Rename proc-macro-srv::server to server_impl

crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs

@@ -0,0 +1,476 @@
+//! proc-macro server backend based on rust-analyzer's internal span representation
+//! This backend is used solely by rust-analyzer as it ties into rust-analyzer internals.
+//!
+//! It is an unfortunate result of how the proc-macro API works that we need to look into the
+//! concrete representation of the spans, and as such, RustRover cannot make use of this unless they
+//! change their representation to be compatible with rust-analyzer's.
+use std::{
+    collections::{HashMap, HashSet},
+    iter,
+    ops::{Bound, Range},
+};
+
+use proc_macro::bridge::{self, server};
+use span::{Span, FIXUP_ERASED_FILE_AST_ID_MARKER};
+use tt::{TextRange, TextSize};
+
+use crate::server_impl::{
+    delim_to_external, delim_to_internal, literal_with_stringify_parts,
+    token_stream::TokenStreamBuilder, Symbol, SymbolInternerRef, SYMBOL_INTERNER,
+};
+mod tt {
+    pub use tt::*;
+
+    pub type Subtree = ::tt::Subtree<super::Span>;
+    pub type TokenTree = ::tt::TokenTree<super::Span>;
+    pub type Leaf = ::tt::Leaf<super::Span>;
+    pub type Literal = ::tt::Literal<super::Span>;
+    pub type Punct = ::tt::Punct<super::Span>;
+    pub type Ident = ::tt::Ident<super::Span>;
+}
+
+type TokenStream = crate::server_impl::TokenStream<Span>;
+
+#[derive(Clone)]
+pub struct SourceFile;
+pub struct FreeFunctions;
+
+pub struct RaSpanServer {
+    pub(crate) interner: SymbolInternerRef,
+    // FIXME: Report this back to the caller to track as dependencies
+    pub tracked_env_vars: HashMap<Box<str>, Option<Box<str>>>,
+    // FIXME: Report this back to the caller to track as dependencies
+    pub tracked_paths: HashSet<Box<str>>,
+    pub call_site: Span,
+    pub def_site: Span,
+    pub mixed_site: Span,
+}
+
+impl server::Types for RaSpanServer {
+    type FreeFunctions = FreeFunctions;
+    type TokenStream = TokenStream;
+    type SourceFile = SourceFile;
+    type Span = Span;
+    type Symbol = Symbol;
+}
+
+impl server::FreeFunctions for RaSpanServer {
+    fn injected_env_var(&mut self, _: &str) -> Option<std::string::String> {
+        None
+    }
+
+    fn track_env_var(&mut self, var: &str, value: Option<&str>) {
+        self.tracked_env_vars.insert(var.into(), value.map(Into::into));
+    }
+    fn track_path(&mut self, path: &str) {
+        self.tracked_paths.insert(path.into());
+    }
+
+    fn literal_from_str(
+        &mut self,
+        s: &str,
+    ) -> Result<bridge::Literal<Self::Span, Self::Symbol>, ()> {
+        use proc_macro::bridge::LitKind;
+        use rustc_lexer::{LiteralKind, Token, TokenKind};
+
+        let mut tokens = rustc_lexer::tokenize(s);
+        let minus_or_lit = tokens.next().unwrap_or(Token { kind: TokenKind::Eof, len: 0 });
+
+        let lit = if minus_or_lit.kind == TokenKind::Minus {
+            let lit = tokens.next().ok_or(())?;
+            if !matches!(
+                lit.kind,
+                TokenKind::Literal {
+                    kind: LiteralKind::Int { .. } | LiteralKind::Float { .. },
+                    ..
