• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 //===--- ParseTentative.cpp - Ambiguity Resolution Parsing ----------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file implements the tentative parsing portions of the Parser
11 //  interfaces, for ambiguity resolution.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/Parse/Parser.h"
16 #include "clang/Parse/ParseDiagnostic.h"
17 #include "clang/Sema/ParsedTemplate.h"
18 using namespace clang;
19 
20 /// isCXXDeclarationStatement - C++-specialized function that disambiguates
21 /// between a declaration or an expression statement, when parsing function
22 /// bodies. Returns true for declaration, false for expression.
23 ///
24 ///         declaration-statement:
25 ///           block-declaration
26 ///
27 ///         block-declaration:
28 ///           simple-declaration
29 ///           asm-definition
30 ///           namespace-alias-definition
31 ///           using-declaration
32 ///           using-directive
33 /// [C++0x]   static_assert-declaration
34 ///
35 ///         asm-definition:
36 ///           'asm' '(' string-literal ')' ';'
37 ///
38 ///         namespace-alias-definition:
39 ///           'namespace' identifier = qualified-namespace-specifier ';'
40 ///
41 ///         using-declaration:
42 ///           'using' typename[opt] '::'[opt] nested-name-specifier
43 ///                 unqualified-id ';'
44 ///           'using' '::' unqualified-id ;
45 ///
46 ///         using-directive:
47 ///           'using' 'namespace' '::'[opt] nested-name-specifier[opt]
48 ///                 namespace-name ';'
49 ///
isCXXDeclarationStatement()50 bool Parser::isCXXDeclarationStatement() {
51   switch (Tok.getKind()) {
52     // asm-definition
53   case tok::kw_asm:
54     // namespace-alias-definition
55   case tok::kw_namespace:
56     // using-declaration
57     // using-directive
58   case tok::kw_using:
59     // static_assert-declaration
60   case tok::kw_static_assert:
61   case tok::kw__Static_assert:
62     return true;
63     // simple-declaration
64   default:
65     return isCXXSimpleDeclaration(/*AllowForRangeDecl=*/false);
66   }
67 }
68 
69 /// isCXXSimpleDeclaration - C++-specialized function that disambiguates
70 /// between a simple-declaration or an expression-statement.
71 /// If during the disambiguation process a parsing error is encountered,
72 /// the function returns true to let the declaration parsing code handle it.
73 /// Returns false if the statement is disambiguated as expression.
74 ///
75 /// simple-declaration:
76 ///   decl-specifier-seq init-declarator-list[opt] ';'
77 ///
78 /// (if AllowForRangeDecl specified)
79 /// for ( for-range-declaration : for-range-initializer ) statement
80 /// for-range-declaration:
81 ///    attribute-specifier-seqopt type-specifier-seq declarator
isCXXSimpleDeclaration(bool AllowForRangeDecl)82 bool Parser::isCXXSimpleDeclaration(bool AllowForRangeDecl) {
83   // C++ 6.8p1:
84   // There is an ambiguity in the grammar involving expression-statements and
85   // declarations: An expression-statement with a function-style explicit type
86   // conversion (5.2.3) as its leftmost subexpression can be indistinguishable
87   // from a declaration where the first declarator starts with a '('. In those
88   // cases the statement is a declaration. [Note: To disambiguate, the whole
89   // statement might have to be examined to determine if it is an
90   // expression-statement or a declaration].
91 
92   // C++ 6.8p3:
93   // The disambiguation is purely syntactic; that is, the meaning of the names
94   // occurring in such a statement, beyond whether they are type-names or not,
95   // is not generally used in or changed by the disambiguation. Class
96   // templates are instantiated as necessary to determine if a qualified name
97   // is a type-name. Disambiguation precedes parsing, and a statement
98   // disambiguated as a declaration may be an ill-formed declaration.
99 
100   // We don't have to parse all of the decl-specifier-seq part. There's only
101   // an ambiguity if the first decl-specifier is
102   // simple-type-specifier/typename-specifier followed by a '(', which may
103   // indicate a function-style cast expression.
104   // isCXXDeclarationSpecifier will return TPResult::Ambiguous only in such
105   // a case.
106 
107   bool InvalidAsDeclaration = false;
108   TPResult TPR = isCXXDeclarationSpecifier(TPResult::False,
109                                            &InvalidAsDeclaration);
110   if (TPR != TPResult::Ambiguous)
111     return TPR != TPResult::False; // Returns true for TPResult::True or
112                                    // TPResult::Error.
113 
114   // FIXME: TryParseSimpleDeclaration doesn't look past the first initializer,
115   // and so gets some cases wrong. We can't carry on if we've already seen
116   // something which makes this statement invalid as a declaration in this case,
117   // since it can cause us to misparse valid code. Revisit this once
118   // TryParseInitDeclaratorList is fixed.
119   if (InvalidAsDeclaration)
120     return false;
121 
122   // FIXME: Add statistics about the number of ambiguous statements encountered
123   // and how they were resolved (number of declarations+number of expressions).
124 
125   // Ok, we have a simple-type-specifier/typename-specifier followed by a '(',
126   // or an identifier which doesn't resolve as anything. We need tentative
127   // parsing...
128 
129   {
130     RevertingTentativeParsingAction PA(*this);
131     TPR = TryParseSimpleDeclaration(AllowForRangeDecl);
132   }
133 
134   // In case of an error, let the declaration parsing code handle it.
135   if (TPR == TPResult::Error)
136     return true;
137 
138   // Declarations take precedence over expressions.
139   if (TPR == TPResult::Ambiguous)
140     TPR = TPResult::True;
141 
142   assert(TPR == TPResult::True || TPR == TPResult::False);
143   return TPR == TPResult::True;
144 }
145 
146 /// Try to consume a token sequence that we've already identified as
147 /// (potentially) starting a decl-specifier.
TryConsumeDeclarationSpecifier()148 Parser::TPResult Parser::TryConsumeDeclarationSpecifier() {
149   switch (Tok.getKind()) {
150   case tok::kw__Atomic:
151     if (NextToken().isNot(tok::l_paren)) {
152       ConsumeToken();
153       break;
154     }
155     // Fall through.
156   case tok::kw_typeof:
157   case tok::kw___attribute:
158   case tok::kw___underlying_type: {
159     ConsumeToken();
160     if (Tok.isNot(tok::l_paren))
161       return TPResult::Error;
162     ConsumeParen();
163     if (!SkipUntil(tok::r_paren))
164       return TPResult::Error;
165     break;
166   }
167 
168   case tok::kw_class:
169   case tok::kw_struct:
170   case tok::kw_union:
171   case tok::kw___interface:
172   case tok::kw_enum:
173     // elaborated-type-specifier:
174     //     class-key attribute-specifier-seq[opt]
175     //         nested-name-specifier[opt] identifier
176     //     class-key nested-name-specifier[opt] template[opt] simple-template-id
177     //     enum nested-name-specifier[opt] identifier
178     //
179     // FIXME: We don't support class-specifiers nor enum-specifiers here.
180     ConsumeToken();
181 
182     // Skip attributes.
183     while (Tok.isOneOf(tok::l_square, tok::kw___attribute, tok::kw___declspec,
184                        tok::kw_alignas)) {
185       if (Tok.is(tok::l_square)) {
186         ConsumeBracket();
187         if (!SkipUntil(tok::r_square))
188           return TPResult::Error;
189       } else {
190         ConsumeToken();
191         if (Tok.isNot(tok::l_paren))
192           return TPResult::Error;
193         ConsumeParen();
194         if (!SkipUntil(tok::r_paren))
195           return TPResult::Error;
196       }
197     }
198 
199     if (Tok.isOneOf(tok::identifier, tok::coloncolon, tok::kw_decltype,
200                     tok::annot_template_id) &&
201         TryAnnotateCXXScopeToken())
202       return TPResult::Error;
203     if (Tok.is(tok::annot_cxxscope))
204       ConsumeToken();
205     if (Tok.isNot(tok::identifier) && Tok.isNot(tok::annot_template_id))
206       return TPResult::Error;
207     ConsumeToken();
208     break;
209 
210   case tok::annot_cxxscope:
211     ConsumeToken();
212     // Fall through.
213   default:
214     ConsumeToken();
215 
216     if (getLangOpts().ObjC1 && Tok.is(tok::less))
217       return TryParseProtocolQualifiers();
218     break;
219   }
220 
221   return TPResult::Ambiguous;
222 }
223 
224 /// simple-declaration:
225 ///   decl-specifier-seq init-declarator-list[opt] ';'
226 ///
227 /// (if AllowForRangeDecl specified)
228 /// for ( for-range-declaration : for-range-initializer ) statement
229 /// for-range-declaration:
230 ///    attribute-specifier-seqopt type-specifier-seq declarator
231 ///
TryParseSimpleDeclaration(bool AllowForRangeDecl)232 Parser::TPResult Parser::TryParseSimpleDeclaration(bool AllowForRangeDecl) {
233   if (TryConsumeDeclarationSpecifier() == TPResult::Error)
234     return TPResult::Error;
235 
236   // Two decl-specifiers in a row conclusively disambiguate this as being a
237   // simple-declaration. Don't bother calling isCXXDeclarationSpecifier in the
238   // overwhelmingly common case that the next token is a '('.
