3 files changed, 76 insertions, 6 deletions

diff --git a/src/yellow/builder.rs b/src/yellow/builder.rs
new file mode 100644
index 000000000..346d561cd
--- /dev/null
+++ b/src/yellow/builder.rs
@@ -0,0 +1,68 @@
+use std::sync::Arc;
+use {
+    SyntaxKind, TextRange, TextUnit,
+    yellow::{SyntaxNode, GreenNode, SyntaxError},
+    parser::Sink
+};
+
+pub(crate) struct GreenBuilder {
+    text: String,
+    stack: Vec<GreenNode>,
+    pos: TextUnit,
+    root: Option<GreenNode>,
+    errors: Vec<SyntaxError>,
+}
+
+impl GreenBuilder {
+
+}
+
+impl Sink for GreenBuilder {
+    type Tree = SyntaxNode;
+
+    fn new(text: String) -> Self {
+        GreenBuilder {
+            text,
+            stack: Vec::new(),
+            pos: 0.into(),
+            root: None,
+            errors: Vec::new(),
+        }
+    }
+
+    fn leaf(&mut self, kind: SyntaxKind, len: TextUnit) {
+        let range = TextRange::offset_len(self.pos, len);
+        self.pos += len;
+        let text = self.text[range].to_owned();
+        let parent = self.stack.last_mut().unwrap();
+        if kind.is_trivia() {
+            parent.push_trivia(kind, text);
+        } else {
+            let node = GreenNode::new_leaf(kind, text);
+            parent.push_child(Arc::new(node));
+        }
+    }
+
+    fn start_internal(&mut self, kind: SyntaxKind) {
+        self.stack.push(GreenNode::new_branch(kind))
+    }
+
+    fn finish_internal(&mut self) {
+        let node = self.stack.pop().unwrap();
+        if let Some(parent) = self.stack.last_mut() {
+            parent.push_child(Arc::new(node))
+        } else {
+            self.root = Some(node);
+        }
+    }
+
+    fn error(&mut self, message: String) {
+        self.errors.push(SyntaxError { message, offset: self.pos })
+    }
+
+    fn finish(self) -> SyntaxNode {
+        SyntaxNode::new(Arc::new(self.root.unwrap()), self.errors)
+    }
+}
+
+
diff --git a/src/yellow/mod.rs b/src/yellow/mod.rs
index 88d88e226..9e64d042f 100644
--- a/src/yellow/mod.rs
+++ b/src/yellow/mod.rs
@@ -1,6 +1,7 @@
 mod green;
 mod red;
 mod syntax;
+mod builder;
 
 use std::{
     sync::{Arc, Weak},
@@ -9,7 +10,8 @@ use std::{
 pub(crate) use self::{
     green::{GreenNode, TextLen},
     red::RedNode,
-    syntax::SError,
+    syntax::SyntaxError,
+    builder::GreenBuilder,
 };
 pub use self::syntax::SyntaxNode;
 
diff --git a/src/yellow/syntax.rs b/src/yellow/syntax.rs
index 7b1a05cd9..78fa5bf95 100644
--- a/src/yellow/syntax.rs
+++ b/src/yellow/syntax.rs
@@ -4,7 +4,8 @@ use std::{
 };
 
 use {
-    TextRange, TextUnit, SyntaxKind,
+    TextRange, TextUnit,
+    SyntaxKind::{self, *},
     yellow::{Ptr, RedNode, GreenNode, TextLen},
 };
 
@@ -18,17 +19,17 @@ pub struct SyntaxNode {
 #[derive(Clone)]
 pub struct SyntaxRoot {
     red: Arc<RedNode>,
-    pub(crate) errors: Arc<Vec<SError>>,
+    pub(crate) errors: Arc<Vec<SyntaxError>>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
-pub(crate) struct SError {
+pub(crate) struct SyntaxError {
     pub(crate) message: String,
     pub(crate) offset: TextUnit,
 }
 
 impl SyntaxNode {
-    pub(crate) fn new(root: Arc<GreenNode>, errors: Vec<SError>) -> SyntaxNode {
+    pub(crate) fn new(root: Arc<GreenNode>, errors: Vec<SyntaxError>) -> SyntaxNode {
         let root = Arc::new(RedNode::new_root(root));
         let red = Ptr::new(&root);
         let root = SyntaxRoot { red: root, errors: Arc::new(errors) };
@@ -123,7 +124,6 @@ impl fmt::Debug for SyntaxNode {
 }
 
 fn has_short_text(kind: SyntaxKind) -> bool {
-    use syntax_kinds::*;
     match kind {
         IDENT | LIFETIME => true,
         _ => false,