9 files changed, 809 insertions, 25 deletions

diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index c698d6e8c..5ba5254fd 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -132,13 +132,12 @@ mod handlers {
 
     pub(crate) fn all() -> &'static [AssistHandler] {
         &[
+            // These are alphabetic for the foolish consistency
             add_custom_impl::add_custom_impl,
             add_derive::add_derive,
             add_explicit_type::add_explicit_type,
             add_function::add_function,
             add_impl::add_impl,
-            add_missing_impl_members::add_missing_default_members,
-            add_missing_impl_members::add_missing_impl_members,
             add_new::add_new,
             apply_demorgan::apply_demorgan,
             auto_import::auto_import,
@@ -168,6 +167,9 @@ mod handlers {
             replace_unwrap_with_match::replace_unwrap_with_match,
             split_import::split_import,
             add_from_impl_for_enum::add_from_impl_for_enum,
+            // These are manually sorted for better priorities
+            add_missing_impl_members::add_missing_impl_members,
+            add_missing_impl_members::add_missing_default_members,
         ]
     }
 }
diff --git a/crates/ra_hir_def/src/adt.rs b/crates/ra_hir_def/src/adt.rs
index de07fc952..7fc4cd76e 100644
--- a/crates/ra_hir_def/src/adt.rs
+++ b/crates/ra_hir_def/src/adt.rs
@@ -54,6 +54,7 @@ pub struct StructFieldData {
 impl StructData {
     pub(crate) fn struct_data_query(db: &dyn DefDatabase, id: StructId) -> Arc<StructData> {
         let src = id.lookup(db).source(db);
+
         let name = src.value.name().map_or_else(Name::missing, |n| n.as_name());
         let variant_data = VariantData::new(db, src.map(|s| s.kind()));
         let variant_data = Arc::new(variant_data);
diff --git a/crates/ra_hir_def/src/data.rs b/crates/ra_hir_def/src/data.rs
index 04bd4a305..606ec48b0 100644
--- a/crates/ra_hir_def/src/data.rs
+++ b/crates/ra_hir_def/src/data.rs
@@ -3,15 +3,18 @@
 use std::sync::Arc;
 
 use hir_expand::{
+    hygiene::Hygiene,
     name::{name, AsName, Name},
     AstId, InFile,
 };
+use ra_cfg::CfgOptions;
 use ra_prof::profile;
 use ra_syntax::ast::{
     self, AstNode, ImplItem, ModuleItemOwner, NameOwner, TypeAscriptionOwner, VisibilityOwner,
 };
 
 use crate::{
+    attr::Attrs,
     db::DefDatabase,
     path::{path, GenericArgs, Path},
     src::HasSource,
@@ -26,6 +29,7 @@ pub struct FunctionData {
     pub name: Name,
     pub params: Vec<TypeRef>,
     pub ret_type: TypeRef,
+    pub attrs: Attrs,
     /// True if the first param is `self`. This is relevant to decide whether this
     /// can be called as a method.
     pub has_self_param: bool,
@@ -63,6 +67,8 @@ impl FunctionData {
                 params.push(type_ref);
             }
         }
+        let attrs = Attrs::new(&src.value, &Hygiene::new(db.upcast(), src.file_id));
+
         let ret_type = if let Some(type_ref) = src.value.ret_type().and_then(|rt| rt.type_ref()) {
             TypeRef::from_ast(type_ref)
         } else {
@@ -81,7 +87,7 @@ impl FunctionData {
         let visibility =
             RawVisibility::from_ast_with_default(db, vis_default, src.map(|s| s.visibility()));
 
-        let sig = FunctionData { name, params, ret_type, has_self_param, visibility };
+        let sig = FunctionData { name, params, ret_type, has_self_param, visibility, attrs };
         Arc::new(sig)
     }
 }
@@ -211,6 +217,7 @@ impl ImplData {
         let module_id = impl_loc.container.module(db);
 
         let mut items = Vec::new();
+
         if let Some(item_list) = src.value.item_list() {
             items.extend(collect_impl_items(db, item_list.impl_items(), src.file_id, id));
             items.extend(collect_impl_items_in_macros(
@@ -311,6 +318,10 @@ fn collect_impl_items_in_macro(
     }
 }
 