239   if (Tok.isNot(tok::l_paren)) {
240     TPResult TPR = isCXXDeclarationSpecifier();
241     if (TPR == TPResult::Ambiguous)
242       return TPResult::True;
243     if (TPR == TPResult::True || TPR == TPResult::Error)
244       return TPR;
245     assert(TPR == TPResult::False);
246   }
247 
248   TPResult TPR = TryParseInitDeclaratorList();
249   if (TPR != TPResult::Ambiguous)
250     return TPR;
251 
252   if (Tok.isNot(tok::semi) && (!AllowForRangeDecl || Tok.isNot(tok::colon)))
253     return TPResult::False;
254 
255   return TPResult::Ambiguous;
256 }
257 
258 /// Tentatively parse an init-declarator-list in order to disambiguate it from
259 /// an expression.
260 ///
261 ///       init-declarator-list:
262 ///         init-declarator
263 ///         init-declarator-list ',' init-declarator
264 ///
265 ///       init-declarator:
266 ///         declarator initializer[opt]
267 /// [GNU]   declarator simple-asm-expr[opt] attributes[opt] initializer[opt]
268 ///
269 ///       initializer:
270 ///         brace-or-equal-initializer
271 ///         '(' expression-list ')'
272 ///
273 ///       brace-or-equal-initializer:
274 ///         '=' initializer-clause
275 /// [C++11] braced-init-list
276 ///
277 ///       initializer-clause:
278 ///         assignment-expression
279 ///         braced-init-list
280 ///
281 ///       braced-init-list:
282 ///         '{' initializer-list ','[opt] '}'
283 ///         '{' '}'
284 ///
TryParseInitDeclaratorList()285 Parser::TPResult Parser::TryParseInitDeclaratorList() {
286   while (1) {
287     // declarator
288     TPResult TPR = TryParseDeclarator(false/*mayBeAbstract*/);
289     if (TPR != TPResult::Ambiguous)
290       return TPR;
291 
292     // [GNU] simple-asm-expr[opt] attributes[opt]
293     if (Tok.isOneOf(tok::kw_asm, tok::kw___attribute))
294       return TPResult::True;
295 
296     // initializer[opt]
297     if (Tok.is(tok::l_paren)) {
298       // Parse through the parens.
299       ConsumeParen();
300       if (!SkipUntil(tok::r_paren, StopAtSemi))
301         return TPResult::Error;
302     } else if (Tok.is(tok::l_brace)) {
303       // A left-brace here is sufficient to disambiguate the parse; an
304       // expression can never be followed directly by a braced-init-list.
305       return TPResult::True;
306     } else if (Tok.is(tok::equal) || isTokIdentifier_in()) {
307       // MSVC and g++ won't examine the rest of declarators if '=' is
308       // encountered; they just conclude that we have a declaration.
309       // EDG parses the initializer completely, which is the proper behavior
310       // for this case.
311       //
312       // At present, Clang follows MSVC and g++, since the parser does not have
313       // the ability to parse an expression fully without recording the
314       // results of that parse.
315       // FIXME: Handle this case correctly.
316       //
317       // Also allow 'in' after an Objective-C declaration as in:
318       // for (int (^b)(void) in array). Ideally this should be done in the
319       // context of parsing for-init-statement of a foreach statement only. But,
320       // in any other context 'in' is invalid after a declaration and parser
321       // issues the error regardless of outcome of this decision.
322       // FIXME: Change if above assumption does not hold.
323       return TPResult::True;
324     }
325 
326     if (!TryConsumeToken(tok::comma))
327       break;
328   }
329 
330   return TPResult::Ambiguous;
331 }
332 
333 struct Parser::ConditionDeclarationOrInitStatementState {
334   Parser &P;
335   bool CanBeExpression = true;
336   bool CanBeCondition = true;
337   bool CanBeInitStatement;
338 
ConditionDeclarationOrInitStatementStateParser::ConditionDeclarationOrInitStatementState339   ConditionDeclarationOrInitStatementState(Parser &P, bool CanBeInitStatement)
340       : P(P), CanBeInitStatement(CanBeInitStatement) {}
341 
markNotExpressionParser::ConditionDeclarationOrInitStatementState342   void markNotExpression() {
343     CanBeExpression = false;
344 
345     if (CanBeCondition && CanBeInitStatement) {
346       // FIXME: Unify the parsing codepaths for condition variables and
347       // simple-declarations so that we don't need to eagerly figure out which
348       // kind we have here. (Just parse init-declarators until we reach a
349       // semicolon or right paren.)
350       RevertingTentativeParsingAction PA(P);
351       P.SkipUntil(tok::r_paren, tok::semi, StopBeforeMatch);
352       if (P.Tok.isNot(tok::r_paren))
353         CanBeCondition = false;
354       if (P.Tok.isNot(tok::semi))
355         CanBeInitStatement = false;
356     }
357   }
358 
markNotConditionParser::ConditionDeclarationOrInitStatementState359   bool markNotCondition() {
360     CanBeCondition = false;
361     return !CanBeInitStatement || !CanBeExpression;
362   }
363 
updateParser::ConditionDeclarationOrInitStatementState364   bool update(TPResult IsDecl) {
365     switch (IsDecl) {
366     case TPResult::True:
367       markNotExpression();
368       return true;
369     case TPResult::False:
370       CanBeCondition = CanBeInitStatement = false;
371       return true;
372     case TPResult::Ambiguous:
373       return false;
374     case TPResult::Error:
375       CanBeExpression = CanBeCondition = CanBeInitStatement = false;
376       return true;
377     }
378     llvm_unreachable("unknown tentative parse result");
379   }
380 
resultParser::ConditionDeclarationOrInitStatementState381   ConditionOrInitStatement result() const {
382     assert(CanBeExpression + CanBeCondition + CanBeInitStatement < 2 &&
383            "result called but not yet resolved");
384     if (CanBeExpression)
385       return ConditionOrInitStatement::Expression;
386     if (CanBeCondition)
387       return ConditionOrInitStatement::ConditionDecl;
388     if (CanBeInitStatement)
389       return ConditionOrInitStatement::InitStmtDecl;
390     return ConditionOrInitStatement::Error;
391   }
392 };
393 
394 /// \brief Disambiguates between a declaration in a condition, a
395 /// simple-declaration in an init-statement, and an expression for
396 /// a condition of a if/switch statement.
397 ///
398 ///       condition:
399 ///         expression
400 ///         type-specifier-seq declarator '=' assignment-expression
401 /// [C++11] type-specifier-seq declarator '=' initializer-clause
402 /// [C++11] type-specifier-seq declarator braced-init-list
403 /// [GNU]   type-specifier-seq declarator simple-asm-expr[opt] attributes[opt]
404 ///             '=' assignment-expression
405 ///       simple-declaration:
406 ///         decl-specifier-seq init-declarator-list[opt] ';'
407 ///
408 /// Note that, unlike isCXXSimpleDeclaration, we must disambiguate all the way
409 /// to the ';' to disambiguate cases like 'int(x))' (an expression) from
410 /// 'int(x);' (a simple-declaration in an init-statement).
411 Parser::ConditionOrInitStatement
isCXXConditionDeclarationOrInitStatement(bool CanBeInitStatement)412 Parser::isCXXConditionDeclarationOrInitStatement(bool CanBeInitStatement) {
413   ConditionDeclarationOrInitStatementState State(*this, CanBeInitStatement);
414 
415   if (State.update(isCXXDeclarationSpecifier()))
416     return State.result();
417 
418   // It might be a declaration; we need tentative parsing.
419   RevertingTentativeParsingAction PA(*this);
420 
421   // FIXME: A tag definition unambiguously tells us this is an init-statement.
422   if (State.update(TryConsumeDeclarationSpecifier()))
423     return State.result();
424   assert(Tok.is(tok::l_paren) && "Expected '('");
425 
426   while (true) {
427     // Consume a declarator.
428     if (State.update(TryParseDeclarator(false/*mayBeAbstract*/)))
429       return State.result();
430 
431     // Attributes, asm label, or an initializer imply this is not an expression.
432     // FIXME: Disambiguate properly after an = instead of assuming that it's a
433     // valid declaration.
434     if (Tok.isOneOf(tok::equal, tok::kw_asm, tok::kw___attribute) ||
435         (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace))) {
436       State.markNotExpression();
437       return State.result();
438     }
439 
440     // At this point, it can't be a condition any more, because a condition
441     // must have a brace-or-equal-initializer.
442     if (State.markNotCondition())
443       return State.result();
444 
445     // A parenthesized initializer could be part of an expression or a
446     // simple-declaration.
447     if (Tok.is(tok::l_paren)) {
448       ConsumeParen();
449       SkipUntil(tok::r_paren, StopAtSemi);
450     }
451 
452     if (!TryConsumeToken(tok::comma))
453       break;
454   }
455 
456   // We reached the end. If it can now be some kind of decl, then it is.
457   if (State.CanBeCondition && Tok.is(tok::r_paren))
458     return ConditionOrInitStatement::ConditionDecl;
459   else if (State.CanBeInitStatement && Tok.is(tok::semi))
460     return ConditionOrInitStatement::InitStmtDecl;
461   else
462     return ConditionOrInitStatement::Expression;
463 }
464 
465   /// \brief Determine whether the next set of tokens contains a type-id.
