;
+#[forbid(unsafe_code)]
+pub mod client;
+#[allow(unsafe_code)]
+mod closure;
+#[forbid(unsafe_code)]
+mod handle;
+#[macro_use]
+#[forbid(unsafe_code)]
+mod rpc;
+#[allow(unsafe_code)]
+mod scoped_cell;
+#[forbid(unsafe_code)]
+pub mod server;
+
+use buffer::Buffer;
+pub use rpc::PanicMessage;
+use rpc::{Decode, DecodeMut, Encode, Reader, Writer};
+
+/// An active connection between a server and a client.
+/// The server creates the bridge (`Bridge::run_server` in `server.rs`),
+/// then passes it to the client through the function pointer in the `run`
+/// field of `client::Client`. The client holds its copy of the `Bridge`
+/// in TLS during its execution (`Bridge::{enter, with}` in `client.rs`).
+#[repr(C)]
+pub struct Bridge<'a> {
+    /// Reusable buffer (only `clear`-ed, never shrunk), primarily
+    /// used for making requests, but also for passing input to client.
+    cached_buffer: Buffer<u8>,
+
+    /// Server-side function that the client uses to make requests.
+    dispatch: closure::Closure<'a, Buffer<u8>, Buffer<u8>>,
+}
+
+// impl<'a> !Sync for Bridge<'a> {}
+// impl<'a> !Send for Bridge<'a> {}
+
+#[forbid(unsafe_code)]
+#[allow(non_camel_case_types)]
+mod api_tags {
+    use super::rpc::{DecodeMut, Encode, Reader, Writer};
+
+    macro_rules! declare_tags {
+        ($($name:ident {
+            $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)*;)*
+        }),* $(,)?) => {
+            $(
+                pub(super) enum $name {
+                    $($method),*
+                }
+                rpc_encode_decode!(enum $name { $($method),* });
+            )*
+
+
+            pub(super) enum Method {
+                $($name($name)),*
+            }
+            rpc_encode_decode!(enum Method { $($name(m)),* });
+        }
+    }
+    with_api!(self, self, declare_tags);
+}
+
+/// Helper to wrap associated types to allow trait impl dispatch.
+/// That is, normally a pair of impls for `T::Foo` and `T::Bar`
+/// can overlap, but if the impls are, instead, on types like
+/// `Marked<T::Foo, Foo>` and `Marked<T::Bar, Bar>`, they can't.
+trait Mark {
+    type Unmarked;
+    fn mark(unmarked: Self::Unmarked) -> Self;
+}
+
+/// Unwrap types wrapped by `Mark::mark` (see `Mark` for details).
+trait Unmark {
+    type Unmarked;
+    fn unmark(self) -> Self::Unmarked;
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+struct Marked<T, M> {
+    value: T,
+    _marker: marker::PhantomData<M>,
+}
+
+impl<T, M> Mark for Marked<T, M> {
+    type Unmarked = T;
+    fn mark(unmarked: Self::Unmarked) -> Self {
+        Marked { value: unmarked, _marker: marker::PhantomData }
+    }
+}
+impl<T, M> Unmark for Marked<T, M> {
+    type Unmarked = T;
+    fn unmark(self) -> Self::Unmarked {
+        self.value
+    }
+}
+impl<'a, T, M> Unmark for &'a Marked<T, M> {
+    type Unmarked = &'a T;
+    fn unmark(self) -> Self::Unmarked {
+        &self.value
+    }
+}
+impl<'a, T, M> Unmark for &'a mut Marked<T, M> {
+    type Unmarked = &'a mut T;
+    fn unmark(self) -> Self::Unmarked {
+        &mut self.value
+    }
+}
+
+impl<T: Mark> Mark for Option<T> {
+    type Unmarked = Option<T::Unmarked>;
+    fn mark(unmarked: Self::Unmarked) -> Self {
+        unmarked.map(T::mark)
+    }
+}
+impl<T: Unmark> Unmark for Option<T> {
+    type Unmarked = Option<T::Unmarked>;
+    fn unmark(self) -> Self::Unmarked {
+        self.map(T::unmark)
+    }
+}
+
+macro_rules! mark_noop {
+    ($($ty:ty),* $(,)?) => {
+        $(
+            impl Mark for $ty {
+                type Unmarked = Self;
+                fn mark(unmarked: Self::Unmarked) -> Self {
+                    unmarked
+                }
+            }
+            impl Unmark for $ty {
+                type Unmarked = Self;
+                fn unmark(self) -> Self::Unmarked {
+                    self
+                }
+            }
+        )*
+    }
+}
+mark_noop! {
+    (),
+    bool,
+    char,
+    &'_ [u8],
+    &'_ str,
+    String,
+    Delimiter,
+    Level,
+    LineColumn,
+    Spacing,
+    Bound<usize>,
+}
+
+rpc_encode_decode!(
+    enum Delimiter {
+        Parenthesis,
+        Brace,
+        Bracket,
+        None,
+    }
+);
+rpc_encode_decode!(
+    enum Level {
+        Error,
+        Warning,
+        Note,
+        Help,
+    }
+);
+rpc_encode_decode!(struct LineColumn { line, column });
+rpc_encode_decode!(
+    enum Spacing {
+        Alone,
+        Joint,
+    }
+);
+
+#[derive(Clone)]
+pub enum TokenTree<G, P, I, L> {
+    Group(G),
+    Punct(P),
+    Ident(I),
+    Literal(L),
+}
+
+impl<G: Mark, P: Mark, I: Mark, L: Mark> Mark for TokenTree<G, P, I, L> {
+    type Unmarked = TokenTree<G::Unmarked, P::Unmarked, I::Unmarked, L::Unmarked>;
+    fn mark(unmarked: Self::Unmarked) -> Self {
+        match unmarked {
+            TokenTree::Group(tt) => TokenTree::Group(G::mark(tt)),
+            TokenTree::Punct(tt) => TokenTree::Punct(P::mark(tt)),
+            TokenTree::Ident(tt) => TokenTree::Ident(I::mark(tt)),
+            TokenTree::Literal(tt) => TokenTree::Literal(L::mark(tt)),
+        }
+    }
+}
+impl<G: Unmark, P: Unmark, I: Unmark, L: Unmark> Unmark for TokenTree<G, P, I, L> {
+    type Unmarked = TokenTree<G::Unmarked, P::Unmarked, I::Unmarked, L::Unmarked>;
+    fn unmark(self) -> Self::Unmarked {
+        match self {
+            TokenTree::Group(tt) => TokenTree::Group(tt.unmark()),
+            TokenTree::Punct(tt) => TokenTree::Punct(tt.unmark()),
+            TokenTree::Ident(tt) => TokenTree::Ident(tt.unmark()),
+            TokenTree::Literal(tt) => TokenTree::Literal(tt.unmark()),
+        }
+    }
+}
+
+rpc_encode_decode!(
+    enum TokenTree<G, P, I, L> {
+        Group(tt),
+        Punct(tt),
+        Ident(tt),
+        Literal(tt),
+    }
+);
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/rpc.rs b/crates/proc_macro_srv/src/proc_macro/bridge/rpc.rs
new file mode 100644
index 000000000..3528d5c99
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/rpc.rs
@@ -0,0 +1,311 @@
+//! lib-proc-macro Serialization for client-server communication.
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/rpc.rs
+//! augmented with removing unstable features
+//!
+//! Serialization for client-server communication.
+
+use std::any::Any;
+use std::char;
+use std::io::Write;
+use std::num::NonZeroU32;
+use std::ops::Bound;
+use std::str;
+
+pub(super) type Writer = super::buffer::Buffer<u8>;
+
+pub(super) trait Encode<S>: Sized {
+    fn encode(self, w: &mut Writer, s: &mut S);
+}
+
+pub(super) type Reader<'a> = &'a [u8];
+
+pub(super) trait Decode<'a, 's, S>: Sized {
+    fn decode(r: &mut Reader<'a>, s: &'s S) -> Self;
+}
+
+pub(super) trait DecodeMut<'a, 's, S>: Sized {
+    fn decode(r: &mut Reader<'a>, s: &'s mut S) -> Self;
+}
+
+macro_rules! rpc_encode_decode {
+    (le $ty:ty) => {
+        impl<S> Encode<S> for $ty {
+            fn encode(self, w: &mut Writer, _: &mut S) {
+                w.write_all(&self.to_le_bytes()).unwrap();
+            }
+        }
+
+        impl<S> DecodeMut<'_, '_, S> for $ty {
+            fn decode(r: &mut Reader<'_>, _: &mut S) -> Self {
+                const N: usize = ::std::mem::size_of::<$ty>();
+
+                let mut bytes = [0; N];
+                bytes.copy_from_slice(&r[..N]);
+                *r = &r[N..];
+
+                Self::from_le_bytes(bytes)
+            }
+        }
+    };
+    (struct $name:ident { $($field:ident),* $(,)? }) => {
+        impl<S> Encode<S> for $name {
+            fn encode(self, w: &mut Writer, s: &mut S) {
+                $(self.$field.encode(w, s);)*
+            }
+        }
+
+        impl<S> DecodeMut<'_, '_, S> for $name {
+            fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+                $name {
+                    $($field: DecodeMut::decode(r, s)),*
+                }
+            }
+        }
+    };
+    (enum $name:ident $(<$($T:ident),+>)? { $($variant:ident $(($field:ident))*),* $(,)? }) => {
+        impl<S, $($($T: Encode<S>),+)?> Encode<S> for $name $(<$($T),+>)? {
+            fn encode(self, w: &mut Writer, s: &mut S) {
+                // HACK(eddyb): `Tag` enum duplicated between the
+                // two impls as there's no other place to stash it.
+                #[allow(non_upper_case_globals)]
+                mod tag {
+                    #[repr(u8)] enum Tag { $($variant),* }
+
+                    $(pub const $variant: u8 = Tag::$variant as u8;)*
+                }
+
+                match self {
+                    $($name::$variant $(($field))* => {
+                        tag::$variant.encode(w, s);
+                        $($field.encode(w, s);)*
+                    })*
+                }
+            }
+        }
+
+        impl<'a, S, $($($T: for<'s> DecodeMut<'a, 's, S>),+)?> DecodeMut<'a, '_, S>
+            for $name $(<$($T),+>)?
+        {
+            fn decode(r: &mut Reader<'a>, s: &mut S) -> Self {
+                // HACK(eddyb): `Tag` enum duplicated between the
+                // two impls as there's no other place to stash it.
+                #[allow(non_upper_case_globals)]
+                mod tag {
+                    #[repr(u8)] enum Tag { $($variant),* }
+
+                    $(pub const $variant: u8 = Tag::$variant as u8;)*
+                }
+
+                match u8::decode(r, s) {
+                    $(tag::$variant => {
+                        $(let $field = DecodeMut::decode(r, s);)*
+                        $name::$variant $(($field))*
+                    })*
+                    _ => unreachable!(),
+                }
+            }
+        }
+    }
+}
+
+impl<S> Encode<S> for () {
+    fn encode(self, _: &mut Writer, _: &mut S) {}
+}
+
+impl<S> DecodeMut<'_, '_, S> for () {
+    fn decode(_: &mut Reader<'_>, _: &mut S) -> Self {}
+}
+
+impl<S> Encode<S> for u8 {
+    fn encode(self, w: &mut Writer, _: &mut S) {
+        w.write_all(&[self]).unwrap();
+    }
+}
+
+impl<S> DecodeMut<'_, '_, S> for u8 {
+    fn decode(r: &mut Reader<'_>, _: &mut S) -> Self {
+        let x = r[0];
+        *r = &r[1..];
+        x
+    }
+}
+
+rpc_encode_decode!(le u32);
+rpc_encode_decode!(le usize);
+
+impl<S> Encode<S> for bool {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        (self as u8).encode(w, s);
+    }
+}
+
+impl<S> DecodeMut<'_, '_, S> for bool {
+    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+        match u8::decode(r, s) {
+            0 => false,
+            1 => true,
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl<S> Encode<S> for char {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        (self as u32).encode(w, s);
+    }
+}
+
+impl<S> DecodeMut<'_, '_, S> for char {
+    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+        char::from_u32(u32::decode(r, s)).unwrap()
+    }
+}
+
+impl<S> Encode<S> for NonZeroU32 {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        self.get().encode(w, s);
+    }
+}
+
+impl<S> DecodeMut<'_, '_, S> for NonZeroU32 {
+    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+        Self::new(u32::decode(r, s)).unwrap()
+    }
+}
+
+impl<S, A: Encode<S>, B: Encode<S>> Encode<S> for (A, B) {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        self.0.encode(w, s);
+        self.1.encode(w, s);
+    }
+}
+
+impl<'a, S, A: for<'s> DecodeMut<'a, 's, S>, B: for<'s> DecodeMut<'a, 's, S>> DecodeMut<'a, '_, S>
+    for (A, B)
+{
+    fn decode(r: &mut Reader<'a>, s: &mut S) -> Self {
+        (DecodeMut::decode(r, s), DecodeMut::decode(r, s))
+    }
+}
+
+rpc_encode_decode!(
+    enum Bound<T> {
+        Included(x),
+        Excluded(x),
+        Unbounded,
+    }
+);
+
+rpc_encode_decode!(
+    enum Option<T> {
+        None,
+        Some(x),
+    }
+);
+
+rpc_encode_decode!(
+    enum Result<T, E> {
+        Ok(x),
+        Err(e),
+    }
+);
+
+impl<S> Encode<S> for &[u8] {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        self.len().encode(w, s);
+        w.write_all(self).unwrap();
+    }
+}
+
+impl<'a, S> DecodeMut<'a, '_, S> for &'a [u8] {
+    fn decode(r: &mut Reader<'a>, s: &mut S) -> Self {
+        let len = usize::decode(r, s);
+        let xs = &r[..len];
+        *r = &r[len..];
+        xs
+    }
+}
+
+impl<S> Encode<S> for &str {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        self.as_bytes().encode(w, s);
+    }
+}
+
+impl<'a, S> DecodeMut<'a, '_, S> for &'a str {
+    fn decode(r: &mut Reader<'a>, s: &mut S) -> Self {
+        str::from_utf8(<&[u8]>::decode(r, s)).unwrap()
+    }
+}
+
+impl<S> Encode<S> for String {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        self[..].encode(w, s);
+    }
+}
+
+impl<S> DecodeMut<'_, '_, S> for String {
+    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+        <&str>::decode(r, s).to_string()
+    }
+}
+
+/// Simplied version of panic payloads, ignoring
+/// types other than `&'static str` and `String`.
