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llvm-for-llvmta/tools/clang/lib/Parse/ParseTentative.cpp

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2022-04-25 13:02:35 +02:00
//===--- ParseTentative.cpp - Ambiguity Resolution Parsing ----------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the tentative parsing portions of the Parser
// interfaces, for ambiguity resolution.
//
//===----------------------------------------------------------------------===//
#include "clang/Parse/Parser.h"
#include "clang/Parse/ParseDiagnostic.h"
#include "clang/Sema/ParsedTemplate.h"
using namespace clang;
/// isCXXDeclarationStatement - C++-specialized function that disambiguates
/// between a declaration or an expression statement, when parsing function
/// bodies. Returns true for declaration, false for expression.
///
/// declaration-statement:
/// block-declaration
///
/// block-declaration:
/// simple-declaration
/// asm-definition
/// namespace-alias-definition
/// using-declaration
/// using-directive
/// [C++0x] static_assert-declaration
///
/// asm-definition:
/// 'asm' '(' string-literal ')' ';'
///
/// namespace-alias-definition:
/// 'namespace' identifier = qualified-namespace-specifier ';'
///
/// using-declaration:
/// 'using' typename[opt] '::'[opt] nested-name-specifier
/// unqualified-id ';'
/// 'using' '::' unqualified-id ;
///
/// using-directive:
/// 'using' 'namespace' '::'[opt] nested-name-specifier[opt]
/// namespace-name ';'
///
bool Parser::isCXXDeclarationStatement() {
switch (Tok.getKind()) {
// asm-definition
case tok::kw_asm:
// namespace-alias-definition
case tok::kw_namespace:
// using-declaration
// using-directive
case tok::kw_using:
// static_assert-declaration
case tok::kw_static_assert:
case tok::kw__Static_assert:
return true;
// simple-declaration
default:
return isCXXSimpleDeclaration(/*AllowForRangeDecl=*/false);
}
}
/// isCXXSimpleDeclaration - C++-specialized function that disambiguates
/// between a simple-declaration or an expression-statement.
/// If during the disambiguation process a parsing error is encountered,
/// the function returns true to let the declaration parsing code handle it.
/// Returns false if the statement is disambiguated as expression.
///
/// simple-declaration:
/// decl-specifier-seq init-declarator-list[opt] ';'
/// decl-specifier-seq ref-qualifier[opt] '[' identifier-list ']'
/// brace-or-equal-initializer ';' [C++17]
///
/// (if AllowForRangeDecl specified)
/// for ( for-range-declaration : for-range-initializer ) statement
///
/// for-range-declaration:
/// decl-specifier-seq declarator
/// decl-specifier-seq ref-qualifier[opt] '[' identifier-list ']'
///
/// In any of the above cases there can be a preceding attribute-specifier-seq,
/// but the caller is expected to handle that.
bool Parser::isCXXSimpleDeclaration(bool AllowForRangeDecl) {
// C++ 6.8p1:
// There is an ambiguity in the grammar involving expression-statements and
// declarations: An expression-statement with a function-style explicit type
// conversion (5.2.3) as its leftmost subexpression can be indistinguishable
// from a declaration where the first declarator starts with a '('. In those
// cases the statement is a declaration. [Note: To disambiguate, the whole
// statement might have to be examined to determine if it is an
// expression-statement or a declaration].
// C++ 6.8p3:
// The disambiguation is purely syntactic; that is, the meaning of the names
// occurring in such a statement, beyond whether they are type-names or not,
// is not generally used in or changed by the disambiguation. Class
// templates are instantiated as necessary to determine if a qualified name
// is a type-name. Disambiguation precedes parsing, and a statement
// disambiguated as a declaration may be an ill-formed declaration.
// We don't have to parse all of the decl-specifier-seq part. There's only
// an ambiguity if the first decl-specifier is
// simple-type-specifier/typename-specifier followed by a '(', which may
// indicate a function-style cast expression.
// isCXXDeclarationSpecifier will return TPResult::Ambiguous only in such
// a case.
bool InvalidAsDeclaration = false;
TPResult TPR = isCXXDeclarationSpecifier(TPResult::False,
&InvalidAsDeclaration);
if (TPR != TPResult::Ambiguous)
return TPR != TPResult::False; // Returns true for TPResult::True or
// TPResult::Error.
// FIXME: TryParseSimpleDeclaration doesn't look past the first initializer,
// and so gets some cases wrong. We can't carry on if we've already seen
// something which makes this statement invalid as a declaration in this case,
// since it can cause us to misparse valid code. Revisit this once
// TryParseInitDeclaratorList is fixed.
if (InvalidAsDeclaration)
return false;
// FIXME: Add statistics about the number of ambiguous statements encountered
// and how they were resolved (number of declarations+number of expressions).
// Ok, we have a simple-type-specifier/typename-specifier followed by a '(',
// or an identifier which doesn't resolve as anything. We need tentative
// parsing...
{
RevertingTentativeParsingAction PA(*this);
TPR = TryParseSimpleDeclaration(AllowForRangeDecl);
}
// In case of an error, let the declaration parsing code handle it.
if (TPR == TPResult::Error)
return true;
// Declarations take precedence over expressions.
if (TPR == TPResult::Ambiguous)
TPR = TPResult::True;
assert(TPR == TPResult::True || TPR == TPResult::False);
return TPR == TPResult::True;
}
/// Try to consume a token sequence that we've already identified as
/// (potentially) starting a decl-specifier.