466   ///
467   /// The context parameter states what context we're parsing right
468   /// now, which affects how this routine copes with the token
469   /// following the type-id. If the context is TypeIdInParens, we have
470   /// already parsed the '(' and we will cease lookahead when we hit
471   /// the corresponding ')'. If the context is
472   /// TypeIdAsTemplateArgument, we've already parsed the '<' or ','
473   /// before this template argument, and will cease lookahead when we
474   /// hit a '>', '>>' (in C++0x), or ','. Returns true for a type-id
475   /// and false for an expression.  If during the disambiguation
476   /// process a parsing error is encountered, the function returns
477   /// true to let the declaration parsing code handle it.
478   ///
479   /// type-id:
480   ///   type-specifier-seq abstract-declarator[opt]
481   ///
isCXXTypeId(TentativeCXXTypeIdContext Context,bool & isAmbiguous)482 bool Parser::isCXXTypeId(TentativeCXXTypeIdContext Context, bool &isAmbiguous) {
483 
484   isAmbiguous = false;
485 
486   // C++ 8.2p2:
487   // The ambiguity arising from the similarity between a function-style cast and
488   // a type-id can occur in different contexts. The ambiguity appears as a
489   // choice between a function-style cast expression and a declaration of a
490   // type. The resolution is that any construct that could possibly be a type-id
491   // in its syntactic context shall be considered a type-id.
492 
493   TPResult TPR = isCXXDeclarationSpecifier();
494   if (TPR != TPResult::Ambiguous)
495     return TPR != TPResult::False; // Returns true for TPResult::True or
496                                      // TPResult::Error.
497 
498   // FIXME: Add statistics about the number of ambiguous statements encountered
499   // and how they were resolved (number of declarations+number of expressions).
500 
501   // Ok, we have a simple-type-specifier/typename-specifier followed by a '('.
502   // We need tentative parsing...
503 
504   RevertingTentativeParsingAction PA(*this);
505 
506   // type-specifier-seq
507   TryConsumeDeclarationSpecifier();
508   assert(Tok.is(tok::l_paren) && "Expected '('");
509 
510   // declarator
511   TPR = TryParseDeclarator(true/*mayBeAbstract*/, false/*mayHaveIdentifier*/);
512 
513   // In case of an error, let the declaration parsing code handle it.
514   if (TPR == TPResult::Error)
515     TPR = TPResult::True;
516 
517   if (TPR == TPResult::Ambiguous) {
518     // We are supposed to be inside parens, so if after the abstract declarator
519     // we encounter a ')' this is a type-id, otherwise it's an expression.
520     if (Context == TypeIdInParens && Tok.is(tok::r_paren)) {
521       TPR = TPResult::True;
522       isAmbiguous = true;
523 
524     // We are supposed to be inside a template argument, so if after
525     // the abstract declarator we encounter a '>', '>>' (in C++0x), or
526     // ',', this is a type-id. Otherwise, it's an expression.
527     } else if (Context == TypeIdAsTemplateArgument &&
528                (Tok.isOneOf(tok::greater, tok::comma) ||
529                 (getLangOpts().CPlusPlus11 && Tok.is(tok::greatergreater)))) {
530       TPR = TPResult::True;
531       isAmbiguous = true;
532 
533     } else
534       TPR = TPResult::False;
535   }
536 
537   assert(TPR == TPResult::True || TPR == TPResult::False);
538   return TPR == TPResult::True;
539 }
540 
541 /// \brief Returns true if this is a C++11 attribute-specifier. Per
542 /// C++11 [dcl.attr.grammar]p6, two consecutive left square bracket tokens
543 /// always introduce an attribute. In Objective-C++11, this rule does not
544 /// apply if either '[' begins a message-send.
545 ///
546 /// If Disambiguate is true, we try harder to determine whether a '[[' starts
547 /// an attribute-specifier, and return CAK_InvalidAttributeSpecifier if not.
548 ///
549 /// If OuterMightBeMessageSend is true, we assume the outer '[' is either an
550 /// Obj-C message send or the start of an attribute. Otherwise, we assume it
551 /// is not an Obj-C message send.
552 ///
553 /// C++11 [dcl.attr.grammar]:
554 ///
555 ///     attribute-specifier:
556 ///         '[' '[' attribute-list ']' ']'
557 ///         alignment-specifier
558 ///
559 ///     attribute-list:
560 ///         attribute[opt]
561 ///         attribute-list ',' attribute[opt]
562 ///         attribute '...'
563 ///         attribute-list ',' attribute '...'
564 ///
565 ///     attribute:
566 ///         attribute-token attribute-argument-clause[opt]
567 ///
568 ///     attribute-token:
569 ///         identifier
570 ///         identifier '::' identifier
571 ///
572 ///     attribute-argument-clause:
573 ///         '(' balanced-token-seq ')'
574 Parser::CXX11AttributeKind
isCXX11AttributeSpecifier(bool Disambiguate,bool OuterMightBeMessageSend)575 Parser::isCXX11AttributeSpecifier(bool Disambiguate,
576                                   bool OuterMightBeMessageSend) {
577   if (Tok.is(tok::kw_alignas))
578     return CAK_AttributeSpecifier;
579 
580   if (Tok.isNot(tok::l_square) || NextToken().isNot(tok::l_square))
581     return CAK_NotAttributeSpecifier;
582 
583   // No tentative parsing if we don't need to look for ']]' or a lambda.
584   if (!Disambiguate && !getLangOpts().ObjC1)
585     return CAK_AttributeSpecifier;
586 
587   RevertingTentativeParsingAction PA(*this);
588 
589   // Opening brackets were checked for above.
590   ConsumeBracket();
591 
592   // Outside Obj-C++11, treat anything with a matching ']]' as an attribute.
593   if (!getLangOpts().ObjC1) {
594     ConsumeBracket();
595 
596     bool IsAttribute = SkipUntil(tok::r_square);
597     IsAttribute &= Tok.is(tok::r_square);
598 
599     return IsAttribute ? CAK_AttributeSpecifier : CAK_InvalidAttributeSpecifier;
600   }
601 
602   // In Obj-C++11, we need to distinguish four situations:
603   //  1a) int x[[attr]];                     C++11 attribute.
604   //  1b) [[attr]];                          C++11 statement attribute.
605   //   2) int x[[obj](){ return 1; }()];     Lambda in array size/index.
606   //  3a) int x[[obj get]];                  Message send in array size/index.
607   //  3b) [[Class alloc] init];              Message send in message send.
608   //   4) [[obj]{ return self; }() doStuff]; Lambda in message send.
609   // (1) is an attribute, (2) is ill-formed, and (3) and (4) are accepted.
610 
611   // If we have a lambda-introducer, then this is definitely not a message send.
612   // FIXME: If this disambiguation is too slow, fold the tentative lambda parse
613   // into the tentative attribute parse below.
614   LambdaIntroducer Intro;
615   if (!TryParseLambdaIntroducer(Intro)) {
616     // A lambda cannot end with ']]', and an attribute must.
617     bool IsAttribute = Tok.is(tok::r_square);
618 
619     if (IsAttribute)
620       // Case 1: C++11 attribute.
621       return CAK_AttributeSpecifier;
622 
623     if (OuterMightBeMessageSend)
624       // Case 4: Lambda in message send.
625       return CAK_NotAttributeSpecifier;
626 
627     // Case 2: Lambda in array size / index.
628     return CAK_InvalidAttributeSpecifier;
629   }
630 
631   ConsumeBracket();
632 
633   // If we don't have a lambda-introducer, then we have an attribute or a
634   // message-send.
635   bool IsAttribute = true;
636   while (Tok.isNot(tok::r_square)) {
637     if (Tok.is(tok::comma)) {
638       // Case 1: Stray commas can only occur in attributes.
639       return CAK_AttributeSpecifier;
640     }
641 
642     // Parse the attribute-token, if present.
643     // C++11 [dcl.attr.grammar]:
644     //   If a keyword or an alternative token that satisfies the syntactic
645     //   requirements of an identifier is contained in an attribute-token,
646     //   it is considered an identifier.
647     SourceLocation Loc;
648     if (!TryParseCXX11AttributeIdentifier(Loc)) {
649       IsAttribute = false;
650       break;
651     }
652     if (Tok.is(tok::coloncolon)) {
653       ConsumeToken();
654       if (!TryParseCXX11AttributeIdentifier(Loc)) {
655         IsAttribute = false;
656         break;
657       }
658     }
659 
660     // Parse the attribute-argument-clause, if present.
661     if (Tok.is(tok::l_paren)) {
662       ConsumeParen();
663       if (!SkipUntil(tok::r_paren)) {
664         IsAttribute = false;
665         break;
666       }
667     }
668 
669     TryConsumeToken(tok::ellipsis);
670 
671     if (!TryConsumeToken(tok::comma))
672       break;
673   }
674 
675   // An attribute must end ']]'.
676   if (IsAttribute) {
677     if (Tok.is(tok::r_square)) {
678       ConsumeBracket();
679       IsAttribute = Tok.is(tok::r_square);
680     } else {
681       IsAttribute = false;
682     }
683   }
684 
685   if (IsAttribute)
686     // Case 1: C++11 statement attribute.
687     return CAK_AttributeSpecifier;
688 
689   // Case 3: Message send.