+                }
+            ) {
+                return Err(());
+            }
+            lit
+        } else {
+            minus_or_lit
+        };
+
+        if tokens.next().is_some() {
+            return Err(());
+        }
+
+        let TokenKind::Literal { kind, suffix_start } = lit.kind else { return Err(()) };
+        let (kind, start_offset, end_offset) = match kind {
+            LiteralKind::Int { .. } => (LitKind::Integer, 0, 0),
+            LiteralKind::Float { .. } => (LitKind::Float, 0, 0),
+            LiteralKind::Char { terminated } => (LitKind::Char, 1, terminated as usize),
+            LiteralKind::Byte { terminated } => (LitKind::Byte, 2, terminated as usize),
+            LiteralKind::Str { terminated } => (LitKind::Str, 1, terminated as usize),
+            LiteralKind::ByteStr { terminated } => (LitKind::ByteStr, 2, terminated as usize),
+            LiteralKind::CStr { terminated } => (LitKind::CStr, 2, terminated as usize),
+            LiteralKind::RawStr { n_hashes } => (
+                LitKind::StrRaw(n_hashes.unwrap_or_default()),
+                2 + n_hashes.unwrap_or_default() as usize,
+                1 + n_hashes.unwrap_or_default() as usize,
+            ),
+            LiteralKind::RawByteStr { n_hashes } => (
+                LitKind::ByteStrRaw(n_hashes.unwrap_or_default()),
+                3 + n_hashes.unwrap_or_default() as usize,
+                1 + n_hashes.unwrap_or_default() as usize,
+            ),
+            LiteralKind::RawCStr { n_hashes } => (
+                LitKind::CStrRaw(n_hashes.unwrap_or_default()),
+                3 + n_hashes.unwrap_or_default() as usize,
+                1 + n_hashes.unwrap_or_default() as usize,
+            ),
+        };
+
+        let (lit, suffix) = s.split_at(suffix_start as usize);
+        let lit = &lit[start_offset..lit.len() - end_offset];
+        let suffix = match suffix {
+            "" | "_" => None,
+            suffix => Some(Symbol::intern(self.interner, suffix)),
+        };
+
+        Ok(bridge::Literal {
+            kind,
+            symbol: Symbol::intern(self.interner, lit),
+            suffix,
+            span: self.call_site,
+        })
+    }
+
+    fn emit_diagnostic(&mut self, _: bridge::Diagnostic<Self::Span>) {
+        // FIXME handle diagnostic
+    }
+}
+
+impl server::TokenStream for RaSpanServer {
+    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, self.call_site).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::TokenStream, Self::Span, Self::Symbol>,
+    ) -> Self::TokenStream {
+        match tree {
+            bridge::TokenTree::Group(group) => {
+                let group = tt::Subtree {
+                    delimiter: delim_to_internal(group.delimiter, group.span),
+                    token_trees: match group.stream {
+                        Some(stream) => stream.into_iter().collect(),
+                        None => Box::new([]),
+                    },
+                };
+                let tree = tt::TokenTree::from(group);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+
+            bridge::TokenTree::Ident(ident) => {
+                let text = ident.sym.text(self.interner);
+                let text =
+                    if ident.is_raw { ::tt::SmolStr::from_iter(["r#", &text]) } else { text };
+                let ident: tt::Ident = tt::Ident { text, span: ident.span };
+                let leaf = tt::Leaf::from(ident);
+                let tree = tt::TokenTree::from(leaf);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+
+            bridge::TokenTree::Literal(literal) => {
+                let text = literal_with_stringify_parts(&literal, self.interner, |parts| {
+                    ::tt::SmolStr::from_iter(parts.iter().copied())
+                });
+
+                let literal = tt::Literal { text, span: literal.span };
+                let leaf: tt::Leaf = tt::Leaf::from(literal);
+                let tree = tt::TokenTree::from(leaf);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+
+            bridge::TokenTree::Punct(p) => {
+                let punct = tt::Punct {
+                    char: p.ch as char,
+                    spacing: if p.joint { tt::Spacing::Joint } else { tt::Spacing::Alone },
+                    span: p.span,
+                };
+                let leaf = tt::Leaf::from(punct);
+                let tree = tt::TokenTree::from(leaf);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+        }
+    }
+
+    fn expand_expr(&mut self, self_: &Self::TokenStream) -> Result<Self::TokenStream, ()> {
+        // FIXME: requires db, more importantly this requires name resolution so we would need to
+        // eagerly expand this proc-macro, but we can't know that this proc-macro is eager until we
+        // expand it ...
+        // This calls for some kind of marker that a proc-macro wants to access this eager API,
+        // otherwise we need to treat every proc-macro eagerly / or not support this.
+        Ok(self_.clone())
+    }
+
+    fn concat_trees(
+        &mut self,
+        base: Option<Self::TokenStream>,
+        trees: Vec<bridge::TokenTree<Self::TokenStream, Self::Span, Self::Symbol>>,
+    ) -> Self::TokenStream {
+        let mut builder = TokenStreamBuilder::new();
+        if let Some(base) = base {
+            builder.push(base);
+        }
+        for tree in trees {
+            builder.push(self.from_token_tree(tree));
+        }
+        builder.build()
+    }
+
+    fn concat_streams(
+        &mut self,
+        base: Option<Self::TokenStream>,
+        streams: Vec<Self::TokenStream>,
+    ) -> Self::TokenStream {
+        let mut builder = TokenStreamBuilder::new();
+        if let Some(base) = base {
+            builder.push(base);
+        }
+        for stream in streams {
+            builder.push(stream);
+        }
+        builder.build()
+    }
+
+    fn into_trees(
+        &mut self,
+        stream: Self::TokenStream,
+    ) -> Vec<bridge::TokenTree<Self::TokenStream, Self::Span, Self::Symbol>> {
