4 files changed, 386 insertions, 364 deletions

diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index a5b7fab52..38d3ec7e1 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -15,10 +15,12 @@ macro_rules! impl_froms {
     }
 }
 
-mod tt_cursor;
+// mod tt_cursor;
 mod mbe_parser;
 mod mbe_expander;
 mod syntax_bridge;
+mod tt_cursor;
+mod subtree_source;
 
 use ra_syntax::SmolStr;
 
diff --git a/crates/ra_mbe/src/subtree_source.rs b/crates/ra_mbe/src/subtree_source.rs
new file mode 100644
index 000000000..8f5ce4ed5
--- /dev/null
+++ b/crates/ra_mbe/src/subtree_source.rs
@@ -0,0 +1,352 @@
+use ra_parser::{TokenSource};
+use ra_syntax::{classify_literal, SmolStr, SyntaxKind, SyntaxKind::*};
+
+#[derive(Debug)]
+struct TtToken {
+    pub kind: SyntaxKind,
+    pub is_joint_to_next: bool,
+    pub text: SmolStr,
+    pub n_tokens: usize,
+}
+
+/// SubtreeSourceQuerier let outside to query internal tokens as string
+pub(crate) struct SubtreeSourceQuerier<'a> {
+    src: &'a SubtreeTokenSource<'a>,
+}
+
+impl<'a> SubtreeSourceQuerier<'a> {
+    pub(crate) fn token(&self, uidx: usize) -> (SyntaxKind, &SmolStr) {
+        let tkn = &self.src.tokens[uidx];
+        (tkn.kind, &tkn.text)
+    }
+}
+
+pub(crate) struct SubtreeTokenSource<'a> {
+    tt_pos: usize,
+    tokens: Vec<TtToken>,
+    subtree: &'a tt::Subtree,
+}
+
+impl<'a> SubtreeTokenSource<'a> {
+    pub fn new(subtree: &tt::Subtree) -> SubtreeTokenSource {
+        SubtreeTokenSource { tokens: TtTokenBuilder::build(subtree), tt_pos: 0, subtree }
+    }
+
+    pub fn advance(&mut self, curr: usize, skip_first_delimiter: bool) {
+        if skip_first_delimiter {
+            self.tt_pos += 1;
+        }
+
+        // Matching `TtToken` cursor to `tt::TokenTree` cursor
+        // It is because TtToken is not One to One mapping to tt::Token
+        // There are 3 case (`TtToken` <=> `tt::TokenTree`) :
+        // * One to One =>  ident, single char punch
+        // * Many to One => `tt::TokenTree::SubTree`
+        // * One to Many => multibyte punct
+        //
+        // Such that we cannot simpliy advance the cursor
+        // We have to bump it one by one
+        let mut pos = 0;
+        while pos < curr {
+            pos += self.bump(&self.subtree.token_trees[pos]);
+        }
+    }
+
+    pub fn querier(&self) -> SubtreeSourceQuerier {
+        SubtreeSourceQuerier { src: self }
+    }
+
+    fn count(&self, tt: &tt::TokenTree) -> usize {
+        assert!(!self.tokens.is_empty());
+        TtTokenBuilder::count_tt_tokens(tt, None)
+    }
+
+    pub(crate) fn bump(&mut self, tt: &tt::TokenTree) -> usize {
+        let cur = &self.tokens[self.tt_pos];
+        let n_tokens = cur.n_tokens;
+        self.tt_pos += self.count(tt);
+        n_tokens
+    }
+
+    pub(crate) fn bump_n(
+        &mut self,
+        n_tokens: usize,
+        mut token_pos: usize,
+    ) -> (usize, Vec<&tt::TokenTree>) {
+        let mut res = vec![];
+        // Matching `TtToken` cursor to `tt::TokenTree` cursor
+        // It is because TtToken is not One to One mapping to tt::Token
+        // There are 3 case (`TtToken` <=> `tt::TokenTree`) :
+        // * One to One =>  ident, single char punch
+        // * Many to One => `tt::TokenTree::SubTree`