690   return CAK_NotAttributeSpecifier;
691 }
692 
TryParsePtrOperatorSeq()693 Parser::TPResult Parser::TryParsePtrOperatorSeq() {
694   while (true) {
695     if (Tok.isOneOf(tok::coloncolon, tok::identifier))
696       if (TryAnnotateCXXScopeToken(true))
697         return TPResult::Error;
698 
699     if (Tok.isOneOf(tok::star, tok::amp, tok::caret, tok::ampamp) ||
700         (Tok.is(tok::annot_cxxscope) && NextToken().is(tok::star))) {
701       // ptr-operator
702       ConsumeToken();
703       while (Tok.isOneOf(tok::kw_const, tok::kw_volatile, tok::kw_restrict,
704                          tok::kw__Nonnull, tok::kw__Nullable,
705                          tok::kw__Null_unspecified))
706         ConsumeToken();
707     } else {
708       return TPResult::True;
709     }
710   }
711 }
712 
713 ///         operator-function-id:
714 ///           'operator' operator
715 ///
716 ///         operator: one of
717 ///           new  delete  new[]  delete[]  +  -  *  /  %  ^  [...]
718 ///
719 ///         conversion-function-id:
720 ///           'operator' conversion-type-id
721 ///
722 ///         conversion-type-id:
723 ///           type-specifier-seq conversion-declarator[opt]
724 ///
725 ///         conversion-declarator:
726 ///           ptr-operator conversion-declarator[opt]
727 ///
728 ///         literal-operator-id:
729 ///           'operator' string-literal identifier
730 ///           'operator' user-defined-string-literal
TryParseOperatorId()731 Parser::TPResult Parser::TryParseOperatorId() {
732   assert(Tok.is(tok::kw_operator));
733   ConsumeToken();
734 
735   // Maybe this is an operator-function-id.
736   switch (Tok.getKind()) {
737   case tok::kw_new: case tok::kw_delete:
738     ConsumeToken();
739     if (Tok.is(tok::l_square) && NextToken().is(tok::r_square)) {
740       ConsumeBracket();
741       ConsumeBracket();
742     }
743     return TPResult::True;
744 
745 #define OVERLOADED_OPERATOR(Name, Spelling, Token, Unary, Binary, MemOnly) \
746   case tok::Token:
747 #define OVERLOADED_OPERATOR_MULTI(Name, Spelling, Unary, Binary, MemOnly)
748 #include "clang/Basic/OperatorKinds.def"
749     ConsumeToken();
750     return TPResult::True;
751 
752   case tok::l_square:
753     if (NextToken().is(tok::r_square)) {
754       ConsumeBracket();
755       ConsumeBracket();
756       return TPResult::True;
757     }
758     break;
759 
760   case tok::l_paren:
761     if (NextToken().is(tok::r_paren)) {
762       ConsumeParen();
763       ConsumeParen();
764       return TPResult::True;
765     }
766     break;
767 
768   default:
769     break;
770   }
771 
772   // Maybe this is a literal-operator-id.
773   if (getLangOpts().CPlusPlus11 && isTokenStringLiteral()) {
774     bool FoundUDSuffix = false;
775     do {
776       FoundUDSuffix |= Tok.hasUDSuffix();
777       ConsumeStringToken();
778     } while (isTokenStringLiteral());
779 
780     if (!FoundUDSuffix) {
781       if (Tok.is(tok::identifier))
782         ConsumeToken();
783       else
784         return TPResult::Error;
785     }
786     return TPResult::True;
787   }
788 
789   // Maybe this is a conversion-function-id.
790   bool AnyDeclSpecifiers = false;
791   while (true) {
792     TPResult TPR = isCXXDeclarationSpecifier();
793     if (TPR == TPResult::Error)
794       return TPR;
795     if (TPR == TPResult::False) {
796       if (!AnyDeclSpecifiers)
797         return TPResult::Error;
798       break;
799     }
800     if (TryConsumeDeclarationSpecifier() == TPResult::Error)
801       return TPResult::Error;
802     AnyDeclSpecifiers = true;
803   }
804   return TryParsePtrOperatorSeq();
805 }
806 
807 ///         declarator:
808 ///           direct-declarator
809 ///           ptr-operator declarator
810 ///
811 ///         direct-declarator:
812 ///           declarator-id
813 ///           direct-declarator '(' parameter-declaration-clause ')'
814 ///                 cv-qualifier-seq[opt] exception-specification[opt]
815 ///           direct-declarator '[' constant-expression[opt] ']'
816 ///           '(' declarator ')'
817 /// [GNU]     '(' attributes declarator ')'
818 ///
819 ///         abstract-declarator:
820 ///           ptr-operator abstract-declarator[opt]
821 ///           direct-abstract-declarator
822 ///           ...
823 ///
824 ///         direct-abstract-declarator:
825 ///           direct-abstract-declarator[opt]
826 ///           '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
827 ///                 exception-specification[opt]
828 ///           direct-abstract-declarator[opt] '[' constant-expression[opt] ']'
829 ///           '(' abstract-declarator ')'
830 ///
831 ///         ptr-operator:
832 ///           '*' cv-qualifier-seq[opt]
833 ///           '&'
834 /// [C++0x]   '&&'                                                        [TODO]
835 ///           '::'[opt] nested-name-specifier '*' cv-qualifier-seq[opt]
836 ///
837 ///         cv-qualifier-seq:
838 ///           cv-qualifier cv-qualifier-seq[opt]
839 ///
840 ///         cv-qualifier:
841 ///           'const'
842 ///           'volatile'
843 ///
844 ///         declarator-id:
845 ///           '...'[opt] id-expression
846 ///
847 ///         id-expression:
848 ///           unqualified-id
849 ///           qualified-id                                                [TODO]
850 ///
851 ///         unqualified-id:
852 ///           identifier
853 ///           operator-function-id
854 ///           conversion-function-id
855 ///           literal-operator-id
856 ///           '~' class-name                                              [TODO]
857 ///           '~' decltype-specifier                                      [TODO]
858 ///           template-id                                                 [TODO]
859 ///
TryParseDeclarator(bool mayBeAbstract,bool mayHaveIdentifier)860 Parser::TPResult Parser::TryParseDeclarator(bool mayBeAbstract,
861                                             bool mayHaveIdentifier) {
862   // declarator:
863   //   direct-declarator
864   //   ptr-operator declarator
865   if (TryParsePtrOperatorSeq() == TPResult::Error)
866     return TPResult::Error;
867 
868   // direct-declarator:
869   // direct-abstract-declarator:
870   if (Tok.is(tok::ellipsis))
871     ConsumeToken();
872 
873   if ((Tok.isOneOf(tok::identifier, tok::kw_operator) ||
874        (Tok.is(tok::annot_cxxscope) && (NextToken().is(tok::identifier) ||
875                                         NextToken().is(tok::kw_operator)))) &&
876       mayHaveIdentifier) {
877     // declarator-id
878     if (Tok.is(tok::annot_cxxscope))
879       ConsumeToken();
880     else if (Tok.is(tok::identifier))
881       TentativelyDeclaredIdentifiers.push_back(Tok.getIdentifierInfo());
882     if (Tok.is(tok::kw_operator)) {
883       if (TryParseOperatorId() == TPResult::Error)
884         return TPResult::Error;
885     } else
886       ConsumeToken();
887   } else if (Tok.is(tok::l_paren)) {
888     ConsumeParen();
889     if (mayBeAbstract &&
890         (Tok.is(tok::r_paren) ||       // 'int()' is a function.
891          // 'int(...)' is a function.
892          (Tok.is(tok::ellipsis) && NextToken().is(tok::r_paren)) ||
893          isDeclarationSpecifier())) {   // 'int(int)' is a function.
894       // '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
895       //        exception-specification[opt]
896       TPResult TPR = TryParseFunctionDeclarator();
897       if (TPR != TPResult::Ambiguous)
898         return TPR;
899     } else {
900       // '(' declarator ')'
901       // '(' attributes declarator ')'
902       // '(' abstract-declarator ')'
903       if (Tok.isOneOf(tok::kw___attribute, tok::kw___declspec, tok::kw___cdecl,
904                       tok::kw___stdcall, tok::kw___fastcall, tok::kw___thiscall,
905                       tok::kw___vectorcall))
906         return TPResult::True; // attributes indicate declaration
907       TPResult TPR = TryParseDeclarator(mayBeAbstract, mayHaveIdentifier);
908       if (TPR != TPResult::Ambiguous)
909         return TPR;
910       if (Tok.isNot(tok::r_paren))
911         return TPResult::False;
912       ConsumeParen();
913     }
914   } else if (!mayBeAbstract) {
915     return TPResult::False;
916   }
917 
918   while (1) {
919     TPResult TPR(TPResult::Ambiguous);
920 
921     // abstract-declarator: ...
922     if (Tok.is(tok::ellipsis))
923       ConsumeToken();
924 
925     if (Tok.is(tok::l_paren)) {
926       // Check whether we have a function declarator or a possible ctor-style
927       // initializer that follows the declarator. Note that ctor-style
928       // initializers are not possible in contexts where abstract declarators
929       // are allowed.
