Add data structures to AST to indicate potentially mutated variables.

pkg/analyzer/lib/src/dart/ast/ast.dart

Index: pkg/analyzer/lib/src/dart/ast/ast.dart
diff --git a/pkg/analyzer/lib/src/dart/ast/ast.dart b/pkg/analyzer/lib/src/dart/ast/ast.dart
index dafbff2a599875377fb12b9562bb0fff78fe640c..58586c01afa363d8d6c1c26f0d83bca12af16a6f 100644
--- a/pkg/analyzer/lib/src/dart/ast/ast.dart
+++ b/pkg/analyzer/lib/src/dart/ast/ast.dart
@@ -4721,6 +4721,9 @@ class ForStatementImpl extends StatementImpl implements ForStatement {
  * >   | [ExpressionFunctionBody]
  */
 abstract class FunctionBodyImpl extends AstNodeImpl implements FunctionBody {
+  @override
+  LocalVariableInfoImpl localVariableInfo;
+
   /**
    * Return `true` if this function body is asynchronous.
    */
@@ -6557,6 +6560,19 @@ abstract class LiteralImpl extends ExpressionImpl implements Literal {
 }
 
 /**
+ * Concrete implementation of [LocalVariableInfo].
+ */
+class LocalVariableInfoImpl extends LocalVariableInfo {
+  @override
+  final Set<VariableElement> potentiallyMutatedInClosure =
+      new Set<VariableElement>();
+
+  @override
+  final Set<VariableElement> potentiallyMutatedInScope =
+      new Set<VariableElement>();
+}
+
+/**
  * A single key/value pair in a map literal.
  *
  * > mapLiteralEntry ::=