Implement more message argument kinds.

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 18 matching lines @@
 # the compiler reports a problem, it may also specify a map with the following
 # keys to be substituted into the message:
 #
 # `#character` a Unicode character.
 #
 # `#unicode` a Unicode short identifier (U+xxxx). We use this to represent code
 #  units or code points.
 #
 # `#name` a name (a string).
 #
+# `#name2` another name (a string).
+#
 # `#lexeme` a token. The token's `lexeme` property is used.
 #
 # `#string` a string.
+#
+# `#string2` another string.
+#
+# `#uri` a Uri.
 
 AsciiControlCharacter:
   template: "The control character #unicode can only be used in strings and comments."
   dart2jsCode: BAD_INPUT_CHARACTER
   analyzerCode: ILLEGAL_CHARACTER
   expression: "\x1b 1"
 
 NonAsciiIdentifier:
   template: "The non-ASCII character '#character' (#unicode) can't be used in identifiers, only in strings and comments."
   tip: "Try using an US-ASCII letter, a digit, '_' (an underscore), or '$' (a dollar sign)."
@@ skipping 499 matching lines @@
       --fatal=warnings
       --fatal=nits
         Makes messages of the given kinds fatal, that is, immediately stop the
         compiler with a non-zero exit-code. In --verbose mode, also display an
         internal stack trace from the compiler. Multiple kinds can be separated by
         commas, for example, --fatal=errors,warnings.
 
 FastaCLIArgumentRequired:
   template: "Expected value after '#name'."
 
-Unhandled:
-  template: "Unhandled: #string in #name."
-
-Unimplemented:
-  template: "Unimplemented: #string."
-
-Unexpected:
-  template: "Expected '#string', but got '#name'."
-
-Unsupported:
-  template: "Unsupported operation: '#name'."
-
 NamedFunctionExpression:
   template: "A function expression can't have a name."
   dart2jsCode: "*ignored*"
 
 ReturnTypeFunctionExpression:
   template: "A function expression can't have a return type."
   dart2jsCode: "*ignored*"
+
+Unhandled:
+  template: "Internal error: Unhandled #string in #string2."
+
+Unimplemented:
+  template: "Internal error: Unimplemented #string."
+
+Unexpected:
+  template: "Internal error: Expected '#string', but got '#string2'."
+
+Unsupported:
+  template: "Internal error: Unsupported operation: '#name'."