+        stream
+            .into_iter()
+            .map(|tree| match tree {
+                tt::TokenTree::Leaf(tt::Leaf::Ident(ident)) => {
+                    bridge::TokenTree::Ident(match ident.text.strip_prefix("r#") {
+                        Some(text) => bridge::Ident {
+                            sym: Symbol::intern(self.interner, text),
+                            is_raw: true,
+                            span: ident.span,
+                        },
+                        None => bridge::Ident {
+                            sym: Symbol::intern(self.interner, &ident.text),
+                            is_raw: false,
+                            span: ident.span,
+                        },
+                    })
+                }
+                tt::TokenTree::Leaf(tt::Leaf::Literal(lit)) => {
+                    bridge::TokenTree::Literal(bridge::Literal {
+                        span: lit.span,
+                        ..server::FreeFunctions::literal_from_str(self, &lit.text).unwrap()
+                    })
+                }
+                tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) => {
+                    bridge::TokenTree::Punct(bridge::Punct {
+                        ch: punct.char as u8,
+                        joint: punct.spacing == tt::Spacing::Joint,
+                        span: punct.span,
+                    })
+                }
+                tt::TokenTree::Subtree(subtree) => bridge::TokenTree::Group(bridge::Group {
+                    delimiter: delim_to_external(subtree.delimiter),
+                    stream: if subtree.token_trees.is_empty() {
+                        None
+                    } else {
+                        Some(subtree.token_trees.into_vec().into_iter().collect())
+                    },
+                    span: bridge::DelimSpan::from_single(subtree.delimiter.open),
+                }),
+            })
+            .collect()
+    }
+}
+
+impl server::SourceFile for RaSpanServer {
+    fn eq(&mut self, _file1: &Self::SourceFile, _file2: &Self::SourceFile) -> bool {
+        // FIXME
+        true
+    }
+    fn path(&mut self, _file: &Self::SourceFile) -> String {
+        // FIXME
+        String::new()
+    }
+    fn is_real(&mut self, _file: &Self::SourceFile) -> bool {
+        true
+    }
+}
+
+impl server::Span for RaSpanServer {
+    fn debug(&mut self, span: Self::Span) -> String {
+        format!("{:?}", span)
+    }
+    fn source_file(&mut self, _span: Self::Span) -> Self::SourceFile {
+        // FIXME stub, requires db
+        SourceFile {}
+    }
+    fn save_span(&mut self, _span: Self::Span) -> usize {
+        // FIXME, quote is incompatible with third-party tools
+        // This is called by the quote proc-macro which is expanded when the proc-macro is compiled
+        // As such, r-a will never observe this
+        0
+    }
+    fn recover_proc_macro_span(&mut self, _id: usize) -> Self::Span {
+        // FIXME, quote is incompatible with third-party tools
+        // This is called by the expansion of quote!, r-a will observe this, but we don't have
+        // access to the spans that were encoded
+        self.call_site
+    }
+    /// 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> {
+        // FIXME requires db, needs special handling wrt fixup spans
+        None
+    }
+
+    fn parent(&mut self, _span: Self::Span) -> Option<Self::Span> {
+        // FIXME requires db, looks up the parent call site
+        None
+    }
+    fn source(&mut self, span: Self::Span) -> Self::Span {
+        // FIXME requires db, returns the top level call site
+        span
+    }
+    fn byte_range(&mut self, span: Self::Span) -> Range<usize> {
+        // FIXME requires db to resolve the ast id, THIS IS NOT INCREMENTAL
+        Range { start: span.range.start().into(), end: span.range.end().into() }
+    }
+    fn join(&mut self, first: Self::Span, second: Self::Span) -> Option<Self::Span> {
+        // We can't modify the span range for fixup spans, those are meaningful to fixup, so just
+        // prefer the non-fixup span.
+        if first.anchor.ast_id == FIXUP_ERASED_FILE_AST_ID_MARKER {
+            return Some(second);
+        }
+        if second.anchor.ast_id == FIXUP_ERASED_FILE_AST_ID_MARKER {
+            return Some(first);
+        }
+        // FIXME: Once we can talk back to the client, implement a "long join" request for anchors
+        // that differ in [AstId]s as joining those spans requires resolving the AstIds.
+        if first.anchor != second.anchor {
+            return None;
+        }
+        // Differing context, we can't merge these so prefer the one that's root
+        if first.ctx != second.ctx {
+            if first.ctx.is_root() {
+                return Some(second);
+            } else if second.ctx.is_root() {
+                return Some(first);
+            }
+        }
+        Some(Span {
+            range: first.range.cover(second.range),
+            anchor: second.anchor,
+            ctx: second.ctx,
+        })
+    }
+    fn subspan(
+        &mut self,
+        span: Self::Span,
+        start: Bound<usize>,
+        end: Bound<usize>,
+    ) -> Option<Self::Span> {
+        // We can't modify the span range for fixup spans, those are meaningful to fixup.
+        if span.anchor.ast_id == FIXUP_ERASED_FILE_AST_ID_MARKER {
+            return Some(span);
+        }
+        let length = span.range.len().into();
+
+        let start: u32 = match start {
+            Bound::Included(lo) => lo,
+            Bound::Excluded(lo) => lo.checked_add(1)?,
+            Bound::Unbounded => 0,
+        }
+        .try_into()
+        .ok()?;
+
+        let end: u32 = match end {
+            Bound::Included(hi) => hi.checked_add(1)?,
+            Bound::Excluded(hi) => hi,
+            Bound::Unbounded => span.range.len().into(),
+        }
+        .try_into()
+        .ok()?;
+
+        // Bounds check the values, preventing addition overflow and OOB spans.
