4 files changed, 159 insertions, 188 deletions

diff --git a/crates/ra_syntax/src/parsing.rs b/crates/ra_syntax/src/parsing.rs
index 138d1394a..7e1b32035 100644
--- a/crates/ra_syntax/src/parsing.rs
+++ b/crates/ra_syntax/src/parsing.rs
@@ -9,11 +9,11 @@ mod grammar;
 mod reparsing;
 
 use crate::{
-    SyntaxKind, SmolStr, SyntaxError,
+    SyntaxKind, SyntaxError,
     parsing::{
-        builder::GreenBuilder,
+        builder::TreeBuilder,
         input::ParserInput,
-        event::EventProcessor,
+        event::process,
         parser::Parser,
     },
     syntax_node::GreenNode,
@@ -28,22 +28,24 @@ pub(crate) use self::reparsing::incremental_reparse;
 
 pub(crate) fn parse_text(text: &str) -> (GreenNode, Vec<SyntaxError>) {
     let tokens = tokenize(&text);
-    parse_with(GreenBuilder::default(), text, &tokens, grammar::root)
+    let tree_sink = TreeBuilder::new(text, &tokens);
+    parse_with(tree_sink, text, &tokens, grammar::root)
 }
 
 fn parse_with<S: TreeSink>(
-    tree_sink: S,
+    mut tree_sink: S,
     text: &str,
     tokens: &[Token],
     f: fn(&mut Parser),
 ) -> S::Tree {
-    let mut events = {
+    let events = {
         let input = ParserInput::new(text, &tokens);
         let mut p = Parser::new(&input);
         f(&mut p);
         p.finish()
     };
-    EventProcessor::new(tree_sink, text, tokens, &mut events).process().finish()
+    process(&mut tree_sink, events);
+    tree_sink.finish()
 }
 
 /// `TreeSink` abstracts details of a particular syntax tree implementation.
@@ -51,14 +53,14 @@ trait TreeSink {
     type Tree;
 
     /// Adds new leaf to the current branch.
-    fn leaf(&mut self, kind: SyntaxKind, text: SmolStr);
+    fn leaf(&mut self, kind: SyntaxKind, n_tokens: u8);
 
     /// Start new branch and make it current.
-    fn start_branch(&mut self, kind: SyntaxKind);
+    fn start_branch(&mut self, kind: SyntaxKind, root: bool);
 
     /// Finish current branch and restore previous
     /// branch as current.
-    fn finish_branch(&mut self);
+    fn finish_branch(&mut self, root: bool);
 
     fn error(&mut self, error: ParseError);
 
diff --git a/crates/ra_syntax/src/parsing/builder.rs b/crates/ra_syntax/src/parsing/builder.rs
index ee0e2cce7..1041c6a7b 100644
--- a/crates/ra_syntax/src/parsing/builder.rs
+++ b/crates/ra_syntax/src/parsing/builder.rs
@@ -1,40 +1,63 @@
 use crate::{
-    SmolStr, SyntaxKind, SyntaxError, SyntaxErrorKind, TextUnit,
-    parsing::{TreeSink, ParseError},
+    SmolStr, SyntaxError, SyntaxErrorKind, TextUnit, TextRange,
+    SyntaxKind::{self, *},
+    parsing::{TreeSink, ParseError, Token},
     syntax_node::{GreenNode, RaTypes},
 };
 
 use rowan::GreenNodeBuilder;
 
-pub(crate) struct GreenBuilder {
+pub(crate) struct TreeBuilder<'a> {
+    text: &'a str,
+    tokens: &'a [Token],
     text_pos: TextUnit,
+    token_pos: usize,
     errors: Vec<SyntaxError>,
     inner: GreenNodeBuilder<RaTypes>,
 }
 
-impl Default for GreenBuilder {
-    fn default() -> GreenBuilder {
-        GreenBuilder {
-            text_pos: TextUnit::default(),
-            errors: Vec::new(),
-            inner: GreenNodeBuilder::new(),
-        }
-    }
-}
-
-impl TreeSink for GreenBuilder {
+impl<'a> TreeSink for TreeBuilder<'a> {
     type Tree = (GreenNode, Vec<SyntaxError>);
 