+#[derive(Debug)]
+pub enum PanicMessage {
+    StaticStr(&'static str),
+    String(String),
+    Unknown,
+}
+
+impl From<Box<dyn Any + Send>> for PanicMessage {
+    fn from(payload: Box<dyn Any + Send + 'static>) -> Self {
+        if let Some(s) = payload.downcast_ref::<&'static str>() {
+            return PanicMessage::StaticStr(s);
+        }
+        if let Ok(s) = payload.downcast::<String>() {
+            return PanicMessage::String(*s);
+        }
+        PanicMessage::Unknown
+    }
+}
+
+impl Into<Box<dyn Any + Send>> for PanicMessage {
+    fn into(self) -> Box<dyn Any + Send> {
+        match self {
+            PanicMessage::StaticStr(s) => Box::new(s),
+            PanicMessage::String(s) => Box::new(s),
+            PanicMessage::Unknown => {
+                struct UnknownPanicMessage;
+                Box::new(UnknownPanicMessage)
+            }
+        }
+    }
+}
+
+impl PanicMessage {
+    pub fn as_str(&self) -> Option<&str> {
+        match self {
+            PanicMessage::StaticStr(s) => Some(s),
+            PanicMessage::String(s) => Some(s),
+            PanicMessage::Unknown => None,
+        }
+    }
+}
+
+impl<S> Encode<S> for PanicMessage {
+    fn encode(self, w: &mut Writer, s: &mut S) {
+        self.as_str().encode(w, s);
+    }
+}
+
+impl<S> DecodeMut<'_, '_, S> for PanicMessage {
+    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
+        match Option::<String>::decode(r, s) {
+            Some(s) => PanicMessage::String(s),
+            None => PanicMessage::Unknown,
+        }
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/scoped_cell.rs b/crates/proc_macro_srv/src/proc_macro/bridge/scoped_cell.rs
new file mode 100644
index 000000000..6ef7ea43c
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/scoped_cell.rs
@@ -0,0 +1,84 @@
+//! lib-proc-macro `Cell` variant for (scoped) existential lifetimes.
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/scoped_cell.rs#L1
+//! augmented with removing unstable features
+
+use std::cell::Cell;
+use std::mem;
+use std::ops::{Deref, DerefMut};
+
+/// Type lambda application, with a lifetime.
+#[allow(unused_lifetimes)]
+pub trait ApplyL<'a> {
+    type Out;
+}
+
+/// Type lambda taking a lifetime, i.e., `Lifetime -> Type`.
+pub trait LambdaL: for<'a> ApplyL<'a> {}
+
+impl<T: for<'a> ApplyL<'a>> LambdaL for T {}
+
+// HACK(eddyb) work around projection limitations with a newtype
+// FIXME(#52812) replace with `&'a mut <T as ApplyL<'b>>::Out`
+pub struct RefMutL<'a, 'b, T: LambdaL>(&'a mut <T as ApplyL<'b>>::Out);
+
+impl<'a, 'b, T: LambdaL> Deref for RefMutL<'a, 'b, T> {
+    type Target = <T as ApplyL<'b>>::Out;
+    fn deref(&self) -> &Self::Target {
+        self.0
+    }
+}
+
+impl<'a, 'b, T: LambdaL> DerefMut for RefMutL<'a, 'b, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.0
+    }
+}
+
+pub struct ScopedCell<T: LambdaL>(Cell<<T as ApplyL<'static>>::Out>);
+
+impl<T: LambdaL> ScopedCell<T> {
+    pub fn new(value: <T as ApplyL<'static>>::Out) -> Self {
+        ScopedCell(Cell::new(value))
+    }
+
+    /// Sets the value in `self` to `replacement` while
+    /// running `f`, which gets the old value, mutably.
+    /// The old value will be restored after `f` exits, even
+    /// by panic, including modifications made to it by `f`.
+    pub fn replace<'a, R>(
+        &self,
+        replacement: <T as ApplyL<'a>>::Out,
+        f: impl for<'b, 'c> FnOnce(RefMutL<'b, 'c, T>) -> R,
+    ) -> R {
+        /// Wrapper that ensures that the cell always gets filled
+        /// (with the original state, optionally changed by `f`),
+        /// even if `f` had panicked.
+        struct PutBackOnDrop<'a, T: LambdaL> {
+            cell: &'a ScopedCell<T>,
+            value: Option<<T as ApplyL<'static>>::Out>,
+        }
+
+        impl<'a, T: LambdaL> Drop for PutBackOnDrop<'a, T> {
+            fn drop(&mut self) {
+                self.cell.0.set(self.value.take().unwrap());
+            }
+        }
+
+        let mut put_back_on_drop = PutBackOnDrop {
+            cell: self,
+            value: Some(self.0.replace(unsafe {
+                let erased = mem::transmute_copy(&replacement);
+                mem::forget(replacement);
+                erased
+            })),
+        };
+
+        f(RefMutL(put_back_on_drop.value.as_mut().unwrap()))
+    }
+
+    /// Sets the value in `self` to `value` while running `f`.
+    pub fn set<R>(&self, value: <T as ApplyL<'_>>::Out, f: impl FnOnce() -> R) -> R {
+        self.replace(value, |_| f())
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/bridge/server.rs b/crates/proc_macro_srv/src/proc_macro/bridge/server.rs
new file mode 100644
index 000000000..45d41ac02
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/bridge/server.rs
@@ -0,0 +1,323 @@
+//! lib-proc-macro server-side traits
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/server.rs
+//! augmented with removing unstable features
+
+use super::*;
+
+// FIXME(eddyb) generate the definition of `HandleStore` in `server.rs`.
+use super::client::HandleStore;
+
+/// Declare an associated item of one of the traits below, optionally
+/// adjusting it (i.e., adding bounds to types and default bodies to methods).
+macro_rules! associated_item {
+    (type TokenStream) =>
+        (type TokenStream: 'static + Clone;);
+    (type TokenStreamBuilder) =>
+        (type TokenStreamBuilder: 'static;);
+    (type TokenStreamIter) =>
+        (type TokenStreamIter: 'static + Clone;);
+    (type Group) =>
+        (type Group: 'static + Clone;);
+    (type Punct) =>
+        (type Punct: 'static + Copy + Eq + Hash;);
+    (type Ident) =>
+        (type Ident: 'static + Copy + Eq + Hash;);
+    (type Literal) =>
+        (type Literal: 'static + Clone;);
+    (type SourceFile) =>
+        (type SourceFile: 'static + Clone;);
+    (type MultiSpan) =>
+        (type MultiSpan: 'static;);
+    (type Diagnostic) =>
+        (type Diagnostic: 'static;);
+    (type Span) =>
+        (type Span: 'static + Copy + Eq + Hash;);
+    (fn drop(&mut self, $arg:ident: $arg_ty:ty)) =>
+        (fn drop(&mut self, $arg: $arg_ty) { mem::drop($arg) });
+    (fn clone(&mut self, $arg:ident: $arg_ty:ty) -> $ret_ty:ty) =>
+        (fn clone(&mut self, $arg: $arg_ty) -> $ret_ty { $arg.clone() });
+    ($($item:tt)*) => ($($item)*;)
+}
+
+macro_rules! declare_server_traits {
+    ($($name:ident {
+        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)?;)*
+    }),* $(,)?) => {
+        pub trait Types {
+            $(associated_item!(type $name);)*
+        }
+
+        $(pub trait $name: Types {
+            $(associated_item!(fn $method(&mut self, $($arg: $arg_ty),*) $(-> $ret_ty)?);)*
+        })*
+
+        pub trait Server: Types $(+ $name)* {}
+        impl<S: Types $(+ $name)*> Server for S {}
+    }
+}
+with_api!(Self, self_, declare_server_traits);
+
+pub(super) struct MarkedTypes<S: Types>(S);
+
+macro_rules! define_mark_types_impls {
+    ($($name:ident {
+        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)?;)*
+    }),* $(,)?) => {
+        impl<S: Types> Types for MarkedTypes<S> {
+            $(type $name = Marked<S::$name, client::$name>;)*
+        }
+
+        $(impl<S: $name> $name for MarkedTypes<S> {
+            $(fn $method(&mut self, $($arg: $arg_ty),*) $(-> $ret_ty)? {
+                <_>::mark($name::$method(&mut self.0, $($arg.unmark()),*))
+            })*
+        })*
+    }
+}
+with_api!(Self, self_, define_mark_types_impls);
+
+struct Dispatcher<S: Types> {
+    handle_store: HandleStore<S>,
+    server: S,
+}
+
+macro_rules! define_dispatcher_impl {
+    ($($name:ident {
+        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)?;)*
+    }),* $(,)?) => {
+        // FIXME(eddyb) `pub` only for `ExecutionStrategy` below.
+        pub trait DispatcherTrait {
+            // HACK(eddyb) these are here to allow `Self::$name` to work below.
+            $(type $name;)*
+            fn dispatch(&mut self, b: Buffer<u8>) -> Buffer<u8>;
+        }
+
+        impl<S: Server> DispatcherTrait for Dispatcher<MarkedTypes<S>> {
+            $(type $name = <MarkedTypes<S> as Types>::$name;)*
+            fn dispatch(&mut self, mut b: Buffer<u8>) -> Buffer<u8> {
+                let Dispatcher { handle_store, server } = self;
+
+                let mut reader = &b[..];
+                match api_tags::Method::decode(&mut reader, &mut ()) {
+                    $(api_tags::Method::$name(m) => match m {
+                        $(api_tags::$name::$method => {
+                            let mut call_method = || {
+                                reverse_decode!(reader, handle_store; $($arg: $arg_ty),*);
+                                $name::$method(server, $($arg),*)
+                            };
+                            // HACK(eddyb) don't use `panic::catch_unwind` in a panic.
+                            // If client and server happen to use the same `libstd`,
+                            // `catch_unwind` asserts that the panic counter was 0,
+                            // even when the closure passed to it didn't panic.
+                            let r = if thread::panicking() {
+                                Ok(call_method())
+                            } else {
+                                panic::catch_unwind(panic::AssertUnwindSafe(call_method))
+                                    .map_err(PanicMessage::from)
+                            };
+
+                            b.clear();
+                            r.encode(&mut b, handle_store);
+                        })*
+                    }),*
+                }
+                b
+            }
+        }
+    }
+}
+with_api!(Self, self_, define_dispatcher_impl);
+
+pub trait ExecutionStrategy {
+    fn run_bridge_and_client<D: Copy + Send + 'static>(
+        &self,
+        dispatcher: &mut impl DispatcherTrait,
+        input: Buffer<u8>,
+        run_client: extern "C" fn(Bridge<'_>, D) -> Buffer<u8>,
+        client_data: D,
+    ) -> Buffer<u8>;
+}
+
+pub struct SameThread;
+
+impl ExecutionStrategy for SameThread {
+    fn run_bridge_and_client<D: Copy + Send + 'static>(
+        &self,
+        dispatcher: &mut impl DispatcherTrait,
+        input: Buffer<u8>,
+        run_client: extern "C" fn(Bridge<'_>, D) -> Buffer<u8>,
+        client_data: D,
+    ) -> Buffer<u8> {
+        let mut dispatch = |b| dispatcher.dispatch(b);
+
+        run_client(Bridge { cached_buffer: input, dispatch: (&mut dispatch).into() }, client_data)
+    }
+}
+
+// NOTE(eddyb) Two implementations are provided, the second one is a bit
+// faster but neither is anywhere near as fast as same-thread execution.
