add comment

1 files changed, 9 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index 2826ec7f2..45747e21d 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -16,6 +16,15 @@ pub fn find_leaf_at_offset(node: &SyntaxNode, offset: TextUnit) -> LeafAtOffset<
     }
 }
 
+/// Finds a node of specific Ast type at offset. Note that this is slightly
+/// impercise: if the cursor is strictly betwen two nodes of the desired type,
+/// as in
+///
+/// ```no-run
+/// struct Foo {}|struct Bar;
+/// ```
+///
+/// then the left node will be silently prefered.
 pub fn find_node_at_offset<N: AstNode>(syntax: &SyntaxNode, offset: TextUnit) -> Option<&N> {
     find_leaf_at_offset(syntax, offset).find_map(|leaf| leaf.ancestors().find_map(N::cast))
 }