930       if (!mayBeAbstract && !isCXXFunctionDeclarator())
931         break;
932 
933       // direct-declarator '(' parameter-declaration-clause ')'
934       //        cv-qualifier-seq[opt] exception-specification[opt]
935       ConsumeParen();
936       TPR = TryParseFunctionDeclarator();
937     } else if (Tok.is(tok::l_square)) {
938       // direct-declarator '[' constant-expression[opt] ']'
939       // direct-abstract-declarator[opt] '[' constant-expression[opt] ']'
940       TPR = TryParseBracketDeclarator();
941     } else {
942       break;
943     }
944 
945     if (TPR != TPResult::Ambiguous)
946       return TPR;
947   }
948 
949   return TPResult::Ambiguous;
950 }
951 
952 Parser::TPResult
isExpressionOrTypeSpecifierSimple(tok::TokenKind Kind)953 Parser::isExpressionOrTypeSpecifierSimple(tok::TokenKind Kind) {
954   switch (Kind) {
955   // Obviously starts an expression.
956   case tok::numeric_constant:
957   case tok::char_constant:
958   case tok::wide_char_constant:
959   case tok::utf8_char_constant:
960   case tok::utf16_char_constant:
961   case tok::utf32_char_constant:
962   case tok::string_literal:
963   case tok::wide_string_literal:
964   case tok::utf8_string_literal:
965   case tok::utf16_string_literal:
966   case tok::utf32_string_literal:
967   case tok::l_square:
968   case tok::l_paren:
969   case tok::amp:
970   case tok::ampamp:
971   case tok::star:
972   case tok::plus:
973   case tok::plusplus:
974   case tok::minus:
975   case tok::minusminus:
976   case tok::tilde:
977   case tok::exclaim:
978   case tok::kw_sizeof:
979   case tok::kw___func__:
980   case tok::kw_const_cast:
981   case tok::kw_delete:
982   case tok::kw_dynamic_cast:
983   case tok::kw_false:
984   case tok::kw_new:
985   case tok::kw_operator:
986   case tok::kw_reinterpret_cast:
987   case tok::kw_static_cast:
988   case tok::kw_this:
989   case tok::kw_throw:
990   case tok::kw_true:
991   case tok::kw_typeid:
992   case tok::kw_alignof:
993   case tok::kw_noexcept:
994   case tok::kw_nullptr:
995   case tok::kw__Alignof:
996   case tok::kw___null:
997   case tok::kw___alignof:
998   case tok::kw___builtin_choose_expr:
999   case tok::kw___builtin_offsetof:
1000   case tok::kw___builtin_va_arg:
1001   case tok::kw___imag:
1002   case tok::kw___real:
1003   case tok::kw___FUNCTION__:
1004   case tok::kw___FUNCDNAME__:
1005   case tok::kw___FUNCSIG__:
1006   case tok::kw_L__FUNCTION__:
1007   case tok::kw___PRETTY_FUNCTION__:
1008   case tok::kw___uuidof:
1009 #define TYPE_TRAIT(N,Spelling,K) \
1010   case tok::kw_##Spelling:
1011 #include "clang/Basic/TokenKinds.def"
1012     return TPResult::True;
1013 
1014   // Obviously starts a type-specifier-seq:
1015   case tok::kw_char:
1016   case tok::kw_const:
1017   case tok::kw_double:
1018   case tok::kw___float128:
1019   case tok::kw_enum:
1020   case tok::kw_half:
1021   case tok::kw_float:
1022   case tok::kw_int:
1023   case tok::kw_long:
1024   case tok::kw___int64:
1025   case tok::kw___int128:
1026   case tok::kw_restrict:
1027   case tok::kw_short:
1028   case tok::kw_signed:
1029   case tok::kw_struct:
1030   case tok::kw_union:
1031   case tok::kw_unsigned:
1032   case tok::kw_void:
1033   case tok::kw_volatile:
1034   case tok::kw__Bool:
1035   case tok::kw__Complex:
1036   case tok::kw_class:
1037   case tok::kw_typename:
1038   case tok::kw_wchar_t:
1039   case tok::kw_char16_t:
1040   case tok::kw_char32_t:
1041   case tok::kw__Decimal32:
1042   case tok::kw__Decimal64:
1043   case tok::kw__Decimal128:
1044   case tok::kw___interface:
1045   case tok::kw___thread:
1046   case tok::kw_thread_local:
1047   case tok::kw__Thread_local:
1048   case tok::kw_typeof:
1049   case tok::kw___underlying_type:
1050   case tok::kw___cdecl:
1051   case tok::kw___stdcall:
1052   case tok::kw___fastcall:
1053   case tok::kw___thiscall:
1054   case tok::kw___vectorcall:
1055   case tok::kw___unaligned:
1056   case tok::kw___vector:
1057   case tok::kw___pixel:
1058   case tok::kw___bool:
1059   case tok::kw__Atomic:
1060 #define GENERIC_IMAGE_TYPE(ImgType, Id) case tok::kw_##ImgType##_t:
1061 #include "clang/Basic/OpenCLImageTypes.def"
1062   case tok::kw___unknown_anytype:
1063     return TPResult::False;
1064 
1065   default:
1066     break;
1067   }
1068 
1069   return TPResult::Ambiguous;
1070 }
1071 
isTentativelyDeclared(IdentifierInfo * II)1072 bool Parser::isTentativelyDeclared(IdentifierInfo *II) {
1073   return std::find(TentativelyDeclaredIdentifiers.begin(),
1074                    TentativelyDeclaredIdentifiers.end(), II)
1075       != TentativelyDeclaredIdentifiers.end();
1076 }
1077 
1078 namespace {
1079 class TentativeParseCCC : public CorrectionCandidateCallback {
1080 public:
TentativeParseCCC(const Token & Next)1081   TentativeParseCCC(const Token &Next) {
1082     WantRemainingKeywords = false;
1083     WantTypeSpecifiers = Next.isOneOf(tok::l_paren, tok::r_paren, tok::greater,
1084                                       tok::l_brace, tok::identifier);
1085   }
1086 
ValidateCandidate(const TypoCorrection & Candidate)1087   bool ValidateCandidate(const TypoCorrection &Candidate) override {
1088     // Reject any candidate that only resolves to instance members since they
1089     // aren't viable as standalone identifiers instead of member references.
1090     if (Candidate.isResolved() && !Candidate.isKeyword() &&
1091         std::all_of(Candidate.begin(), Candidate.end(),
1092                     [](NamedDecl *ND) { return ND->isCXXInstanceMember(); }))
1093       return false;
1094 
1095     return CorrectionCandidateCallback::ValidateCandidate(Candidate);
1096   }
1097 };
1098 }
1099 /// isCXXDeclarationSpecifier - Returns TPResult::True if it is a declaration
1100 /// specifier, TPResult::False if it is not, TPResult::Ambiguous if it could
1101 /// be either a decl-specifier or a function-style cast, and TPResult::Error
1102 /// if a parsing error was found and reported.
1103 ///
1104 /// If HasMissingTypename is provided, a name with a dependent scope specifier
1105 /// will be treated as ambiguous if the 'typename' keyword is missing. If this
1106 /// happens, *HasMissingTypename will be set to 'true'. This will also be used
1107 /// as an indicator that undeclared identifiers (which will trigger a later
1108 /// parse error) should be treated as types. Returns TPResult::Ambiguous in
1109 /// such cases.
1110 ///
1111 ///         decl-specifier:
1112 ///           storage-class-specifier
1113 ///           type-specifier
1114 ///           function-specifier
1115 ///           'friend'
1116 ///           'typedef'
1117 /// [C++11]   'constexpr'
1118 /// [GNU]     attributes declaration-specifiers[opt]
1119 ///
1120 ///         storage-class-specifier:
1121 ///           'register'
1122 ///           'static'
1123 ///           'extern'
1124 ///           'mutable'
1125 ///           'auto'
1126 /// [GNU]     '__thread'
1127 /// [C++11]   'thread_local'
1128 /// [C11]     '_Thread_local'
1129 ///
1130 ///         function-specifier:
1131 ///           'inline'
1132 ///           'virtual'
1133 ///           'explicit'
1134 ///
1135 ///         typedef-name:
1136 ///           identifier
1137 ///
1138 ///         type-specifier:
1139 ///           simple-type-specifier
1140 ///           class-specifier
1141 ///           enum-specifier
1142 ///           elaborated-type-specifier
1143 ///           typename-specifier
1144 ///           cv-qualifier
1145 ///
1146 ///         simple-type-specifier:
1147 ///           '::'[opt] nested-name-specifier[opt] type-name
1148 ///           '::'[opt] nested-name-specifier 'template'
1149 ///                 simple-template-id                              [TODO]
1150 ///           'char'
1151 ///           'wchar_t'
1152 ///           'bool'
1153 ///           'short'
1154 ///           'int'
1155 ///           'long'
1156 ///           'signed'
1157 ///           'unsigned'
1158 ///           'float'
1159 ///           'double'
1160 ///           'void'
1161 /// [GNU]     typeof-specifier
1162 /// [GNU]     '_Complex'
1163 /// [C++11]   'auto'
1164 /// [GNU]     '__auto_type'
1165 /// [C++11]   'decltype' ( expression )
1166 /// [C++1y]   'decltype' ( 'auto' )
1167 ///
1168 ///         type-name:
1169 ///           class-name
1170 ///           enum-name
1171 ///           typedef-name
1172 ///
1173 ///         elaborated-type-specifier:
1174 ///           class-key '::'[opt] nested-name-specifier[opt] identifier
1175 ///           class-key '::'[opt] nested-name-specifier[opt] 'template'[opt]
1176 ///               simple-template-id
1177 ///           'enum' '::'[opt] nested-name-specifier[opt] identifier
1178 ///
1179 ///         enum-name:
1180 ///           identifier
1181 ///
1182 ///         enum-specifier:
1183 ///           'enum' identifier[opt] '{' enumerator-list[opt] '}'
1184 ///           'enum' identifier[opt] '{' enumerator-list ',' '}'
1185 ///
1186 ///         class-specifier:
1187 ///           class-head '{' member-specification[opt] '}'
1188 ///
1189 ///         class-head:
1190 ///           class-key identifier[opt] base-clause[opt]
1191 ///           class-key nested-name-specifier identifier base-clause[opt]
1192 ///           class-key nested-name-specifier[opt] simple-template-id
1193 ///               base-clause[opt]
1194 ///
1195 ///         class-key:
1196 ///           'class'
1197 ///           'struct'
1198 ///           'union'
1199 ///
1200 ///         cv-qualifier:
1201 ///           'const'
1202 ///           'volatile'
1203 /// [GNU]     restrict
1204 ///
1205 Parser::TPResult
isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,bool * HasMissingTypename)1206 Parser::isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,
1207                                   bool *HasMissingTypename) {
1208   switch (Tok.getKind()) {
1209   case tok::identifier: {
1210     // Check for need to substitute AltiVec __vector keyword
1211     // for "vector" identifier.
