Various semantic checks on formal parameters.

pkg/front_end/messages.yaml

 # Copyright (c) 2017, 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.
 
 # Each entry in this map corresponds to a diagnostic message. Ideally, each
 # entry contains three parts:
 #
 # 1. A message template (template).
 #
 # 2. A suggestion for how to correct the problem (tip).
@@ skipping 388 matching lines @@
   template: "A type or modifier is required here."
   tip: "Try adding a type, 'var', 'const', or 'final'."
 
 AssertExtraneousArgument:
   template: "`assert` can't have more than two arguments."
   dart2jsCode: FASTA_FATAL
 
 AssertAsExpression:
   template: "`assert` can't be used as an expression."
   dart2jsCode: FASTA_FATAL
+
+FunctionTypeDefaultValue:
+  template: "Can't have a default value in a function type."
+  dart2jsCode: FASTA_IGNORED

[ahe, 2017/06/08 20:28:40]

This makes dart2js ignore this message. Dart2js already implements all these
semantic checks, but at later phases.

+
+PrivateNamedParameter:
+  template: "An optional named parameter can't start with '_'."
+  dart2jsCode: FASTA_IGNORED
+
+NoFormals:
+  template: "A function should have formal parameters."
+  tip: "Try adding '()' after '#lexeme', or add 'get' before '#lexeme' to declare a getter."
+  dart2jsCode: FASTA_IGNORED
+
+GetterWithFormals:
+  template: "A getter can't have formal parameters."
+  tip: "Try removing '(...)'."
+  dart2jsCode: FASTA_IGNORED
+
+CatchSyntax:
+  template: "'catch' must be followed by '(identifier)' or '(identifier, identifier)'."
+  tip: "No types are needed, the first is given by 'on', the second is always 'StackTrace'."