+        // * One to Many => multibyte punct
+        //
+        // Such that we cannot simpliy advance the cursor
+        // We have to bump it one by one
+        let next_pos = self.tt_pos + n_tokens;
+        let old_token_pos = token_pos;
+
+        while self.tt_pos < next_pos {
+            let current = &self.subtree.token_trees[token_pos];
+            let n = self.bump(current);
+            res.extend((0..n).map(|i| &self.subtree.token_trees[token_pos + i]));
+            token_pos += n;
+        }
+
+        (token_pos - old_token_pos, res)
+    }
+}
+
+impl<'a> TokenSource for SubtreeTokenSource<'a> {
+    fn token_kind(&self, pos: usize) -> SyntaxKind {
+        if let Some(tok) = self.tokens.get(self.tt_pos + pos) {
+            tok.kind
+        } else {
+            SyntaxKind::EOF
+        }
+    }
+    fn is_token_joint_to_next(&self, pos: usize) -> bool {
+        self.tokens[self.tt_pos + pos].is_joint_to_next
+    }
+    fn is_keyword(&self, pos: usize, kw: &str) -> bool {
+        self.tokens[self.tt_pos + pos].text == *kw
+    }
+}
+
+struct TokenPeek<'a, I>
+where
+    I: Iterator<Item = &'a tt::TokenTree>,
+{
+    iter: itertools::MultiPeek<I>,
+}
+
+// helper function
+fn to_punct(tt: &tt::TokenTree) -> Option<&tt::Punct> {
+    if let tt::TokenTree::Leaf(tt::Leaf::Punct(pp)) = tt {
+        return Some(pp);
+    }
+    None
+}
+
+impl<'a, I> TokenPeek<'a, I>
+where
+    I: Iterator<Item = &'a tt::TokenTree>,
+{
+    pub fn new(iter: I) -> Self {
+        TokenPeek { iter: itertools::multipeek(iter) }
+    }
+
+    pub fn next(&mut self) -> Option<&tt::TokenTree> {
+        self.iter.next()
+    }
+
+    fn current_punct2(&mut self, p: &tt::Punct) -> Option<((char, char), bool)> {
+        if p.spacing != tt::Spacing::Joint {
+            return None;
+        }
+
+        self.iter.reset_peek();
+        let p1 = to_punct(self.iter.peek()?)?;
+        Some(((p.char, p1.char), p1.spacing == tt::Spacing::Joint))
+    }
+
+    fn current_punct3(&mut self, p: &tt::Punct) -> Option<((char, char, char), bool)> {
+        self.current_punct2(p).and_then(|((p0, p1), last_joint)| {
+            if !last_joint {
+                None
+            } else {
+                let p2 = to_punct(*self.iter.peek()?)?;
+                Some(((p0, p1, p2.char), p2.spacing == tt::Spacing::Joint))
+            }
+        })
+    }
+}
+
+struct TtTokenBuilder {
+    tokens: Vec<TtToken>,
+}
+
+impl TtTokenBuilder {
+    fn build(sub: &tt::Subtree) -> Vec<TtToken> {
+        let mut res = TtTokenBuilder { tokens: vec![] };
+        res.convert_subtree(sub);
+        res.tokens
+    }
+
+    fn convert_subtree(&mut self, sub: &tt::Subtree) {
+        self.push_delim(sub.delimiter, false);
+        let mut peek = TokenPeek::new(sub.token_trees.iter());
+        while let Some(tt) = peek.iter.next() {
+            self.convert_tt(tt, &mut peek);
+        }
+        self.push_delim(sub.delimiter, true)
+    }
+
+    fn convert_tt<'b, I>(&mut self, tt: &tt::TokenTree, iter: &mut TokenPeek<'b, I>)
+    where
+        I: Iterator<Item = &'b tt::TokenTree>,
+    {
+        match tt {
+            tt::TokenTree::Leaf(token) => self.convert_token(token, iter),
+            tt::TokenTree::Subtree(sub) => self.convert_subtree(sub),