1212     if (TryAltiVecVectorToken())
1213       return TPResult::True;
1214 
1215     const Token &Next = NextToken();
1216     // In 'foo bar', 'foo' is always a type name outside of Objective-C.
1217     if (!getLangOpts().ObjC1 && Next.is(tok::identifier))
1218       return TPResult::True;
1219 
1220     if (Next.isNot(tok::coloncolon) && Next.isNot(tok::less)) {
1221       // Determine whether this is a valid expression. If not, we will hit
1222       // a parse error one way or another. In that case, tell the caller that
1223       // this is ambiguous. Typo-correct to type and expression keywords and
1224       // to types and identifiers, in order to try to recover from errors.
1225       switch (TryAnnotateName(false /* no nested name specifier */,
1226                               llvm::make_unique<TentativeParseCCC>(Next))) {
1227       case ANK_Error:
1228         return TPResult::Error;
1229       case ANK_TentativeDecl:
1230         return TPResult::False;
1231       case ANK_TemplateName:
1232         // A bare type template-name which can't be a template template
1233         // argument is an error, and was probably intended to be a type.
1234         return GreaterThanIsOperator ? TPResult::True : TPResult::False;
1235       case ANK_Unresolved:
1236         return HasMissingTypename ? TPResult::Ambiguous : TPResult::False;
1237       case ANK_Success:
1238         break;
1239       }
1240       assert(Tok.isNot(tok::identifier) &&
1241              "TryAnnotateName succeeded without producing an annotation");
1242     } else {
1243       // This might possibly be a type with a dependent scope specifier and
1244       // a missing 'typename' keyword. Don't use TryAnnotateName in this case,
1245       // since it will annotate as a primary expression, and we want to use the
1246       // "missing 'typename'" logic.
1247       if (TryAnnotateTypeOrScopeToken())
1248         return TPResult::Error;
1249       // If annotation failed, assume it's a non-type.
1250       // FIXME: If this happens due to an undeclared identifier, treat it as
1251       // ambiguous.
1252       if (Tok.is(tok::identifier))
1253         return TPResult::False;
1254     }
1255 
1256     // We annotated this token as something. Recurse to handle whatever we got.
1257     return isCXXDeclarationSpecifier(BracedCastResult, HasMissingTypename);
1258   }
1259 
1260   case tok::kw_typename:  // typename T::type
1261     // Annotate typenames and C++ scope specifiers.  If we get one, just
1262     // recurse to handle whatever we get.
1263     if (TryAnnotateTypeOrScopeToken())
1264       return TPResult::Error;
1265     return isCXXDeclarationSpecifier(BracedCastResult, HasMissingTypename);
1266 
1267   case tok::coloncolon: {    // ::foo::bar
1268     const Token &Next = NextToken();
1269     if (Next.isOneOf(tok::kw_new,       // ::new
1270                      tok::kw_delete))   // ::delete
1271       return TPResult::False;
1272   }
1273     // Fall through.
1274   case tok::kw___super:
1275   case tok::kw_decltype:
1276     // Annotate typenames and C++ scope specifiers.  If we get one, just
1277     // recurse to handle whatever we get.
1278     if (TryAnnotateTypeOrScopeToken())
1279       return TPResult::Error;
1280     return isCXXDeclarationSpecifier(BracedCastResult, HasMissingTypename);
1281 
1282     // decl-specifier:
1283     //   storage-class-specifier
1284     //   type-specifier
1285     //   function-specifier
1286     //   'friend'
1287     //   'typedef'
1288     //   'constexpr'
1289     //   'concept'
1290   case tok::kw_friend:
1291   case tok::kw_typedef:
1292   case tok::kw_constexpr:
1293   case tok::kw_concept:
1294     // storage-class-specifier
1295   case tok::kw_register:
1296   case tok::kw_static:
1297   case tok::kw_extern:
1298   case tok::kw_mutable:
1299   case tok::kw_auto:
1300   case tok::kw___thread:
1301   case tok::kw_thread_local:
1302   case tok::kw__Thread_local:
1303     // function-specifier
1304   case tok::kw_inline:
1305   case tok::kw_virtual:
1306   case tok::kw_explicit:
1307 
1308     // Modules
1309   case tok::kw___module_private__:
1310 
1311     // Debugger support
1312   case tok::kw___unknown_anytype:
1313 
1314     // type-specifier:
1315     //   simple-type-specifier
1316     //   class-specifier
1317     //   enum-specifier
1318     //   elaborated-type-specifier
1319     //   typename-specifier
1320     //   cv-qualifier
1321 
1322     // class-specifier
1323     // elaborated-type-specifier
1324   case tok::kw_class:
1325   case tok::kw_struct:
1326   case tok::kw_union:
1327   case tok::kw___interface:
1328     // enum-specifier
1329   case tok::kw_enum:
1330     // cv-qualifier
1331   case tok::kw_const:
1332   case tok::kw_volatile:
1333 
1334     // GNU
1335   case tok::kw_restrict:
1336   case tok::kw__Complex:
1337   case tok::kw___attribute:
1338   case tok::kw___auto_type:
1339     return TPResult::True;
1340 
1341     // Microsoft
1342   case tok::kw___declspec:
1343   case tok::kw___cdecl:
1344   case tok::kw___stdcall:
1345   case tok::kw___fastcall:
1346   case tok::kw___thiscall:
1347   case tok::kw___vectorcall:
1348   case tok::kw___w64:
1349   case tok::kw___sptr:
1350   case tok::kw___uptr:
1351   case tok::kw___ptr64:
1352   case tok::kw___ptr32:
1353   case tok::kw___forceinline:
1354   case tok::kw___unaligned:
1355   case tok::kw__Nonnull:
1356   case tok::kw__Nullable:
1357   case tok::kw__Null_unspecified:
1358   case tok::kw___kindof:
1359     return TPResult::True;
1360 
1361     // Borland
1362   case tok::kw___pascal:
1363     return TPResult::True;
1364 
1365     // AltiVec
1366   case tok::kw___vector:
1367     return TPResult::True;
1368 
1369   case tok::annot_template_id: {
1370     TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
1371     if (TemplateId->Kind != TNK_Type_template)
1372       return TPResult::False;
1373     CXXScopeSpec SS;
1374     AnnotateTemplateIdTokenAsType();
1375     assert(Tok.is(tok::annot_typename));
1376     goto case_typename;
1377   }
1378 
1379   case tok::annot_cxxscope: // foo::bar or ::foo::bar, but already parsed
1380     // We've already annotated a scope; try to annotate a type.
1381     if (TryAnnotateTypeOrScopeToken())
1382       return TPResult::Error;
1383     if (!Tok.is(tok::annot_typename)) {
1384       // If the next token is an identifier or a type qualifier, then this
1385       // can't possibly be a valid expression either.
1386       if (Tok.is(tok::annot_cxxscope) && NextToken().is(tok::identifier)) {
1387         CXXScopeSpec SS;
1388         Actions.RestoreNestedNameSpecifierAnnotation(Tok.getAnnotationValue(),
1389                                                      Tok.getAnnotationRange(),
1390                                                      SS);
1391         if (SS.getScopeRep() && SS.getScopeRep()->isDependent()) {
1392           RevertingTentativeParsingAction PA(*this);
1393           ConsumeToken();
1394           ConsumeToken();
1395           bool isIdentifier = Tok.is(tok::identifier);
1396           TPResult TPR = TPResult::False;
1397           if (!isIdentifier)
1398             TPR = isCXXDeclarationSpecifier(BracedCastResult,
1399                                             HasMissingTypename);
1400 
1401           if (isIdentifier ||
1402               TPR == TPResult::True || TPR == TPResult::Error)
1403             return TPResult::Error;
1404 
1405           if (HasMissingTypename) {
1406             // We can't tell whether this is a missing 'typename' or a valid
1407             // expression.
1408             *HasMissingTypename = true;
1409             return TPResult::Ambiguous;
1410           }
1411 
1412           // FIXME: Fails to either revert or commit the tentative parse!
1413         } else {
1414           // Try to resolve the name. If it doesn't exist, assume it was
1415           // intended to name a type and keep disambiguating.