+
+pub struct CrossThread1;
+
+impl ExecutionStrategy for CrossThread1 {
+    fn run_bridge_and_client<D: Copy + Send + 'static>(
+        &self,
+        dispatcher: &mut impl DispatcherTrait,
+        input: Buffer<u8>,
+        run_client: extern "C" fn(Bridge<'_>, D) -> Buffer<u8>,
+        client_data: D,
+    ) -> Buffer<u8> {
+        use std::sync::mpsc::channel;
+
+        let (req_tx, req_rx) = channel();
+        let (res_tx, res_rx) = channel();
+
+        let join_handle = thread::spawn(move || {
+            let mut dispatch = |b| {
+                req_tx.send(b).unwrap();
+                res_rx.recv().unwrap()
+            };
+
+            run_client(
+                Bridge { cached_buffer: input, dispatch: (&mut dispatch).into() },
+                client_data,
+            )
+        });
+
+        for b in req_rx {
+            res_tx.send(dispatcher.dispatch(b)).unwrap();
+        }
+
+        join_handle.join().unwrap()
+    }
+}
+
+pub struct CrossThread2;
+
+impl ExecutionStrategy for CrossThread2 {
+    fn run_bridge_and_client<D: Copy + Send + 'static>(
+        &self,
+        dispatcher: &mut impl DispatcherTrait,
+        input: Buffer<u8>,
+        run_client: extern "C" fn(Bridge<'_>, D) -> Buffer<u8>,
+        client_data: D,
+    ) -> Buffer<u8> {
+        use std::sync::{Arc, Mutex};
+
+        enum State<T> {
+            Req(T),
+            Res(T),
+        }
+
+        let mut state = Arc::new(Mutex::new(State::Res(Buffer::new())));
+
+        let server_thread = thread::current();
+        let state2 = state.clone();
+        let join_handle = thread::spawn(move || {
+            let mut dispatch = |b| {
+                *state2.lock().unwrap() = State::Req(b);
+                server_thread.unpark();
+                loop {
+                    thread::park();
+                    if let State::Res(b) = &mut *state2.lock().unwrap() {
+                        break b.take();
+                    }
+                }
+            };
+
+            let r = run_client(
+                Bridge { cached_buffer: input, dispatch: (&mut dispatch).into() },
+                client_data,
+            );
+
+            // Wake up the server so it can exit the dispatch loop.
+            drop(state2);
+            server_thread.unpark();
+
+            r
+        });
+
+        // Check whether `state2` was dropped, to know when to stop.
+        while Arc::get_mut(&mut state).is_none() {
+            thread::park();
+            let mut b = match &mut *state.lock().unwrap() {
+                State::Req(b) => b.take(),
+                _ => continue,
+            };
+            b = dispatcher.dispatch(b.take());
+            *state.lock().unwrap() = State::Res(b);
+            join_handle.thread().unpark();
+        }
+
+        join_handle.join().unwrap()
+    }
+}
+
+fn run_server<
+    S: Server,
+    I: Encode<HandleStore<MarkedTypes<S>>>,
+    O: for<'a, 's> DecodeMut<'a, 's, HandleStore<MarkedTypes<S>>>,
+    D: Copy + Send + 'static,
+>(
+    strategy: &impl ExecutionStrategy,
+    handle_counters: &'static client::HandleCounters,
+    server: S,
+    input: I,
+    run_client: extern "C" fn(Bridge<'_>, D) -> Buffer<u8>,
+    client_data: D,
+) -> Result<O, PanicMessage> {
+    let mut dispatcher =
+        Dispatcher { handle_store: HandleStore::new(handle_counters), server: MarkedTypes(server) };
+
+    let mut b = Buffer::new();
+    input.encode(&mut b, &mut dispatcher.handle_store);
+
+    b = strategy.run_bridge_and_client(&mut dispatcher, b, run_client, client_data);
+
+    Result::decode(&mut &b[..], &mut dispatcher.handle_store)
+}
+
+impl client::Client<fn(crate::TokenStream) -> crate::TokenStream> {
+    pub fn run<S: Server>(
+        &self,
+        strategy: &impl ExecutionStrategy,
+        server: S,
+        input: S::TokenStream,
+    ) -> Result<S::TokenStream, PanicMessage> {
+        let client::Client { get_handle_counters, run, f } = *self;
+        run_server(
+            strategy,
+            get_handle_counters(),
+            server,
+            <MarkedTypes<S> as Types>::TokenStream::mark(input),
+            run,
+            f,
+        )
+        .map(<MarkedTypes<S> as Types>::TokenStream::unmark)
+    }
+}
+
+impl client::Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream> {
+    pub fn run<S: Server>(
+        &self,
+        strategy: &impl ExecutionStrategy,
+        server: S,
+        input: S::TokenStream,
+        input2: S::TokenStream,
+    ) -> Result<S::TokenStream, PanicMessage> {
+        let client::Client { get_handle_counters, run, f } = *self;
+        run_server(
+            strategy,
+            get_handle_counters(),
+            server,
+            (
+                <MarkedTypes<S> as Types>::TokenStream::mark(input),
+                <MarkedTypes<S> as Types>::TokenStream::mark(input2),
+            ),
+            run,
+            f,
+        )
+        .map(<MarkedTypes<S> as Types>::TokenStream::unmark)
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/diagnostic.rs b/crates/proc_macro_srv/src/proc_macro/diagnostic.rs
new file mode 100644
index 000000000..55d93917c
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/diagnostic.rs
@@ -0,0 +1,172 @@
+//! lib-proc-macro diagnostic
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/diagnostic.rs
+//! augmented with removing unstable features
+
+use crate::proc_macro::Span;
+
+/// An enum representing a diagnostic level.
+#[derive(Copy, Clone, Debug)]
+#[non_exhaustive]
+pub enum Level {
+    /// An error.
+    Error,
+    /// A warning.
+    Warning,
+    /// A note.
+    Note,
+    /// A help message.
+    Help,
+}
+
+/// Trait implemented by types that can be converted into a set of `Span`s.
+pub trait MultiSpan {
+    /// Converts `self` into a `Vec<Span>`.
+    fn into_spans(self) -> Vec<Span>;
+}
+
+impl MultiSpan for Span {
+    fn into_spans(self) -> Vec<Span> {
+        vec![self]
+    }
+}
+
+impl MultiSpan for Vec<Span> {
+    fn into_spans(self) -> Vec<Span> {
+        self
+    }
+}
+
+impl<'a> MultiSpan for &'a [Span] {
+    fn into_spans(self) -> Vec<Span> {
+        self.to_vec()
+    }
+}
+
+/// A structure representing a diagnostic message and associated children
+/// messages.
+#[derive(Clone, Debug)]
+pub struct Diagnostic {
+    level: Level,
+    message: String,
+    spans: Vec<Span>,
+    children: Vec<Diagnostic>,
+}
+
+macro_rules! diagnostic_child_methods {
+    ($spanned:ident, $regular:ident, $level:expr) => {
+        /// Adds a new child diagnostic message to `self` with the level
+        /// identified by this method's name with the given `spans` and
+        /// `message`.
+        pub fn $spanned<S, T>(mut self, spans: S, message: T) -> Diagnostic
+        where
+            S: MultiSpan,
+            T: Into<String>,
+        {
+            self.children.push(Diagnostic::spanned(spans, $level, message));
+            self
+        }
+
+        /// Adds a new child diagnostic message to `self` with the level
+        /// identified by this method's name with the given `message`.
+        pub fn $regular<T: Into<String>>(mut self, message: T) -> Diagnostic {
+            self.children.push(Diagnostic::new($level, message));
+            self
+        }
+    };
+}
+
+/// Iterator over the children diagnostics of a `Diagnostic`.
+#[derive(Debug, Clone)]
+pub struct Children<'a>(std::slice::Iter<'a, Diagnostic>);
+
+impl<'a> Iterator for Children<'a> {
+    type Item = &'a Diagnostic;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+}
+
+impl Diagnostic {
+    /// Creates a new diagnostic with the given `level` and `message`.
+    pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
+        Diagnostic { level: level, message: message.into(), spans: vec![], children: vec![] }
+    }
+
+    /// Creates a new diagnostic with the given `level` and `message` pointing to
+    /// the given set of `spans`.
+    pub fn spanned<S, T>(spans: S, level: Level, message: T) -> Diagnostic
+    where
+        S: MultiSpan,
+        T: Into<String>,
+    {
+        Diagnostic {
+            level: level,
+            message: message.into(),
+            spans: spans.into_spans(),
+            children: vec![],
+        }
+    }
+
+    diagnostic_child_methods!(span_error, error, Level::Error);
+    diagnostic_child_methods!(span_warning, warning, Level::Warning);
+    diagnostic_child_methods!(span_note, note, Level::Note);
+    diagnostic_child_methods!(span_help, help, Level::Help);
+
+    /// Returns the diagnostic `level` for `self`.
+    pub fn level(&self) -> Level {
+        self.level
+    }
+
+    /// Sets the level in `self` to `level`.
+    pub fn set_level(&mut self, level: Level) {
+        self.level = level;
+    }
+
+    /// Returns the message in `self`.
+    pub fn message(&self) -> &str {
+        &self.message
+    }
+
+    /// Sets the message in `self` to `message`.
+    pub fn set_message<T: Into<String>>(&mut self, message: T) {
+        self.message = message.into();
+    }
+
+    /// Returns the `Span`s in `self`.
+    pub fn spans(&self) -> &[Span] {
+        &self.spans
+    }
+
+    /// Sets the `Span`s in `self` to `spans`.
+    pub fn set_spans<S: MultiSpan>(&mut self, spans: S) {
+        self.spans = spans.into_spans();
+    }
+
+    /// Returns an iterator over the children diagnostics of `self`.
+    pub fn children(&self) -> Children<'_> {
+        Children(self.children.iter())
+    }
+
+    /// Emit the diagnostic.
+    pub fn emit(self) {
+        fn to_internal(spans: Vec<Span>) -> crate::proc_macro::bridge::client::MultiSpan {
+            let mut multi_span = crate::proc_macro::bridge::client::MultiSpan::new();
+            for span in spans {
+                multi_span.push(span.0);
+            }
+            multi_span
+        }
+
+        let mut diag = crate::proc_macro::bridge::client::Diagnostic::new(
+            self.level,
+            &self.message[..],
+            to_internal(self.spans),
+        );
+        for c in self.children {
+            diag.sub(c.level, &c.message[..], to_internal(c.spans));
+        }
+        diag.emit();
+    }
+}
diff --git a/crates/proc_macro_srv/src/proc_macro/mod.rs b/crates/proc_macro_srv/src/proc_macro/mod.rs
new file mode 100644
index 000000000..ee0dc9722
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/mod.rs
@@ -0,0 +1,926 @@
+//! lib-proc-macro main module
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/lib.rs
+//! augmented with removing unstable features
+
+// NOTE(@edwin0cheng):
+// Because we just copy the bridge module from rustc for ABI compatible
+// There are some unused stuffs inside it.
+// We suppress these warning here.
+#[doc(hidden)]
+#[allow(unused_macros)]
+#[allow(unused_variables)]
+pub mod bridge;
+
+mod diagnostic;
+
+pub use diagnostic::{Diagnostic, Level, MultiSpan};
+
+use std::ops::{Bound, RangeBounds};
+use std::path::PathBuf;
+use std::str::FromStr;
+use std::{fmt, iter, mem};
+
+/// The main type provided by this crate, representing an abstract stream of
+/// tokens, or, more specifically, a sequence of token trees.
+/// The type provide interfaces for iterating over those token trees and, conversely,
+/// collecting a number of token trees into one stream.
+///
+/// This is both the input and output of `#[proc_macro]`, `#[proc_macro_attribute]`
+/// and `#[proc_macro_derive]` definitions.
+#[derive(Clone)]
+pub struct TokenStream(bridge::client::TokenStream);
+
+/// Error returned from `TokenStream::from_str`
+#[derive(Debug)]
+pub struct LexError {
+    _inner: (),
+}
+
+impl TokenStream {
+    /// Returns an empty `TokenStream` containing no token trees.
+    pub fn new() -> TokenStream {
+        TokenStream(bridge::client::TokenStream::new())
+    }
+
+    /// Checks if this `TokenStream` is empty.
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+}
+
+/// Attempts to break the string into tokens and parse those tokens into a token stream.
+/// May fail for a number of reasons, for example, if the string contains unbalanced delimiters
+/// or characters not existing in the language.
+/// All tokens in the parsed stream get `Span::call_site()` spans.
+///
+/// NOTE: some errors may cause panics instead of returning `LexError`. We reserve the right to
+/// change these errors into `LexError`s later.
+impl FromStr for TokenStream {
+    type Err = LexError;
+
+    fn from_str(src: &str) -> Result<TokenStream, LexError> {
+        Ok(TokenStream(bridge::client::TokenStream::from_str(src)))
+    }
+}
+
+// N.B., the bridge only provides `to_string`, implement `fmt::Display`
+// based on it (the reverse of the usual relationship between the two).