Parser::TPResult Parser::TryConsumeDeclarationSpecifier() {
switch (Tok.getKind()) {
case tok::kw__Atomic:
if (NextToken().isNot(tok::l_paren)) {
ConsumeToken();
break;
}
LLVM_FALLTHROUGH;
case tok::kw_typeof:
case tok::kw___attribute:
case tok::kw___underlying_type: {
ConsumeToken();
if (Tok.isNot(tok::l_paren))
return TPResult::Error;
ConsumeParen();
if (!SkipUntil(tok::r_paren))
return TPResult::Error;
break;
}
case tok::kw_class:
case tok::kw_struct:
case tok::kw_union:
case tok::kw___interface:
case tok::kw_enum:
// elaborated-type-specifier:
// class-key attribute-specifier-seq[opt]
// nested-name-specifier[opt] identifier
// class-key nested-name-specifier[opt] template[opt] simple-template-id
// enum nested-name-specifier[opt] identifier
//
// FIXME: We don't support class-specifiers nor enum-specifiers here.
ConsumeToken();
// Skip attributes.
if (!TrySkipAttributes())
return TPResult::Error;
if (TryAnnotateOptionalCXXScopeToken())
return TPResult::Error;
if (Tok.is(tok::annot_cxxscope))
ConsumeAnnotationToken();
if (Tok.is(tok::identifier))
ConsumeToken();
else if (Tok.is(tok::annot_template_id))
ConsumeAnnotationToken();
else
return TPResult::Error;
break;
case tok::annot_cxxscope:
ConsumeAnnotationToken();
LLVM_FALLTHROUGH;
default:
ConsumeAnyToken();
if (getLangOpts().ObjC && Tok.is(tok::less))
return TryParseProtocolQualifiers();
break;
}
return TPResult::Ambiguous;
}
/// simple-declaration:
/// decl-specifier-seq init-declarator-list[opt] ';'
///
/// (if AllowForRangeDecl specified)
/// for ( for-range-declaration : for-range-initializer ) statement
/// for-range-declaration:
/// attribute-specifier-seqopt type-specifier-seq declarator
///
Parser::TPResult Parser::TryParseSimpleDeclaration(bool AllowForRangeDecl) {
if (TryConsumeDeclarationSpecifier() == TPResult::Error)
return TPResult::Error;
// Two decl-specifiers in a row conclusively disambiguate this as being a
// simple-declaration. Don't bother calling isCXXDeclarationSpecifier in the
// overwhelmingly common case that the next token is a '('.
if (Tok.isNot(tok::l_paren)) {
TPResult TPR = isCXXDeclarationSpecifier();
if (TPR == TPResult::Ambiguous)
return TPResult::True;
if (TPR == TPResult::True || TPR == TPResult::Error)
return TPR;
assert(TPR == TPResult::False);
}
TPResult TPR = TryParseInitDeclaratorList();
if (TPR != TPResult::Ambiguous)
return TPR;
if (Tok.isNot(tok::semi) && (!AllowForRangeDecl || Tok.isNot(tok::colon)))
return TPResult::False;
return TPResult::Ambiguous;
}
/// Tentatively parse an init-declarator-list in order to disambiguate it from
/// an expression.
///
/// init-declarator-list:
/// init-declarator
/// init-declarator-list ',' init-declarator
///
/// init-declarator:
/// declarator initializer[opt]
/// [GNU] declarator simple-asm-expr[opt] attributes[opt] initializer[opt]
///
/// initializer:
/// brace-or-equal-initializer
/// '(' expression-list ')'
///
/// brace-or-equal-initializer:
/// '=' initializer-clause
/// [C++11] braced-init-list
///
/// initializer-clause:
/// assignment-expression
/// braced-init-list
///
/// braced-init-list:
/// '{' initializer-list ','[opt] '}'
/// '{' '}'
///
Parser::TPResult Parser::TryParseInitDeclaratorList() {
while (1) {
// declarator
TPResult TPR = TryParseDeclarator(false/*mayBeAbstract*/);
if (TPR != TPResult::Ambiguous)
return TPR;
// [GNU] simple-asm-expr[opt] attributes[opt]
if (Tok.isOneOf(tok::kw_asm, tok::kw___attribute))
return TPResult::True;
// initializer[opt]
if (Tok.is(tok::l_paren)) {
// Parse through the parens.
ConsumeParen();
if (!SkipUntil(tok::r_paren, StopAtSemi))
return TPResult::Error;
} else if (Tok.is(tok::l_brace)) {
// A left-brace here is sufficient to disambiguate the parse; an
// expression can never be followed directly by a braced-init-list.
return TPResult::True;
} else if (Tok.is(tok::equal) || isTokIdentifier_in()) {
// MSVC and g++ won't examine the rest of declarators if '=' is
// encountered; they just conclude that we have a declaration.
// EDG parses the initializer completely, which is the proper behavior
// for this case.
//
// At present, Clang follows MSVC and g++, since the parser does not have
// the ability to parse an expression fully without recording the
// results of that parse.
// FIXME: Handle this case correctly.
//
// Also allow 'in' after an Objective-C declaration as in:
// for (int (^b)(void) in array). Ideally this should be done in the
// context of parsing for-init-statement of a foreach statement only. But,
// in any other context 'in' is invalid after a declaration and parser
// issues the error regardless of outcome of this decision.
// FIXME: Change if above assumption does not hold.
return TPResult::True;
}
if (!TryConsumeToken(tok::comma))
break;
}
return TPResult::Ambiguous;
}
struct Parser::ConditionDeclarationOrInitStatementState {
Parser &P;
bool CanBeExpression = true;
bool CanBeCondition = true;
bool CanBeInitStatement;
bool CanBeForRangeDecl;
ConditionDeclarationOrInitStatementState(Parser &P, bool CanBeInitStatement,
bool CanBeForRangeDecl)
: P(P), CanBeInitStatement(CanBeInitStatement),
CanBeForRangeDecl(CanBeForRangeDecl) {}
bool resolved() {
return CanBeExpression + CanBeCondition + CanBeInitStatement +
CanBeForRangeDecl < 2;
}
void markNotExpression() {
CanBeExpression = false;
if (!resolved()) {
// FIXME: Unify the parsing codepaths for condition variables and
// simple-declarations so that we don't need to eagerly figure out which
// kind we have here. (Just parse init-declarators until we reach a
// semicolon or right paren.)