1416           switch (TryAnnotateName(false /* SS is not dependent */)) {
1417           case ANK_Error:
1418             return TPResult::Error;
1419           case ANK_TentativeDecl:
1420             return TPResult::False;
1421           case ANK_TemplateName:
1422             // A bare type template-name which can't be a template template
1423             // argument is an error, and was probably intended to be a type.
1424             return GreaterThanIsOperator ? TPResult::True : TPResult::False;
1425           case ANK_Unresolved:
1426             return HasMissingTypename ? TPResult::Ambiguous
1427                                       : TPResult::False;
1428           case ANK_Success:
1429             // Annotated it, check again.
1430             assert(Tok.isNot(tok::annot_cxxscope) ||
1431                    NextToken().isNot(tok::identifier));
1432             return isCXXDeclarationSpecifier(BracedCastResult,
1433                                              HasMissingTypename);
1434           }
1435         }
1436       }
1437       return TPResult::False;
1438     }
1439     // If that succeeded, fallthrough into the generic simple-type-id case.
1440 
1441     // The ambiguity resides in a simple-type-specifier/typename-specifier
1442     // followed by a '('. The '(' could either be the start of:
1443     //
1444     //   direct-declarator:
1445     //     '(' declarator ')'
1446     //
1447     //   direct-abstract-declarator:
1448     //     '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
1449     //              exception-specification[opt]
1450     //     '(' abstract-declarator ')'
1451     //
1452     // or part of a function-style cast expression:
1453     //
1454     //     simple-type-specifier '(' expression-list[opt] ')'
1455     //
1456 
1457     // simple-type-specifier:
1458 
1459   case tok::annot_typename:
1460   case_typename:
1461     // In Objective-C, we might have a protocol-qualified type.
1462     if (getLangOpts().ObjC1 && NextToken().is(tok::less)) {
1463       // Tentatively parse the protocol qualifiers.
1464       RevertingTentativeParsingAction PA(*this);
1465       ConsumeToken(); // The type token
1466 
1467       TPResult TPR = TryParseProtocolQualifiers();
1468       bool isFollowedByParen = Tok.is(tok::l_paren);
1469       bool isFollowedByBrace = Tok.is(tok::l_brace);
1470 
1471       if (TPR == TPResult::Error)
1472         return TPResult::Error;
1473 
1474       if (isFollowedByParen)
1475         return TPResult::Ambiguous;
1476 
1477       if (getLangOpts().CPlusPlus11 && isFollowedByBrace)
1478         return BracedCastResult;
1479 
1480       return TPResult::True;
1481     }
1482 
1483   case tok::kw_char:
1484   case tok::kw_wchar_t:
1485   case tok::kw_char16_t:
1486   case tok::kw_char32_t:
1487   case tok::kw_bool:
1488   case tok::kw_short:
1489   case tok::kw_int:
1490   case tok::kw_long:
1491   case tok::kw___int64:
1492   case tok::kw___int128:
1493   case tok::kw_signed:
1494   case tok::kw_unsigned:
1495   case tok::kw_half:
1496   case tok::kw_float:
1497   case tok::kw_double:
1498   case tok::kw___float128:
1499   case tok::kw_void:
1500   case tok::annot_decltype:
1501     if (NextToken().is(tok::l_paren))
1502       return TPResult::Ambiguous;
1503 
1504     // This is a function-style cast in all cases we disambiguate other than
1505     // one:
1506     //   struct S {
1507     //     enum E : int { a = 4 }; // enum
1508     //     enum E : int { 4 };     // bit-field
1509     //   };
1510     if (getLangOpts().CPlusPlus11 && NextToken().is(tok::l_brace))
1511       return BracedCastResult;
1512 
1513     if (isStartOfObjCClassMessageMissingOpenBracket())
1514       return TPResult::False;
1515 
1516     return TPResult::True;
1517 
1518   // GNU typeof support.
1519   case tok::kw_typeof: {
1520     if (NextToken().isNot(tok::l_paren))
1521       return TPResult::True;
1522 
1523     RevertingTentativeParsingAction PA(*this);
1524 
1525     TPResult TPR = TryParseTypeofSpecifier();
1526     bool isFollowedByParen = Tok.is(tok::l_paren);
1527     bool isFollowedByBrace = Tok.is(tok::l_brace);
1528 
1529     if (TPR == TPResult::Error)
1530       return TPResult::Error;
1531 
1532     if (isFollowedByParen)
1533       return TPResult::Ambiguous;
1534 
1535     if (getLangOpts().CPlusPlus11 && isFollowedByBrace)
1536       return BracedCastResult;
1537 
1538     return TPResult::True;
1539   }
1540 
1541   // C++0x type traits support
1542   case tok::kw___underlying_type:
1543     return TPResult::True;
1544 
1545   // C11 _Atomic
1546   case tok::kw__Atomic:
1547     return TPResult::True;
1548 
1549   default:
1550     return TPResult::False;
1551   }
1552 }
1553 
isCXXDeclarationSpecifierAType()1554 bool Parser::isCXXDeclarationSpecifierAType() {
1555   switch (Tok.getKind()) {
1556     // typename-specifier
1557   case tok::annot_decltype:
1558   case tok::annot_template_id:
1559   case tok::annot_typename:
1560   case tok::kw_typeof:
1561   case tok::kw___underlying_type:
1562     return true;
1563 
1564     // elaborated-type-specifier
1565   case tok::kw_class:
1566   case tok::kw_struct:
1567   case tok::kw_union:
1568   case tok::kw___interface:
1569   case tok::kw_enum:
1570     return true;
1571 
1572     // simple-type-specifier
1573   case tok::kw_char:
1574   case tok::kw_wchar_t:
1575   case tok::kw_char16_t:
1576   case tok::kw_char32_t:
1577   case tok::kw_bool:
1578   case tok::kw_short:
1579   case tok::kw_int:
1580   case tok::kw_long:
1581   case tok::kw___int64:
1582   case tok::kw___int128:
1583   case tok::kw_signed:
1584   case tok::kw_unsigned:
1585   case tok::kw_half:
1586   case tok::kw_float:
1587   case tok::kw_double:
1588   case tok::kw___float128:
1589   case tok::kw_void:
1590   case tok::kw___unknown_anytype:
1591   case tok::kw___auto_type:
1592     return true;
1593 
1594   case tok::kw_auto:
1595     return getLangOpts().CPlusPlus11;
1596 
1597   case tok::kw__Atomic:
1598     // "_Atomic foo"
1599     return NextToken().is(tok::l_paren);
1600 
1601   default:
1602     return false;
1603   }
1604 }
1605 
1606 /// [GNU] typeof-specifier:
1607 ///         'typeof' '(' expressions ')'
1608 ///         'typeof' '(' type-name ')'
1609 ///
TryParseTypeofSpecifier()1610 Parser::TPResult Parser::TryParseTypeofSpecifier() {
1611   assert(Tok.is(tok::kw_typeof) && "Expected 'typeof'!");
1612   ConsumeToken();
1613 
1614   assert(Tok.is(tok::l_paren) && "Expected '('");
1615   // Parse through the parens after 'typeof'.
1616   ConsumeParen();
1617   if (!SkipUntil(tok::r_paren, StopAtSemi))
1618     return TPResult::Error;
1619 
1620   return TPResult::Ambiguous;
1621 }
1622 
1623 /// [ObjC] protocol-qualifiers:
1624 ////         '<' identifier-list '>'
TryParseProtocolQualifiers()1625 Parser::TPResult Parser::TryParseProtocolQualifiers() {
1626   assert(Tok.is(tok::less) && "Expected '<' for qualifier list");
1627   ConsumeToken();
1628   do {
1629     if (Tok.isNot(tok::identifier))
1630       return TPResult::Error;
1631     ConsumeToken();
1632 
1633     if (Tok.is(tok::comma)) {
1634       ConsumeToken();
1635       continue;
1636     }
1637 
1638     if (Tok.is(tok::greater)) {
1639       ConsumeToken();
1640       return TPResult::Ambiguous;
1641     }
1642   } while (false);
1643 
1644   return TPResult::Error;
1645 }
1646 
1647 /// isCXXFunctionDeclarator - Disambiguates between a function declarator or
1648 /// a constructor-style initializer, when parsing declaration statements.
1649 /// Returns true for function declarator and false for constructor-style
1650 /// initializer.
1651 /// If during the disambiguation process a parsing error is encountered,
1652 /// the function returns true to let the declaration parsing code handle it.
1653 ///
1654 /// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
1655 ///         exception-specification[opt]
1656 ///
isCXXFunctionDeclarator(bool * IsAmbiguous)1657 bool Parser::isCXXFunctionDeclarator(bool *IsAmbiguous) {
1658 
1659   // C++ 8.2p1:
1660   // The ambiguity arising from the similarity between a function-style cast and
1661   // a declaration mentioned in 6.8 can also occur in the context of a
1662   // declaration. In that context, the choice is between a function declaration
1663   // with a redundant set of parentheses around a parameter name and an object
1664   // declaration with a function-style cast as the initializer. Just as for the
1665   // ambiguities mentioned in 6.8, the resolution is to consider any construct
1666   // that could possibly be a declaration a declaration.