+fn is_cfg_enabled(cfg_options: &CfgOptions, attrs: &Attrs) -> bool {
+    attrs.by_key("cfg").tt_values().all(|tt| cfg_options.is_cfg_enabled(tt) != Some(false))
+}
+
 fn collect_impl_items(
     db: &dyn DefDatabase,
     impl_items: impl Iterator<Item = ImplItem>,
@@ -318,16 +329,26 @@ fn collect_impl_items(
     id: ImplId,
 ) -> Vec<AssocItemId> {
     let items = db.ast_id_map(file_id);
+    let crate_graph = db.crate_graph();
+    let module_id = id.lookup(db).container.module(db);
 
     impl_items
-        .map(|item_node| match item_node {
+        .filter_map(|item_node| match item_node {
             ast::ImplItem::FnDef(it) => {
                 let def = FunctionLoc {
                     container: AssocContainerId::ImplId(id),
                     ast_id: AstId::new(file_id, items.ast_id(&it)),
                 }
                 .intern(db);
-                def.into()
+
+                if !is_cfg_enabled(
+                    &crate_graph[module_id.krate].cfg_options,
+                    &db.function_data(def).attrs,
+                ) {
+                    None
+                } else {
+                    Some(def.into())
+                }
             }
             ast::ImplItem::ConstDef(it) => {
                 let def = ConstLoc {
@@ -335,7 +356,7 @@ fn collect_impl_items(
                     ast_id: AstId::new(file_id, items.ast_id(&it)),
                 }
                 .intern(db);
-                def.into()
+                Some(def.into())
             }
             ast::ImplItem::TypeAliasDef(it) => {
                 let def = TypeAliasLoc {
@@ -343,7 +364,7 @@ fn collect_impl_items(
                     ast_id: AstId::new(file_id, items.ast_id(&it)),
                 }
                 .intern(db);
-                def.into()
+                Some(def.into())
             }
         })
         .collect()
diff --git a/crates/ra_hir_ty/src/_match.rs b/crates/ra_hir_ty/src/_match.rs
index f29a25505..9e9a9d047 100644
--- a/crates/ra_hir_ty/src/_match.rs
+++ b/crates/ra_hir_ty/src/_match.rs
@@ -235,7 +235,10 @@ impl From<PatId> for PatIdOrWild {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq)]
-pub struct MatchCheckNotImplemented;
+pub enum MatchCheckErr {
+    NotImplemented,
+    MalformedMatchArm,
+}
 
 /// The return type of `is_useful` is either an indication of usefulness
 /// of the match arm, or an error in the case the match statement
@@ -244,7 +247,7 @@ pub struct MatchCheckNotImplemented;
 ///
 /// The `std::result::Result` type is used here rather than a custom enum
 /// to allow the use of `?`.
-pub type MatchCheckResult<T> = Result<T, MatchCheckNotImplemented>;
+pub type MatchCheckResult<T> = Result<T, MatchCheckErr>;
 
 #[derive(Debug)]
 /// A row in a Matrix.
@@ -335,12 +338,12 @@ impl PatStack {
                     Expr::Literal(Literal::Bool(_)) => None,
                     // perhaps this is actually unreachable given we have
                     // already checked that these match arms have the appropriate type?
-                    _ => return Err(MatchCheckNotImplemented),
+                    _ => return Err(MatchCheckErr::NotImplemented),
                 }
             }
             (Pat::Wild, constructor) => Some(self.expand_wildcard(cx, constructor)?),
             (Pat::Path(_), Constructor::Enum(constructor)) => {
-                // enums with no associated data become `Pat::Path`
+                // unit enum variants become `Pat::Path`
                 let pat_id = self.head().as_id().expect("we know this isn't a wild");
                 if !enum_variant_matches(cx, pat_id, *constructor) {
                     None
@@ -348,16 +351,23 @@ impl PatStack {
                     Some(self.to_tail())
                 }
             }
-            (Pat::TupleStruct { args: ref pat_ids, .. }, Constructor::Enum(constructor)) => {
+            (Pat::TupleStruct { args: ref pat_ids, .. }, Constructor::Enum(enum_constructor)) => {
                 let pat_id = self.head().as_id().expect("we know this isn't a wild");
-                if !enum_variant_matches(cx, pat_id, *constructor) {
+                if !enum_variant_matches(cx, pat_id, *enum_constructor) {
                     None
                 } else {
+                    // If the enum variant matches, then we need to confirm
+                    // that the number of patterns aligns with the expected
+                    // number of patterns for that enum variant.
+                    if pat_ids.len() != constructor.arity(cx)? {
+                        return Err(MatchCheckErr::MalformedMatchArm);
+                    }
+
                     Some(self.replace_head_with(pat_ids))
                 }
             }
-            (Pat::Or(_), _) => return Err(MatchCheckNotImplemented),
-            (_, _) => return Err(MatchCheckNotImplemented),
+            (Pat::Or(_), _) => return Err(MatchCheckErr::NotImplemented),
+            (_, _) => return Err(MatchCheckErr::NotImplemented),
         };
 