+        let span_start = span.range.start().into();
+        if (u32::MAX - start) < span_start
+            || (u32::MAX - end) < span_start
+            || start >= end
+            || end > length
+        {
+            return None;
+        }
+
+        Some(Span {
+            range: TextRange::new(TextSize::from(start), TextSize::from(end)) + span.range.start(),
+            ..span
+        })
+    }
+
+    fn resolved_at(&mut self, span: Self::Span, at: Self::Span) -> Self::Span {
+        Span { ctx: at.ctx, ..span }
+    }
+
+    fn end(&mut self, span: Self::Span) -> Self::Span {
+        // We can't modify the span range for fixup spans, those are meaningful to fixup.
+        if span.anchor.ast_id == FIXUP_ERASED_FILE_AST_ID_MARKER {
+            return span;
+        }
+        Span { range: TextRange::empty(span.range.end()), ..span }
+    }
+
+    fn start(&mut self, span: Self::Span) -> Self::Span {
+        // We can't modify the span range for fixup spans, those are meaningful to fixup.
+        if span.anchor.ast_id == FIXUP_ERASED_FILE_AST_ID_MARKER {
+            return span;
+        }
+        Span { range: TextRange::empty(span.range.start()), ..span }
+    }
+
+    fn line(&mut self, _span: Self::Span) -> usize {
+        // FIXME requires db to resolve line index, THIS IS NOT INCREMENTAL
+        0
+    }
+
+    fn column(&mut self, _span: Self::Span) -> usize {
+        // FIXME requires db to resolve line index, THIS IS NOT INCREMENTAL
+        0
+    }
+}
+
+impl server::Symbol for RaSpanServer {
+    fn normalize_and_validate_ident(&mut self, string: &str) -> Result<Self::Symbol, ()> {
+        // FIXME: nfc-normalize and validate idents
+        Ok(<Self as server::Server>::intern_symbol(string))
+    }
+}
+
+impl server::Server for RaSpanServer {
+    fn globals(&mut self) -> bridge::ExpnGlobals<Self::Span> {
+        bridge::ExpnGlobals {
+            def_site: self.def_site,
+            call_site: self.call_site,
+            mixed_site: self.mixed_site,
+        }
+    }
+
+    fn intern_symbol(ident: &str) -> Self::Symbol {
+        // FIXME: should be `self.interner` once the proc-macro api allows it.
+        Symbol::intern(&SYMBOL_INTERNER, &::tt::SmolStr::from(ident))
+    }
+
+    fn with_symbol_string(symbol: &Self::Symbol, f: impl FnOnce(&str)) {
+        // FIXME: should be `self.interner` once the proc-macro api allows it.
+        f(symbol.text(&SYMBOL_INTERNER).as_str())
+    }
+}

crates/proc-macro-srv/src/server_impl/symbol.rs

@@ -0,0 +1,48 @@
+//! Symbol interner for proc-macro-srv
+
+use std::{cell::RefCell, collections::HashMap, thread::LocalKey};
+use tt::SmolStr;
+
+thread_local! {
+    pub(crate) static SYMBOL_INTERNER: RefCell<SymbolInterner> = Default::default();
+}
+
+// ID for an interned symbol.
+#[derive(Hash, Eq, PartialEq, Copy, Clone)]
+pub struct Symbol(u32);
+
+pub(crate) type SymbolInternerRef = &'static LocalKey<RefCell<SymbolInterner>>;
+
+impl Symbol {
+    pub(super) fn intern(interner: SymbolInternerRef, data: &str) -> Symbol {
+        interner.with(|i| i.borrow_mut().intern(data))
+    }
+
+    pub(super) fn text(&self, interner: SymbolInternerRef) -> SmolStr {
+        interner.with(|i| i.borrow().get(self).clone())
+    }
+}
+
+#[derive(Default)]
+pub(crate) struct SymbolInterner {
+    idents: HashMap<SmolStr, u32>,
+    ident_data: Vec<SmolStr>,
+}
+
+impl SymbolInterner {
+    fn intern(&mut self, data: &str) -> Symbol {
+        if let Some(index) = self.idents.get(data) {
+            return Symbol(*index);
+        }
+
+        let index = self.idents.len() as u32;
+        let data = SmolStr::from(data);
+        self.ident_data.push(data.clone());
+        self.idents.insert(data, index);
+        Symbol(index)
+    }
+
+    fn get(&self, sym: &Symbol) -> &SmolStr {
+        &self.ident_data[sym.0 as usize]
+    }
+}

crates/proc-macro-srv/src/server_impl/token_id.rs

@@ -0,0 +1,436 @@
+//! proc-macro server backend based on [`proc_macro_api::msg::TokenId`] as the backing span.