RevertingTentativeParsingAction PA(P);
if (CanBeForRangeDecl) {
// Skip until we hit a ')', ';', or a ':' with no matching '?'.
// The final case is a for range declaration, the rest are not.
while (true) {
unsigned QuestionColonDepth = 0;
P.SkipUntil({tok::r_paren, tok::semi, tok::question, tok::colon},
StopBeforeMatch);
if (P.Tok.is(tok::question))
++QuestionColonDepth;
else if (P.Tok.is(tok::colon)) {
if (QuestionColonDepth)
--QuestionColonDepth;
else {
CanBeCondition = CanBeInitStatement = false;
return;
}
} else {
CanBeForRangeDecl = false;
break;
}
P.ConsumeToken();
}
} else {
// Just skip until we hit a ')' or ';'.
P.SkipUntil(tok::r_paren, tok::semi, StopBeforeMatch);
}
if (P.Tok.isNot(tok::r_paren))
CanBeCondition = CanBeForRangeDecl = false;
if (P.Tok.isNot(tok::semi))
CanBeInitStatement = false;
}
}
bool markNotCondition() {
CanBeCondition = false;
return resolved();
}
bool markNotForRangeDecl() {
CanBeForRangeDecl = false;
return resolved();
}
bool update(TPResult IsDecl) {
switch (IsDecl) {
case TPResult::True:
markNotExpression();
assert(resolved() && "can't continue after tentative parsing bails out");
break;
case TPResult::False:
CanBeCondition = CanBeInitStatement = CanBeForRangeDecl = false;
break;
case TPResult::Ambiguous:
break;
case TPResult::Error:
CanBeExpression = CanBeCondition = CanBeInitStatement =
CanBeForRangeDecl = false;
break;
}
return resolved();
}
ConditionOrInitStatement result() const {
assert(CanBeExpression + CanBeCondition + CanBeInitStatement +
CanBeForRangeDecl < 2 &&
"result called but not yet resolved");
if (CanBeExpression)
return ConditionOrInitStatement::Expression;
if (CanBeCondition)
return ConditionOrInitStatement::ConditionDecl;
if (CanBeInitStatement)
return ConditionOrInitStatement::InitStmtDecl;
if (CanBeForRangeDecl)
return ConditionOrInitStatement::ForRangeDecl;
return ConditionOrInitStatement::Error;
}
};
bool Parser::isEnumBase(bool AllowSemi) {
assert(Tok.is(tok::colon) && "should be looking at the ':'");
RevertingTentativeParsingAction PA(*this);
// ':'
ConsumeToken();
// type-specifier-seq
bool InvalidAsDeclSpec = false;
// FIXME: We could disallow non-type decl-specifiers here, but it makes no
// difference: those specifiers are ill-formed regardless of the
// interpretation.
TPResult R = isCXXDeclarationSpecifier(/*BracedCastResult*/ TPResult::True,
&InvalidAsDeclSpec);
if (R == TPResult::Ambiguous) {
// We either have a decl-specifier followed by '(' or an undeclared
// identifier.
if (TryConsumeDeclarationSpecifier() == TPResult::Error)
return true;
// If we get to the end of the enum-base, we hit either a '{' or a ';'.
// Don't bother checking the enumerator-list.
if (Tok.is(tok::l_brace) || (AllowSemi && Tok.is(tok::semi)))
return true;
// A second decl-specifier unambiguously indicatges an enum-base.
R = isCXXDeclarationSpecifier(TPResult::True, &InvalidAsDeclSpec);
}
return R != TPResult::False;
}
/// Disambiguates between a declaration in a condition, a
/// simple-declaration in an init-statement, and an expression for
/// a condition of a if/switch statement.
///
/// condition:
/// expression
/// type-specifier-seq declarator '=' assignment-expression
/// [C++11] type-specifier-seq declarator '=' initializer-clause
/// [C++11] type-specifier-seq declarator braced-init-list
/// [GNU] type-specifier-seq declarator simple-asm-expr[opt] attributes[opt]
/// '=' assignment-expression
/// simple-declaration:
/// decl-specifier-seq init-declarator-list[opt] ';'
///
/// Note that, unlike isCXXSimpleDeclaration, we must disambiguate all the way
/// to the ';' to disambiguate cases like 'int(x))' (an expression) from
/// 'int(x);' (a simple-declaration in an init-statement).
Parser::ConditionOrInitStatement
Parser::isCXXConditionDeclarationOrInitStatement(bool CanBeInitStatement,
bool CanBeForRangeDecl) {
ConditionDeclarationOrInitStatementState State(*this, CanBeInitStatement,
CanBeForRangeDecl);
if (State.update(isCXXDeclarationSpecifier()))
return State.result();
// It might be a declaration; we need tentative parsing.
RevertingTentativeParsingAction PA(*this);
// FIXME: A tag definition unambiguously tells us this is an init-statement.
if (State.update(TryConsumeDeclarationSpecifier()))
return State.result();
assert(Tok.is(tok::l_paren) && "Expected '('");
while (true) {
// Consume a declarator.
if (State.update(TryParseDeclarator(false/*mayBeAbstract*/)))
return State.result();
// Attributes, asm label, or an initializer imply this is not an expression.
// FIXME: Disambiguate properly after an = instead of assuming that it's a
// valid declaration.
if (Tok.isOneOf(tok::equal, tok::kw_asm, tok::kw___attribute) ||
(getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace))) {
State.markNotExpression();
return State.result();
}
// A colon here identifies a for-range declaration.
if (State.CanBeForRangeDecl && Tok.is(tok::colon))
return ConditionOrInitStatement::ForRangeDecl;
// At this point, it can't be a condition any more, because a condition
// must have a brace-or-equal-initializer.
if (State.markNotCondition())
return State.result();
// Likewise, it can't be a for-range declaration any more.
if (State.markNotForRangeDecl())
return State.result();
// A parenthesized initializer could be part of an expression or a
// simple-declaration.
if (Tok.is(tok::l_paren)) {
ConsumeParen();
SkipUntil(tok::r_paren, StopAtSemi);
}
if (!TryConsumeToken(tok::comma))
break;
}
// We reached the end. If it can now be some kind of decl, then it is.
if (State.CanBeCondition && Tok.is(tok::r_paren))
return ConditionOrInitStatement::ConditionDecl;
else if (State.CanBeInitStatement && Tok.is(tok::semi))
return ConditionOrInitStatement::InitStmtDecl;
else
return ConditionOrInitStatement::Expression;
}
/// Determine whether the next set of tokens contains a type-id.
