Implement reflection on annotations of parameters.

tests/lib/mirrors/parameter_annotation_mirror_test.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@MirrorsUsed(targets: "Foo")
+import "dart:mirrors";
+
+import 'package:expect/expect.dart';
+
+class ParameterAnnotation {
+  final String value;
+  const ParameterAnnotation(this.value);
+}
+
+class Foo {
+  f1(@ParameterAnnotation("hest") p) {}
+  f2(@ParameterAnnotation("hest") @ParameterAnnotation("fisk") p) {}
+  f3(a, @ParameterAnnotation("fugl") p) {}
+  f4(@ParameterAnnotation("fisk") a,
+     {@ParameterAnnotation("hval") p}) {}
+  f5(@ParameterAnnotation("fisk") a,
+     [@ParameterAnnotation("hval") p]) {}
+}
+
+expectAnnotations(Type type, Symbol method, int parameterIndex,
+                  List<String> expectedValues) {
+  MethodMirror mirror = reflectClass(type).declarations[method];
+  ParameterMirror parameter = mirror.parameters[parameterIndex];
+  List<InstanceMirror> annotations = parameter.metadata;
+  Expect.equals(annotations.length, expectedValues.length,
+                "wrong number of parameter annotations");
+  for (int i = 0; i < annotations.length; i++) {
+    Expect.equals(expectedValues[i], annotations[i].reflectee.value,
+                  "annotation #$i of parameter #$parameterIndex "
+                  "of $type.$method.");
+  }
+}
+
+main() {
+  expectAnnotations(Foo, #f1, 0, ["hest"]);
+  expectAnnotations(Foo, #f2, 0, ["hest", "fisk"]);
+  expectAnnotations(Foo, #f3, 0, []);
+  expectAnnotations(Foo, #f3, 1, ["fugl"]);
+  expectAnnotations(Foo, #f4, 0, ["fisk"]);
+  expectAnnotations(Foo, #f4, 1, ["hval"]);
+  expectAnnotations(Foo, #f5, 0, ["fisk"]);
+  expectAnnotations(Foo, #f5, 1, ["hval"]);
+}