         Ok(result)
@@ -514,7 +524,7 @@ pub(crate) fn is_useful(
         return if any_useful {
             Ok(Usefulness::Useful)
         } else if found_unimplemented {
-            Err(MatchCheckNotImplemented)
+            Err(MatchCheckErr::NotImplemented)
         } else {
             Ok(Usefulness::NotUseful)
         };
@@ -567,7 +577,7 @@ pub(crate) fn is_useful(
                 }
 
                 if found_unimplemented {
-                    Err(MatchCheckNotImplemented)
+                    Err(MatchCheckErr::NotImplemented)
                 } else {
                     Ok(Usefulness::NotUseful)
                 }
@@ -604,7 +614,7 @@ impl Constructor {
                 match cx.db.enum_data(e.parent).variants[e.local_id].variant_data.as_ref() {
                     VariantData::Tuple(struct_field_data) => struct_field_data.len(),
                     VariantData::Unit => 0,
-                    _ => return Err(MatchCheckNotImplemented),
+                    _ => return Err(MatchCheckErr::NotImplemented),
                 }
             }
         };
@@ -637,20 +647,20 @@ fn pat_constructor(cx: &MatchCheckCtx, pat: PatIdOrWild) -> MatchCheckResult<Opt
         Pat::Tuple(pats) => Some(Constructor::Tuple { arity: pats.len() }),
         Pat::Lit(lit_expr) => match cx.body.exprs[lit_expr] {
             Expr::Literal(Literal::Bool(val)) => Some(Constructor::Bool(val)),
-            _ => return Err(MatchCheckNotImplemented),
+            _ => return Err(MatchCheckErr::NotImplemented),
         },
         Pat::TupleStruct { .. } | Pat::Path(_) => {
             let pat_id = pat.as_id().expect("we already know this pattern is not a wild");
             let variant_id =
-                cx.infer.variant_resolution_for_pat(pat_id).ok_or(MatchCheckNotImplemented)?;
+                cx.infer.variant_resolution_for_pat(pat_id).ok_or(MatchCheckErr::NotImplemented)?;
             match variant_id {
                 VariantId::EnumVariantId(enum_variant_id) => {
                     Some(Constructor::Enum(enum_variant_id))
                 }
-                _ => return Err(MatchCheckNotImplemented),
+                _ => return Err(MatchCheckErr::NotImplemented),
             }
         }
-        _ => return Err(MatchCheckNotImplemented),
+        _ => return Err(MatchCheckErr::NotImplemented),
     };
 
     Ok(res)
@@ -1325,6 +1335,40 @@ mod tests {
     }
 
     #[test]
+    fn malformed_match_arm_tuple_missing_pattern() {
+        let content = r"
+            fn test_fn() {
+                match (0) {
+                    () => (),
+                }
+            }
+        ";
+
+        // Match arms with the incorrect type are filtered out.
+        check_diagnostic(content);
+    }
+
+    #[test]
+    fn malformed_match_arm_tuple_enum_missing_pattern() {
+        let content = r"
+            enum Either {
+                A,
+                B(u32),
+            }
+            fn test_fn() {
+                match Either::A {
+                    Either::A => (),
+                    Either::B() => (),
+                }
+            }
+        ";
+
+        // We are testing to be sure we don't panic here when the match
+        // arm `Either::B` is missing its pattern.
+        check_no_diagnostic(content);
+    }
+
+    #[test]
     fn enum_not_in_scope() {
         let content = r"
             fn test_fn() {
diff --git a/crates/ra_hir_ty/src/expr.rs b/crates/ra_hir_ty/src/expr.rs
index b4592fbf5..e45e9ea14 100644
--- a/crates/ra_hir_ty/src/expr.rs
+++ b/crates/ra_hir_ty/src/expr.rs
@@ -4,8 +4,7 @@ use std::sync::Arc;
 
 use hir_def::{path::path, resolver::HasResolver, AdtId, FunctionId};
 use hir_expand::diagnostics::DiagnosticSink;
-use ra_syntax::ast;
-use ra_syntax::AstPtr;
+use ra_syntax::{ast, AstPtr};
 use rustc_hash::FxHashSet;
 
 use crate::{
diff --git a/crates/ra_hir_ty/src/tests.rs b/crates/ra_hir_ty/src/tests.rs
index e4a103d1b..608408d88 100644
--- a/crates/ra_hir_ty/src/tests.rs
+++ b/crates/ra_hir_ty/src/tests.rs
@@ -319,3 +319,33 @@ fn no_such_field_diagnostics() {
     "###
     );
 }
+
+#[test]
+fn no_such_field_with_feature_flag_diagnostics() {
+    let diagnostics = TestDB::with_files(
+        r#"
+        //- /lib.rs crate:foo cfg:feature=foo
+        struct MyStruct {
+            my_val: usize,
+            #[cfg(feature = "foo")]
+            bar: bool,
+        }
+
+        impl MyStruct {
+            #[cfg(feature = "foo")]
+            pub(crate) fn new(my_val: usize, bar: bool) -> Self {
+                Self { my_val, bar }
+            }
+
+            #[cfg(not(feature = "foo"))]
+            pub(crate) fn new(my_val: usize, _bar: bool) -> Self {
+                Self { my_val }
+            }
+        }
+        "#,
+    )
+    .diagnostics()
+    .0;
+
+    assert_snapshot!(diagnostics, @r###""###);
+}
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\"");
+    }
+}