///
/// The context parameter states what context we're parsing right
/// now, which affects how this routine copes with the token
/// following the type-id. If the context is TypeIdInParens, we have
/// already parsed the '(' and we will cease lookahead when we hit
/// the corresponding ')'. If the context is
/// TypeIdAsTemplateArgument, we've already parsed the '<' or ','
/// before this template argument, and will cease lookahead when we
/// hit a '>', '>>' (in C++0x), or ','; or, in C++0x, an ellipsis immediately
/// preceding such. Returns true for a type-id and false for an expression.
/// If during the disambiguation process a parsing error is encountered,
/// the function returns true to let the declaration parsing code handle it.
///
/// type-id:
/// type-specifier-seq abstract-declarator[opt]
///
bool Parser::isCXXTypeId(TentativeCXXTypeIdContext Context, bool &isAmbiguous) {
isAmbiguous = false;
// C++ 8.2p2:
// The ambiguity arising from the similarity between a function-style cast and
// a type-id can occur in different contexts. The ambiguity appears as a
// choice between a function-style cast expression and a declaration of a
// type. The resolution is that any construct that could possibly be a type-id
// in its syntactic context shall be considered a type-id.
TPResult TPR = isCXXDeclarationSpecifier();
if (TPR != TPResult::Ambiguous)
return TPR != TPResult::False; // Returns true for TPResult::True or
// TPResult::Error.
// FIXME: Add statistics about the number of ambiguous statements encountered
// and how they were resolved (number of declarations+number of expressions).
// Ok, we have a simple-type-specifier/typename-specifier followed by a '('.
// We need tentative parsing...
RevertingTentativeParsingAction PA(*this);
// type-specifier-seq
TryConsumeDeclarationSpecifier();
assert(Tok.is(tok::l_paren) && "Expected '('");
// declarator
TPR = TryParseDeclarator(true/*mayBeAbstract*/, false/*mayHaveIdentifier*/);
// In case of an error, let the declaration parsing code handle it.
if (TPR == TPResult::Error)
TPR = TPResult::True;
if (TPR == TPResult::Ambiguous) {
// We are supposed to be inside parens, so if after the abstract declarator
// we encounter a ')' this is a type-id, otherwise it's an expression.
if (Context == TypeIdInParens && Tok.is(tok::r_paren)) {
TPR = TPResult::True;
isAmbiguous = true;
// We are supposed to be inside a template argument, so if after
// the abstract declarator we encounter a '>', '>>' (in C++0x), or
// ','; or, in C++0x, an ellipsis immediately preceding such, this
// is a type-id. Otherwise, it's an expression.
} else if (Context == TypeIdAsTemplateArgument &&
(Tok.isOneOf(tok::greater, tok::comma) ||
(getLangOpts().CPlusPlus11 &&
(Tok.isOneOf(tok::greatergreater,
tok::greatergreatergreater) ||
(Tok.is(tok::ellipsis) &&
NextToken().isOneOf(tok::greater, tok::greatergreater,
tok::greatergreatergreater,
tok::comma)))))) {
TPR = TPResult::True;
isAmbiguous = true;
} else
TPR = TPResult::False;
}
assert(TPR == TPResult::True || TPR == TPResult::False);
return TPR == TPResult::True;
}
/// Returns true if this is a C++11 attribute-specifier. Per
/// C++11 [dcl.attr.grammar]p6, two consecutive left square bracket tokens
/// always introduce an attribute. In Objective-C++11, this rule does not
/// apply if either '[' begins a message-send.
///
/// If Disambiguate is true, we try harder to determine whether a '[[' starts
/// an attribute-specifier, and return CAK_InvalidAttributeSpecifier if not.
///
/// If OuterMightBeMessageSend is true, we assume the outer '[' is either an
/// Obj-C message send or the start of an attribute. Otherwise, we assume it
/// is not an Obj-C message send.
///
/// C++11 [dcl.attr.grammar]:
///
/// attribute-specifier:
/// '[' '[' attribute-list ']' ']'
/// alignment-specifier
///
/// attribute-list:
/// attribute[opt]
/// attribute-list ',' attribute[opt]
/// attribute '...'
/// attribute-list ',' attribute '...'
///
/// attribute:
/// attribute-token attribute-argument-clause[opt]
///
/// attribute-token:
/// identifier
/// identifier '::' identifier
///
/// attribute-argument-clause:
/// '(' balanced-token-seq ')'
Parser::CXX11AttributeKind
Parser::isCXX11AttributeSpecifier(bool Disambiguate,
bool OuterMightBeMessageSend) {
if (Tok.is(tok::kw_alignas))
return CAK_AttributeSpecifier;
if (Tok.isNot(tok::l_square) || NextToken().isNot(tok::l_square))
return CAK_NotAttributeSpecifier;
// No tentative parsing if we don't need to look for ']]' or a lambda.
if (!Disambiguate && !getLangOpts().ObjC)
return CAK_AttributeSpecifier;
// '[[using ns: ...]]' is an attribute.
if (GetLookAheadToken(2).is(tok::kw_using))
return CAK_AttributeSpecifier;
RevertingTentativeParsingAction PA(*this);
// Opening brackets were checked for above.