+// impl ToString for TokenStream {
+//     fn to_string(&self) -> String {
+//         self.0.to_string()
+//     }
+// }
+
+/// Prints the token stream as a string that is supposed to be losslessly convertible back
+/// into the same token stream (modulo spans), except for possibly `TokenTree::Group`s
+/// with `Delimiter::None` delimiters and negative numeric literals.
+impl fmt::Display for TokenStream {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.to_string())
+    }
+}
+
+/// Prints token in a form convenient for debugging.
+impl fmt::Debug for TokenStream {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("TokenStream ")?;
+        f.debug_list().entries(self.clone()).finish()
+    }
+}
+
+/// Creates a token stream containing a single token tree.
+impl From<TokenTree> for TokenStream {
+    fn from(tree: TokenTree) -> TokenStream {
+        TokenStream(bridge::client::TokenStream::from_token_tree(match tree {
+            TokenTree::Group(tt) => bridge::TokenTree::Group(tt.0),
+            TokenTree::Punct(tt) => bridge::TokenTree::Punct(tt.0),
+            TokenTree::Ident(tt) => bridge::TokenTree::Ident(tt.0),
+            TokenTree::Literal(tt) => bridge::TokenTree::Literal(tt.0),
+        }))
+    }
+}
+
+/// Collects a number of token trees into a single stream.
+impl iter::FromIterator<TokenTree> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
+        trees.into_iter().map(TokenStream::from).collect()
+    }
+}
+
+/// A "flattening" operation on token streams, collects token trees
+/// from multiple token streams into a single stream.
+impl iter::FromIterator<TokenStream> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
+        let mut builder = bridge::client::TokenStreamBuilder::new();
+        streams.into_iter().for_each(|stream| builder.push(stream.0));
+        TokenStream(builder.build())
+    }
+}
+
+impl Extend<TokenTree> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: I) {
+        self.extend(trees.into_iter().map(TokenStream::from));
+    }
+}
+
+impl Extend<TokenStream> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
+        // FIXME(eddyb) Use an optimized implementation if/when possible.
+        *self = iter::once(mem::replace(self, Self::new())).chain(streams).collect();
+    }
+}
+
+/// Public implementation details for the `TokenStream` type, such as iterators.
+pub mod token_stream {
+    use crate::proc_macro::{bridge, Group, Ident, Literal, Punct, TokenStream, TokenTree};
+
+    /// An iterator over `TokenStream`'s `TokenTree`s.
+    /// The iteration is "shallow", e.g., the iterator doesn't recurse into delimited groups,
+    /// and returns whole groups as token trees.
+    #[derive(Clone)]
+    pub struct IntoIter(bridge::client::TokenStreamIter);
+
+    impl Iterator for IntoIter {
+        type Item = TokenTree;
+
+        fn next(&mut self) -> Option<TokenTree> {
+            self.0.next().map(|tree| match tree {
+                bridge::TokenTree::Group(tt) => TokenTree::Group(Group(tt)),
+                bridge::TokenTree::Punct(tt) => TokenTree::Punct(Punct(tt)),
+                bridge::TokenTree::Ident(tt) => TokenTree::Ident(Ident(tt)),
+                bridge::TokenTree::Literal(tt) => TokenTree::Literal(Literal(tt)),
+            })
+        }
+    }
+
+    impl IntoIterator for TokenStream {
+        type Item = TokenTree;
+        type IntoIter = IntoIter;
+
+        fn into_iter(self) -> IntoIter {
+            IntoIter(self.0.into_iter())
+        }
+    }
+}
+
+/// A region of source code, along with macro expansion information.
+#[derive(Copy, Clone)]
+pub struct Span(bridge::client::Span);
+
+macro_rules! diagnostic_method {
+    ($name:ident, $level:expr) => {
+        /// Creates a new `Diagnostic` with the given `message` at the span
+        /// `self`.
+        pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
+            Diagnostic::spanned(self, $level, message)
+        }
+    };
+}
+
+impl Span {
+    /// A span that resolves at the macro definition site.
+    pub fn def_site() -> Span {
+        Span(bridge::client::Span::def_site())
+    }
+
+    /// The span of the invocation of the current procedural macro.
+    /// Identifiers created with this span will be resolved as if they were written
+    /// directly at the macro call location (call-site hygiene) and other code
+    /// at the macro call site will be able to refer to them as well.
+    pub fn call_site() -> Span {
+        Span(bridge::client::Span::call_site())
+    }
+
+    /// A span that represents `macro_rules` hygiene, and sometimes resolves at the macro
+    /// definition site (local variables, labels, `$crate`) and sometimes at the macro
+    /// call site (everything else).
+    /// The span location is taken from the call-site.
+    pub fn mixed_site() -> Span {
+        Span(bridge::client::Span::mixed_site())
+    }
+
+    /// The original source file into which this span points.
+    pub fn source_file(&self) -> SourceFile {
+        SourceFile(self.0.source_file())
+    }
+
+    /// The `Span` for the tokens in the previous macro expansion from which
+    /// `self` was generated from, if any.
+    pub fn parent(&self) -> Option<Span> {
+        self.0.parent().map(Span)
+    }
+
+    /// The span for the origin source code that `self` was generated from. If
+    /// this `Span` wasn't generated from other macro expansions then the return
+    /// value is the same as `*self`.
+    pub fn source(&self) -> Span {
+        Span(self.0.source())
+    }
+
+    /// Gets the starting line/column in the source file for this span.
+    pub fn start(&self) -> LineColumn {
+        self.0.start()
+    }
+
+    /// Gets the ending line/column in the source file for this span.
+    pub fn end(&self) -> LineColumn {
+        self.0.end()
+    }
+
+    /// Creates a new span encompassing `self` and `other`.
+    ///
+    /// Returns `None` if `self` and `other` are from different files.
+    pub fn join(&self, other: Span) -> Option<Span> {
+        self.0.join(other.0).map(Span)
+    }
+
+    /// Creates a new span with the same line/column information as `self` but
+    /// that resolves symbols as though it were at `other`.
+    pub fn resolved_at(&self, other: Span) -> Span {
+        Span(self.0.resolved_at(other.0))
+    }
+
+    /// Creates a new span with the same name resolution behavior as `self` but
+    /// with the line/column information of `other`.
+    pub fn located_at(&self, other: Span) -> Span {
+        other.resolved_at(*self)
+    }
+
+    /// Compares to spans to see if they're equal.
+    pub fn eq(&self, other: &Span) -> bool {
+        self.0 == other.0
+    }
+
+    /// Returns the source text behind a span. This preserves the original source
+    /// code, including spaces and comments. It only returns a result if the span
+    /// corresponds to real source code.
+    ///
+    /// Note: The observable result of a macro should only rely on the tokens and
+    /// not on this source text. The result of this function is a best effort to
+    /// be used for diagnostics only.
+    pub fn source_text(&self) -> Option<String> {
+        self.0.source_text()
+    }
+
+    diagnostic_method!(error, Level::Error);
+    diagnostic_method!(warning, Level::Warning);
+    diagnostic_method!(note, Level::Note);
+    diagnostic_method!(help, Level::Help);
+}
+
+/// Prints a span in a form convenient for debugging.
+impl fmt::Debug for Span {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+/// A line-column pair representing the start or end of a `Span`.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct LineColumn {
+    /// The 1-indexed line in the source file on which the span starts or ends (inclusive).
+    pub line: usize,
+    /// The 0-indexed column (in UTF-8 characters) in the source file on which
+    /// the span starts or ends (inclusive).
+    pub column: usize,
+}
+
+/// The source file of a given `Span`.
+#[derive(Clone)]
+pub struct SourceFile(bridge::client::SourceFile);
+
+impl SourceFile {
+    /// Gets the path to this source file.
+    ///
+    /// ### Note
+    /// If the code span associated with this `SourceFile` was generated by an external macro, this
+    /// macro, this may not be an actual path on the filesystem. Use [`is_real`] to check.
+    ///
+    /// Also note that even if `is_real` returns `true`, if `--remap-path-prefix` was passed on
+    /// the command line, the path as given may not actually be valid.
+    ///
+    /// [`is_real`]: #method.is_real
+    pub fn path(&self) -> PathBuf {
+        PathBuf::from(self.0.path())
+    }
+
+    /// Returns `true` if this source file is a real source file, and not generated by an external
+    /// macro's expansion.
+    pub fn is_real(&self) -> bool {
+        // This is a hack until intercrate spans are implemented and we can have real source files
+        // for spans generated in external macros.
+        // https://github.com/rust-lang/rust/pull/43604#issuecomment-333334368
+        self.0.is_real()
+    }
+}
+
+impl fmt::Debug for SourceFile {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("SourceFile")
+            .field("path", &self.path())
+            .field("is_real", &self.is_real())
+            .finish()
+    }
+}
+
+impl PartialEq for SourceFile {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.eq(&other.0)
+    }
+}
+
+impl Eq for SourceFile {}
+
+/// A single token or a delimited sequence of token trees (e.g., `[1, (), ..]`).
+#[derive(Clone)]
+pub enum TokenTree {
+    /// A token stream surrounded by bracket delimiters.
+    Group(Group),
+    /// An identifier.
+    Ident(Ident),
+    /// A single punctuation character (`+`, `,`, `$`, etc.).
+    Punct(Punct),
+    /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
+    Literal(Literal),
+}
+
+impl TokenTree {
+    /// Returns the span of this tree, delegating to the `span` method of
+    /// the contained token or a delimited stream.
+    pub fn span(&self) -> Span {
+        match *self {
+            TokenTree::Group(ref t) => t.span(),
+            TokenTree::Ident(ref t) => t.span(),
+            TokenTree::Punct(ref t) => t.span(),
+            TokenTree::Literal(ref t) => t.span(),
+        }
+    }
+
+    /// Configures the span for *only this token*.
+    ///
+    /// Note that if this token is a `Group` then this method will not configure
+    /// the span of each of the internal tokens, this will simply delegate to
+    /// the `set_span` method of each variant.
+    pub fn set_span(&mut self, span: Span) {
+        match *self {
+            TokenTree::Group(ref mut t) => t.set_span(span),
+            TokenTree::Ident(ref mut t) => t.set_span(span),
+            TokenTree::Punct(ref mut t) => t.set_span(span),
+            TokenTree::Literal(ref mut t) => t.set_span(span),
+        }
+    }
+}
+
+/// Prints token tree in a form convenient for debugging.
+impl fmt::Debug for TokenTree {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // Each of these has the name in the struct type in the derived debug,
+        // so don't bother with an extra layer of indirection
+        match *self {
+            TokenTree::Group(ref tt) => tt.fmt(f),
+            TokenTree::Ident(ref tt) => tt.fmt(f),
+            TokenTree::Punct(ref tt) => tt.fmt(f),
+            TokenTree::Literal(ref tt) => tt.fmt(f),
+        }
+    }
+}
+
+impl From<Group> for TokenTree {
+    fn from(g: Group) -> TokenTree {
+        TokenTree::Group(g)
+    }
+}
+
+impl From<Ident> for TokenTree {
+    fn from(g: Ident) -> TokenTree {
+        TokenTree::Ident(g)
+    }
+}
+
+impl From<Punct> for TokenTree {
+    fn from(g: Punct) -> TokenTree {
+        TokenTree::Punct(g)
+    }
+}
+
+impl From<Literal> for TokenTree {
+    fn from(g: Literal) -> TokenTree {
+        TokenTree::Literal(g)
+    }
+}
+
+// N.B., the bridge only provides `to_string`, implement `fmt::Display`
+// based on it (the reverse of the usual relationship between the two).
+// impl ToString for TokenTree {
+//     fn to_string(&self) -> String {
+//         match *self {
+//             TokenTree::Group(ref t) => t.to_string(),
+//             TokenTree::Ident(ref t) => t.to_string(),
+//             TokenTree::Punct(ref t) => t.to_string(),
+//             TokenTree::Literal(ref t) => t.to_string(),
+//         }
+//     }
+// }
+
+/// Prints the token tree as a string that is supposed to be losslessly convertible back
+/// into the same token tree (modulo spans), except for possibly `TokenTree::Group`s
+/// with `Delimiter::None` delimiters and negative numeric literals.
+impl fmt::Display for TokenTree {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.to_string())
+    }
+}
+
+/// A delimited token stream.
+///
+/// A `Group` internally contains a `TokenStream` which is surrounded by `Delimiter`s.
+#[derive(Clone)]
+pub struct Group(bridge::client::Group);
+
+/// Describes how a sequence of token trees is delimited.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Delimiter {
+    /// `( ... )`
+    Parenthesis,
+    /// `{ ... }`
+    Brace,
+    /// `[ ... ]`
+    Bracket,
+    /// `Ø ... Ø`
+    /// An implicit delimiter, that may, for example, appear around tokens coming from a
+    /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
+    /// `$var * 3` where `$var` is `1 + 2`.
+    /// Implicit delimiters may not survive roundtrip of a token stream through a string.
