Support multiple categories per message.

pkg/dart_messages/lib/generated/shared_messages.json

 {
   "exampleMessage": {
     "id": "use an Id generated by bin/message_id.dart",
     "subId": 0,
-    "category": "AnalysisOptionsError",
+    "categories": [
+      "AnalysisOptionsError"
+    ],
     "template": "#use #named #arguments",
     "templateHoleOrder": [
       "arguments",
       "named",
       "use"
     ],
     "howToFix": "an explanation on how to fix things",
     "options": null,
     "usedBy": [],
     "examples": [
       "      Some multiline example;\n      That generates the bug.",
       {
         "fileA.dart": "        or a map from file to content.\n        again multiline",
         "fileB.dart": "        with possibly multiple files.\n        muliline too"
       }
     ]
   },
   "CONST_CONSTRUCTOR_OR_FACTORY_WITH_BODY": {
     "id": "LGJGHW",
     "subId": 0,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Const constructor or factory can't have a body.",
     "templateHoleOrder": null,
     "howToFix": "Remove the 'const' keyword or the body.",
     "options": null,
     "usedBy": [
       "Platform.dart2js"
     ],
     "examples": [
       "         class C {\n           const C() {}\n         }\n\n         main() => new C();",
       "         class C {\n           const factory C() {}\n         }\n\n         main() => new C();"
     ]
   },
   "CONST_CONSTRUCTOR_WITH_BODY": {
     "id": "LGJGHW",
     "subId": 1,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Const constructor can't have a body.",
     "templateHoleOrder": null,
     "howToFix": "Try removing the 'const' keyword or the body.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "         class C {\n           const C() {}\n         }\n\n         main() => new C();"
     ]
   },
   "CONST_FACTORY": {
     "id": "LGJGHW",
     "subId": 2,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Only redirecting factory constructors can be declared to be 'const'.",
     "templateHoleOrder": null,
     "howToFix": "Try removing the 'const' keyword or replacing the body with '=' followed by a valid target.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "         class C {\n           const factory C() {}\n         }\n\n         main() => new C();"
     ]
   },
   "EXTRANEOUS_MODIFIER": {
     "id": "GRKIQE",
     "subId": 0,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Can't have modifier '#{modifier}' here.",
     "templateHoleOrder": null,
     "howToFix": "Try removing '#{modifier}'.",
     "options": null,
     "usedBy": [
       "Platform.dart2js"
     ],
     "examples": [
       "var String foo; main(){}",
       "var set foo; main(){}",
       "var final foo; main(){}",
       "var var foo; main(){}",
       "var const foo; main(){}",
       "var abstract foo; main(){}",
       "var static foo; main(){}",
       "var external foo; main(){}",
       "get var foo; main(){}",
       "set var foo; main(){}",
       "final var foo; main(){}",
       "var var foo; main(){}",
       "const var foo; main(){}",
       "abstract var foo; main(){}",
       "static var foo; main(){}",
       "external var foo; main(){}"
     ]
   },
   "EXTRANEOUS_MODIFIER_REPLACE": {
     "id": "GRKIQE",
     "subId": 1,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Can't have modifier '#{modifier}' here.",
     "templateHoleOrder": null,
     "howToFix": "Try replacing modifier '#{modifier}' with 'var', 'final', or a type.",
     "options": null,
     "usedBy": [
       "Platform.dart2js"
     ],
     "examples": [
       "set foo; main(){}",
       "abstract foo; main(){}",
       "static foo; main(){}",
       "external foo; main(){}"
     ]
   },
   "CONST_CLASS": {
     "id": "GRKIQE",
     "subId": 2,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Classes can't be declared to be 'const'",
     "templateHoleOrder": null,
     "howToFix": "Try removing the 'const' keyword or moving to the class' constructor(s).",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "        const class C {}\n\n        main() => new C();\n        "
     ]
   },
   "CONST_METHOD": {
     "id": "GRKIQE",
     "subId": 3,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Getters, setters and methods can't be declared to be 'const'",
     "templateHoleOrder": null,
     "howToFix": "Try removing the 'const' keyword.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "const int foo() => 499; main() {}",
       "const int get foo => 499; main() {}",
       "const set foo(v) => 499; main() {}",
       "class A { const int foo() => 499; } main() { new A(); }",
       "class A { const int get foo => 499; } main() { new A(); }",
       "class A { const set foo(v) => 499; } main() { new A(); }"
     ]
   },
   "CONST_ENUM": {
     "id": "GRKIQE",
     "subId": 4,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Enums can't be declared to be 'const'",
     "templateHoleOrder": null,
     "howToFix": "Try removing the 'const' keyword.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "const enum Foo { x } main() {}"
     ]
   },
   "CONST_TYPEDEF": {
     "id": "GRKIQE",
     "subId": 5,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Type aliases can't be declared to be 'const'",
     "templateHoleOrder": null,
     "howToFix": "Try removing the 'const' keyword.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "const typedef void Foo(); main() {}"
     ]
   },
   "CONST_AND_FINAL": {
     "id": "GRKIQE",
     "subId": 6,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Members can't be declared to be both 'const' and 'final'",
     "templateHoleOrder": null,
