diff --git a/src/go/ast/ast.go b/src/go/ast/ast.go
index 1061f1d..300966a 100644
--- a/src/go/ast/ast.go
+++ b/src/go/ast/ast.go
@@ -57,6 +57,11 @@
 // Comments
 
 // A Comment node represents a single //-style or /*-style comment.
+//
+// The Text field contains the comment text without carriage returns (\r) that
+// may have been present in the source. Because a comment's end position is
+// computed using len(Text), the position reported by End() does not match the
+// true source end position for comments containing carriage returns.
 type Comment struct {
 	Slash token.Pos // position of "/" starting the comment
 	Text  string    // comment text (excluding '\n' for //-style comments)