fasta.Keyword implement analyzer.Keyword

pkg/front_end/lib/src/fasta/scanner/keyword.dart

 // Copyright (c) 2011, 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.
 
 library fasta.scanner.keywords;
 
+import '../../scanner/token.dart' as analyzer;
+
 import 'characters.dart' show $a, $z, $A, $Z;
 
 import 'precedence.dart' show PrecedenceInfo;
 
 import 'precedence.dart' show AS_INFO, IS_INFO, KEYWORD_INFO;
 
 /**
  * A keyword in the Dart programming language.
  */
-class Keyword {
+class Keyword implements analyzer.Keyword {
+  static const ASSERT = const Keyword("assert");
+  static const BREAK = const Keyword("break");
+  static const CASE = const Keyword("case");
+  static const CATCH = const Keyword("catch");
+  static const CLASS = const Keyword("class");
+  static const CONST = const Keyword("const");
+  static const CONTINUE = const Keyword("continue");
+  static const DEFAULT = const Keyword("default");
+  static const DO = const Keyword("do");
+  static const ELSE = const Keyword("else");
+  static const ENUM = const Keyword("enum");
+  static const EXTENDS = const Keyword("extends");
+  static const FALSE = const Keyword("false");
+  static const FINAL = const Keyword("final");
+  static const FINALLY = const Keyword("finally");
+  static const FOR = const Keyword("for");
+  static const IF = const Keyword("if");
+  static const IN = const Keyword("in");
+  static const NEW = const Keyword("new");
+  static const NULL = const Keyword("null");
+  static const RETHROW = const Keyword("rethrow");
+  static const RETURN = const Keyword("return");
+  static const SUPER = const Keyword("super");
+  static const SWITCH = const Keyword("switch");
+  static const THIS = const Keyword("this");
+  static const THROW = const Keyword("throw");
+  static const TRUE = const Keyword("true");
+  static const TRY = const Keyword("try");
+  static const VAR = const Keyword("var");
+  static const VOID = const Keyword("void");
+  static const WHILE = const Keyword("while");
+  static const WITH = const Keyword("with");
+
+  // TODO(ahe): Don't think this is a reserved word.
+  // See: http://dartbug.com/5579
+  static const IS = const Keyword("is", info: IS_INFO);
+
+  static const ABSTRACT = const Keyword("abstract", isBuiltIn: true);
+  static const AS = const Keyword("as", info: AS_INFO, isBuiltIn: true);
+  static const COVARIANT = const Keyword("covariant", isBuiltIn: true);
+  static const DYNAMIC = const Keyword("dynamic", isBuiltIn: true);
+  static const EXPORT = const Keyword("export", isBuiltIn: true);
+  static const EXTERNAL = const Keyword("external", isBuiltIn: true);
+  static const FACTORY = const Keyword("factory", isBuiltIn: true);
+  static const GET = const Keyword("get", isBuiltIn: true);
+  static const IMPLEMENTS = const Keyword("implements", isBuiltIn: true);
+  static const IMPORT = const Keyword("import", isBuiltIn: true);
+  static const LIBRARY = const Keyword("library", isBuiltIn: true);
+  static const OPERATOR = const Keyword("operator", isBuiltIn: true);
+  static const PART = const Keyword("part", isBuiltIn: true);
+  static const SET = const Keyword("set", isBuiltIn: true);
+  static const STATIC = const Keyword("static", isBuiltIn: true);
+  static const TYPEDEF = const Keyword("typedef", isBuiltIn: true);
+
+  static const ASYNC = const Keyword("async", isPseudo: true);
+  static const AWAIT = const Keyword("await", isPseudo: true);
+  static const DEFERRED = const Keyword("deferred", isPseudo: true);
+  static const FUNCTION = const Keyword("Function", isPseudo: true);
+  static const HIDE = const Keyword("hide", isPseudo: true);
+  static const NATIVE = const Keyword("native", isPseudo: true);