+    None,
+}
+
+impl Group {
+    /// Creates a new `Group` with the given delimiter and token stream.
+    ///
+    /// This constructor will set the span for this group to
+    /// `Span::call_site()`. To change the span you can use the `set_span`
+    /// method below.
+    pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
+        Group(bridge::client::Group::new(delimiter, stream.0))
+    }
+
+    /// Returns the delimiter of this `Group`
+    pub fn delimiter(&self) -> Delimiter {
+        self.0.delimiter()
+    }
+
+    /// Returns the `TokenStream` of tokens that are delimited in this `Group`.
+    ///
+    /// Note that the returned token stream does not include the delimiter
+    /// returned above.
+    pub fn stream(&self) -> TokenStream {
+        TokenStream(self.0.stream())
+    }
+
+    /// Returns the span for the delimiters of this token stream, spanning the
+    /// entire `Group`.
+    ///
+    /// ```text
+    /// pub fn span(&self) -> Span {
+    ///            ^^^^^^^
+    /// ```
+    pub fn span(&self) -> Span {
+        Span(self.0.span())
+    }
+
+    /// Returns the span pointing to the opening delimiter of this group.
+    ///
+    /// ```text
+    /// pub fn span_open(&self) -> Span {
+    ///                 ^
+    /// ```
+    pub fn span_open(&self) -> Span {
+        Span(self.0.span_open())
+    }
+
+    /// Returns the span pointing to the closing delimiter of this group.
+    ///
+    /// ```text
+    /// pub fn span_close(&self) -> Span {
+    ///                        ^
+    /// ```
+    pub fn span_close(&self) -> Span {
+        Span(self.0.span_close())
+    }
+
+    /// Configures the span for this `Group`'s delimiters, but not its internal
+    /// tokens.
+    ///
+    /// This method will **not** set the span of all the internal tokens spanned
+    /// by this group, but rather it will only set the span of the delimiter
+    /// tokens at the level of the `Group`.
+    pub fn set_span(&mut self, span: Span) {
+        self.0.set_span(span.0);
+    }
+}
+
+// N.B., the bridge only provides `to_string`, implement `fmt::Display`
+// based on it (the reverse of the usual relationship between the two).
+// impl ToString for Group {
+//     fn to_string(&self) -> String {
+//         TokenStream::from(TokenTree::from(self.clone())).to_string()
+//     }
+// }
+
+/// Prints the group as a string that should be losslessly convertible back
+/// into the same group (modulo spans), except for possibly `TokenTree::Group`s
+/// with `Delimiter::None` delimiters.
+impl fmt::Display for Group {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.to_string())
+    }
+}
+
+impl fmt::Debug for Group {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Group")
+            .field("delimiter", &self.delimiter())
+            .field("stream", &self.stream())
+            .field("span", &self.span())
+            .finish()
+    }
+}
+
+/// An `Punct` is an single punctuation character like `+`, `-` or `#`.
+///
+/// Multi-character operators like `+=` are represented as two instances of `Punct` with different
+/// forms of `Spacing` returned.
+#[derive(Clone)]
+pub struct Punct(bridge::client::Punct);
+
+/// Whether an `Punct` is followed immediately by another `Punct` or
+/// followed by another token or whitespace.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Spacing {
+    /// e.g., `+` is `Alone` in `+ =`, `+ident` or `+()`.
+    Alone,
+    /// e.g., `+` is `Joint` in `+=` or `'#`.
+    /// Additionally, single quote `'` can join with identifiers to form lifetimes `'ident`.
+    Joint,
+}
+
+impl Punct {
+    /// Creates a new `Punct` from the given character and spacing.
+    /// The `ch` argument must be a valid punctuation character permitted by the language,
+    /// otherwise the function will panic.
+    ///
+    /// The returned `Punct` will have the default span of `Span::call_site()`
+    /// which can be further configured with the `set_span` method below.
+    pub fn new(ch: char, spacing: Spacing) -> Punct {
+        Punct(bridge::client::Punct::new(ch, spacing))
+    }
+
+    /// Returns the value of this punctuation character as `char`.
+    pub fn as_char(&self) -> char {
+        self.0.as_char()
+    }
+
+    /// Returns the spacing of this punctuation character, indicating whether it's immediately
+    /// followed by another `Punct` in the token stream, so they can potentially be combined into
+    /// a multi-character operator (`Joint`), or it's followed by some other token or whitespace
+    /// (`Alone`) so the operator has certainly ended.
+    pub fn spacing(&self) -> Spacing {
+        self.0.spacing()
+    }
+
+    /// Returns the span for this punctuation character.
+    pub fn span(&self) -> Span {
+        Span(self.0.span())
+    }
+
+    /// Configure the span for this punctuation character.
+    pub fn set_span(&mut self, span: Span) {
+        self.0 = self.0.with_span(span.0);
+    }
+}
+
+// N.B., the bridge only provides `to_string`, implement `fmt::Display`
+// based on it (the reverse of the usual relationship between the two).
+// impl ToString for Punct {
+//     fn to_string(&self) -> String {
+//         TokenStream::from(TokenTree::from(self.clone())).to_string()
+//     }
+// }
+
+/// Prints the punctuation character as a string that should be losslessly convertible
+/// back into the same character.
+impl fmt::Display for Punct {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.to_string())
+    }
+}
+
+impl fmt::Debug for Punct {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Punct")
+            .field("ch", &self.as_char())
+            .field("spacing", &self.spacing())
+            .field("span", &self.span())
+            .finish()
+    }
+}
+
+/// An identifier (`ident`).
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct Ident(bridge::client::Ident);
+
+impl Ident {
+    /// Creates a new `Ident` with the given `string` as well as the specified
+    /// `span`.
+    /// The `string` argument must be a valid identifier permitted by the
+    /// language, otherwise the function will panic.
+    ///
+    /// Note that `span`, currently in rustc, configures the hygiene information
+    /// for this identifier.
+    ///
+    /// As of this time `Span::call_site()` explicitly opts-in to "call-site" hygiene
+    /// meaning that identifiers created with this span will be resolved as if they were written
+    /// directly at the location of the macro call, and other code at the macro call site will be
+    /// able to refer to them as well.
+    ///
+    /// Later spans like `Span::def_site()` will allow to opt-in to "definition-site" hygiene
+    /// meaning that identifiers created with this span will be resolved at the location of the
+    /// macro definition and other code at the macro call site will not be able to refer to them.
+    ///
+    /// Due to the current importance of hygiene this constructor, unlike other
+    /// tokens, requires a `Span` to be specified at construction.
+    pub fn new(string: &str, span: Span) -> Ident {
+        Ident(bridge::client::Ident::new(string, span.0, false))
+    }
+
+    /// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
+    pub fn new_raw(string: &str, span: Span) -> Ident {
+        Ident(bridge::client::Ident::new(string, span.0, true))
+    }
+
+    /// Returns the span of this `Ident`, encompassing the entire string returned
+    /// by `as_str`.
+    pub fn span(&self) -> Span {
+        Span(self.0.span())
+    }
+
+    /// Configures the span of this `Ident`, possibly changing its hygiene context.
+    pub fn set_span(&mut self, span: Span) {
+        self.0 = self.0.with_span(span.0);
+    }
+}
+
+// N.B., the bridge only provides `to_string`, implement `fmt::Display`
+// based on it (the reverse of the usual relationship between the two).
+// impl ToString for Ident {
+//     fn to_string(&self) -> String {
+//         TokenStream::from(TokenTree::from(self.clone())).to_string()
+//     }
+// }
+
+/// Prints the identifier as a string that should be losslessly convertible
+/// back into the same identifier.
+impl fmt::Display for Ident {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.to_string())
+    }
+}
+
+impl fmt::Debug for Ident {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Ident")
+            .field("ident", &self.to_string())
+            .field("span", &self.span())
+            .finish()
+    }
+}
+
+/// A literal string (`"hello"`), byte string (`b"hello"`),
+/// character (`'a'`), byte character (`b'a'`), an integer or floating point number
+/// with or without a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
+/// Boolean literals like `true` and `false` do not belong here, they are `Ident`s.
+#[derive(Clone)]
+pub struct Literal(bridge::client::Literal);
+
+macro_rules! suffixed_int_literals {
+    ($($name:ident => $kind:ident,)*) => ($(
+        /// Creates a new suffixed integer literal with the specified value.
+        ///
+        /// This function will create an integer like `1u32` where the integer
+        /// value specified is the first part of the token and the integral is
+        /// also suffixed at the end.
+        /// Literals created from negative numbers may not survive round-trips through
+        /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
+        ///
+        /// Literals created through this method have the `Span::call_site()`
+        /// span by default, which can be configured with the `set_span` method
+        /// below.
+        pub fn $name(n: $kind) -> Literal {
+            Literal(bridge::client::Literal::typed_integer(&n.to_string(), stringify!($kind)))
+        }
+    )*)
+}
+
+macro_rules! unsuffixed_int_literals {
+    ($($name:ident => $kind:ident,)*) => ($(
+        /// Creates a new unsuffixed integer literal with the specified value.
+        ///
+        /// This function will create an integer like `1` where the integer
+        /// value specified is the first part of the token. No suffix is
+        /// specified on this token, meaning that invocations like
+        /// `Literal::i8_unsuffixed(1)` are equivalent to
+        /// `Literal::u32_unsuffixed(1)`.
+        /// Literals created from negative numbers may not survive rountrips through
+        /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
+        ///
+        /// Literals created through this method have the `Span::call_site()`
+        /// span by default, which can be configured with the `set_span` method
+        /// below.
+        pub fn $name(n: $kind) -> Literal {
+            Literal(bridge::client::Literal::integer(&n.to_string()))
+        }
+    )*)
+}
+
+impl Literal {
+    suffixed_int_literals! {
+        u8_suffixed => u8,
+        u16_suffixed => u16,
+        u32_suffixed => u32,
+        u64_suffixed => u64,
+        u128_suffixed => u128,
+        usize_suffixed => usize,
+        i8_suffixed => i8,
+        i16_suffixed => i16,
+        i32_suffixed => i32,
+        i64_suffixed => i64,
+        i128_suffixed => i128,
+        isize_suffixed => isize,
+    }
+
+    unsuffixed_int_literals! {
+        u8_unsuffixed => u8,
+        u16_unsuffixed => u16,
+        u32_unsuffixed => u32,
+        u64_unsuffixed => u64,
+        u128_unsuffixed => u128,
+        usize_unsuffixed => usize,
+        i8_unsuffixed => i8,
+        i16_unsuffixed => i16,
+        i32_unsuffixed => i32,
+        i64_unsuffixed => i64,
+        i128_unsuffixed => i128,
+        isize_unsuffixed => isize,
+    }
+
+    /// Creates a new unsuffixed floating-point literal.
+    ///
+    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
+    /// the float's value is emitted directly into the token but no suffix is
+    /// used, so it may be inferred to be a `f64` later in the compiler.
+    /// Literals created from negative numbers may not survive rountrips through
+    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for
+    /// example if it is infinity or NaN this function will panic.
+    pub fn f32_unsuffixed(n: f32) -> Literal {
+        if !n.is_finite() {
+            panic!("Invalid float literal {}", n);
+        }
+        Literal(bridge::client::Literal::float(&n.to_string()))
+    }
+
+    /// Creates a new suffixed floating-point literal.
+    ///
+    /// This constructor will create a literal like `1.0f32` where the value
+    /// specified is the preceding part of the token and `f32` is the suffix of
+    /// the token. This token will always be inferred to be an `f32` in the
+    /// compiler.
+    /// Literals created from negative numbers may not survive rountrips through
+    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for
+    /// example if it is infinity or NaN this function will panic.
+    pub fn f32_suffixed(n: f32) -> Literal {
+        if !n.is_finite() {
+            panic!("Invalid float literal {}", n);
+        }
+        Literal(bridge::client::Literal::f32(&n.to_string()))
+    }
+
+    /// Creates a new unsuffixed floating-point literal.
+    ///
+    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
+    /// the float's value is emitted directly into the token but no suffix is
+    /// used, so it may be inferred to be a `f64` later in the compiler.
+    /// Literals created from negative numbers may not survive rountrips through
+    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for
+    /// example if it is infinity or NaN this function will panic.
+    pub fn f64_unsuffixed(n: f64) -> Literal {
+        if !n.is_finite() {
+            panic!("Invalid float literal {}", n);
+        }
+        Literal(bridge::client::Literal::float(&n.to_string()))
+    }
+
+    /// Creates a new suffixed floating-point literal.
+    ///
+    /// This constructor will create a literal like `1.0f64` where the value
+    /// specified is the preceding part of the token and `f64` is the suffix of
+    /// the token. This token will always be inferred to be an `f64` in the
+    /// compiler.
+    /// Literals created from negative numbers may not survive rountrips through
+    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
+    ///
+    /// # Panics
+    ///
+    /// This function requires that the specified float is finite, for
+    /// example if it is infinity or NaN this function will panic.