+        }
+    }
+
+    fn convert_token<'b, I>(&mut self, token: &tt::Leaf, iter: &mut TokenPeek<'b, I>)
+    where
+        I: Iterator<Item = &'b tt::TokenTree>,
+    {
+        let tok = match token {
+            tt::Leaf::Literal(l) => TtToken {
+                kind: classify_literal(&l.text).unwrap().kind,
+                is_joint_to_next: false,
+                text: l.text.clone(),
+                n_tokens: 1,
+            },
+            tt::Leaf::Punct(p) => {
+                if let Some((kind, is_joint_to_next, text, size)) =
+                    Self::convert_multi_char_punct(p, iter)
+                {
+                    for _ in 0..size - 1 {
+                        iter.next();
+                    }
+
+                    TtToken { kind, is_joint_to_next, text: text.into(), n_tokens: size }
+                } else {
+                    let kind = match p.char {
+                        // lexer may produce combpund tokens for these ones
+                        '.' => DOT,
+                        ':' => COLON,
+                        '=' => EQ,
+                        '!' => EXCL,
+                        '-' => MINUS,
+                        c => SyntaxKind::from_char(c).unwrap(),
+                    };
+                    let text = {
+                        let mut buf = [0u8; 4];
+                        let s: &str = p.char.encode_utf8(&mut buf);
+                        SmolStr::new(s)
+                    };
+                    TtToken {
+                        kind,
+                        is_joint_to_next: p.spacing == tt::Spacing::Joint,
+                        text,
+                        n_tokens: 1,
+                    }
+                }
+            }
+            tt::Leaf::Ident(ident) => {
+                let kind = SyntaxKind::from_keyword(ident.text.as_str()).unwrap_or(IDENT);
+                TtToken { kind, is_joint_to_next: false, text: ident.text.clone(), n_tokens: 1 }
+            }
+        };
+        self.tokens.push(tok)
+    }
+
+    fn convert_multi_char_punct<'b, I>(
+        p: &tt::Punct,
+        iter: &mut TokenPeek<'b, I>,
+    ) -> Option<(SyntaxKind, bool, &'static str, usize)>
+    where
+        I: Iterator<Item = &'b tt::TokenTree>,
+    {
+        if let Some((m, is_joint_to_next)) = iter.current_punct3(p) {
+            if let Some((kind, text)) = match m {
+                ('<', '<', '=') => Some((SHLEQ, "<<=")),
+                ('>', '>', '=') => Some((SHREQ, ">>=")),
+                ('.', '.', '.') => Some((DOTDOTDOT, "...")),
+                ('.', '.', '=') => Some((DOTDOTEQ, "..=")),
+                _ => None,
+            } {
+                return Some((kind, is_joint_to_next, text, 3));
+            }
+        }
+
+        if let Some((m, is_joint_to_next)) = iter.current_punct2(p) {
+            if let Some((kind, text)) = match m {
+                ('<', '<') => Some((SHL, "<<")),
+                ('>', '>') => Some((SHR, ">>")),
+
+                ('|', '|') => Some((PIPEPIPE, "||")),
+                ('&', '&') => Some((AMPAMP, "&&")),
+                ('%', '=') => Some((PERCENTEQ, "%=")),
+                ('*', '=') => Some((STAREQ, "*=")),
+                ('/', '=') => Some((SLASHEQ, "/=")),