     "howToFix": "Try removing either the 'const' or 'final' keyword.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "final const int x = 499; main() {}",
       "const final int x = 499; main() {}",
       "class A { static final const int x = 499; } main() {}",
       "class A { static const final int x = 499; } main() {}"
     ]
   },
   "CONST_AND_VAR": {
     "id": "GRKIQE",
     "subId": 7,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Members can't be declared to be both 'const' and 'var'",
     "templateHoleOrder": null,
     "howToFix": "Try removing either the 'const' or 'var' keyword.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "var const x = 499; main() {}",
       "const var x = 499; main() {}",
       "class A { var const x = 499; } main() {}",
       "class A { const var x = 499; } main() {}"
     ]
   },
   "CLASS_IN_CLASS": {
     "id": "DOTHQH",
     "subId": 0,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Classes can't be declared inside other classes.",
     "templateHoleOrder": null,
     "howToFix": "Try moving the class to the top-level.",
     "options": null,
     "usedBy": [
       "Platform.analyzer"
     ],
     "examples": [
       "class A { class B {} } main() { new A(); }"
     ]
   },
   "CONSTRUCTOR_WITH_RETURN_TYPE": {
     "id": "VOJBWY",
     "subId": 0,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Constructors can't have a return type",
     "templateHoleOrder": null,
     "howToFix": "Try removing the return type.",
     "options": null,
     "usedBy": [
       "Platform.analyzer",
       "Platform.dart2js"
     ],
     "examples": [
       "class A { int A() {} } main() { new A(); }"
     ]
   },
   "MISSING_EXPRESSION_IN_THROW": {
     "id": "FTGGMJ",
     "subId": 0,
-    "category": "ParserError",
+    "categories": [
+      "ParserError"
+    ],
     "template": "Missing expression after 'throw'.",
     "templateHoleOrder": null,
     "howToFix": "Did you mean 'rethrow'?",
     "options": null,
     "usedBy": [
       "Platform.analyzer",
       "Platform.dart2js"
     ],
     "examples": [
       "main() { throw; }",
       "main() { try { throw 0; } catch(e) { throw; } }"
     ]
   },
   "RETHROW_OUTSIDE_CATCH": {
     "id": "MWETLC",
     "subId": 0,
-    "category": "CompileTimeError",
+    "categories": [
+      "CompileTimeError"
+    ],
     "template": "Rethrow must be inside of catch clause",
     "templateHoleOrder": null,
     "howToFix": "Try moving the expression into a catch clause, or using a 'throw' expression.",
     "options": null,
     "usedBy": [
       "Platform.analyzer",
       "Platform.dart2js"
     ],
     "examples": [
       "main() { rethrow; }"
     ]
   },
   "RETURN_IN_GENERATIVE_CONSTRUCTOR": {
     "id": "UOTDQH",
     "subId": 0,
-    "category": "CompileTimeError",
+    "categories": [
+      "CompileTimeError"
+    ],
     "template": "Constructors can't return values.",
     "templateHoleOrder": null,
     "howToFix": "Try removing the return statement or using a factory constructor.",
     "options": null,
     "usedBy": [
       "Platform.analyzer",
       "Platform.dart2js"
     ],
     "examples": [
       "        class C {\n          C() {\n            return 1;\n          }\n        }\n\n        main() => new C();"
     ]
   },
   "RETURN_IN_GENERATOR": {
     "id": "JRUTUQ",
     "subId": 0,
-    "category": "CompileTimeError",
+    "categories": [
+      "CompileTimeError"
+    ],
     "template": "Can't return a value from a generator function (using the '#{modifier}' modifier).",
     "templateHoleOrder": null,
     "howToFix": "Try removing the value, replacing 'return' with 'yield' or changing the method body modifier",
     "options": null,
     "usedBy": [
       "Platform.analyzer",
       "Platform.dart2js"
     ],
     "examples": [
       "        foo() async* { return 0; }\n        main() => foo();\n        ",
       "        foo() sync* { return 0; }\n        main() => foo();\n        "
     ]
+  },
+  "NOT_ASSIGNABLE": {
+    "id": "FYQYXB",
+    "subId": 0,
+    "categories": [
+      "StaticTypeWarning"
+    ],
+    "template": "'#{fromType}' is not assignable to '#{toType}'.",
+    "templateHoleOrder": null,
+    "howToFix": null,
+    "options": null,
+    "usedBy": [
+      "Platform.dart2js"
+    ],
+    "examples": null
+  },
+  "FORIN_NOT_ASSIGNABLE": {
+    "id": "FYQYXB",
+    "subId": 1,
+    "categories": [
+      "Hint"
+    ],
+    "template": "The element type '#{currentType}' of '#{expressionType}' is not assignable to '#{elementType}'.",
+    "templateHoleOrder": null,
+    "howToFix": null,
+    "options": null,
+    "usedBy": [
+      "Platform.dart2js"
+    ],
+    "examples": [
+      "        main() {\n          List<int> list = <int>[1, 2];\n          for (String x in list) x;\n        }\n        "
+    ]
+  },
+  "RETURN_OF_INVALID_TYPE": {
+    "id": "FYQYXB",
+    "subId": 2,
+    "categories": [
+      "StaticTypeWarning"
+    ],
+    "template": "The return type '#{fromType}' is not a '#{toType}', as defined by the method '#{method}'.",
+    "templateHoleOrder": null,
+    "howToFix": null,
+    "options": null,
+    "usedBy": [
+      "Platform.analyzer"
+    ],
+    "examples": [
+      "int foo() => 'foo'; main() { foo(); }"
+    ]
+  },
+  "ARGUMENT_TYPE_NOT_ASSIGNABLE": {
+    "id": "FYQYXB",
+    "subId": 3,
+    "categories": [
+      "Hint",
+      "StaticWarning"
+    ],
+    "template": "The argument type '#{fromType}' cannot be assigned to the parameter type '#{toType}'.",
+    "templateHoleOrder": null,
+    "howToFix": null,
+    "options": null,
+    "usedBy": [
+      "Platform.analyzer"
+    ],
+    "examples": [
+      "foo(int x) => x; main() { foo('bar'); }"
+    ]
   }
 }