NNBD migrator: Visit metadata on top-level functions

Change-Id: I6825f03ca754e05a6a8a7d4a9d3c13d9baa5ddaa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127400
Reviewed-by: Janice Collins <jcollins@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>

pkg/nnbd_migration/lib/src/edge_builder.dart

@@ -642,6 +642,7 @@ class EdgeBuilder extends GeneralizingAstVisitor<DecoratedType>
 
   @override
   DecoratedType visitFunctionDeclaration(FunctionDeclaration node) {
+    node.metadata.accept(this);
     if (_flowAnalysis != null) {
       // This is a local function.
       node.functionExpression.accept(this);

pkg/nnbd_migration/test/edge_builder_test.dart

@@ -2077,6 +2077,15 @@ bar() {
     expect(type.returnType, isNotNull);
   }
 
+  test_function_metadata() async {
+    await analyze('''
+@deprecated
+void f() {}
+''');
+    // No assertions needed; the AnnotationTracker mixin verifies that the
+    // metadata was visited.
+  }
+
   test_functionDeclaration_expression_body() async {
     await analyze('''
 int/*1*/ f(int/*2*/ i) => i/*3*/;