Rename special dart2js error codes.

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).
 #
 # 3. Examples that produce the message (one of expression, statement,
 #    declaration, member, script, or bytes).
 #
 # In addition, an entry can contain an analyzer error code (analyzerCode) and a
 # dart2js error code (dart2jsCode).
 #
+# For dart2js, there's a few special error codes:
+#
+# - `*ignored*` this error is ignored by dart2js (normally a recoverable parser
+#   error that dart2js reports in later phase for historical reasons).
+#
+# - `*fatal*` this is an error that is considered fatal by dart2js (normally a
+#   recoverable parser error that dart2js can't reliably recover from).
+#
 # ## Parameter Substitution in Template and Tip
 #
 # The fields `template` and `tip` are subject to parameter substitution. When
 # 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.
@@ skipping 17 matching lines @@
   expression: "å"
 
 NonAsciiWhitespace:
   template: "The non-ASCII space character #unicode can only be used in strings and comments."
   analyzerCode: ILLEGAL_CHARACTER
   dart2jsCode: BAD_INPUT_CHARACTER
   expression: "\u2028 1"
 
 Encoding:
   template: "Unable to decode bytes as UTF-8."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
   bytes: [255]
 
 EmptyNamedParameterList:
   template: "Named parameter lists cannot be empty."
   tip: "Try adding a named parameter to the list."
   dart2jsCode: EMPTY_NAMED_PARAMETER_LIST
   script: >
     foo({}) {}
 
     main() {
@@ skipping 31 matching lines @@
   # a ',' would also have worked. We don't have enough information to give a
   # good suggestion.
   tip: DONT_KNOW_HOW_TO_FIX,
   dart2jsCode: MISSING_TOKEN_BEFORE_THIS
   script:
     - "main() => true ? 1;"
     - "main() => foo(x: 1 y: 2);"
 
 ExpectedClassBody:
   template: "Expected a class body, but got '#lexeme'."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 ExpectedClassBodyToSkip: ExpectedClassBody
 
 ExpectedDeclaration:
   template: "Expected a declaration, but got '#lexeme'."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 ExpectedExpression:
   template: "Expected an expression, but got '#lexeme'."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 ExpectedFunctionBody:
   template: "Expected a function body, but got '#lexeme'."
   dart2jsCode: NATIVE_OR_FATAL
 
 ExpectedHexDigit:
   template: "A hex digit (0-9 or A-F) must follow '0x'."
   # No tip, seems obvious from the error message.
   analyzerCode: MISSING_HEX_DIGIT
   dart2jsCode: HEX_DIGIT_EXPECTED
   script: >
     main() {
       var i = 0x;
     }
 
 ExpectedIdentifier:
   template: "'#lexeme' is a reserved word and can't be used here."
   tip: "Try using a different name."
   dart2jsCode: EXPECTED_IDENTIFIER
   script: "do() {} main() {}"
 
 ExpectedOpenParens:
   template: "Expected '('."
   dart2jsCode: GENERIC
 
 ExpectedString:
   template: "Expected a String, but got '#lexeme'."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 ExpectedType:
   template: "Expected a type, but got '#lexeme'."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 ExtraneousModifier:
   template: "Can't have modifier '#lexeme' here."
   tip: "Try removing '#lexeme'."
   dart2jsCode: EXTRANEOUS_MODIFIER
   script:
     - "var String foo; main(){}"
     - "var set foo; main(){}"
     - "var final foo; main(){}"
     - "var var foo; main(){}"
@@ skipping 94 matching lines @@
       main() {
         return '''$''';
       }
     - >
       main() {
         return """$""";
       }
 
 UnexpectedToken:
   template: "Unexpected token '#lexeme'."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 UnmatchedToken:
   template: "Can't find '#string' to match '#lexeme'."
   dart2jsCode: UNMATCHED_TOKEN
   script:
     - "main("
     - "main(){"
     - "main(){[}"
 
 UnsupportedPrefixPlus:
@@ skipping 49 matching lines @@
   # This is a fall-back message that shouldn't happen.
   template: "Incomplete token."
   dart2jsCode: UNTERMINATED_TOKEN
 
 Unspecified:
   template: "#string"
   dart2jsCode: GENERIC
 
 AbstractNotSync:
   template: "Abstract methods can't use 'async', 'async*', or 'sync*'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 AsyncAsIdentifier:
   analyzerCode: ASYNC_KEYWORD_USED_AS_IDENTIFIER
   template: "'async' can't be used as an identifier in 'async', 'async*', or 'sync*' methods."
   dart2jsCode: GENERIC
 
 AwaitAsIdentifier:
   template: "'await' can't be used as an identifier in 'async', 'async*', or 'sync*' methods."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 AwaitNotAsync:
   template: "'await' can only be used in 'async' or 'async*' methods."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 BuiltInIdentifierAsType:
   template: "Can't use '#lexeme' as a type."
   analyzerCode: EXPECTED_TYPE_NAME
   dart2jsCode: EXTRANEOUS_MODIFIER
 
 BuiltInIdentifierInDeclaration:
   template: "Can't use '#lexeme' as a name here."
   dart2jsCode: GENERIC
 
 AwaitForNotAsync:
   template: "Asynchronous for-loop can only be used in 'async' or 'async*' methods."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 FactoryNotSync:
   template: "Factories can't use 'async', 'async*', or 'sync*'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 GeneratorReturnsValue:
   template: "'sync*' and 'async*' can't return a value."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 InvalidInlineFunctionType:
   template: "Invalid inline function type."
   tip: "Try changing the inline function type (as in 'int f()') to a prefixed function type using the `Function` keyword (as in 'int Function() f')."
   dart2jsCode: INVALID_INLINE_FUNCTION_TYPE
   declaration: "typedef F = Function(int f(String x)); main() { F f; }"
 
 SetterNotSync:
   template: "Setters can't use 'async', 'async*', or 'sync*'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 YieldAsIdentifier:
   template: "'yield' can't be used as an identifier in 'async', 'async*', or 'sync*' methods."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 YieldNotGenerator:
   template: "'yield' can only be used in 'sync*' or 'async*' methods."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 OnlyTry:
   template: "Try block should be followed by 'on', 'catch', or 'finally' block."
   tip: "Did you forget to add a 'finally' block?"
   statement: "try {}"
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 TypeAfterVar:
   template: "Can't have both a type and 'var'."
   tip: "Try removing 'var.'"
   dart2jsCode: EXTRANEOUS_MODIFIER
 
 TypeRequired:
   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
+  dart2jsCode: "*fatal*"
 
 AssertAsExpression:
   template: "`assert` can't be used as an expression."
-  dart2jsCode: FASTA_FATAL
+  dart2jsCode: "*fatal*"
 
 FunctionTypeDefaultValue:
   template: "Can't have a default value in a function type."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 PrivateNamedParameter:
   template: "An optional named parameter can't start with '_'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*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
+  dart2jsCode: "*ignored*"
 
 GetterWithFormals:
   template: "A getter can't have formal parameters."
   tip: "Try removing '(...)'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*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'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 SuperNullAware:
   template: "'super' can't be null."
   tip: "Try replacing '?.' with '.'"
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 ConstFieldWithoutInitializer:
   template: "A 'const' field must be initialized."
   tip: "Try adding '= <initializer>'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 FinalFieldWithoutInitializer:
   template: "A 'final' field must be initialized."
   tip: "Try adding '= <initializer>'."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"
 
 MetadataTypeArguments:
   template: "An annotation (metadata) can't use type arguments."
-  dart2jsCode: FASTA_IGNORED
+  dart2jsCode: "*ignored*"