+                ('^', '=') => Some((CARETEQ, "^=")),
+
+                ('&', '=') => Some((AMPEQ, "&=")),
+                ('|', '=') => Some((PIPEEQ, "|=")),
+                ('-', '=') => Some((MINUSEQ, "-=")),
+                ('+', '=') => Some((PLUSEQ, "+=")),
+                ('>', '=') => Some((GTEQ, ">=")),
+                ('<', '=') => Some((LTEQ, "<=")),
+
+                ('-', '>') => Some((THIN_ARROW, "->")),
+                ('!', '=') => Some((NEQ, "!=")),
+                ('=', '>') => Some((FAT_ARROW, "=>")),
+                ('=', '=') => Some((EQEQ, "==")),
+                ('.', '.') => Some((DOTDOT, "..")),
+                (':', ':') => Some((COLONCOLON, "::")),
+
+                _ => None,
+            } {
+                return Some((kind, is_joint_to_next, text, 2));
+            }
+        }
+
+        None
+    }
+
+    fn push_delim(&mut self, d: tt::Delimiter, closing: bool) {
+        let (kinds, texts) = match d {
+            tt::Delimiter::Parenthesis => ([L_PAREN, R_PAREN], "()"),
+            tt::Delimiter::Brace => ([L_CURLY, R_CURLY], "{}"),
+            tt::Delimiter::Bracket => ([L_BRACK, R_BRACK], "[]"),
+            tt::Delimiter::None => return,
+        };
+        let idx = closing as usize;
+        let kind = kinds[idx];
+        let text = &texts[idx..texts.len() - (1 - idx)];
+        let tok = TtToken { kind, is_joint_to_next: false, text: SmolStr::new(text), n_tokens: 1 };
+        self.tokens.push(tok)
+    }
+
+    fn skip_sibling_leaf(leaf: &tt::Leaf, iter: &mut std::slice::Iter<tt::TokenTree>) {
+        if let tt::Leaf::Punct(p) = leaf {
+            let mut peek = TokenPeek::new(iter);
+            if let Some((_, _, _, size)) = TtTokenBuilder::convert_multi_char_punct(p, &mut peek) {
+                for _ in 0..size - 1 {
+                    peek.next();
+                }
+            }
+        }
+    }
+
+    fn count_tt_tokens(
+        tt: &tt::TokenTree,
+        iter: Option<&mut std::slice::Iter<tt::TokenTree>>,
+    ) -> usize {
+        match tt {
+            tt::TokenTree::Subtree(sub_tree) => {
+                let mut iter = sub_tree.token_trees.iter();
+                let mut count = match sub_tree.delimiter {
+                    tt::Delimiter::None => 0,
+                    _ => 2,
+                };
+
+                while let Some(tt) = iter.next() {
+                    count += Self::count_tt_tokens(&tt, Some(&mut iter));
+                }
+                count
+            }
+
+            tt::TokenTree::Leaf(leaf) => {
+                iter.map(|iter| {
+                    Self::skip_sibling_leaf(leaf, iter);
+                });
+
+                1
+            }
+        }
+    }
+}
diff --git a/crates/ra_mbe/src/syntax_bridge.rs b/crates/ra_mbe/src/syntax_bridge.rs
index 3a0702a30..102bba341 100644
--- a/crates/ra_mbe/src/syntax_bridge.rs
+++ b/crates/ra_mbe/src/syntax_bridge.rs
@@ -1,9 +1,11 @@
-use ra_parser::{TokenSource, TreeSink, ParseError};
+use ra_parser::{TreeSink, ParseError};
 use ra_syntax::{
     AstNode, SyntaxNode, TextRange, SyntaxKind, SmolStr, SyntaxTreeBuilder, TreeArc, SyntaxElement,
-    ast, SyntaxKind::*, TextUnit, classify_literal
+    ast, SyntaxKind::*, TextUnit
 };
 