+  static const OF = const Keyword("of", isPseudo: true);
+  static const ON = const Keyword("on", isPseudo: true);
+  static const PATCH = const Keyword("patch", isPseudo: true);
+  static const SHOW = const Keyword("show", isPseudo: true);
+  static const SOURCE = const Keyword("source", isPseudo: true);
+  static const SYNC = const Keyword("sync", isPseudo: true);
+  static const YIELD = const Keyword("yield", isPseudo: true);
+
   static const List<Keyword> values = const <Keyword>[
-    const Keyword("assert"),
-    const Keyword("break"),
-    const Keyword("case"),
-    const Keyword("catch"),
-    const Keyword("class"),
-    const Keyword("const"),
-    const Keyword("continue"),
-    const Keyword("default"),
-    const Keyword("do"),
-    const Keyword("else"),
-    const Keyword("enum"),
-    const Keyword("extends"),
-    const Keyword("false"),
-    const Keyword("final"),
-    const Keyword("finally"),
-    const Keyword("for"),
-    const Keyword("if"),
-    const Keyword("in"),
-    const Keyword("new"),
-    const Keyword("null"),
-    const Keyword("rethrow"),
-    const Keyword("return"),
-    const Keyword("super"),
-    const Keyword("switch"),
-    const Keyword("this"),
-    const Keyword("throw"),
-    const Keyword("true"),
-    const Keyword("try"),
-    const Keyword("var"),
-    const Keyword("void"),
-    const Keyword("while"),
-    const Keyword("with"),
-
-    // TODO(ahe): Don't think this is a reserved word.
-    // See: http://dartbug.com/5579
-    const Keyword("is", info: IS_INFO),
-
-    const Keyword("abstract", isBuiltIn: true),
-    const Keyword("as", info: AS_INFO, isBuiltIn: true),
-    const Keyword("covariant", isBuiltIn: true),
-    const Keyword("dynamic", isBuiltIn: true),
-    const Keyword("export", isBuiltIn: true),
-    const Keyword("external", isBuiltIn: true),
-    const Keyword("factory", isBuiltIn: true),
-    const Keyword("get", isBuiltIn: true),
-    const Keyword("implements", isBuiltIn: true),
-    const Keyword("import", isBuiltIn: true),
-    const Keyword("library", isBuiltIn: true),
-    const Keyword("operator", isBuiltIn: true),
-    const Keyword("part", isBuiltIn: true),
-    const Keyword("set", isBuiltIn: true),
-    const Keyword("static", isBuiltIn: true),
-    const Keyword("typedef", isBuiltIn: true),
-
-    const Keyword("async", isPseudo: true),
-    const Keyword("await", isPseudo: true),
-    const Keyword("deferred", isPseudo: true),
-    const Keyword("Function", isPseudo: true),
-    const Keyword("hide", isPseudo: true),
-    const Keyword("native", isPseudo: true),
-    const Keyword("of", isPseudo: true),
-    const Keyword("on", isPseudo: true),
-    const Keyword("patch", isPseudo: true),
-    const Keyword("show", isPseudo: true),
-    const Keyword("source", isPseudo: true),
-    const Keyword("sync", isPseudo: true),
-    const Keyword("yield", isPseudo: true),
+    ASSERT,
+    BREAK,
+    CASE,
+    CATCH,
+    CLASS,
+    CONST,
+    CONTINUE,
+    DEFAULT,
+    DO,
+    ELSE,
+    ENUM,
+    EXTENDS,
+    FALSE,
+    FINAL,
+    FINALLY,
+    FOR,
+    IF,
+    IN,
+    NEW,
+    NULL,
+    RETHROW,
+    RETURN,
+    SUPER,
+    SWITCH,
+    THIS,
+    THROW,
+    TRUE,
+    TRY,
+    VAR,
+    VOID,
+    WHILE,
+    WITH,
+    // ====
+    IS,
+    // ==== Built In
+    ABSTRACT,
+    AS,
+    COVARIANT,
+    DYNAMIC,
+    EXPORT,
+    EXTERNAL,
+    FACTORY,
+    GET,
+    IMPLEMENTS,
+    IMPORT,
+    LIBRARY,
+    OPERATOR,
+    PART,
+    SET,
+    STATIC,
+    TYPEDEF,
+    // ==== Pseudo
+    ASYNC,
+    AWAIT,
+    DEFERRED,
+    FUNCTION,
+    HIDE,
+    NATIVE,
+    OF,
+    ON,
+    PATCH,
+    SHOW,
+    SOURCE,
+    SYNC,
+    YIELD,
   ];
 