-    fn leaf(&mut self, kind: SyntaxKind, text: SmolStr) {
-        self.text_pos += TextUnit::of_str(text.as_str());
-        self.inner.leaf(kind, text);
+    fn leaf(&mut self, kind: SyntaxKind, n_tokens: u8) {
+        self.eat_trivias();
+        let n_tokens = n_tokens as usize;
+        let len = self.tokens[self.token_pos..self.token_pos + n_tokens]
+            .iter()
+            .map(|it| it.len)
+            .sum::<TextUnit>();
+        self.do_leaf(kind, len, n_tokens);
     }
 
-    fn start_branch(&mut self, kind: SyntaxKind) {
-        self.inner.start_internal(kind)
+    fn start_branch(&mut self, kind: SyntaxKind, root: bool) {
+        if root {
+            self.inner.start_internal(kind);
+            return;
+        }
+        let n_trivias =
+            self.tokens[self.token_pos..].iter().take_while(|it| it.kind.is_trivia()).count();
+        let leading_trivias = &self.tokens[self.token_pos..self.token_pos + n_trivias];
+        let mut trivia_end =
+            self.text_pos + leading_trivias.iter().map(|it| it.len).sum::<TextUnit>();
+
+        let n_attached_trivias = {
+            let leading_trivias = leading_trivias.iter().rev().map(|it| {
+                let next_end = trivia_end - it.len;
+                let range = TextRange::from_to(next_end, trivia_end);
+                trivia_end = next_end;
+                (it.kind, &self.text[range])
+            });
+            n_attached_trivias(kind, leading_trivias)
+        };
+        self.eat_n_trivias(n_trivias - n_attached_trivias);
+        self.inner.start_internal(kind);
+        self.eat_n_trivias(n_attached_trivias);
     }
 
-    fn finish_branch(&mut self) {
+    fn finish_branch(&mut self, root: bool) {
+        if root {
+            self.eat_trivias()
+        }
         self.inner.finish_internal();
     }
 
@@ -47,3 +70,67 @@ impl TreeSink for GreenBuilder {
         (self.inner.finish(), self.errors)
     }
 }
+
+impl<'a> TreeBuilder<'a> {
+    pub(super) fn new(text: &'a str, tokens: &'a [Token]) -> TreeBuilder<'a> {
+        TreeBuilder {
+            text,
+            tokens,
+            text_pos: 0.into(),
+            token_pos: 0,
+            errors: Vec::new(),
+            inner: GreenNodeBuilder::new(),
+        }
+    }
+    fn eat_trivias(&mut self) {
+        while let Some(&token) = self.tokens.get(self.token_pos) {
+            if !token.kind.is_trivia() {
+                break;
+            }
+            self.do_leaf(token.kind, token.len, 1);
+        }
+    }
+
+    fn eat_n_trivias(&mut self, n: usize) {
+        for _ in 0..n {
+            let token = self.tokens[self.token_pos];
+            assert!(token.kind.is_trivia());
+            self.do_leaf(token.kind, token.len, 1);
+        }
+    }
+
+    fn do_leaf(&mut self, kind: SyntaxKind, len: TextUnit, n_tokens: usize) {
+        let range = TextRange::offset_len(self.text_pos, len);
+        let text: SmolStr = self.text[range].into();
+        self.text_pos += len;
+        self.token_pos += n_tokens;
+        self.inner.leaf(kind, text);
+    }
+}
+
+fn n_attached_trivias<'a>(
+    kind: SyntaxKind,
+    trivias: impl Iterator<Item = (SyntaxKind, &'a str)>,
+) -> usize {
+    match kind {
+        CONST_DEF | TYPE_DEF | STRUCT_DEF | ENUM_DEF | ENUM_VARIANT | FN_DEF | TRAIT_DEF
+        | MODULE | NAMED_FIELD_DEF => {
+            let mut res = 0;
+            for (i, (kind, text)) in trivias.enumerate() {
+                match kind {
+                    WHITESPACE => {
+                        if text.contains("\n\n") {
+                            break;
+                        }
+                    }
+                    COMMENT => {
+                        res = i + 1;
+                    }
+                    _ => (),
+                }
+            }
+            res
+        }
+        _ => 0,
+    }
+}
diff --git a/crates/ra_syntax/src/parsing/event.rs b/crates/ra_syntax/src/parsing/event.rs
index f6f020eab..d6cbdffe0 100644
--- a/crates/ra_syntax/src/parsing/event.rs
+++ b/crates/ra_syntax/src/parsing/event.rs
@@ -10,13 +10,8 @@
 use std::mem;
 
 use crate::{
-    SmolStr,
     SyntaxKind::{self, *},
-    TextRange, TextUnit,
-    parsing::{
-        ParseError, TreeSink,
-        lexer::Token,
-    },
+    parsing::{ParseError, TreeSink},
 };
 