+//! This backend is rather inflexible, used by RustRover and older rust-analyzer versions.
+use std::{
+    iter,
+    ops::{Bound, Range},
+};
+
+use proc_macro::bridge::{self, server};
+
+use crate::server_impl::{
+    delim_to_external, delim_to_internal, literal_with_stringify_parts,
+    token_stream::TokenStreamBuilder, Symbol, SymbolInternerRef, SYMBOL_INTERNER,
+};
+mod tt {
+    pub use proc_macro_api::msg::TokenId;
+
+    pub use tt::*;
+
+    pub type Subtree = ::tt::Subtree<TokenId>;
+    pub type TokenTree = ::tt::TokenTree<TokenId>;
+    pub type Leaf = ::tt::Leaf<TokenId>;
+    pub type Literal = ::tt::Literal<TokenId>;
+    pub type Punct = ::tt::Punct<TokenId>;
+    pub type Ident = ::tt::Ident<TokenId>;
+}
+type Group = tt::Subtree;
+type TokenTree = tt::TokenTree;
+#[allow(unused)]
+type Punct = tt::Punct;
+type Spacing = tt::Spacing;
+#[allow(unused)]
+type Literal = tt::Literal;
+type Span = tt::TokenId;
+type TokenStream = crate::server_impl::TokenStream<Span>;
+
+#[derive(Clone)]
+pub struct SourceFile;
+pub struct FreeFunctions;
+
+pub struct TokenIdServer {
+    pub(crate) interner: SymbolInternerRef,
+    pub call_site: Span,
+    pub def_site: Span,
+    pub mixed_site: Span,
+}
+
+impl server::Types for TokenIdServer {
+    type FreeFunctions = FreeFunctions;
+    type TokenStream = TokenStream;
+    type SourceFile = SourceFile;
+    type Span = Span;
+    type Symbol = Symbol;
+}
+
+impl server::FreeFunctions for TokenIdServer {
+    fn injected_env_var(&mut self, _: &str) -> Option<std::string::String> {
+        None
+    }
+    fn track_env_var(&mut self, _var: &str, _value: Option<&str>) {}
+    fn track_path(&mut self, _path: &str) {}
+    fn literal_from_str(
+        &mut self,
+        s: &str,
+    ) -> Result<bridge::Literal<Self::Span, Self::Symbol>, ()> {
+        use proc_macro::bridge::LitKind;
+        use rustc_lexer::{LiteralKind, Token, TokenKind};
+
+        let mut tokens = rustc_lexer::tokenize(s);
+        let minus_or_lit = tokens.next().unwrap_or(Token { kind: TokenKind::Eof, len: 0 });
+
+        let lit = if minus_or_lit.kind == TokenKind::Minus {
+            let lit = tokens.next().ok_or(())?;
+            if !matches!(
+                lit.kind,
+                TokenKind::Literal {
+                    kind: LiteralKind::Int { .. } | LiteralKind::Float { .. },
+                    ..
+                }
+            ) {
+                return Err(());
+            }
+            lit
+        } else {
+            minus_or_lit
+        };
+
+        if tokens.next().is_some() {
+            return Err(());
+        }
+
+        let TokenKind::Literal { kind, suffix_start } = lit.kind else { return Err(()) };
+
+        let (kind, start_offset, end_offset) = match kind {
+            LiteralKind::Int { .. } => (LitKind::Integer, 0, 0),
+            LiteralKind::Float { .. } => (LitKind::Float, 0, 0),
+            LiteralKind::Char { terminated } => (LitKind::Char, 1, terminated as usize),
+            LiteralKind::Byte { terminated } => (LitKind::Byte, 2, terminated as usize),
+            LiteralKind::Str { terminated } => (LitKind::Str, 1, terminated as usize),
+            LiteralKind::ByteStr { terminated } => (LitKind::ByteStr, 2, terminated as usize),
+            LiteralKind::CStr { terminated } => (LitKind::CStr, 2, terminated as usize),
+            LiteralKind::RawStr { n_hashes } => (
+                LitKind::StrRaw(n_hashes.unwrap_or_default()),
+                2 + n_hashes.unwrap_or_default() as usize,
+                1 + n_hashes.unwrap_or_default() as usize,
+            ),
+            LiteralKind::RawByteStr { n_hashes } => (
+                LitKind::ByteStrRaw(n_hashes.unwrap_or_default()),
+                3 + n_hashes.unwrap_or_default() as usize,
+                1 + n_hashes.unwrap_or_default() as usize,
+            ),
+            LiteralKind::RawCStr { n_hashes } => (
+                LitKind::CStrRaw(n_hashes.unwrap_or_default()),
+                3 + n_hashes.unwrap_or_default() as usize,
+                1 + n_hashes.unwrap_or_default() as usize,
+            ),
+        };
+
+        let (lit, suffix) = s.split_at(suffix_start as usize);
+        let lit = &lit[start_offset..lit.len() - end_offset];
+        let suffix = match suffix {
+            "" | "_" => None,
+            suffix => Some(Symbol::intern(self.interner, suffix)),
+        };
+
+        Ok(bridge::Literal {
+            kind,
+            symbol: Symbol::intern(self.interner, lit),
+            suffix,
+            span: self.call_site,
+        })
+    }
+
+    fn emit_diagnostic(&mut self, _: bridge::Diagnostic<Self::Span>) {}
+}
+
+impl server::TokenStream for TokenIdServer {
+    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, self.call_site).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::TokenStream, Self::Span, Self::Symbol>,
+    ) -> Self::TokenStream {
+        match tree {
+            bridge::TokenTree::Group(group) => {
+                let group = Group {
+                    delimiter: delim_to_internal(group.delimiter, group.span),
+                    token_trees: match group.stream {
+                        Some(stream) => stream.into_iter().collect(),
+                        None => Box::new([]),
+                    },
+                };
+                let tree = TokenTree::from(group);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+
+            bridge::TokenTree::Ident(ident) => {