ConsumeBracket();
if (!getLangOpts().ObjC) {
ConsumeBracket();
bool IsAttribute = SkipUntil(tok::r_square);
IsAttribute &= Tok.is(tok::r_square);
return IsAttribute ? CAK_AttributeSpecifier : CAK_InvalidAttributeSpecifier;
}
// In Obj-C++11, we need to distinguish four situations:
// 1a) int x[[attr]]; C++11 attribute.
// 1b) [[attr]]; C++11 statement attribute.
// 2) int x[[obj](){ return 1; }()]; Lambda in array size/index.
// 3a) int x[[obj get]]; Message send in array size/index.
// 3b) [[Class alloc] init]; Message send in message send.
// 4) [[obj]{ return self; }() doStuff]; Lambda in message send.
// (1) is an attribute, (2) is ill-formed, and (3) and (4) are accepted.
// Check to see if this is a lambda-expression.
// FIXME: If this disambiguation is too slow, fold the tentative lambda parse
// into the tentative attribute parse below.
{
RevertingTentativeParsingAction LambdaTPA(*this);
LambdaIntroducer Intro;
LambdaIntroducerTentativeParse Tentative;
if (ParseLambdaIntroducer(Intro, &Tentative)) {
// We hit a hard error after deciding this was not an attribute.
// FIXME: Don't parse and annotate expressions when disambiguating
// against an attribute.
return CAK_NotAttributeSpecifier;
}
switch (Tentative) {
case LambdaIntroducerTentativeParse::MessageSend:
// Case 3: The inner construct is definitely a message send, so the
// outer construct is definitely not an attribute.
return CAK_NotAttributeSpecifier;
case LambdaIntroducerTentativeParse::Success:
case LambdaIntroducerTentativeParse::Incomplete:
// This is a lambda-introducer or attribute-specifier.
if (Tok.is(tok::r_square))
// Case 1: C++11 attribute.
return CAK_AttributeSpecifier;
if (OuterMightBeMessageSend)
// Case 4: Lambda in message send.
return CAK_NotAttributeSpecifier;
// Case 2: Lambda in array size / index.
return CAK_InvalidAttributeSpecifier;
case LambdaIntroducerTentativeParse::Invalid:
// No idea what this is; we couldn't parse it as a lambda-introducer.
// Might still be an attribute-specifier or a message send.
break;
}
}
ConsumeBracket();
// If we don't have a lambda-introducer, then we have an attribute or a
// message-send.
bool IsAttribute = true;
while (Tok.isNot(tok::r_square)) {
if (Tok.is(tok::comma)) {
// Case 1: Stray commas can only occur in attributes.
return CAK_AttributeSpecifier;
}
// Parse the attribute-token, if present.
// C++11 [dcl.attr.grammar]:
// If a keyword or an alternative token that satisfies the syntactic
// requirements of an identifier is contained in an attribute-token,
// it is considered an identifier.
SourceLocation Loc;
if (!TryParseCXX11AttributeIdentifier(Loc)) {
IsAttribute = false;
break;
}
if (Tok.is(tok::coloncolon)) {
ConsumeToken();
if (!TryParseCXX11AttributeIdentifier(Loc)) {
IsAttribute = false;
break;
}
}
// Parse the attribute-argument-clause, if present.
if (Tok.is(tok::l_paren)) {
ConsumeParen();
if (!SkipUntil(tok::r_paren)) {
IsAttribute = false;
break;
}
}
TryConsumeToken(tok::ellipsis);
if (!TryConsumeToken(tok::comma))
break;
}
// An attribute must end ']]'.
if (IsAttribute) {
if (Tok.is(tok::r_square)) {
ConsumeBracket();
IsAttribute = Tok.is(tok::r_square);
} else {
IsAttribute = false;
}
}
if (IsAttribute)
// Case 1: C++11 statement attribute.
return CAK_AttributeSpecifier;
// Case 3: Message send.
return CAK_NotAttributeSpecifier;
}
bool Parser::TrySkipAttributes() {
while (Tok.isOneOf(tok::l_square, tok::kw___attribute, tok::kw___declspec,
tok::kw_alignas)) {
if (Tok.is(tok::l_square)) {
ConsumeBracket();
if (Tok.isNot(tok::l_square))
return false;
ConsumeBracket();
if (!SkipUntil(tok::r_square) || Tok.isNot(tok::r_square))
return false;
// Note that explicitly checking for `[[` and `]]` allows to fail as
// expected in the case of the Objective-C message send syntax.
ConsumeBracket();
} else {
ConsumeToken();
if (Tok.isNot(tok::l_paren))
return false;
ConsumeParen();
if (!SkipUntil(tok::r_paren))
return false;
}
}
return true;
}
Parser::TPResult Parser::TryParsePtrOperatorSeq() {
while (true) {
if (TryAnnotateOptionalCXXScopeToken(true))
return TPResult::Error;
if (Tok.isOneOf(tok::star, tok::amp, tok::caret, tok::ampamp) ||
(Tok.is(tok::annot_cxxscope) && NextToken().is(tok::star))) {
// ptr-operator
ConsumeAnyToken();
// Skip attributes.
if (!TrySkipAttributes())
return TPResult::Error;
while (Tok.isOneOf(tok::kw_const, tok::kw_volatile, tok::kw_restrict,
tok::kw__Nonnull, tok::kw__Nullable,
tok::kw__Nullable_result, tok::kw__Null_unspecified,
tok::kw__Atomic))
ConsumeToken();
} else {
return TPResult::True;
}
}
}
/// operator-function-id:
/// 'operator' operator
///
/// operator: one of
/// new delete new[] delete[] + - * / % ^ [...]