+use crate::subtree_source::{SubtreeTokenSource, SubtreeSourceQuerier};
+
 /// Maps `tt::TokenId` to the relative range of the original token.
 #[derive(Default)]
 pub struct TokenMap {
@@ -22,8 +24,8 @@ pub fn ast_to_token_tree(ast: &ast::TokenTree) -> Option<(tt::Subtree, TokenMap)
 
 /// Parses the token tree (result of macro expansion) as a sequence of items
 pub fn token_tree_to_ast_item_list(tt: &tt::Subtree) -> TreeArc<ast::SourceFile> {
-    let token_source = TtTokenSource::new(tt);
-    let mut tree_sink = TtTreeSink::new(&token_source.tokens);
+    let token_source = SubtreeTokenSource::new(tt);
+    let mut tree_sink = TtTreeSink::new(token_source.querier());
     ra_parser::parse(&token_source, &mut tree_sink);
     let syntax = tree_sink.inner.finish();
     ast::SourceFile::cast(&syntax).unwrap().to_owned()
@@ -103,243 +105,19 @@ fn convert_tt(
     Some(res)
 }
 
-#[derive(Debug)]
-pub(crate) struct TtTokenSource {
-    pub tokens: Vec<TtToken>,
-}
-
-#[derive(Debug)]
-pub(crate) struct TtToken {
-    pub kind: SyntaxKind,
-    pub is_joint_to_next: bool,
-    pub text: SmolStr,
-    pub n_tokens: usize,
-}
-
-// Some helper functions
-fn to_punct(tt: &tt::TokenTree) -> Option<&tt::Punct> {
-    if let tt::TokenTree::Leaf(tt::Leaf::Punct(pp)) = tt {
-        return Some(pp);
-    }
-    None
-}
-
-pub(crate) struct TokenPeek<'a, I>
-where
-    I: Iterator<Item = &'a tt::TokenTree>,
-{
-    iter: itertools::MultiPeek<I>,
-}
-
-impl<'a, I> TokenPeek<'a, I>
-where
-    I: Iterator<Item = &'a tt::TokenTree>,
-{
-    pub fn new(iter: I) -> Self {
-        TokenPeek { iter: itertools::multipeek(iter) }
-    }
-
-    pub fn next(&mut self) -> Option<&tt::TokenTree> {
-        self.iter.next()
-    }
-
-    fn current_punct2(&mut self, p: &tt::Punct) -> Option<((char, char), bool)> {
-        if p.spacing != tt::Spacing::Joint {
-            return None;
-        }
-
-        self.iter.reset_peek();
-        let p1 = to_punct(self.iter.peek()?)?;
-        Some(((p.char, p1.char), p1.spacing == tt::Spacing::Joint))
-    }
-
-    fn current_punct3(&mut self, p: &tt::Punct) -> Option<((char, char, char), bool)> {
-        self.current_punct2(p).and_then(|((p0, p1), last_joint)| {
-            if !last_joint {
-                None
-            } else {
-                let p2 = to_punct(*self.iter.peek()?)?;
-                Some(((p0, p1, p2.char), p2.spacing == tt::Spacing::Joint))
-            }
-        })
-    }
-}
-
-impl TtTokenSource {
-    pub fn new(tt: &tt::Subtree) -> TtTokenSource {
-        let mut res = TtTokenSource { tokens: Vec::new() };
-        res.convert_subtree(tt);
-        res
-    }
-    fn convert_subtree(&mut self, sub: &tt::Subtree) {
-        self.push_delim(sub.delimiter, false);
-        let mut peek = TokenPeek::new(sub.token_trees.iter());
-        while let Some(tt) = peek.iter.next() {
-            self.convert_tt(tt, &mut peek);
-        }
-        self.push_delim(sub.delimiter, true)
-    }
-
-    fn convert_tt<'a, I>(&mut self, tt: &tt::TokenTree, iter: &mut TokenPeek<'a, I>)
-    where
-        I: Iterator<Item = &'a tt::TokenTree>,
-    {
-        match tt {
-            tt::TokenTree::Leaf(token) => self.convert_token(token, iter),
-            tt::TokenTree::Subtree(sub) => self.convert_subtree(sub),
-        }
-    }
-
-    fn convert_token<'a, I>(&mut self, token: &tt::Leaf, iter: &mut TokenPeek<'a, I>)
-    where
-        I: Iterator<Item = &'a tt::TokenTree>,
-    {
-        let tok = match token {
-            tt::Leaf::Literal(l) => TtToken {
-                kind: classify_literal(&l.text).unwrap().kind,
-                is_joint_to_next: false,
-                text: l.text.clone(),
-                n_tokens: 1,
-            },
-            tt::Leaf::Punct(p) => {
-                if let Some((kind, is_joint_to_next, text, size)) =
-                    Self::convert_multi_char_punct(p, iter)
-                {
-                    for _ in 0..size - 1 {
-                        iter.next();
-                    }
-
-                    TtToken { kind, is_joint_to_next, text: text.into(), n_tokens: size }
-                } else {
-                    let kind = match p.char {
-                        // lexer may produce combpund tokens for these ones
-                        '.' => DOT,
-                        ':' => COLON,