+    pub fn f64_suffixed(n: f64) -> Literal {
+        if !n.is_finite() {
+            panic!("Invalid float literal {}", n);
+        }
+        Literal(bridge::client::Literal::f64(&n.to_string()))
+    }
+
+    /// String literal.
+    pub fn string(string: &str) -> Literal {
+        Literal(bridge::client::Literal::string(string))
+    }
+
+    /// Character literal.
+    pub fn character(ch: char) -> Literal {
+        Literal(bridge::client::Literal::character(ch))
+    }
+
+    /// Byte string literal.
+    pub fn byte_string(bytes: &[u8]) -> Literal {
+        Literal(bridge::client::Literal::byte_string(bytes))
+    }
+
+    /// Returns the span encompassing this literal.
+    pub fn span(&self) -> Span {
+        Span(self.0.span())
+    }
+
+    /// Configures the span associated for this literal.
+    pub fn set_span(&mut self, span: Span) {
+        self.0.set_span(span.0);
+    }
+
+    /// Returns a `Span` that is a subset of `self.span()` containing only the
+    /// source bytes in range `range`. Returns `None` if the would-be trimmed
+    /// span is outside the bounds of `self`.
+    // FIXME(SergioBenitez): check that the byte range starts and ends at a
+    // UTF-8 boundary of the source. otherwise, it's likely that a panic will
+    // occur elsewhere when the source text is printed.
+    // FIXME(SergioBenitez): there is no way for the user to know what
+    // `self.span()` actually maps to, so this method can currently only be
+    // called blindly. For example, `to_string()` for the character 'c' returns
+    // "'\u{63}'"; there is no way for the user to know whether the source text
+    // was 'c' or whether it was '\u{63}'.
+    pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
+        // HACK(eddyb) something akin to `Option::cloned`, but for `Bound<&T>`.
+        fn cloned_bound<T: Clone>(bound: Bound<&T>) -> Bound<T> {
+            match bound {
+                Bound::Included(x) => Bound::Included(x.clone()),
+                Bound::Excluded(x) => Bound::Excluded(x.clone()),
+                Bound::Unbounded => Bound::Unbounded,
+            }
+        }
+
+        self.0.subspan(cloned_bound(range.start_bound()), cloned_bound(range.end_bound())).map(Span)
+    }
+}
+
+// N.B., the bridge only provides `to_string`, implement `fmt::Display`
+// based on it (the reverse of the usual relationship between the two).
+// impl ToString for Literal {
+//     fn to_string(&self) -> String {
+//         TokenStream::from(TokenTree::from(self.clone())).to_string()
+//     }
+// }
+
+/// Prints the literal as a string that should be losslessly convertible
+/// back into the same literal (except for possible rounding for floating point literals).
+impl fmt::Display for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.to_string())
+    }
+}
+
+impl fmt::Debug for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
+        self.0.fmt(f)
+    }
+}
diff --git a/crates/proc_macro_srv/src/rustc_server.rs b/crates/proc_macro_srv/src/rustc_server.rs
new file mode 100644
index 000000000..7d1695c86
--- /dev/null
+++ b/crates/proc_macro_srv/src/rustc_server.rs
@@ -0,0 +1,704 @@
+//! Rustc proc-macro server implementation with tt
+//!
+//! Based on idea from https://github.com/fedochet/rust-proc-macro-expander
+//! The lib-proc-macro server backend is `TokenStream`-agnostic, such that
+//! we could provide any TokenStream implementation.
+//! The original idea from fedochet is using proc-macro2 as backend,
+//! we use tt instead for better intergation with RA.
+//!
+//! FIXME: No span and source file information is implemented yet
+
+use crate::proc_macro::bridge::{self, server};
+
+use std::collections::{Bound, HashMap};
+use std::hash::Hash;
+use std::iter::FromIterator;
+use std::str::FromStr;
+use std::{ascii, vec::IntoIter};
+
+type Group = tt::Subtree;
+type TokenTree = tt::TokenTree;
+type Punct = tt::Punct;
+type Spacing = tt::Spacing;
+type Literal = tt::Literal;
+type Span = tt::TokenId;
+
+#[derive(Debug, Clone)]
+pub struct TokenStream {
+    pub subtree: tt::Subtree,
+}
+
+impl TokenStream {
+    pub fn new() -> Self {
+        TokenStream { subtree: Default::default() }
+    }
+
+    pub fn with_subtree(subtree: tt::Subtree) -> Self {
+        TokenStream { subtree }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.subtree.token_trees.is_empty()
+    }
+}
+
+/// Creates a token stream containing a single token tree.
+impl From<TokenTree> for TokenStream {
+    fn from(tree: TokenTree) -> TokenStream {
+        TokenStream { subtree: tt::Subtree { delimiter: None, token_trees: vec![tree] } }
+    }
+}
+
+/// Collects a number of token trees into a single stream.
+impl FromIterator<TokenTree> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
+        trees.into_iter().map(TokenStream::from).collect()
+    }
+}
+
+/// A "flattening" operation on token streams, collects token trees
+/// from multiple token streams into a single stream.
+impl FromIterator<TokenStream> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
+        let mut builder = TokenStreamBuilder::new();
+        streams.into_iter().for_each(|stream| builder.push(stream));
+        builder.build()
+    }
+}
+
+impl Extend<TokenTree> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: I) {
+        self.extend(trees.into_iter().map(TokenStream::from));
+    }
+}
+
+impl Extend<TokenStream> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
+        for item in streams {
+            for tkn in item {
+                match tkn {
+                    tt::TokenTree::Subtree(subtree) if subtree.delimiter.is_none() => {
+                        self.subtree.token_trees.extend(subtree.token_trees);
+                    }
+                    _ => {
+                        self.subtree.token_trees.push(tkn);
+                    }
+                }
+            }
+        }
+    }
+}
+
+type Level = crate::proc_macro::Level;
+type LineColumn = crate::proc_macro::LineColumn;
+type SourceFile = crate::proc_macro::SourceFile;
+
+/// A structure representing a diagnostic message and associated children
+/// messages.
+#[derive(Clone, Debug)]
+pub struct Diagnostic {
+    level: Level,
+    message: String,
+    spans: Vec<Span>,
+    children: Vec<Diagnostic>,
+}
+
+impl Diagnostic {
+    /// Creates a new diagnostic with the given `level` and `message`.
+    pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
+        Diagnostic { level, message: message.into(), spans: vec![], children: vec![] }
+    }
+}
+
+// Rustc Server Ident has to be `Copyable`
+// We use a stub here for bypassing
+#[derive(Hash, Eq, PartialEq, Copy, Clone)]
+pub struct IdentId(u32);
+
+#[derive(Clone, Hash, Eq, PartialEq)]
+struct IdentData(tt::Ident);
+
+#[derive(Default)]
+struct IdentInterner {
+    idents: HashMap<IdentData, u32>,
+    ident_data: Vec<IdentData>,
+}
+
+impl IdentInterner {
+    fn intern(&mut self, data: &IdentData) -> u32 {
+        if let Some(index) = self.idents.get(data) {
+            return *index;
+        }
+
+        let index = self.idents.len() as u32;
+        self.ident_data.push(data.clone());
+        self.idents.insert(data.clone(), index);
+        index
+    }
+
+    fn get(&self, index: u32) -> &IdentData {
+        &self.ident_data[index as usize]
+    }
+
+    #[allow(unused)]
+    fn get_mut(&mut self, index: u32) -> &mut IdentData {
+        self.ident_data.get_mut(index as usize).expect("Should be consistent")
+    }
+}
+
+pub struct TokenStreamBuilder {
+    acc: TokenStream,
+}
+
+/// Public implementation details for the `TokenStream` type, such as iterators.
+pub mod token_stream {
+    use std::str::FromStr;
+
+    use super::{TokenStream, TokenTree};
+
+    /// An iterator over `TokenStream`'s `TokenTree`s.
+    /// The iteration is "shallow", e.g., the iterator doesn't recurse into delimited groups,
+    /// and returns whole groups as token trees.
+    impl IntoIterator for TokenStream {
+        type Item = TokenTree;
+        type IntoIter = super::IntoIter<TokenTree>;
+
+        fn into_iter(self) -> Self::IntoIter {
+            self.subtree.token_trees.into_iter()
+        }
+    }
+
+    type LexError = String;
+
+    /// Attempts to break the string into tokens and parse those tokens into a token stream.
+    /// May fail for a number of reasons, for example, if the string contains unbalanced delimiters
+    /// or characters not existing in the language.
+    /// All tokens in the parsed stream get `Span::call_site()` spans.
+    ///
+    /// NOTE: some errors may cause panics instead of returning `LexError`. We reserve the right to
+    /// change these errors into `LexError`s later.
+    impl FromStr for TokenStream {
+        type Err = LexError;
+
+        fn from_str(src: &str) -> Result<TokenStream, LexError> {
+            let (subtree, _token_map) =
+                mbe::parse_to_token_tree(src).ok_or("Failed to parse from mbe")?;
+
+            let tt: tt::TokenTree = subtree.into();
+            Ok(tt.into())
+        }
+    }
+
+    impl ToString for TokenStream {
+        fn to_string(&self) -> String {
+            let tt = self.subtree.clone().into();
+            to_text(&tt)
+        }
+    }
+
+    fn to_text(tkn: &tt::TokenTree) -> String {
+        match tkn {
+            tt::TokenTree::Leaf(tt::Leaf::Ident(ident)) => ident.text.clone().into(),
+            tt::TokenTree::Leaf(tt::Leaf::Literal(literal)) => literal.text.clone().into(),
+            tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) => format!("{}", punct.char),
+            tt::TokenTree::Subtree(subtree) => {
+                let content = subtree
+                    .token_trees
+                    .iter()
+                    .map(|tkn| {
+                        let s = to_text(tkn);
+                        if let tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) = tkn {
+                            if punct.spacing == tt::Spacing::Alone {
+                                return s + " ";
+                            }
+                        }
+                        s
+                    })
+                    .collect::<Vec<_>>()
+                    .concat();
+                let (open, close) = match subtree.delimiter.map(|it| it.kind) {
+                    None => ("", ""),
+                    Some(tt::DelimiterKind::Brace) => ("{", "}"),
+                    Some(tt::DelimiterKind::Parenthesis) => ("(", ")"),
+                    Some(tt::DelimiterKind::Bracket) => ("[", "]"),
+                };
+                format!("{}{}{}", open, content, close)
+            }
+        }
+    }
+}
+
+impl TokenStreamBuilder {
+    fn new() -> TokenStreamBuilder {
+        TokenStreamBuilder { acc: TokenStream::new() }
+    }
+
+    fn push(&mut self, stream: TokenStream) {
+        self.acc.extend(stream.into_iter())
+    }
+
+    fn build(self) -> TokenStream {
+        self.acc
+    }
+}
+
+#[derive(Clone)]
+pub struct TokenStreamIter {
+    trees: IntoIter<TokenTree>,
+}
+
+#[derive(Default)]
+pub struct Rustc {
+    ident_interner: IdentInterner,
+    // FIXME: store span information here.