 /// `Parser` produces a flat list of `Event`s.
@@ -88,160 +83,46 @@ impl Event {
     }
 }
 
-pub(super) struct EventProcessor<'a, S: TreeSink> {
-    sink: S,
-    text_pos: TextUnit,
-    text: &'a str,
-    token_pos: usize,
-    tokens: &'a [Token],
-    events: &'a mut [Event],
-}
-
-impl<'a, S: TreeSink> EventProcessor<'a, S> {
-    pub(super) fn new(
-        sink: S,
-        text: &'a str,
-        tokens: &'a [Token],
-        events: &'a mut [Event],
-    ) -> EventProcessor<'a, S> {
-        EventProcessor { sink, text_pos: 0.into(), text, token_pos: 0, tokens, events }
-    }
-
-    /// Generate the syntax tree with the control of events.
-    pub(crate) fn process(mut self) -> S {
-        let mut forward_parents = Vec::new();
-
-        for i in 0..self.events.len() {
-            match mem::replace(&mut self.events[i], Event::tombstone()) {
-                Event::Start { kind: TOMBSTONE, .. } => (),
-
-                Event::Start { kind, forward_parent } => {
-                    // For events[A, B, C], B is A's forward_parent, C is B's forward_parent,
-                    // in the normal control flow, the parent-child relation: `A -> B -> C`,
-                    // while with the magic forward_parent, it writes: `C <- B <- A`.
-
-                    // append `A` into parents.
-                    forward_parents.push(kind);
-                    let mut idx = i;
-                    let mut fp = forward_parent;
-                    while let Some(fwd) = fp {
-                        idx += fwd as usize;
-                        // append `A`'s forward_parent `B`
-                        fp = match mem::replace(&mut self.events[idx], Event::tombstone()) {
-                            Event::Start { kind, forward_parent } => {
-                                forward_parents.push(kind);
-                                forward_parent
-                            }
-                            _ => unreachable!(),
-                        };
-                        // append `B`'s forward_parent `C` in the next stage.
-                    }
-
-                    for kind in forward_parents.drain(..).rev() {
-                        self.start(kind);
-                    }
-                }
-                Event::Finish => {
-                    let is_last = i == self.events.len() - 1;
-                    self.finish(is_last);
-                }
-                Event::Token { kind, n_raw_tokens } => {
-                    self.eat_trivias();
-                    let n_raw_tokens = n_raw_tokens as usize;
-                    let len = self.tokens[self.token_pos..self.token_pos + n_raw_tokens]
-                        .iter()
-                        .map(|it| it.len)
-                        .sum::<TextUnit>();
-                    self.leaf(kind, len, n_raw_tokens);
+/// Generate the syntax tree with the control of events.
+pub(super) fn process(sink: &mut impl TreeSink, mut events: Vec<Event>) {
+    let mut forward_parents = Vec::new();
+
+    for i in 0..events.len() {
+        match mem::replace(&mut events[i], Event::tombstone()) {
+            Event::Start { kind: TOMBSTONE, .. } => (),
+
+            Event::Start { kind, forward_parent } => {
+                // For events[A, B, C], B is A's forward_parent, C is B's forward_parent,
+                // in the normal control flow, the parent-child relation: `A -> B -> C`,
+                // while with the magic forward_parent, it writes: `C <- B <- A`.
+
+                // append `A` into parents.
+                forward_parents.push(kind);
+                let mut idx = i;
+                let mut fp = forward_parent;
+                while let Some(fwd) = fp {
+                    idx += fwd as usize;
+                    // append `A`'s forward_parent `B`
+                    fp = match mem::replace(&mut events[idx], Event::tombstone()) {
+                        Event::Start { kind, forward_parent } => {
+                            forward_parents.push(kind);
+                            forward_parent
+                        }
+                        _ => unreachable!(),
+                    };
+                    // append `B`'s forward_parent `C` in the next stage.
                 }
-                Event::Error { msg } => self.sink.error(msg),
-            }
-        }
-        self.sink
-    }
-
-    /// Add the node into syntax tree but discard the comments/whitespaces.
-    fn start(&mut self, kind: SyntaxKind) {
-        if kind == SOURCE_FILE {
-            self.sink.start_branch(kind);
-            return;
-        }
-        let n_trivias =
-            self.tokens[self.token_pos..].iter().take_while(|it| it.kind.is_trivia()).count();
-        let leading_trivias = &self.tokens[self.token_pos..self.token_pos + n_trivias];
-        let mut trivia_end =
-            self.text_pos + leading_trivias.iter().map(|it| it.len).sum::<TextUnit>();
 