-                        '=' => EQ,
-                        '!' => EXCL,
-                        '-' => MINUS,
-                        c => SyntaxKind::from_char(c).unwrap(),
-                    };
-                    let text = {
-                        let mut buf = [0u8; 4];
-                        let s: &str = p.char.encode_utf8(&mut buf);
-                        SmolStr::new(s)
-                    };
-                    TtToken {
-                        kind,
-                        is_joint_to_next: p.spacing == tt::Spacing::Joint,
-                        text,
-                        n_tokens: 1,
-                    }
-                }
-            }
-            tt::Leaf::Ident(ident) => {
-                let kind = SyntaxKind::from_keyword(ident.text.as_str()).unwrap_or(IDENT);
-                TtToken { kind, is_joint_to_next: false, text: ident.text.clone(), n_tokens: 1 }
-            }
-        };
-        self.tokens.push(tok)
-    }
-
-    pub(crate) fn convert_multi_char_punct<'a, I>(
-        p: &tt::Punct,
-        iter: &mut TokenPeek<'a, I>,
-    ) -> Option<(SyntaxKind, bool, &'static str, usize)>
-    where
-        I: Iterator<Item = &'a tt::TokenTree>,
-    {
-        if let Some((m, is_joint_to_next)) = iter.current_punct3(p) {
-            if let Some((kind, text)) = match m {
-                ('<', '<', '=') => Some((SHLEQ, "<<=")),
-                ('>', '>', '=') => Some((SHREQ, ">>=")),
-                ('.', '.', '.') => Some((DOTDOTDOT, "...")),
-                ('.', '.', '=') => Some((DOTDOTEQ, "..=")),
-                _ => None,
-            } {
-                return Some((kind, is_joint_to_next, text, 3));
-            }
-        }
-
-        if let Some((m, is_joint_to_next)) = iter.current_punct2(p) {
-            if let Some((kind, text)) = match m {
-                ('<', '<') => Some((SHL, "<<")),
-                ('>', '>') => Some((SHR, ">>")),
-
-                ('|', '|') => Some((PIPEPIPE, "||")),
-                ('&', '&') => Some((AMPAMP, "&&")),
-                ('%', '=') => Some((PERCENTEQ, "%=")),
-                ('*', '=') => Some((STAREQ, "*=")),
-                ('/', '=') => Some((SLASHEQ, "/=")),
-                ('^', '=') => Some((CARETEQ, "^=")),
-
-                ('&', '=') => Some((AMPEQ, "&=")),
-                ('|', '=') => Some((PIPEEQ, "|=")),
-                ('-', '=') => Some((MINUSEQ, "-=")),
-                ('+', '=') => Some((PLUSEQ, "+=")),
-                ('>', '=') => Some((GTEQ, ">=")),
-                ('<', '=') => Some((LTEQ, "<=")),
-
-                ('-', '>') => Some((THIN_ARROW, "->")),
-                ('!', '=') => Some((NEQ, "!=")),
-                ('=', '>') => Some((FAT_ARROW, "=>")),
-                ('=', '=') => Some((EQEQ, "==")),
-                ('.', '.') => Some((DOTDOT, "..")),
-                (':', ':') => Some((COLONCOLON, "::")),
-
-                _ => None,
-            } {
-                return Some((kind, is_joint_to_next, text, 2));
-            }
-        }
-
-        None
-    }
-
-    fn push_delim(&mut self, d: tt::Delimiter, closing: bool) {
-        let (kinds, texts) = match d {
-            tt::Delimiter::Parenthesis => ([L_PAREN, R_PAREN], "()"),
-            tt::Delimiter::Brace => ([L_CURLY, R_CURLY], "{}"),
-            tt::Delimiter::Bracket => ([L_BRACK, R_BRACK], "[]"),
-            tt::Delimiter::None => return,
-        };
-        let idx = closing as usize;
-        let kind = kinds[idx];
-        let text = &texts[idx..texts.len() - (1 - idx)];
-        let tok = TtToken { kind, is_joint_to_next: false, text: SmolStr::new(text), n_tokens: 1 };
-        self.tokens.push(tok)
-    }
-}
-
-impl TokenSource for TtTokenSource {
-    fn token_kind(&self, pos: usize) -> SyntaxKind {
-        if let Some(tok) = self.tokens.get(pos) {
-            tok.kind
-        } else {
-            SyntaxKind::EOF
-        }
-    }
-    fn is_token_joint_to_next(&self, pos: usize) -> bool {
-        self.tokens[pos].is_joint_to_next
-    }
-    fn is_keyword(&self, pos: usize, kw: &str) -> bool {
-        self.tokens[pos].text == *kw
-    }
-}
-
-#[derive(Default)]
 struct TtTreeSink<'a> {
     buf: String,
-    tokens: &'a [TtToken],
+    src_querier: SubtreeSourceQuerier<'a>,
     text_pos: TextUnit,
     token_pos: usize,
     inner: SyntaxTreeBuilder,
 }
 
