1 files changed, 119 insertions, 0 deletions
diff --git a/vendor/rowan/src/green/builder.rs b/vendor/rowan/src/green/builder.rs
new file mode 100644
index 000000000..1dbc8bb08
--- /dev/null
+++ b/vendor/rowan/src/green/builder.rs
@@ -0,0 +1,119 @@
+use crate::{
+    cow_mut::CowMut,
+    green::{node_cache::NodeCache, GreenElement, GreenNode, SyntaxKind},
+    NodeOrToken,
+};
+
+/// A checkpoint for maybe wrapping a node. See `GreenNodeBuilder::checkpoint` for details.
+#[derive(Clone, Copy, Debug)]
+pub struct Checkpoint(usize);
+
+/// A builder for a green tree.
+#[derive(Default, Debug)]
+pub struct GreenNodeBuilder<'cache> {
+    cache: CowMut<'cache, NodeCache>,
+    parents: Vec<(SyntaxKind, usize)>,
+    children: Vec<(u64, GreenElement)>,
+}
+
+impl GreenNodeBuilder<'_> {
+    /// Creates new builder.
+    pub fn new() -> GreenNodeBuilder<'static> {
+        GreenNodeBuilder::default()
+    }
+
+    /// Reusing `NodeCache` between different `GreenNodeBuilder`s saves memory.
+    /// It allows to structurally share underlying trees.
+    pub fn with_cache(cache: &mut NodeCache) -> GreenNodeBuilder<'_> {
+        GreenNodeBuilder {
+            cache: CowMut::Borrowed(cache),
+            parents: Vec::new(),
+            children: Vec::new(),
+        }
+    }
+
+    /// Adds new token to the current branch.
+    #[inline]
+    pub fn token(&mut self, kind: SyntaxKind, text: &str) {
+        let (hash, token) = self.cache.token(kind, text);
+        self.children.push((hash, token.into()));
+    }
+
+    /// Start new node and make it current.
+    #[inline]
+    pub fn start_node(&mut self, kind: SyntaxKind) {
+        let len = self.children.len();
+        self.parents.push((kind, len));
+    }
+
+    /// Finish current branch and restore previous
+    /// branch as current.
+    #[inline]
+    pub fn finish_node(&mut self) {
+        let (kind, first_child) = self.parents.pop().unwrap();
+        let (hash, node) = self.cache.node(kind, &mut self.children, first_child);
+        self.children.push((hash, node.into()));
+    }
+
+    /// Prepare for maybe wrapping the next node.
+    /// The way wrapping works is that you first of all get a checkpoint,
+    /// then you place all tokens you want to wrap, and then *maybe* call
+    /// `start_node_at`.
+    /// Example:
+    /// ```rust
+    /// # use rowan::{GreenNodeBuilder, SyntaxKind};
+    /// # const PLUS: SyntaxKind = SyntaxKind(0);
+    /// # const OPERATION: SyntaxKind = SyntaxKind(1);
+    /// # struct Parser;
+    /// # impl Parser {
+    /// #     fn peek(&self) -> Option<SyntaxKind> { None }
+    /// #     fn parse_expr(&mut self) {}
+    /// # }
+    /// # let mut builder = GreenNodeBuilder::new();
+    /// # let mut parser = Parser;
+    /// let checkpoint = builder.checkpoint();
+    /// parser.parse_expr();
+    /// if parser.peek() == Some(PLUS) {
+    ///   // 1 + 2 = Add(1, 2)
+    ///   builder.start_node_at(checkpoint, OPERATION);
+    ///   parser.parse_expr();
+    ///   builder.finish_node();
+    /// }
+    /// ```
+    #[inline]
+    pub fn checkpoint(&self) -> Checkpoint {
+        Checkpoint(self.children.len())
+    }
+
+    /// Wrap the previous branch marked by `checkpoint` in a new branch and
+    /// make it current.
+    #[inline]
+    pub fn start_node_at(&mut self, checkpoint: Checkpoint, kind: SyntaxKind) {
+        let Checkpoint(checkpoint) = checkpoint;
+        assert!(
+            checkpoint <= self.children.len(),
+            "checkpoint no longer valid, was finish_node called early?"
+        );
+
+        if let Some(&(_, first_child)) = self.parents.last() {
+            assert!(
+                checkpoint >= first_child,
+                "checkpoint no longer valid, was an unmatched start_node_at called?"
+            );
+        }
+
+        self.parents.push((kind, checkpoint));
+    }
+
+    /// Complete tree building. Make sure that
+    /// `start_node_at` and `finish_node` calls
+    /// are paired!
+    #[inline]
+    pub fn finish(mut self) -> GreenNode {
+        assert_eq!(self.children.len(), 1);
+        match self.children.pop().unwrap().1 {
+            NodeOrToken::Node(node) => node,
+            NodeOrToken::Token(_) => panic!(),
+        }
+    }
+}