+                let text = ident.sym.text(self.interner);
+                let text =
+                    if ident.is_raw { ::tt::SmolStr::from_iter(["r#", &text]) } else { text };
+                let ident: tt::Ident = tt::Ident { text, span: ident.span };
+                let leaf = tt::Leaf::from(ident);
+                let tree = TokenTree::from(leaf);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+
+            bridge::TokenTree::Literal(literal) => {
+                let text = literal_with_stringify_parts(&literal, self.interner, |parts| {
+                    ::tt::SmolStr::from_iter(parts.iter().copied())
+                });
+
+                let literal = tt::Literal { text, span: literal.span };
+
+                let leaf = tt::Leaf::from(literal);
+                let tree = TokenTree::from(leaf);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+
+            bridge::TokenTree::Punct(p) => {
+                let punct = tt::Punct {
+                    char: p.ch as char,
+                    spacing: if p.joint { Spacing::Joint } else { Spacing::Alone },
+                    span: p.span,
+                };
+                let leaf = tt::Leaf::from(punct);
+                let tree = TokenTree::from(leaf);
+                Self::TokenStream::from_iter(iter::once(tree))
+            }
+        }
+    }
+
+    fn expand_expr(&mut self, self_: &Self::TokenStream) -> Result<Self::TokenStream, ()> {
+        Ok(self_.clone())
+    }
+
+    fn concat_trees(
+        &mut self,
+        base: Option<Self::TokenStream>,
+        trees: Vec<bridge::TokenTree<Self::TokenStream, Self::Span, Self::Symbol>>,
+    ) -> Self::TokenStream {
+        let mut builder = TokenStreamBuilder::new();
+        if let Some(base) = base {
+            builder.push(base);
+        }
+        for tree in trees {
+            builder.push(self.from_token_tree(tree));
+        }
+        builder.build()
+    }
+
+    fn concat_streams(
+        &mut self,
+        base: Option<Self::TokenStream>,
+        streams: Vec<Self::TokenStream>,
+    ) -> Self::TokenStream {
+        let mut builder = TokenStreamBuilder::new();
+        if let Some(base) = base {
+            builder.push(base);
+        }
+        for stream in streams {
+            builder.push(stream);
+        }
+        builder.build()
+    }
+
+    fn into_trees(
+        &mut self,
+        stream: Self::TokenStream,
+    ) -> Vec<bridge::TokenTree<Self::TokenStream, Self::Span, Self::Symbol>> {
+        stream
+            .into_iter()
+            .map(|tree| match tree {
+                tt::TokenTree::Leaf(tt::Leaf::Ident(ident)) => {
+                    bridge::TokenTree::Ident(bridge::Ident {
+                        sym: Symbol::intern(self.interner, ident.text.trim_start_matches("r#")),
+                        is_raw: ident.text.starts_with("r#"),
+                        span: ident.span,
+                    })
+                }
+                tt::TokenTree::Leaf(tt::Leaf::Literal(lit)) => {
+                    bridge::TokenTree::Literal(bridge::Literal {
+                        span: lit.span,
+                        ..server::FreeFunctions::literal_from_str(self, &lit.text)
+                            .unwrap_or_else(|_| panic!("`{}`", lit.text))
+                    })
+                }
+                tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) => {
+                    bridge::TokenTree::Punct(bridge::Punct {
+                        ch: punct.char as u8,
+                        joint: punct.spacing == Spacing::Joint,
+                        span: punct.span,
+                    })
+                }
+                tt::TokenTree::Subtree(subtree) => bridge::TokenTree::Group(bridge::Group {
+                    delimiter: delim_to_external(subtree.delimiter),
+                    stream: if subtree.token_trees.is_empty() {
+                        None
+                    } else {
+                        Some(TokenStream { token_trees: subtree.token_trees.into_vec() })
+                    },
+                    span: bridge::DelimSpan::from_single(subtree.delimiter.open),
+                }),
+            })
+            .collect()
+    }
+}
+
+impl server::SourceFile for TokenIdServer {
+    fn eq(&mut self, _file1: &Self::SourceFile, _file2: &Self::SourceFile) -> bool {
+        true
+    }
+    fn path(&mut self, _file: &Self::SourceFile) -> String {
+        String::new()
+    }
+    fn is_real(&mut self, _file: &Self::SourceFile) -> bool {
+        true
+    }
+}
+
+impl server::Span for TokenIdServer {
+    fn debug(&mut self, span: Self::Span) -> String {
+        format!("{:?}", span.0)
+    }
+    fn source_file(&mut self, _span: Self::Span) -> Self::SourceFile {
+        SourceFile {}
+    }
+    fn save_span(&mut self, _span: Self::Span) -> usize {
+        0
+    }
+    fn recover_proc_macro_span(&mut self, _id: usize) -> Self::Span {
+        self.call_site
+    }
+    /// 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> {
+        None
+    }
+    fn source(&mut self, span: Self::Span) -> Self::Span {
+        span
+    }
+    fn byte_range(&mut self, _span: Self::Span) -> Range<usize> {
+        Range { start: 0, end: 0 }
+    }
+    fn join(&mut self, first: Self::Span, _second: Self::Span) -> Option<Self::Span> {
+        // Just return the first span again, because some macros will unwrap the result.