+}
+
+impl server::Types for Rustc {
+    type TokenStream = TokenStream;
+    type TokenStreamBuilder = TokenStreamBuilder;
+    type TokenStreamIter = TokenStreamIter;
+    type Group = Group;
+    type Punct = Punct;
+    type Ident = IdentId;
+    type Literal = Literal;
+    type SourceFile = SourceFile;
+    type Diagnostic = Diagnostic;
+    type Span = Span;
+    type MultiSpan = Vec<Span>;
+}
+
+impl server::TokenStream for Rustc {
+    fn new(&mut self) -> Self::TokenStream {
+        Self::TokenStream::new()
+    }
+
+    fn is_empty(&mut self, stream: &Self::TokenStream) -> bool {
+        stream.is_empty()
+    }
+    fn from_str(&mut self, src: &str) -> Self::TokenStream {
+        Self::TokenStream::from_str(src).expect("cannot parse string")
+    }
+    fn to_string(&mut self, stream: &Self::TokenStream) -> String {
+        stream.to_string()
+    }
+    fn from_token_tree(
+        &mut self,
+        tree: bridge::TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>,
+    ) -> Self::TokenStream {
+        match tree {
+            bridge::TokenTree::Group(group) => {
+                let tree = TokenTree::from(group);
+                Self::TokenStream::from_iter(vec![tree])
+            }
+
+            bridge::TokenTree::Ident(IdentId(index)) => {
+                let IdentData(ident) = self.ident_interner.get(index).clone();
+                let ident: tt::Ident = ident;
+                let leaf = tt::Leaf::from(ident);
+                let tree = TokenTree::from(leaf);
+                Self::TokenStream::from_iter(vec![tree])
+            }
+
+            bridge::TokenTree::Literal(literal) => {
+                let leaf = tt::Leaf::from(literal);
+                let tree = TokenTree::from(leaf);
+                Self::TokenStream::from_iter(vec![tree])
+            }
+
+            bridge::TokenTree::Punct(p) => {
+                let leaf = tt::Leaf::from(p);
+                let tree = TokenTree::from(leaf);
+                Self::TokenStream::from_iter(vec![tree])
+            }
+        }
+    }
+
+    fn into_iter(&mut self, stream: Self::TokenStream) -> Self::TokenStreamIter {
+        let trees: Vec<TokenTree> = stream.into_iter().collect();
+        TokenStreamIter { trees: trees.into_iter() }
+    }
+}
+
+impl server::TokenStreamBuilder for Rustc {
+    fn new(&mut self) -> Self::TokenStreamBuilder {
+        Self::TokenStreamBuilder::new()
+    }
+    fn push(&mut self, builder: &mut Self::TokenStreamBuilder, stream: Self::TokenStream) {
+        builder.push(stream)
+    }
+    fn build(&mut self, builder: Self::TokenStreamBuilder) -> Self::TokenStream {
+        builder.build()
+    }
+}
+
+impl server::TokenStreamIter for Rustc {
+    fn next(
+        &mut self,
+        iter: &mut Self::TokenStreamIter,
+    ) -> Option<bridge::TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>> {
+        iter.trees.next().map(|tree| match tree {
+            TokenTree::Subtree(group) => bridge::TokenTree::Group(group),
+            TokenTree::Leaf(tt::Leaf::Ident(ident)) => {
+                bridge::TokenTree::Ident(IdentId(self.ident_interner.intern(&IdentData(ident))))
+            }
+            TokenTree::Leaf(tt::Leaf::Literal(literal)) => bridge::TokenTree::Literal(literal),
+            TokenTree::Leaf(tt::Leaf::Punct(punct)) => bridge::TokenTree::Punct(punct),
+        })
+    }
+}
+
+fn delim_to_internal(d: bridge::Delimiter) -> Option<tt::Delimiter> {
+    let kind = match d {
+        bridge::Delimiter::Parenthesis => tt::DelimiterKind::Parenthesis,
+        bridge::Delimiter::Brace => tt::DelimiterKind::Brace,
+        bridge::Delimiter::Bracket => tt::DelimiterKind::Bracket,
+        bridge::Delimiter::None => return None,
+    };
+    Some(tt::Delimiter { id: tt::TokenId::unspecified(), kind })
+}
+
+fn delim_to_external(d: Option<tt::Delimiter>) -> bridge::Delimiter {
+    match d.map(|it| it.kind) {
+        Some(tt::DelimiterKind::Parenthesis) => bridge::Delimiter::Parenthesis,
+        Some(tt::DelimiterKind::Brace) => bridge::Delimiter::Brace,
+        Some(tt::DelimiterKind::Bracket) => bridge::Delimiter::Bracket,
+        None => bridge::Delimiter::None,
+    }
+}
+
+fn spacing_to_internal(spacing: bridge::Spacing) -> Spacing {
+    match spacing {
+        bridge::Spacing::Alone => Spacing::Alone,
+        bridge::Spacing::Joint => Spacing::Joint,
+    }
+}
+
+fn spacing_to_external(spacing: Spacing) -> bridge::Spacing {
+    match spacing {
+        Spacing::Alone => bridge::Spacing::Alone,
+        Spacing::Joint => bridge::Spacing::Joint,
+    }
+}
+
+impl server::Group for Rustc {
+    fn new(&mut self, delimiter: bridge::Delimiter, stream: Self::TokenStream) -> Self::Group {
+        Self::Group {
+            delimiter: delim_to_internal(delimiter),
+            token_trees: stream.subtree.token_trees,
+        }
+    }
+    fn delimiter(&mut self, group: &Self::Group) -> bridge::Delimiter {
+        delim_to_external(group.delimiter)
+    }
+
+    // NOTE: Return value of do not include delimiter
+    fn stream(&mut self, group: &Self::Group) -> Self::TokenStream {
+        TokenStream {
+            subtree: tt::Subtree { delimiter: None, token_trees: group.token_trees.clone() },
+        }
+    }
+
+    fn span(&mut self, group: &Self::Group) -> Self::Span {
+        group.delimiter.map(|it| it.id).unwrap_or_else(|| tt::TokenId::unspecified())
+    }
+
+    fn set_span(&mut self, _group: &mut Self::Group, _span: Self::Span) {
+        // FIXME handle span
+    }
+
+    fn span_open(&mut self, _group: &Self::Group) -> Self::Span {
+        // FIXME handle span
+        // MySpan(self.span_interner.intern(&MySpanData(group.span_open())))
+        tt::TokenId::unspecified()
+    }
+
+    fn span_close(&mut self, _group: &Self::Group) -> Self::Span {
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+}
+
+impl server::Punct for Rustc {
+    fn new(&mut self, ch: char, spacing: bridge::Spacing) -> Self::Punct {
+        tt::Punct {
+            char: ch,
+            spacing: spacing_to_internal(spacing),
+            id: tt::TokenId::unspecified(),
+        }
+    }
+    fn as_char(&mut self, punct: Self::Punct) -> char {
+        punct.char
+    }
+    fn spacing(&mut self, punct: Self::Punct) -> bridge::Spacing {
+        spacing_to_external(punct.spacing)
+    }
+    fn span(&mut self, _punct: Self::Punct) -> Self::Span {
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+    fn with_span(&mut self, punct: Self::Punct, _span: Self::Span) -> Self::Punct {
+        // FIXME handle span
+        punct
+    }
+}
+
+impl server::Ident for Rustc {
+    fn new(&mut self, string: &str, _span: Self::Span, _is_raw: bool) -> Self::Ident {
+        IdentId(
+            self.ident_interner.intern(&IdentData(tt::Ident {
+                text: string.into(),
+                id: tt::TokenId::unspecified(),
+            })),
+        )
+    }
+
+    fn span(&mut self, _ident: Self::Ident) -> Self::Span {
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+    fn with_span(&mut self, ident: Self::Ident, _span: Self::Span) -> Self::Ident {
+        // FIXME handle span
+        ident
+    }
+}
+
+impl server::Literal for Rustc {
+    fn debug_kind(&mut self, _literal: &Self::Literal) -> String {
+        // r-a: debug_kind and suffix are unsupported; corresponding client code has been changed to not call these.
+        // They must still be present to be ABI-compatible and work with upstream proc_macro.
+        "".to_owned()
+    }
+    fn symbol(&mut self, literal: &Self::Literal) -> String {
+        literal.text.to_string()
+    }
+    fn suffix(&mut self, _literal: &Self::Literal) -> Option<String> {
+        None
+    }
+
+    fn integer(&mut self, n: &str) -> Self::Literal {
+        let n: i128 = n.parse().unwrap();
+        Literal { text: n.to_string().into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn typed_integer(&mut self, n: &str, kind: &str) -> Self::Literal {
+        macro_rules! def_suffixed_integer {
+            ($kind:ident, $($ty:ty),*) => {
+                match $kind {
+                    $(
+                        stringify!($ty) => {
+                            let n: $ty = n.parse().unwrap();
+                            format!(concat!("{}", stringify!($ty)), n)
+                        }
+                    )*
+                    _ => unimplemented!("unknown args for typed_integer: n {}, kind {}", n, $kind),
+                }
+            }
+        }
+
+        let text =
+            def_suffixed_integer! {kind, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128};
+
+        Literal { text: text.into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn float(&mut self, n: &str) -> Self::Literal {
+        let n: f64 = n.parse().unwrap();
+        let mut text = f64::to_string(&n);
+        if !text.contains('.') {
+            text += ".0"
+        }
+        Literal { text: text.into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn f32(&mut self, n: &str) -> Self::Literal {
+        let n: f32 = n.parse().unwrap();
+        let text = format!("{}f32", n);
+        Literal { text: text.into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn f64(&mut self, n: &str) -> Self::Literal {
+        let n: f64 = n.parse().unwrap();
+        let text = format!("{}f64", n);
+        Literal { text: text.into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn string(&mut self, string: &str) -> Self::Literal {
+        let mut escaped = String::new();
+        for ch in string.chars() {
+            escaped.extend(ch.escape_debug());
+        }
+        Literal { text: format!("\"{}\"", escaped).into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn character(&mut self, ch: char) -> Self::Literal {
+        Literal { text: format!("'{}'", ch).into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn byte_string(&mut self, bytes: &[u8]) -> Self::Literal {
+        let string = bytes
+            .iter()
+            .cloned()
+            .flat_map(ascii::escape_default)
+            .map(Into::<char>::into)
+            .collect::<String>();
+
+        Literal { text: format!("b\"{}\"", string).into(), id: tt::TokenId::unspecified() }
+    }
+
+    fn span(&mut self, literal: &Self::Literal) -> Self::Span {
+        literal.id
+    }
+
+    fn set_span(&mut self, _literal: &mut Self::Literal, _span: Self::Span) {
+        // FIXME handle span
+    }
+
+    fn subspan(
+        &mut self,
+        _literal: &Self::Literal,
+        _start: Bound<usize>,
+        _end: Bound<usize>,
+    ) -> Option<Self::Span> {
+        // FIXME handle span
+        None
+    }
+}
+
+impl server::SourceFile for Rustc {
+    fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
+        file1.eq(file2)
+    }
+    fn path(&mut self, file: &Self::SourceFile) -> String {
+        String::from(
+            file.path().to_str().expect("non-UTF8 file path in `proc_macro::SourceFile::path`"),
+        )
+    }
+    fn is_real(&mut self, file: &Self::SourceFile) -> bool {
+        file.is_real()
+    }
+}
+
+impl server::Diagnostic for Rustc {
+    fn new(&mut self, level: Level, msg: &str, spans: Self::MultiSpan) -> Self::Diagnostic {
+        let mut diag = Diagnostic::new(level, msg);
+        diag.spans = spans;
+        diag
+    }
+
+    fn sub(
+        &mut self,
+        _diag: &mut Self::Diagnostic,
+        _level: Level,
+        _msg: &str,
+        _spans: Self::MultiSpan,
+    ) {
+        // FIXME handle diagnostic
+        //
+    }
+
+    fn emit(&mut self, _diag: Self::Diagnostic) {
+        // FIXME handle diagnostic
+        // diag.emit()
+    }
+}
+
+impl server::Span for Rustc {
+    fn debug(&mut self, span: Self::Span) -> String {
+        format!("{:?}", span.0)
+    }
+    fn def_site(&mut self) -> Self::Span {
+        // MySpan(self.span_interner.intern(&MySpanData(Span::def_site())))
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+    fn call_site(&mut self) -> Self::Span {
+        // MySpan(self.span_interner.intern(&MySpanData(Span::call_site())))
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+    fn source_file(&mut self, _span: Self::Span) -> Self::SourceFile {
+        // let MySpanData(span) = self.span_interner.get(span.0);
+        unimplemented!()
+    }
+
+    /// Recent feature, not yet in the proc_macro
+    ///
+    /// See PR:
+    /// https://github.com/rust-lang/rust/pull/55780
+    fn source_text(&mut self, _span: Self::Span) -> Option<String> {
+        None
+    }
+
+    fn parent(&mut self, _span: Self::Span) -> Option<Self::Span> {
+        // FIXME handle span
+        None
+    }
+    fn source(&mut self, span: Self::Span) -> Self::Span {