 impl<'a> TtTreeSink<'a> {
-    fn new(tokens: &'a [TtToken]) -> TtTreeSink {
+    fn new(src_querier: SubtreeSourceQuerier<'a>) -> TtTreeSink {
         TtTreeSink {
             buf: String::new(),
-            tokens,
+            src_querier,
             text_pos: 0.into(),
             token_pos: 0,
             inner: SyntaxTreeBuilder::default(),
@@ -350,7 +128,7 @@ impl<'a> TtTreeSink<'a> {
 impl<'a> TreeSink for TtTreeSink<'a> {
     fn token(&mut self, kind: SyntaxKind, n_tokens: u8) {
         for _ in 0..n_tokens {
-            self.buf += self.tokens[self.token_pos].text.as_str();
+            self.buf += self.src_querier.token(self.token_pos).1;
             self.token_pos += 1;
         }
         self.text_pos += TextUnit::of_str(&self.buf);
@@ -394,21 +172,23 @@ mod tests {
             "#,
         );
         let expansion = expand(&rules, "literals!(foo)");
-        let tt_src = TtTokenSource::new(&expansion);
+        let tt_src = SubtreeTokenSource::new(&expansion);
+
+        let query = tt_src.querier();
 
         // [{]
         // [let] [a] [=] ['c'] [;]
-        assert_eq!(tt_src.tokens[1 + 3].text, "'c'");
-        assert_eq!(tt_src.tokens[1 + 3].kind, CHAR);
+        assert_eq!(query.token(1 + 3).1, "'c'");
+        assert_eq!(query.token(1 + 3).0, CHAR);
         // [let] [c] [=] [1000] [;]
-        assert_eq!(tt_src.tokens[1 + 5 + 3].text, "1000");
-        assert_eq!(tt_src.tokens[1 + 5 + 3].kind, INT_NUMBER);
+        assert_eq!(query.token(1 + 5 + 3).1, "1000");
+        assert_eq!(query.token(1 + 5 + 3).0, INT_NUMBER);
         // [let] [f] [=] [12E+99_f64] [;]
-        assert_eq!(tt_src.tokens[1 + 10 + 3].text, "12E+99_f64");
-        assert_eq!(tt_src.tokens[1 + 10 + 3].kind, FLOAT_NUMBER);
+        assert_eq!(query.token(1 + 10 + 3).1, "12E+99_f64");
+        assert_eq!(query.token(1 + 10 + 3).0, FLOAT_NUMBER);
 
         // [let] [s] [=] ["rust1"] [;]
-        assert_eq!(tt_src.tokens[1 + 15 + 3].text, "\"rust1\"");
-        assert_eq!(tt_src.tokens[1 + 15 + 3].kind, STRING);
+        assert_eq!(query.token(1 + 15 + 3).1, "\"rust1\"");
+        assert_eq!(query.token(1 + 15 + 3).0, STRING);
     }
 }
diff --git a/crates/ra_mbe/src/tt_cursor.rs b/crates/ra_mbe/src/tt_cursor.rs
index 6ac3ac187..52e072599 100644
--- a/crates/ra_mbe/src/tt_cursor.rs
+++ b/crates/ra_mbe/src/tt_cursor.rs
@@ -1,116 +1,17 @@
 use crate::ParseError;
-use crate::syntax_bridge::{TtTokenSource, TtToken, TokenPeek};
+use crate::subtree_source::SubtreeTokenSource;
+
 use ra_parser::{TokenSource, TreeSink};
 
 use ra_syntax::{
     SyntaxKind
 };
 