+        Some(first)
+    }
+    fn subspan(
+        &mut self,
+        span: Self::Span,
+        _start: Bound<usize>,
+        _end: Bound<usize>,
+    ) -> Option<Self::Span> {
+        // Just return the span again, because some macros will unwrap the result.
+        Some(span)
+    }
+    fn resolved_at(&mut self, _span: Self::Span, _at: Self::Span) -> Self::Span {
+        self.call_site
+    }
+
+    fn end(&mut self, _self_: Self::Span) -> Self::Span {
+        self.call_site
+    }
+
+    fn start(&mut self, _self_: Self::Span) -> Self::Span {
+        self.call_site
+    }
+
+    fn line(&mut self, _span: Self::Span) -> usize {
+        0
+    }
+
+    fn column(&mut self, _span: Self::Span) -> usize {
+        0
+    }
+}
+
+impl server::Symbol for TokenIdServer {
+    fn normalize_and_validate_ident(&mut self, string: &str) -> Result<Self::Symbol, ()> {
+        // FIXME: nfc-normalize and validate idents
+        Ok(<Self as server::Server>::intern_symbol(string))
+    }
+}
+
+impl server::Server for TokenIdServer {
+    fn globals(&mut self) -> bridge::ExpnGlobals<Self::Span> {
+        bridge::ExpnGlobals {
+            def_site: self.def_site,
+            call_site: self.call_site,
+            mixed_site: self.mixed_site,
+        }
+    }
+
+    fn intern_symbol(ident: &str) -> Self::Symbol {
+        Symbol::intern(&SYMBOL_INTERNER, &::tt::SmolStr::from(ident))
+    }
+
+    fn with_symbol_string(symbol: &Self::Symbol, f: impl FnOnce(&str)) {
+        f(symbol.text(&SYMBOL_INTERNER).as_str())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_ra_server_to_string() {
+        let s = TokenStream {
+            token_trees: vec![
+                tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
+                    text: "struct".into(),
+                    span: tt::TokenId(0),
+                })),
+                tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
+                    text: "T".into(),
+                    span: tt::TokenId(0),
+                })),
+                tt::TokenTree::Subtree(tt::Subtree {
+                    delimiter: tt::Delimiter {
+                        open: tt::TokenId(0),
+                        close: tt::TokenId(0),
+                        kind: tt::DelimiterKind::Brace,
+                    },
+                    token_trees: Box::new([]),
+                }),
+            ],
+        };
+
+        assert_eq!(s.to_string(), "struct T {}");
+    }
+
+    #[test]
+    fn test_ra_server_from_str() {
+        let subtree_paren_a = tt::TokenTree::Subtree(tt::Subtree {
+            delimiter: tt::Delimiter {
+                open: tt::TokenId(0),
+                close: tt::TokenId(0),
+                kind: tt::DelimiterKind::Parenthesis,
+            },
+            token_trees: Box::new([tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
+                text: "a".into(),
+                span: tt::TokenId(0),
+            }))]),
+        });
+
+        let t1 = TokenStream::from_str("(a)", tt::TokenId(0)).unwrap();
+        assert_eq!(t1.token_trees.len(), 1);
+        assert_eq!(t1.token_trees[0], subtree_paren_a);
+
+        let t2 = TokenStream::from_str("(a);", tt::TokenId(0)).unwrap();
+        assert_eq!(t2.token_trees.len(), 2);
+        assert_eq!(t2.token_trees[0], subtree_paren_a);
+
+        let underscore = TokenStream::from_str("_", tt::TokenId(0)).unwrap();
+        assert_eq!(
+            underscore.token_trees[0],
+            tt::TokenTree::Leaf(tt::Leaf::Ident(tt::Ident {
+                text: "_".into(),
+                span: tt::TokenId(0),
+            }))
+        );
+    }
+}

crates/proc-macro-srv/src/server_impl/token_stream.rs

@@ -0,0 +1,155 @@
+//! TokenStream implementation used by sysroot ABI
+
+use tt::TokenTree;
+
+#[derive(Debug, Clone)]
+pub struct TokenStream<S> {
+    pub(super) token_trees: Vec<TokenTree<S>>,
+}
+
+impl<S> Default for TokenStream<S> {