///
/// conversion-function-id:
/// 'operator' conversion-type-id
///
/// conversion-type-id:
/// type-specifier-seq conversion-declarator[opt]
///
/// conversion-declarator:
/// ptr-operator conversion-declarator[opt]
///
/// literal-operator-id:
/// 'operator' string-literal identifier
/// 'operator' user-defined-string-literal
Parser::TPResult Parser::TryParseOperatorId() {
assert(Tok.is(tok::kw_operator));
ConsumeToken();
// Maybe this is an operator-function-id.
switch (Tok.getKind()) {
case tok::kw_new: case tok::kw_delete:
ConsumeToken();
if (Tok.is(tok::l_square) && NextToken().is(tok::r_square)) {
ConsumeBracket();
ConsumeBracket();
}
return TPResult::True;
#define OVERLOADED_OPERATOR(Name, Spelling, Token, Unary, Binary, MemOnly) \
case tok::Token:
#define OVERLOADED_OPERATOR_MULTI(Name, Spelling, Unary, Binary, MemOnly)
#include "clang/Basic/OperatorKinds.def"
ConsumeToken();
return TPResult::True;
case tok::l_square:
if (NextToken().is(tok::r_square)) {
ConsumeBracket();
ConsumeBracket();
return TPResult::True;
}
break;
case tok::l_paren:
if (NextToken().is(tok::r_paren)) {
ConsumeParen();
ConsumeParen();
return TPResult::True;
}
break;
default:
break;
}
// Maybe this is a literal-operator-id.
if (getLangOpts().CPlusPlus11 && isTokenStringLiteral()) {
bool FoundUDSuffix = false;
do {
FoundUDSuffix |= Tok.hasUDSuffix();
ConsumeStringToken();
} while (isTokenStringLiteral());
if (!FoundUDSuffix) {
if (Tok.is(tok::identifier))
ConsumeToken();
else
return TPResult::Error;
}
return TPResult::True;
}
// Maybe this is a conversion-function-id.
bool AnyDeclSpecifiers = false;
while (true) {
TPResult TPR = isCXXDeclarationSpecifier();
if (TPR == TPResult::Error)
return TPR;
if (TPR == TPResult::False) {
if (!AnyDeclSpecifiers)
return TPResult::Error;
break;
}
if (TryConsumeDeclarationSpecifier() == TPResult::Error)
return TPResult::Error;
AnyDeclSpecifiers = true;
}
return TryParsePtrOperatorSeq();
}
/// declarator:
/// direct-declarator
/// ptr-operator declarator
///
/// direct-declarator:
/// declarator-id
/// direct-declarator '(' parameter-declaration-clause ')'
/// cv-qualifier-seq[opt] exception-specification[opt]
/// direct-declarator '[' constant-expression[opt] ']'
/// '(' declarator ')'
/// [GNU] '(' attributes declarator ')'
///
/// abstract-declarator:
/// ptr-operator abstract-declarator[opt]
/// direct-abstract-declarator
///
/// direct-abstract-declarator:
/// direct-abstract-declarator[opt]
/// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
/// exception-specification[opt]
/// direct-abstract-declarator[opt] '[' constant-expression[opt] ']'
/// '(' abstract-declarator ')'
/// [C++0x] ...
///
/// ptr-operator:
/// '*' cv-qualifier-seq[opt]
/// '&'
/// [C++0x] '&&' [TODO]
/// '::'[opt] nested-name-specifier '*' cv-qualifier-seq[opt]
///
/// cv-qualifier-seq:
/// cv-qualifier cv-qualifier-seq[opt]
///
/// cv-qualifier:
/// 'const'
/// 'volatile'
///
/// declarator-id:
/// '...'[opt] id-expression
///
/// id-expression:
/// unqualified-id
/// qualified-id [TODO]
///
/// unqualified-id:
/// identifier
/// operator-function-id
/// conversion-function-id
/// literal-operator-id
/// '~' class-name [TODO]
/// '~' decltype-specifier [TODO]
/// template-id [TODO]
///
Parser::TPResult Parser::TryParseDeclarator(bool mayBeAbstract,
bool mayHaveIdentifier,
bool mayHaveDirectInit) {
// declarator:
// direct-declarator
// ptr-operator declarator
if (TryParsePtrOperatorSeq() == TPResult::Error)
return TPResult::Error;
// direct-declarator:
// direct-abstract-declarator:
if (Tok.is(tok::ellipsis))
ConsumeToken();
if ((Tok.isOneOf(tok::identifier, tok::kw_operator) ||
(Tok.is(tok::annot_cxxscope) && (NextToken().is(tok::identifier) ||
NextToken().is(tok::kw_operator)))) &&
mayHaveIdentifier) {
// declarator-id
if (Tok.is(tok::annot_cxxscope)) {
CXXScopeSpec SS;
Actions.RestoreNestedNameSpecifierAnnotation(
Tok.getAnnotationValue(), Tok.getAnnotationRange(), SS);
if (SS.isInvalid())
return TPResult::Error;
ConsumeAnnotationToken();
} else if (Tok.is(tok::identifier)) {
TentativelyDeclaredIdentifiers.push_back(Tok.getIdentifierInfo());
}
if (Tok.is(tok::kw_operator)) {
if (TryParseOperatorId() == TPResult::Error)
return TPResult::Error;
} else
ConsumeToken();
} else if (Tok.is(tok::l_paren)) {
ConsumeParen();
if (mayBeAbstract &&
(Tok.is(tok::r_paren) || // 'int()' is a function.
// 'int(...)' is a function.
(Tok.is(tok::ellipsis) && NextToken().is(tok::r_paren)) ||
isDeclarationSpecifier())) { // 'int(int)' is a function.
// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
// exception-specification[opt]
TPResult TPR = TryParseFunctionDeclarator();
if (TPR != TPResult::Ambiguous)
return TPR;
} else {
// '(' declarator ')'
// '(' attributes declarator ')'
// '(' abstract-declarator ')'
if (Tok.isOneOf(tok::kw___attribute, tok::kw___declspec, tok::kw___cdecl,
tok::kw___stdcall, tok::kw___fastcall, tok::kw___thiscall,
tok::kw___regcall, tok::kw___vectorcall))
return TPResult::True; // attributes indicate declaration
TPResult TPR = TryParseDeclarator(mayBeAbstract, mayHaveIdentifier);
if (TPR != TPResult::Ambiguous)
return TPR;
if (Tok.isNot(tok::r_paren))
return TPResult::False;
ConsumeParen();
}
} else if (!mayBeAbstract) {
return TPResult::False;
}
if (mayHaveDirectInit)
return TPResult::Ambiguous;
while (1) {
TPResult TPR(TPResult::Ambiguous);
if (Tok.is(tok::l_paren)) {
// Check whether we have a function declarator or a possible ctor-style
// initializer that follows the declarator. Note that ctor-style
// initializers are not possible in contexts where abstract declarators
// are allowed.
if (!mayBeAbstract && !isCXXFunctionDeclarator())
break;
// direct-declarator '(' parameter-declaration-clause ')'
// cv-qualifier-seq[opt] exception-specification[opt]
ConsumeParen();
TPR = TryParseFunctionDeclarator();
} else if (Tok.is(tok::l_square)) {
// direct-declarator '[' constant-expression[opt] ']'
// direct-abstract-declarator[opt] '[' constant-expression[opt] ']'
TPR = TryParseBracketDeclarator();
} else if (Tok.is(tok::kw_requires)) {
// declarator requires-clause
// A requires clause indicates a function declaration.
TPR = TPResult::True;
} else {
break;
}
if (TPR != TPResult::Ambiguous)
return TPR;
}
return TPResult::Ambiguous;
}
bool Parser::isTentativelyDeclared(IdentifierInfo *II) {
return std::find(TentativelyDeclaredIdentifiers.begin(),
TentativelyDeclaredIdentifiers.end(), II)
!= TentativelyDeclaredIdentifiers.end();
}
namespace {
class TentativeParseCCC final : public CorrectionCandidateCallback {
public:
TentativeParseCCC(const Token &Next) {
WantRemainingKeywords = false;
WantTypeSpecifiers =
Next.isOneOf(tok::l_paren, tok::r_paren, tok::greater, tok::l_brace,
tok::identifier, tok::comma);
}
bool ValidateCandidate(const TypoCorrection &Candidate) override {
// Reject any candidate that only resolves to instance members since they
// aren't viable as standalone identifiers instead of member references.
if (Candidate.isResolved() && !Candidate.isKeyword() &&
llvm::all_of(Candidate,
[](NamedDecl *ND) { return ND->isCXXInstanceMember(); }))
return false;
return CorrectionCandidateCallback::ValidateCandidate(Candidate);
}
std::unique_ptr<CorrectionCandidateCallback> clone() override {
return std::make_unique<TentativeParseCCC>(*this);
}
};
}
/// isCXXDeclarationSpecifier - Returns TPResult::True if it is a declaration
/// specifier, TPResult::False if it is not, TPResult::Ambiguous if it could
/// be either a decl-specifier or a function-style cast, and TPResult::Error
/// if a parsing error was found and reported.
///
/// If InvalidAsDeclSpec is not null, some cases that would be ill-formed as
/// declaration specifiers but possibly valid as some other kind of construct
/// return TPResult::Ambiguous instead of TPResult::False. When this happens,
/// the intent is to keep trying to disambiguate, on the basis that we might
/// find a better reason to treat this construct as a declaration later on.
/// When this happens and the name could possibly be valid in some other
/// syntactic context, *InvalidAsDeclSpec is set to 'true'. The current cases
/// that trigger this are:
///
/// * When parsing X::Y (with no 'typename') where X is dependent
/// * When parsing X<Y> where X is undeclared
///
/// decl-specifier:
/// storage-class-specifier
/// type-specifier
/// function-specifier
/// 'friend'
/// 'typedef'
/// [C++11] 'constexpr'
/// [C++20] 'consteval'
/// [GNU] attributes declaration-specifiers[opt]
///
/// storage-class-specifier:
/// 'register'
/// 'static'
/// 'extern'
/// 'mutable'
/// 'auto'
/// [GNU] '__thread'
/// [C++11] 'thread_local'
/// [C11] '_Thread_local'
///
/// function-specifier:
/// 'inline'
/// 'virtual'
/// 'explicit'
///
/// typedef-name:
/// identifier
///
/// type-specifier:
/// simple-type-specifier
/// class-specifier
/// enum-specifier
/// elaborated-type-specifier
/// typename-specifier
/// cv-qualifier
///
/// simple-type-specifier:
/// '::'[opt] nested-name-specifier[opt] type-name
/// '::'[opt] nested-name-specifier 'template'
/// simple-template-id [TODO]
/// 'char'
/// 'wchar_t'
/// 'bool'
/// 'short'
/// 'int'
/// 'long'
/// 'signed'
/// 'unsigned'
/// 'float'
/// 'double'
/// 'void'
/// [GNU] typeof-specifier
/// [GNU] '_Complex'
/// [C++11] 'auto'
/// [GNU] '__auto_type'
/// [C++11] 'decltype' ( expression )
/// [C++1y] 'decltype' ( 'auto' )
///
/// type-name:
/// class-name
/// enum-name
/// typedef-name
///
/// elaborated-type-specifier:
/// class-key '::'[opt] nested-name-specifier[opt] identifier
/// class-key '::'[opt] nested-name-specifier[opt] 'template'[opt]
/// simple-template-id
/// 'enum' '::'[opt] nested-name-specifier[opt] identifier
///
/// enum-name:
/// identifier
///
/// enum-specifier:
/// 'enum' identifier[opt] '{' enumerator-list[opt] '}'
/// 'enum' identifier[opt] '{' enumerator-list ',' '}'
///
/// class-specifier:
/// class-head '{' member-specification[opt] '}'
///
/// class-head:
/// class-key identifier[opt] base-clause[opt]
/// class-key nested-name-specifier identifier base-clause[opt]
/// class-key nested-name-specifier[opt] simple-template-id
/// base-clause[opt]
///
/// class-key:
/// 'class'
/// 'struct'
/// 'union'
///
/// cv-qualifier:
/// 'const'
/// 'volatile'
/// [GNU] restrict
///
Parser::TPResult
Parser::isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,
bool *InvalidAsDeclSpec) {
auto IsPlaceholderSpecifier = [&] (TemplateIdAnnotation *TemplateId,
int Lookahead) {
// We have a placeholder-constraint (we check for 'auto' or 'decltype' to
// distinguish 'C<int>;' from 'C<int> auto c = 1;')
return TemplateId->Kind == TNK_Concept_template &&
GetLookAheadToken(Lookahead + 1).isOneOf(tok::kw_auto, tok::kw_decltype,
// If we have an identifier here, the user probably forgot the
// 'auto' in the placeholder constraint, e.g. 'C<int> x = 2;'
// This will be diagnosed nicely later, so disambiguate as a
// declaration.