-struct TtCursorTokenSource {
-    tt_pos: usize,
-    inner: TtTokenSource,
-}
-
-impl TtCursorTokenSource {
-    fn new(subtree: &tt::Subtree, curr: usize) -> TtCursorTokenSource {
-        let mut res = TtCursorTokenSource { inner: TtTokenSource::new(subtree), tt_pos: 1 };
-
-        // Matching `TtToken` cursor to `tt::TokenTree` cursor
-        // It is because TtToken is not One to One mapping to tt::Token
-        // There are 3 case (`TtToken` <=> `tt::TokenTree`) :
-        // * One to One =>  ident, single char punch
-        // * Many to One => `tt::TokenTree::SubTree`
-        // * One to Many => multibyte punct
-        //
-        // Such that we cannot simpliy advance the cursor
-        // We have to bump it one by one
-        let mut pos = 0;
-        while pos < curr {
-            pos += res.bump(&subtree.token_trees[pos]);
-        }
-
-        res
-    }
-
-    fn skip_sibling_leaf(&self, leaf: &tt::Leaf, iter: &mut std::slice::Iter<tt::TokenTree>) {
-        if let tt::Leaf::Punct(p) = leaf {
-            let mut peek = TokenPeek::new(iter);
-            if let Some((_, _, _, size)) = TtTokenSource::convert_multi_char_punct(p, &mut peek) {
-                for _ in 0..size - 1 {
-                    peek.next();
-                }
-            }
-        }
-    }
-
-    fn count_tt_tokens(
-        &self,
-        tt: &tt::TokenTree,
-        iter: Option<&mut std::slice::Iter<tt::TokenTree>>,
-    ) -> usize {
-        assert!(!self.inner.tokens.is_empty());
-
-        match tt {
-            tt::TokenTree::Subtree(sub_tree) => {
-                let mut iter = sub_tree.token_trees.iter();
-                let mut count = match sub_tree.delimiter {
-                    tt::Delimiter::None => 0,
-                    _ => 2,
-                };
-
-                while let Some(tt) = iter.next() {
-                    count += self.count_tt_tokens(&tt, Some(&mut iter));
-                }
-                count
-            }
-
-            tt::TokenTree::Leaf(leaf) => {
-                iter.map(|iter| {
-                    self.skip_sibling_leaf(leaf, iter);
-                });
-
-                1
-            }
-        }
-    }
-
-    fn count(&self, tt: &tt::TokenTree) -> usize {
-        self.count_tt_tokens(tt, None)
-    }
-
-    fn bump(&mut self, tt: &tt::TokenTree) -> usize {
-        let cur = self.current().unwrap();
-        let n_tokens = cur.n_tokens;
-        self.tt_pos += self.count(tt);
-        n_tokens
-    }
-
-    fn current(&self) -> Option<&TtToken> {
-        self.inner.tokens.get(self.tt_pos)
-    }
-}
-
-impl TokenSource for TtCursorTokenSource {
-    fn token_kind(&self, pos: usize) -> SyntaxKind {
-        if let Some(tok) = self.inner.tokens.get(self.tt_pos + pos) {
-            tok.kind
-        } else {
-            SyntaxKind::EOF
-        }
-    }
-    fn is_token_joint_to_next(&self, pos: usize) -> bool {
-        self.inner.tokens[self.tt_pos + pos].is_joint_to_next
-    }
-    fn is_keyword(&self, pos: usize, kw: &str) -> bool {
-        self.inner.tokens[self.tt_pos + pos].text == *kw
-    }
-}
-
-struct TtCursorTokenSink {
+struct SubtreeTokenSink {
     token_pos: usize,
 }
 
-impl TreeSink for TtCursorTokenSink {
+impl TreeSink for SubtreeTokenSink {
     fn token(&mut self, _kind: SyntaxKind, n_tokens: u8) {
         self.token_pos += n_tokens as usize;
     }
@@ -201,24 +102,10 @@ impl<'a> TtCursor<'a> {
     fn eat_parse_result(
         &mut self,
         parsed_token: usize,
-        src: &mut TtCursorTokenSource,
+        src: &mut SubtreeTokenSource,
     ) -> Option<tt::TokenTree> {
-        let mut res = vec![];
-
-        // Matching `TtToken` cursor to `tt::TokenTree` cursor
-        // It is because TtToken is not One to One mapping to tt::Token
-        // There are 3 case (`TtToken` <=> `tt::TokenTree`) :
-        // * One to One =>  ident, single char punch
-        // * Many to One => `tt::TokenTree::SubTree`
-        // * One to Many => multibyte punct
-        //
-        // Such that we cannot simpliy advance the cursor
-        // We have to bump it one by one
-        let next_pos = src.tt_pos + parsed_token;
-        while src.tt_pos < next_pos {
-            let n = src.bump(self.current().unwrap());
-            res.extend((0..n).map(|_| self.eat().unwrap()));
-        }
+        let (adv, res) = src.bump_n(parsed_token, self.pos);
+        self.pos += adv;
 
         let res: Vec<_> = res.into_iter().cloned().collect();
 
@@ -236,8 +123,9 @@ impl<'a> TtCursor<'a> {
     where
         F: FnOnce(&dyn TokenSource, &mut dyn TreeSink),
     {
-        let mut src = TtCursorTokenSource::new(self.subtree, self.pos);
-        let mut sink = TtCursorTokenSink { token_pos: 0 };
+        let mut src = SubtreeTokenSource::new(self.subtree);
+        src.advance(self.pos, true);
+        let mut sink = SubtreeTokenSink { token_pos: 0 };
 
         f(&src, &mut sink);