Merge #3906

3906: Implement proc_macro rustc server r=matklad a=edwin0cheng

This PR implement the `ra_tt::TokenTree` based rustc server for lib_proc_macro. 

Note that span information is not implemented yet. 

Co-authored-by: Edwin Cheng <[email protected]>

4 files changed, 689 insertions, 1 deletions

diff --git a/Cargo.lock b/Cargo.lock
index eb9824218..34f05e83a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1081,6 +1081,7 @@ version = "0.1.0"
 dependencies = [
  "cargo_metadata",
  "difference",
+ "ra_mbe",
  "ra_proc_macro",
  "ra_tt",
  "serde_derive",
diff --git a/crates/ra_proc_macro_srv/Cargo.toml b/crates/ra_proc_macro_srv/Cargo.toml
index 6300d668a..f08de5fc7 100644
--- a/crates/ra_proc_macro_srv/Cargo.toml
+++ b/crates/ra_proc_macro_srv/Cargo.toml
@@ -10,9 +10,9 @@ doctest = false
 
 [dependencies]
 ra_tt = { path = "../ra_tt" }
+ra_mbe = { path = "../ra_mbe" }
 ra_proc_macro = { path = "../ra_proc_macro" }
 
-
 [dev-dependencies]
 cargo_metadata = "0.9.1"
 difference = "2.0.0"
diff --git a/crates/ra_proc_macro_srv/src/lib.rs b/crates/ra_proc_macro_srv/src/lib.rs
index 80cfa1174..f376df236 100644
--- a/crates/ra_proc_macro_srv/src/lib.rs
+++ b/crates/ra_proc_macro_srv/src/lib.rs
@@ -14,6 +14,9 @@
 #[doc(hidden)]
 mod proc_macro;
 
+#[doc(hidden)]
+mod rustc_server;
+
 use proc_macro::bridge::client::TokenStream;
 use ra_proc_macro::{ExpansionResult, ExpansionTask, ListMacrosResult, ListMacrosTask};
 
diff --git a/crates/ra_proc_macro_srv/src/rustc_server.rs b/crates/ra_proc_macro_srv/src/rustc_server.rs
new file mode 100644
index 000000000..92d1fd989
--- /dev/null
+++ b/crates/ra_proc_macro_srv/src/rustc_server.rs
@@ -0,0 +1,684 @@
+//! Rustc proc-macro server implementation with ra_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 ra_tt instead for better intergation with RA.
+//!
+//! FIXME: No span and source file informatin is implemented yet
+
+use crate::proc_macro::bridge::{self, server};
+use ra_tt as tt;
+
+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 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 {
+            self.subtree.token_trees.extend(&mut item.into_iter())
+        }
+    }
+}
+
+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 super::{tt, TokenStream, TokenTree};
+    use std::str::FromStr;
+
+    /// 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) =
+                ra_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 {
+    // FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
+    fn debug(&mut self, literal: &Self::Literal) -> String {
+        format!("{:?}", literal)
+    }
+
+    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\"");
+    }
+}