-        let n_attached_trivias = {
-            let leading_trivias = leading_trivias.iter().rev().map(|it| {
-                let next_end = trivia_end - it.len;
-                let range = TextRange::from_to(next_end, trivia_end);
-                trivia_end = next_end;
-                (it.kind, &self.text[range])
-            });
-            n_attached_trivias(kind, leading_trivias)
-        };
-        self.eat_n_trivias(n_trivias - n_attached_trivias);
-        self.sink.start_branch(kind);
-        self.eat_n_trivias(n_attached_trivias);
-    }
-
-    fn finish(&mut self, is_last: bool) {
-        if is_last {
-            self.eat_trivias()
-        }
-        self.sink.finish_branch();
-    }
-
-    fn eat_trivias(&mut self) {
-        while let Some(&token) = self.tokens.get(self.token_pos) {
-            if !token.kind.is_trivia() {
-                break;
-            }
-            self.leaf(token.kind, token.len, 1);
-        }
-    }
-
-    fn eat_n_trivias(&mut self, n: usize) {
-        for _ in 0..n {
-            let token = self.tokens[self.token_pos];
-            assert!(token.kind.is_trivia());
-            self.leaf(token.kind, token.len, 1);
-        }
-    }
-
-    fn leaf(&mut self, kind: SyntaxKind, len: TextUnit, n_tokens: usize) {
-        let range = TextRange::offset_len(self.text_pos, len);
-        let text: SmolStr = self.text[range].into();
-        self.text_pos += len;
-        self.token_pos += n_tokens;
-        self.sink.leaf(kind, text);
-    }
-}
-
-fn n_attached_trivias<'a>(
-    kind: SyntaxKind,
-    trivias: impl Iterator<Item = (SyntaxKind, &'a str)>,
-) -> usize {
-    match kind {
-        CONST_DEF | TYPE_DEF | STRUCT_DEF | ENUM_DEF | ENUM_VARIANT | FN_DEF | TRAIT_DEF
-        | MODULE | NAMED_FIELD_DEF => {
-            let mut res = 0;
-            for (i, (kind, text)) in trivias.enumerate() {
-                match kind {
-                    WHITESPACE => {
-                        if text.contains("\n\n") {
-                            break;
-                        }
-                    }
-                    COMMENT => {
-                        res = i + 1;
-                    }
-                    _ => (),
+                for (j, kind) in forward_parents.drain(..).rev().enumerate() {
+                    let is_root_node = i == 0 && j == 0;
+                    sink.start_branch(kind, is_root_node);
                 }
             }
-            res
+            Event::Finish => sink.finish_branch(i == events.len() - 1),
+            Event::Token { kind, n_raw_tokens } => {
+                sink.leaf(kind, n_raw_tokens);
+            }
+            Event::Error { msg } => sink.error(msg),
         }
-        _ => 0,
     }
 }
diff --git a/crates/ra_syntax/src/parsing/reparsing.rs b/crates/ra_syntax/src/parsing/reparsing.rs
index f2d218ab9..f4c2251d7 100644
--- a/crates/ra_syntax/src/parsing/reparsing.rs
+++ b/crates/ra_syntax/src/parsing/reparsing.rs
@@ -5,7 +5,7 @@ use crate::{
     syntax_error::SyntaxError,
     parsing::{
         grammar, parse_with,
-        builder::GreenBuilder,
+        builder::TreeBuilder,
         parser::Parser,
         lexer::{tokenize, Token},
     }
@@ -61,7 +61,8 @@ fn reparse_block<'node>(
     if !is_balanced(&tokens) {
         return None;
     }
-    let (green, new_errors) = parse_with(GreenBuilder::default(), &text, &tokens, reparser);
+    let tree_sink = TreeBuilder::new(&text, &tokens);
+    let (green, new_errors) = parse_with(tree_sink, &text, &tokens, reparser);
     Some((node, green, new_errors))
 }