1 files changed, 143 insertions, 22 deletions

diff --git a/crates/ra_syntax/src/parsing/builder.rs b/crates/ra_syntax/src/parsing/builder.rs
index ee0e2cce7..cfe3139b8 100644
--- a/crates/ra_syntax/src/parsing/builder.rs
+++ b/crates/ra_syntax/src/parsing/builder.rs
@@ -1,49 +1,170 @@
+use std::mem;
+
+use ra_parser::{TreeSink, ParseError};
+use rowan::GreenNodeBuilder;
+
 use crate::{
-    SmolStr, SyntaxKind, SyntaxError, SyntaxErrorKind, TextUnit,
-    parsing::{TreeSink, ParseError},
+    SmolStr, SyntaxError, SyntaxErrorKind, TextUnit, TextRange,
+    SyntaxKind::{self, *},
+    parsing::Token,
     syntax_node::{GreenNode, RaTypes},
 };
 
-use rowan::GreenNodeBuilder;
-
-pub(crate) struct GreenBuilder {
+/// Bridges the parser with our specific syntax tree representation.
+///
+/// `TreeBuilder` also handles attachment of trivia (whitespace) to nodes.
+pub(crate) struct TreeBuilder<'a> {
+    text: &'a str,
+    tokens: &'a [Token],
     text_pos: TextUnit,
+    token_pos: usize,
+    state: State,
     errors: Vec<SyntaxError>,
     inner: GreenNodeBuilder<RaTypes>,
 }
 
-impl Default for GreenBuilder {
-    fn default() -> GreenBuilder {
-        GreenBuilder {
-            text_pos: TextUnit::default(),
-            errors: Vec::new(),
-            inner: GreenNodeBuilder::new(),
-        }
-    }
+enum State {
+    PendingStart,
+    Normal,
+    PendingFinish,
 }
 
-impl TreeSink for GreenBuilder {
-    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);
+impl<'a> TreeSink for TreeBuilder<'a> {
+    fn leaf(&mut self, kind: SyntaxKind, n_tokens: u8) {
+        match mem::replace(&mut self.state, State::Normal) {
+            State::PendingStart => unreachable!(),
+            State::PendingFinish => self.inner.finish_internal(),
+            State::Normal => (),
+        }
+        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)
+        match mem::replace(&mut self.state, State::Normal) {
+            State::PendingStart => {
+                self.inner.start_internal(kind);
+                // No need to attach trivias to previous node: there is no
+                // previous node.
+                return;
+            }
+            State::PendingFinish => self.inner.finish_internal(),
+            State::Normal => (),
+        }
+
+        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) {
-        self.inner.finish_internal();
+        match mem::replace(&mut self.state, State::PendingFinish) {
+            State::PendingStart => unreachable!(),
+            State::PendingFinish => self.inner.finish_internal(),
+            State::Normal => (),
+        }
     }
 
     fn error(&mut self, error: ParseError) {
         let error = SyntaxError::new(SyntaxErrorKind::ParseError(error), self.text_pos);
         self.errors.push(error)
     }
+}
+
+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,
+            state: State::PendingStart,
+            errors: Vec::new(),
+            inner: GreenNodeBuilder::new(),
+        }
+    }
+
+    pub(super) fn finish(mut self) -> (GreenNode, Vec<SyntaxError>) {
+        match mem::replace(&mut self.state, State::Normal) {
+            State::PendingFinish => {
+                self.eat_trivias();
+                self.inner.finish_internal()
+            }
+            State::PendingStart | State::Normal => unreachable!(),
+        }
 
-    fn finish(self) -> (GreenNode, Vec<SyntaxError>) {
         (self.inner.finish(), self.errors)
     }
+
+    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,
+    }
 }