fix #29733, handle variables that completely shadow parameters

pkg/dev_compiler/lib/src/js_ast/nodes.dart

Index: pkg/dev_compiler/lib/src/js_ast/nodes.dart
diff --git a/pkg/dev_compiler/lib/src/js_ast/nodes.dart b/pkg/dev_compiler/lib/src/js_ast/nodes.dart
index 29aa1b50ffd19aa94e116c088242c78a407d0960..354e4f69115119211e029b41d5fc04cc0216e2b4 100644
--- a/pkg/dev_compiler/lib/src/js_ast/nodes.dart
+++ b/pkg/dev_compiler/lib/src/js_ast/nodes.dart
@@ -252,10 +252,8 @@ abstract class Node {
   /// setting this after construction.
   Object sourceInformation;
 
-  ClosureAnnotation _closureAnnotation;
-
   /// Closure annotation of this node.
-  ClosureAnnotation get closureAnnotation => _closureAnnotation;
+  ClosureAnnotation closureAnnotation;
 
   accept(NodeVisitor visitor);
   void visitChildren(NodeVisitor visitor);
@@ -264,14 +262,6 @@ abstract class Node {
   // private method is create a copy with a new position.
   Node _clone();
 
-  withClosureAnnotation(ClosureAnnotation closureAnnotation) {
-    if (this.closureAnnotation == closureAnnotation) return this;
-
-    return _clone()
-      ..sourceInformation = sourceInformation
-      .._closureAnnotation = closureAnnotation;
-  }
-
   // Returns a node equivalent to [this], but with new source position and end
   // source position.
   Node withSourceInformation(sourceInformation) {