+    fn default() -> Self {
+        Self { token_trees: vec![] }
+    }
+}
+
+impl<S> TokenStream<S> {
+    pub(crate) fn new() -> Self {
+        TokenStream::default()
+    }
+
+    pub(crate) fn with_subtree(subtree: tt::Subtree<S>) -> Self {
+        if subtree.delimiter.kind != tt::DelimiterKind::Invisible {
+            TokenStream { token_trees: vec![TokenTree::Subtree(subtree)] }
+        } else {
+            TokenStream { token_trees: subtree.token_trees.into_vec() }
+        }
+    }
+
+    pub(crate) fn into_subtree(self, call_site: S) -> tt::Subtree<S>
+    where
+        S: Copy,
+    {
+        tt::Subtree {
+            delimiter: tt::Delimiter {
+                open: call_site,
+                close: call_site,
+                kind: tt::DelimiterKind::Invisible,
+            },
+            token_trees: self.token_trees.into_boxed_slice(),
+        }
+    }
+
+    pub(super) fn is_empty(&self) -> bool {
+        self.token_trees.is_empty()
+    }
+}
+
+/// Creates a token stream containing a single token tree.
+impl<S> From<TokenTree<S>> for TokenStream<S> {
+    fn from(tree: TokenTree<S>) -> TokenStream<S> {
+        TokenStream { token_trees: vec![tree] }
+    }
+}
+
+/// Collects a number of token trees into a single stream.
+impl<S> FromIterator<TokenTree<S>> for TokenStream<S> {
+    fn from_iter<I: IntoIterator<Item = TokenTree<S>>>(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<S> FromIterator<TokenStream<S>> for TokenStream<S> {
+    fn from_iter<I: IntoIterator<Item = TokenStream<S>>>(streams: I) -> Self {
+        let mut builder = TokenStreamBuilder::new();
+        streams.into_iter().for_each(|stream| builder.push(stream));
+        builder.build()
+    }
+}
+
+impl<S> Extend<TokenTree<S>> for TokenStream<S> {
+    fn extend<I: IntoIterator<Item = TokenTree<S>>>(&mut self, trees: I) {
+        self.extend(trees.into_iter().map(TokenStream::from));
+    }
+}
+
+impl<S> Extend<TokenStream<S>> for TokenStream<S> {
+    fn extend<I: IntoIterator<Item = TokenStream<S>>>(&mut self, streams: I) {
+        for item in streams {
+            for tkn in item {
+                match tkn {
+                    tt::TokenTree::Subtree(subtree)
+                        if subtree.delimiter.kind == tt::DelimiterKind::Invisible =>
+                    {
+                        self.token_trees.extend(subtree.token_trees.into_vec().into_iter());
+                    }
+                    _ => {
+                        self.token_trees.push(tkn);
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub(super) struct TokenStreamBuilder<S> {
+    acc: TokenStream<S>,
+}
+
+/// pub(super)lic implementation details for the `TokenStream` type, such as iterators.
+pub(super) mod token_stream {
+
+    use core::fmt;
+
+    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<S> IntoIterator for TokenStream<S> {
+        type Item = TokenTree<S>;
+        type IntoIter = std::vec::IntoIter<TokenTree<S>>;
+
+        fn into_iter(self) -> Self::IntoIter {
+            self.token_trees.into_iter()
+        }
+    }
+
+    /// 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<S: Copy + fmt::Debug> TokenStream<S> {
+        pub(crate) fn from_str(src: &str, call_site: S) -> Result<TokenStream<S>, String> {
+            let subtree =
+                mbe::parse_to_token_tree_static_span(call_site, src).ok_or("lexing error")?;
+
+            Ok(TokenStream::with_subtree(subtree))
+        }
+    }
+
+    impl<S> ToString for TokenStream<S> {
+        fn to_string(&self) -> String {
+            ::tt::pretty(&self.token_trees)
+        }
+    }
+}
+
+impl<S> TokenStreamBuilder<S> {
+    pub(super) fn new() -> TokenStreamBuilder<S> {
+        TokenStreamBuilder { acc: TokenStream::new() }
+    }
+
+    pub(super) fn push(&mut self, stream: TokenStream<S>) {
+        self.acc.extend(stream.into_iter())
+    }
+
+    pub(super) fn build(self) -> TokenStream<S> {
+        self.acc
+    }
+}