Emit a compile-time error when using default values in function typed parameter.

sdk/lib/_internal/compiler/implementation/warnings.dart

Index: sdk/lib/_internal/compiler/implementation/warnings.dart
diff --git a/sdk/lib/_internal/compiler/implementation/warnings.dart b/sdk/lib/_internal/compiler/implementation/warnings.dart
index a7d664275bce935e3dea3361b3135d3807bbdf01..ad09f95f26a83f210d538e66cca81cf6c0349668 100644
--- a/sdk/lib/_internal/compiler/implementation/warnings.dart
+++ b/sdk/lib/_internal/compiler/implementation/warnings.dart
@@ -587,7 +587,7 @@ main() {
   static const MessageKind TYPEDEF_FORMAL_WITH_DEFAULT = const MessageKind(
       "Error: A parameter of a typedef can't specify a default value.",
       howToFix:
-        "Try removing the default value or making the parameter optional.",
+        "Try removing the default value.",
       examples: const ["""
 typedef void F([int arg = 0]);
 
@@ -600,6 +600,22 @@ main() {
   F f;
 }"""]);
 
+  static const MessageKind FUNCTION_TYPE_FORMAL_WITH_DEFAULT = const MessageKind(
+      "Error: A function type parameters can't specify a default value.",
+      howToFix:
+        "Try removing the default value.",
+      examples: const ["""
+foo(void f(int i, [a = 1]) {}
+
+main() {
+  foo(1, 2);
+}""", """
+foo(void f(int i, {a: 1}) {}
+
+main() {
+  foo(1, a: 2);
+}"""]);
+
   static const MessageKind FORMAL_DECLARED_CONST = const MessageKind(
       "Error: A formal parameter can't be declared const.",
       howToFix: "Try removing 'const'.",