+        // FIXME handle span
+        span
+    }
+    fn start(&mut self, _span: Self::Span) -> LineColumn {
+        // FIXME handle span
+        LineColumn { line: 0, column: 0 }
+    }
+    fn end(&mut self, _span: Self::Span) -> LineColumn {
+        // FIXME handle span
+        LineColumn { line: 0, column: 0 }
+    }
+    fn join(&mut self, _first: Self::Span, _second: Self::Span) -> Option<Self::Span> {
+        None
+    }
+    fn resolved_at(&mut self, _span: Self::Span, _at: Self::Span) -> Self::Span {
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+
+    fn mixed_site(&mut self) -> Self::Span {
+        // FIXME handle span
+        tt::TokenId::unspecified()
+    }
+}
+
+impl server::MultiSpan for Rustc {
+    fn new(&mut self) -> Self::MultiSpan {
+        // FIXME handle span
+        vec![]
+    }
+
+    fn push(&mut self, other: &mut Self::MultiSpan, span: Self::Span) {
+        //TODP
+        other.push(span)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::proc_macro::bridge::server::Literal;
+
+    #[test]
+    fn test_rustc_server_literals() {
+        let mut srv = Rustc { ident_interner: IdentInterner::default() };
+        assert_eq!(srv.integer("1234").text, "1234");
+
+        assert_eq!(srv.typed_integer("12", "u8").text, "12u8");
+        assert_eq!(srv.typed_integer("255", "u16").text, "255u16");
+        assert_eq!(srv.typed_integer("1234", "u32").text, "1234u32");
+        assert_eq!(srv.typed_integer("15846685", "u64").text, "15846685u64");
+        assert_eq!(srv.typed_integer("15846685258", "u128").text, "15846685258u128");
+        assert_eq!(srv.typed_integer("156788984", "usize").text, "156788984usize");
+        assert_eq!(srv.typed_integer("127", "i8").text, "127i8");
+        assert_eq!(srv.typed_integer("255", "i16").text, "255i16");
+        assert_eq!(srv.typed_integer("1234", "i32").text, "1234i32");
+        assert_eq!(srv.typed_integer("15846685", "i64").text, "15846685i64");
+        assert_eq!(srv.typed_integer("15846685258", "i128").text, "15846685258i128");
+        assert_eq!(srv.float("0").text, "0.0");
+        assert_eq!(srv.float("15684.5867").text, "15684.5867");
+        assert_eq!(srv.f32("15684.58").text, "15684.58f32");
+        assert_eq!(srv.f64("15684.58").text, "15684.58f64");
+
+        assert_eq!(srv.string("hello_world").text, "\"hello_world\"");
+        assert_eq!(srv.character('c').text, "'c'");
+        assert_eq!(srv.byte_string(b"1234586\x88").text, "b\"1234586\\x88\"");
+    }
+}
diff --git a/crates/proc_macro_srv/src/tests/fixtures/test_serialize_proc_macro.txt b/crates/proc_macro_srv/src/tests/fixtures/test_serialize_proc_macro.txt
new file mode 100644
index 000000000..e6fd21610
--- /dev/null
+++ b/crates/proc_macro_srv/src/tests/fixtures/test_serialize_proc_macro.txt
@@ -0,0 +1,181 @@
+SUBTREE $
+  PUNCH   # [alone] 4294967295
+  SUBTREE [] 4294967295
+    IDENT   doc 4294967295
+    SUBTREE () 4294967295
+      IDENT   hidden 4294967295
+  PUNCH   # [alone] 4294967295
+  SUBTREE [] 4294967295
+    IDENT   allow 4294967295
+    SUBTREE () 4294967295
+      IDENT   non_upper_case_globals 4294967295
+      PUNCH   , [alone] 4294967295
+      IDENT   unused_attributes 4294967295
+      PUNCH   , [alone] 4294967295
+      IDENT   unused_qualifications 4294967295
+  IDENT   const 4294967295
+  IDENT   _ 4294967295
+  PUNCH   : [alone] 4294967295
+  SUBTREE () 4294967295
+  PUNCH   = [alone] 4294967295
+  SUBTREE {} 4294967295
+    PUNCH   # [alone] 4294967295
+    SUBTREE [] 4294967295
+      IDENT   allow 4294967295
+      SUBTREE () 4294967295
+        IDENT   rust_2018_idioms 4294967295
+        PUNCH   , [alone] 4294967295
+        IDENT   clippy 4294967295
+        PUNCH   : [joint] 4294967295
+        PUNCH   : [alone] 4294967295
+        IDENT   useless_attribute 4294967295
+    IDENT   extern 4294967295
+    IDENT   crate 4294967295
+    IDENT   serde 4294967295
+    IDENT   as 4294967295
+    IDENT   _serde 4294967295
+    PUNCH   ; [alone] 4294967295
+    PUNCH   # [alone] 4294967295
+    SUBTREE [] 4294967295
+      IDENT   allow 4294967295
+      SUBTREE () 4294967295
+        IDENT   unused_macros 4294967295
+    IDENT   macro_rules 4294967295
+    PUNCH   ! [alone] 4294967295
+    IDENT   try 4294967295
+    SUBTREE {} 4294967295
+      SUBTREE () 4294967295
+        PUNCH   $ [alone] 4294967295
+        IDENT   __expr 4294967295
+        PUNCH   : [alone] 4294967295
+        IDENT   expr 4294967295
+      PUNCH   = [joint] 4294967295
+      PUNCH   > [alone] 4294967295
+      SUBTREE {} 4294967295
+        IDENT   match 4294967295
+        PUNCH   $ [alone] 4294967295
+        IDENT   __expr 4294967295
+        SUBTREE {} 4294967295
+          IDENT   _serde 4294967295
+          PUNCH   : [joint] 4294967295
+          PUNCH   : [alone] 4294967295
+          IDENT   export 4294967295
+          PUNCH   : [joint] 4294967295
+          PUNCH   : [alone] 4294967295
+          IDENT   Ok 4294967295
+          SUBTREE () 4294967295
+            IDENT   __val 4294967295
+          PUNCH   = [joint] 4294967295
+          PUNCH   > [alone] 4294967295
+          IDENT   __val 4294967295
+          PUNCH   , [alone] 4294967295
+          IDENT   _serde 4294967295
+          PUNCH   : [joint] 4294967295
+          PUNCH   : [alone] 4294967295
+          IDENT   export 4294967295
+          PUNCH   : [joint] 4294967295
+          PUNCH   : [alone] 4294967295
+          IDENT   Err 4294967295
+          SUBTREE () 4294967295
+            IDENT   __err 4294967295
+          PUNCH   = [joint] 4294967295
+          PUNCH   > [alone] 4294967295
+          SUBTREE {} 4294967295
+            IDENT   return 4294967295
+            IDENT   _serde 4294967295
+            PUNCH   : [joint] 4294967295
+            PUNCH   : [alone] 4294967295
+            IDENT   export 4294967295
+            PUNCH   : [joint] 4294967295
+            PUNCH   : [alone] 4294967295
+            IDENT   Err 4294967295
+            SUBTREE () 4294967295
+              IDENT   __err 4294967295
+            PUNCH   ; [alone] 4294967295
+    PUNCH   # [alone] 4294967295
+    SUBTREE [] 4294967295
+      IDENT   automatically_derived 4294967295
+    IDENT   impl 4294967295
+    IDENT   _serde 4294967295
+    PUNCH   : [joint] 4294967295
+    PUNCH   : [alone] 4294967295
+    IDENT   Serialize 4294967295
+    IDENT   for 4294967295
+    IDENT   Foo 1
+    SUBTREE {} 4294967295
+      IDENT   fn 4294967295
+      IDENT   serialize 4294967295
+      PUNCH   < [alone] 4294967295
+      IDENT   __S 4294967295
+      PUNCH   > [alone] 4294967295
+      SUBTREE () 4294967295
+        PUNCH   & [alone] 4294967295
+        IDENT   self 4294967295
+        PUNCH   , [alone] 4294967295
+        IDENT   __serializer 4294967295
+        PUNCH   : [alone] 4294967295
+        IDENT   __S 4294967295
+      PUNCH   - [joint] 4294967295
+      PUNCH   > [alone] 4294967295
+      IDENT   _serde 4294967295
+      PUNCH   : [joint] 4294967295
+      PUNCH   : [alone] 4294967295
+      IDENT   export 4294967295
+      PUNCH   : [joint] 4294967295
+      PUNCH   : [alone] 4294967295
+      IDENT   Result 4294967295
+      PUNCH   < [alone] 4294967295
+      IDENT   __S 4294967295
+      PUNCH   : [joint] 4294967295
+      PUNCH   : [alone] 4294967295
+      IDENT   Ok 4294967295
+      PUNCH   , [alone] 4294967295
+      IDENT   __S 4294967295
+      PUNCH   : [joint] 4294967295
+      PUNCH   : [alone] 4294967295
+      IDENT   Error 4294967295
+      PUNCH   > [alone] 4294967295
+      IDENT   where 4294967295
+      IDENT   __S 4294967295
+      PUNCH   : [alone] 4294967295
+      IDENT   _serde 4294967295
+      PUNCH   : [joint] 4294967295
+      PUNCH   : [alone] 4294967295
+      IDENT   Serializer 4294967295
+      PUNCH   , [alone] 4294967295
+      SUBTREE {} 4294967295
+        IDENT   let 4294967295
+        IDENT   __serde_state 4294967295
+        PUNCH   = [alone] 4294967295
+        IDENT   try 4294967295
+        PUNCH   ! [alone] 4294967295
+        SUBTREE () 4294967295
+          IDENT   _serde 4294967295
+          PUNCH   : [joint] 4294967295
+          PUNCH   : [alone] 4294967295
+          IDENT   Serializer 4294967295
+          PUNCH   : [joint] 4294967295
+          PUNCH   : [alone] 4294967295
+          IDENT   serialize_struct 4294967295
+          SUBTREE () 4294967295
+            IDENT   __serializer 4294967295
+            PUNCH   , [alone] 4294967295
+            LITERAL "Foo" 4294967295
+            PUNCH   , [alone] 4294967295
+            IDENT   false 4294967295
+            IDENT   as 4294967295
+            IDENT   usize 4294967295
+        PUNCH   ; [alone] 4294967295
+        IDENT   _serde 4294967295
+        PUNCH   : [joint] 4294967295
+        PUNCH   : [alone] 4294967295
+        IDENT   ser 4294967295
+        PUNCH   : [joint] 4294967295
+        PUNCH   : [alone] 4294967295
+        IDENT   SerializeStruct 4294967295
+        PUNCH   : [joint] 4294967295
+        PUNCH   : [alone] 4294967295
+        IDENT   end 4294967295
+        SUBTREE () 4294967295
+          IDENT   __serde_state 4294967295
+  PUNCH   ; [alone] 4294967295
diff --git a/crates/proc_macro_srv/src/tests/mod.rs b/crates/proc_macro_srv/src/tests/mod.rs
new file mode 100644
index 000000000..8e6f28abd
--- /dev/null
+++ b/crates/proc_macro_srv/src/tests/mod.rs
@@ -0,0 +1,45 @@
+//! proc-macro tests
+
+#[macro_use]
+mod utils;
+use test_utils::assert_eq_text;
+use utils::*;
+
+#[test]
+fn test_derive_serialize_proc_macro() {
+    assert_expand(
+        "serde_derive",
+        "Serialize",
+        "1.0",
+        r"struct Foo {}",
+        include_str!("fixtures/test_serialize_proc_macro.txt"),
+    );
+}
+
+#[test]
+fn test_derive_serialize_proc_macro_failed() {
+    assert_expand(
+        "serde_derive",
+        "Serialize",
+        "1.0",
+        r"struct {}",
+        r##"
+SUBTREE $
+  IDENT   compile_error 4294967295
+  PUNCH   ! [alone] 4294967295
+  SUBTREE {} 4294967295
+    LITERAL "expected identifier" 4294967295
+"##,
+    );
+}
+
+#[test]
+fn test_derive_proc_macro_list() {
+    let res = list("serde_derive", "1.0").join("\n");
+
+    assert_eq_text!(
+        &res,
+        r#"Serialize [CustomDerive]
+Deserialize [CustomDerive]"#
+    );
+}
diff --git a/crates/proc_macro_srv/src/tests/utils.rs b/crates/proc_macro_srv/src/tests/utils.rs
new file mode 100644
index 000000000..5828512d6
--- /dev/null
+++ b/crates/proc_macro_srv/src/tests/utils.rs
@@ -0,0 +1,64 @@
+//! utils used in proc-macro tests
+
+use crate::dylib;
+use crate::ProcMacroSrv;
+use proc_macro_api::ListMacrosTask;
+use std::str::FromStr;
+use test_utils::assert_eq_text;
+
+mod fixtures {
+    use cargo_metadata::Message;
+    use std::process::Command;
+
+    // Use current project metadata to get the proc-macro dylib path
+    pub fn dylib_path(crate_name: &str, version: &str) -> std::path::PathBuf {
+        let command = Command::new(toolchain::cargo())
+            .args(&["check", "--message-format", "json"])
+            .output()
+            .unwrap()
+            .stdout;
+
+        for message in Message::parse_stream(command.as_slice()) {
+            match message.unwrap() {
+                Message::CompilerArtifact(artifact) => {
+                    if artifact.target.kind.contains(&"proc-macro".to_string()) {
+                        let repr = format!("{} {}", crate_name, version);
+                        if artifact.package_id.repr.starts_with(&repr) {
+                            return artifact.filenames[0].clone();
+                        }
+                    }
+                }
+                _ => (), // Unknown message
+            }
+        }
+
+        panic!("No proc-macro dylib for {} found!", crate_name);
+    }
+}
+
+fn parse_string(code: &str) -> Option<crate::rustc_server::TokenStream> {
+    Some(crate::rustc_server::TokenStream::from_str(code).unwrap())
+}
+
+pub fn assert_expand(
+    crate_name: &str,
+    macro_name: &str,
+    version: &str,
+    ra_fixture: &str,
+    expect: &str,
+) {
+    let path = fixtures::dylib_path(crate_name, version);
+    let expander = dylib::Expander::new(&path).unwrap();
+    let fixture = parse_string(ra_fixture).unwrap();
+
+    let res = expander.expand(macro_name, &fixture.subtree, None).unwrap();
+    assert_eq_text!(&format!("{:?}", res), &expect.trim());
+}
+
+pub fn list(crate_name: &str, version: &str) -> Vec<String> {
+    let path = fixtures::dylib_path(crate_name, version);
+    let task = ListMacrosTask { lib: path };
+    let mut srv = ProcMacroSrv::default();
+    let res = srv.list_macros(&task).unwrap();
+    res.macros.into_iter().map(|(name, kind)| format!("{} [{:?}]", name, kind)).collect()
+}