3 files changed, 61 insertions, 20 deletions

diff --git a/crates/ra_syntax/src/lib.rs b/crates/ra_syntax/src/lib.rs
index e7d402446..7334d53ef 100644
--- a/crates/ra_syntax/src/lib.rs
+++ b/crates/ra_syntax/src/lib.rs
@@ -36,7 +36,7 @@ pub use crate::{
     ast::AstNode,
     syntax_error::{SyntaxError, SyntaxErrorKind, Location},
     syntax_text::SyntaxText,
-    syntax_node::{Direction,  SyntaxNode, WalkEvent, TreeArc},
+    syntax_node::{Direction,  SyntaxNode, WalkEvent, TreeArc, SyntaxTreeBuilder},
     ptr::{SyntaxNodePtr, AstPtr},
     parsing::{tokenize, Token},
 };
diff --git a/crates/ra_syntax/src/parsing/text_tree_sink.rs b/crates/ra_syntax/src/parsing/text_tree_sink.rs
index 8c1d78deb..961a91d41 100644
--- a/crates/ra_syntax/src/parsing/text_tree_sink.rs
+++ b/crates/ra_syntax/src/parsing/text_tree_sink.rs
@@ -1,13 +1,12 @@
 use std::mem;
 
 use ra_parser::{TreeSink, ParseError};
-use rowan::GreenNodeBuilder;
 
 use crate::{
-    SmolStr, SyntaxError, SyntaxErrorKind, TextUnit, TextRange,
+    SmolStr, SyntaxError, TextUnit, TextRange, SyntaxTreeBuilder,
     SyntaxKind::{self, *},
     parsing::Token,
-    syntax_node::{GreenNode, RaTypes},
+    syntax_node::GreenNode,
 };
 
 /// Bridges the parser with our specific syntax tree representation.
@@ -19,8 +18,7 @@ pub(crate) struct TextTreeSink<'a> {
     text_pos: TextUnit,
     token_pos: usize,
     state: State,
-    errors: Vec<SyntaxError>,
-    inner: GreenNodeBuilder<RaTypes>,
+    inner: SyntaxTreeBuilder,
 }
 
 enum State {
@@ -33,7 +31,7 @@ impl<'a> TreeSink for TextTreeSink<'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::PendingFinish => self.inner.finish_branch(),
             State::Normal => (),
         }
         self.eat_trivias();
@@ -48,12 +46,12 @@ impl<'a> TreeSink for TextTreeSink<'a> {
     fn start_branch(&mut self, kind: SyntaxKind) {
         match mem::replace(&mut self.state, State::Normal) {
             State::PendingStart => {
-                self.inner.start_internal(kind);
+                self.inner.start_branch(kind);
                 // No need to attach trivias to previous node: there is no
                 // previous node.
                 return;
             }
-            State::PendingFinish => self.inner.finish_internal(),
+            State::PendingFinish => self.inner.finish_branch(),
             State::Normal => (),
         }
 
@@ -73,21 +71,20 @@ impl<'a> TreeSink for TextTreeSink<'a> {
             n_attached_trivias(kind, leading_trivias)
         };
         self.eat_n_trivias(n_trivias - n_attached_trivias);
-        self.inner.start_internal(kind);
+        self.inner.start_branch(kind);
         self.eat_n_trivias(n_attached_trivias);
     }
 
     fn finish_branch(&mut self) {
         match mem::replace(&mut self.state, State::PendingFinish) {
             State::PendingStart => unreachable!(),
-            State::PendingFinish => self.inner.finish_internal(),
+            State::PendingFinish => self.inner.finish_branch(),
             State::Normal => (),
         }
     }
 
     fn error(&mut self, error: ParseError) {
-        let error = SyntaxError::new(SyntaxErrorKind::ParseError(error), self.text_pos);
-        self.errors.push(error)
+        self.inner.error(error, self.text_pos)
     }
 }
 
@@ -99,8 +96,7 @@ impl<'a> TextTreeSink<'a> {
             text_pos: 0.into(),
             token_pos: 0,
             state: State::PendingStart,
-            errors: Vec::new(),
-            inner: GreenNodeBuilder::new(),
+            inner: SyntaxTreeBuilder::default(),
         }
     }
 
@@ -108,12 +104,12 @@ impl<'a> TextTreeSink<'a> {
         match mem::replace(&mut self.state, State::Normal) {
             State::PendingFinish => {
                 self.eat_trivias();
-                self.inner.finish_internal()
+                self.inner.finish_branch()
             }
             State::PendingStart | State::Normal => unreachable!(),
         }
 
-        (self.inner.finish(), self.errors)
+        self.inner.finish_raw()
     }
 
     fn eat_trivias(&mut self) {
diff --git a/crates/ra_syntax/src/syntax_node.rs b/crates/ra_syntax/src/syntax_node.rs
index 4d54ae614..e5b4cdb11 100644
--- a/crates/ra_syntax/src/syntax_node.rs
+++ b/crates/ra_syntax/src/syntax_node.rs
@@ -11,11 +11,12 @@ use std::{
     borrow::Borrow,
 };
 
-use rowan::{Types, TransparentNewType};
+use ra_parser::ParseError;
+use rowan::{Types, TransparentNewType, GreenNodeBuilder};
 
 use crate::{
-    SmolStr, SyntaxKind, TextRange, SyntaxText, SourceFile, AstNode,
-    syntax_error::SyntaxError,
+    SmolStr, SyntaxKind, TextUnit, TextRange, SyntaxText, SourceFile, AstNode,
+    syntax_error::{SyntaxError, SyntaxErrorKind},
 };
 
 pub use rowan::WalkEvent;
@@ -276,3 +277,47 @@ fn has_short_text(kind: SyntaxKind) -> bool {
         _ => false,
     }
 }
+
+pub struct SyntaxTreeBuilder {
+    errors: Vec<SyntaxError>,
+    inner: GreenNodeBuilder<RaTypes>,
+}
+
+impl Default for SyntaxTreeBuilder {
+    fn default() -> SyntaxTreeBuilder {
+        SyntaxTreeBuilder { errors: Vec::new(), inner: GreenNodeBuilder::new() }
+    }
+}
+
+impl SyntaxTreeBuilder {
+    pub(crate) fn finish_raw(self) -> (GreenNode, Vec<SyntaxError>) {
+        let green = self.inner.finish();
+        (green, self.errors)
+    }
+
+    pub fn finish(self) -> TreeArc<SyntaxNode> {
+        let (green, errors) = self.finish_raw();
+        let node = SyntaxNode::new(green, errors);
+        if cfg!(debug_assertions) {
+            crate::validation::validate_block_structure(&node);
+        }
+        node
+    }
+
+    pub fn leaf(&mut self, kind: SyntaxKind, text: SmolStr) {
+        self.inner.leaf(kind, text)
+    }
+
+    pub fn start_branch(&mut self, kind: SyntaxKind) {
+        self.inner.start_internal(kind)
+    }
+
+    pub fn finish_branch(&mut self) {
+        self.inner.finish_internal()
+    }
+
+    pub fn error(&mut self, error: ParseError, text_pos: TextUnit) {
+        let error = SyntaxError::new(SyntaxErrorKind::ParseError(error), text_pos);
+        self.errors.push(error)
+    }
+}