   final String syntax;
   final bool isPseudo;
   final bool isBuiltIn;
   final PrecedenceInfo info;
 
   static Map<String, Keyword> _keywords;
   static Map<String, Keyword> get keywords {
     if (_keywords == null) {
       _keywords = computeKeywordMap();
     }
     return _keywords;
   }
 
   const Keyword(this.syntax,
       {this.isPseudo: false, this.isBuiltIn: false, this.info: KEYWORD_INFO});
 
   static Map<String, Keyword> computeKeywordMap() {
     Map<String, Keyword> result = new Map<String, Keyword>();
     for (Keyword keyword in values) {
       result[keyword.syntax] = keyword;
     }
     return result;
   }
 
   String toString() => syntax;
+
+  //=================== analyzer.Token compatibility ==================

[ahe, 2017/03/14 14:28:34]

These kinds of sectioning comments tend to grow stale, so I normally avoid them.

[danrubel, 2017/03/14 15:23:47]

Fair enough. Removed.

+
+  @override
+  bool get isPseudoKeyword => isPseudo;

[Paul Berry, 2017/03/14 03:27:21]

Two problems with this:

1. Analyzer's notion of "pseudo-keyword" corresponds to Fasta's notion of
"built-in keyword".  Fasta's terminology is more consistent with the spec, but
unfortunately we're stuck with analyzer's terminology (at least for now) because
we don't want to introduce a breaking change with zero notice.

So I would recommend changing this to a block-bodied function so that we can put
in an explanatory comment.  E.g. something like:

@override
bool get isPseudoKeyword {
  // The term "pseudo-keyword" doesn't exist in the spec, and
  // Analyzer and Fasta have different notions of what it means.
  // Analyzer's notion of "pseudo-keyword" corresponds with Fasta's
  // notion of "built-in keyword".
  return isBuiltIn;
}

2. There is one difference between Fasta's notion of "built-in identifier" and
analyzer's notion of "pseudo-keyword": Analyzer considers "deferred" to be in
this category; Fasta doesn't.  Based on my reading of the spec, this is a bug in
Fasta).  If we land this CL now (even with the fix I mention above), we will
regress some analyzer functionality due to the change in interpretation of
"deferred".  Either we should fix Fasta's handling of "deferred" before landing
this CL, or we should add a hack into this getter to avoid regressing analyzer.

[danrubel, 2017/03/14 12:46:16]

Thank you for the detailed explanation.

On 2017/03/14 03:27:21, Paul Berry wrote:
I have revised the implementation and added a test so that we don't break the
existing Analyzer API.
I've updated the adapter method to "return isBuiltIn || this == DEFERRED" so
that I can continue adapting the fasta scanner to produce analyzer tokens. Is
there a issue already open for this fasta bug?

[Paul Berry, 2017/03/14 13:01:46]

Good point.  I just opened one: https://github.com/dart-lang/sdk/issues/29069

+
+  @override
+  String get name => syntax.toUpperCase();
 }
 
 /**
  * Abstract state in a state machine for scanning keywords.
  */
 abstract class KeywordState {
   KeywordState next(int c);
   KeywordState nextCapital(int c);
 
   Keyword get keyword;
@@ skipping 120 matching lines @@
 class LeafKeywordState implements KeywordState {
   final Keyword keyword;
 
   LeafKeywordState(String syntax) : keyword = Keyword.keywords[syntax];
 
   KeywordState next(int c) => null;
   KeywordState nextCapital(int c) => null;
 
   String toString() => keyword.syntax;
 }