1667 
1668   RevertingTentativeParsingAction PA(*this);
1669 
1670   ConsumeParen();
1671   bool InvalidAsDeclaration = false;
1672   TPResult TPR = TryParseParameterDeclarationClause(&InvalidAsDeclaration);
1673   if (TPR == TPResult::Ambiguous) {
1674     if (Tok.isNot(tok::r_paren))
1675       TPR = TPResult::False;
1676     else {
1677       const Token &Next = NextToken();
1678       if (Next.isOneOf(tok::amp, tok::ampamp, tok::kw_const, tok::kw_volatile,
1679                        tok::kw_throw, tok::kw_noexcept, tok::l_square,
1680                        tok::l_brace, tok::kw_try, tok::equal, tok::arrow) ||
1681           isCXX11VirtSpecifier(Next))
1682         // The next token cannot appear after a constructor-style initializer,
1683         // and can appear next in a function definition. This must be a function
1684         // declarator.
1685         TPR = TPResult::True;
1686       else if (InvalidAsDeclaration)
1687         // Use the absence of 'typename' as a tie-breaker.
1688         TPR = TPResult::False;
1689     }
1690   }
1691 
1692   if (IsAmbiguous && TPR == TPResult::Ambiguous)
1693     *IsAmbiguous = true;
1694 
1695   // In case of an error, let the declaration parsing code handle it.
1696   return TPR != TPResult::False;
1697 }
1698 
1699 /// parameter-declaration-clause:
1700 ///   parameter-declaration-list[opt] '...'[opt]
1701 ///   parameter-declaration-list ',' '...'
1702 ///
1703 /// parameter-declaration-list:
1704 ///   parameter-declaration
1705 ///   parameter-declaration-list ',' parameter-declaration
1706 ///
1707 /// parameter-declaration:
1708 ///   attribute-specifier-seq[opt] decl-specifier-seq declarator attributes[opt]
1709 ///   attribute-specifier-seq[opt] decl-specifier-seq declarator attributes[opt]
1710 ///     '=' assignment-expression
1711 ///   attribute-specifier-seq[opt] decl-specifier-seq abstract-declarator[opt]
1712 ///     attributes[opt]
1713 ///   attribute-specifier-seq[opt] decl-specifier-seq abstract-declarator[opt]
1714 ///     attributes[opt] '=' assignment-expression
1715 ///
1716 Parser::TPResult
TryParseParameterDeclarationClause(bool * InvalidAsDeclaration,bool VersusTemplateArgument)1717 Parser::TryParseParameterDeclarationClause(bool *InvalidAsDeclaration,
1718                                            bool VersusTemplateArgument) {
1719 
1720   if (Tok.is(tok::r_paren))
1721     return TPResult::Ambiguous;
1722 
1723   //   parameter-declaration-list[opt] '...'[opt]
1724   //   parameter-declaration-list ',' '...'
1725   //
1726   // parameter-declaration-list:
1727   //   parameter-declaration
1728   //   parameter-declaration-list ',' parameter-declaration
1729   //
1730   while (1) {
1731     // '...'[opt]
1732     if (Tok.is(tok::ellipsis)) {
1733       ConsumeToken();
1734       if (Tok.is(tok::r_paren))
1735         return TPResult::True; // '...)' is a sign of a function declarator.
1736       else
1737         return TPResult::False;
1738     }
1739 
1740     // An attribute-specifier-seq here is a sign of a function declarator.
1741     if (isCXX11AttributeSpecifier(/*Disambiguate*/false,
1742                                   /*OuterMightBeMessageSend*/true))
1743       return TPResult::True;
1744 
1745     ParsedAttributes attrs(AttrFactory);
1746     MaybeParseMicrosoftAttributes(attrs);
1747 
1748     // decl-specifier-seq
1749     // A parameter-declaration's initializer must be preceded by an '=', so
1750     // decl-specifier-seq '{' is not a parameter in C++11.
1751     TPResult TPR = isCXXDeclarationSpecifier(TPResult::False,
1752                                              InvalidAsDeclaration);
1753 
1754     if (VersusTemplateArgument && TPR == TPResult::True) {
1755       // Consume the decl-specifier-seq. We have to look past it, since a
1756       // type-id might appear here in a template argument.
1757       bool SeenType = false;
1758       do {
1759         SeenType |= isCXXDeclarationSpecifierAType();
1760         if (TryConsumeDeclarationSpecifier() == TPResult::Error)
1761           return TPResult::Error;
1762 
1763         // If we see a parameter name, this can't be a template argument.
1764         if (SeenType && Tok.is(tok::identifier))
1765           return TPResult::True;
1766 
1767         TPR = isCXXDeclarationSpecifier(TPResult::False,
1768                                         InvalidAsDeclaration);
1769         if (TPR == TPResult::Error)
1770           return TPR;
1771       } while (TPR != TPResult::False);
1772     } else if (TPR == TPResult::Ambiguous) {
1773       // Disambiguate what follows the decl-specifier.
1774       if (TryConsumeDeclarationSpecifier() == TPResult::Error)
1775         return TPResult::Error;
1776     } else
1777       return TPR;
1778 
1779     // declarator
1780     // abstract-declarator[opt]
1781     TPR = TryParseDeclarator(true/*mayBeAbstract*/);
1782     if (TPR != TPResult::Ambiguous)
1783       return TPR;
1784 
1785     // [GNU] attributes[opt]
1786     if (Tok.is(tok::kw___attribute))
1787       return TPResult::True;
1788 
1789     // If we're disambiguating a template argument in a default argument in
1790     // a class definition versus a parameter declaration, an '=' here
1791     // disambiguates the parse one way or the other.
1792     // If this is a parameter, it must have a default argument because
1793     //   (a) the previous parameter did, and
1794     //   (b) this must be the first declaration of the function, so we can't
1795     //       inherit any default arguments from elsewhere.
1796     // If we see an ')', then we've reached the end of a
1797     // parameter-declaration-clause, and the last param is missing its default
1798     // argument.
1799     if (VersusTemplateArgument)
1800       return Tok.isOneOf(tok::equal, tok::r_paren) ? TPResult::True
1801                                                    : TPResult::False;
1802 
1803     if (Tok.is(tok::equal)) {
1804       // '=' assignment-expression
1805       // Parse through assignment-expression.
1806       // FIXME: assignment-expression may contain an unparenthesized comma.
1807       if (!SkipUntil(tok::comma, tok::r_paren, StopAtSemi | StopBeforeMatch))
1808         return TPResult::Error;
1809     }
1810 
1811     if (Tok.is(tok::ellipsis)) {
1812       ConsumeToken();
1813       if (Tok.is(tok::r_paren))
1814         return TPResult::True; // '...)' is a sign of a function declarator.
1815       else
1816         return TPResult::False;
1817     }
1818 
1819     if (!TryConsumeToken(tok::comma))
1820       break;
1821   }
1822 
1823   return TPResult::Ambiguous;
1824 }
1825 
1826 /// TryParseFunctionDeclarator - We parsed a '(' and we want to try to continue
1827 /// parsing as a function declarator.
1828 /// If TryParseFunctionDeclarator fully parsed the function declarator, it will
1829 /// return TPResult::Ambiguous, otherwise it will return either False() or
1830 /// Error().
1831 ///
1832 /// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
1833 ///         exception-specification[opt]
1834 ///
1835 /// exception-specification:
1836 ///   'throw' '(' type-id-list[opt] ')'
1837 ///
TryParseFunctionDeclarator()1838 Parser::TPResult Parser::TryParseFunctionDeclarator() {
1839 
1840   // The '(' is already parsed.
1841 
1842   TPResult TPR = TryParseParameterDeclarationClause();
1843   if (TPR == TPResult::Ambiguous && Tok.isNot(tok::r_paren))
1844     TPR = TPResult::False;
1845 
1846   if (TPR == TPResult::False || TPR == TPResult::Error)
1847     return TPR;
1848 
1849   // Parse through the parens.
1850   if (!SkipUntil(tok::r_paren, StopAtSemi))
1851     return TPResult::Error;
1852 
1853   // cv-qualifier-seq
1854   while (Tok.isOneOf(tok::kw_const, tok::kw_volatile, tok::kw_restrict))
1855     ConsumeToken();
1856 
1857   // ref-qualifier[opt]
1858   if (Tok.isOneOf(tok::amp, tok::ampamp))
1859     ConsumeToken();
1860 
1861   // exception-specification
1862   if (Tok.is(tok::kw_throw)) {
1863     ConsumeToken();
1864     if (Tok.isNot(tok::l_paren))
1865       return TPResult::Error;
1866 
1867     // Parse through the parens after 'throw'.
1868     ConsumeParen();
1869     if (!SkipUntil(tok::r_paren, StopAtSemi))
1870       return TPResult::Error;
1871   }
1872   if (Tok.is(tok::kw_noexcept)) {
1873     ConsumeToken();
1874     // Possibly an expression as well.
1875     if (Tok.is(tok::l_paren)) {
1876       // Find the matching rparen.
1877       ConsumeParen();
1878       if (!SkipUntil(tok::r_paren, StopAtSemi))
1879         return TPResult::Error;
1880     }
1881   }
1882 
1883   return TPResult::Ambiguous;
1884 }
1885 
1886 /// '[' constant-expression[opt] ']'
1887 ///
TryParseBracketDeclarator()1888 Parser::TPResult Parser::TryParseBracketDeclarator() {
1889   ConsumeBracket();
1890   if (!SkipUntil(tok::r_square, StopAtSemi))
1891     return TPResult::Error;
1892 
1893   return TPResult::Ambiguous;
1894 }
1895