tok::identifier);
};
switch (Tok.getKind()) {
case tok::identifier: {
// Check for need to substitute AltiVec __vector keyword
// for "vector" identifier.
if (TryAltiVecVectorToken())
return TPResult::True;
const Token &Next = NextToken();
// In 'foo bar', 'foo' is always a type name outside of Objective-C.
if (!getLangOpts().ObjC && Next.is(tok::identifier))
return TPResult::True;
if (Next.isNot(tok::coloncolon) && Next.isNot(tok::less)) {
// Determine whether this is a valid expression. If not, we will hit
// a parse error one way or another. In that case, tell the caller that
// this is ambiguous. Typo-correct to type and expression keywords and
// to types and identifiers, in order to try to recover from errors.
TentativeParseCCC CCC(Next);
switch (TryAnnotateName(&CCC)) {
case ANK_Error:
return TPResult::Error;
case ANK_TentativeDecl:
return TPResult::False;
case ANK_TemplateName:
// In C++17, this could be a type template for class template argument
// deduction. Try to form a type annotation for it. If we're in a
// template template argument, we'll undo this when checking the
// validity of the argument.
if (getLangOpts().CPlusPlus17) {
if (TryAnnotateTypeOrScopeToken())
return TPResult::Error;
if (Tok.isNot(tok::identifier))
break;
}
// A bare type template-name which can't be a template template
// argument is an error, and was probably intended to be a type.
return GreaterThanIsOperator ? TPResult::True : TPResult::False;
case ANK_Unresolved:
return InvalidAsDeclSpec ? TPResult::Ambiguous : TPResult::False;
case ANK_Success:
break;
}
assert(Tok.isNot(tok::identifier) &&
"TryAnnotateName succeeded without producing an annotation");
} else {
// This might possibly be a type with a dependent scope specifier and
// a missing 'typename' keyword. Don't use TryAnnotateName in this case,
// since it will annotate as a primary expression, and we want to use the
// "missing 'typename'" logic.
if (TryAnnotateTypeOrScopeToken())
return TPResult::Error;
// If annotation failed, assume it's a non-type.
// FIXME: If this happens due to an undeclared identifier, treat it as
// ambiguous.
if (Tok.is(tok::identifier))
return TPResult::False;
}
// We annotated this token as something. Recurse to handle whatever we got.
return isCXXDeclarationSpecifier(BracedCastResult, InvalidAsDeclSpec);
}
case tok::kw_typename: // typename T::type
// Annotate typenames and C++ scope specifiers. If we get one, just
// recurse to handle whatever we get.
if (TryAnnotateTypeOrScopeToken())
return TPResult::Error;
return isCXXDeclarationSpecifier(BracedCastResult, InvalidAsDeclSpec);
case tok::coloncolon: { // ::foo::bar
const Token &Next = NextToken();
if (Next.isOneOf(tok::kw_new, // ::new
tok::kw_delete)) // ::delete
return TPResult::False;
LLVM_FALLTHROUGH;
}
case tok::kw___super:
case tok::kw_decltype:
// Annotate typenames and C++ scope specifiers. If we get one, just
// recurse to handle whatever we get.
if (TryAnnotateTypeOrScopeToken())
return TPResult::Error;
return isCXXDeclarationSpecifier(BracedCastResult, InvalidAsDeclSpec);
// decl-specifier:
// storage-class-specifier
// type-specifier
// function-specifier
// 'friend'
// 'typedef'
// 'constexpr'
case tok::kw_friend:
case tok::kw_typedef:
case tok::kw_constexpr:
case tok::kw_consteval:
case tok::kw_constinit:
// storage-class-specifier
case tok::kw_register:
case tok::kw_static:
case tok::kw_extern:
case tok::kw_mutable:
case tok::kw_auto:
case tok::kw___thread:
case tok::kw_thread_local:
case tok::kw__Thread_local:
// function-specifier
case tok::kw_inline:
case tok::kw_virtual:
case tok::kw_explicit:
// Modules
case tok::kw___module_private__:
// Debugger support
case tok::kw___unknown_anytype:
// type-specifier:
// simple-type-specifier
// class-specifier
// enum-specifier
// elaborated-type-specifier
// typename-specifier
// cv-qualifier
// class-specifier
// elaborated-type-specifier
case tok::kw_class:
case tok::kw_struct:
case tok::kw_union:
case tok::kw___interface:
// enum-specifier
case tok::kw_enum:
// cv-qualifier
case tok::kw_const:
case tok::kw_volatile:
return TPResult::True;
// OpenCL address space qualifiers
case tok::kw_private:
if (!getLangOpts().OpenCL)
return TPResult::False;
LLVM_FALLTHROUGH;
case tok::kw___private:
case tok::kw___local:
case tok::kw___global:
case tok::kw___constant:
case tok::kw___generic:
// OpenCL access qualifiers
case tok::kw___read_only:
case tok::kw___write_only:
case tok::kw___read_write:
// OpenCL pipe
case tok::kw_pipe:
// GNU
case tok::kw_restrict:
case tok::kw__Complex:
case tok::kw___attribute:
case tok::kw___auto_type:
return TPResult::True;
// Microsoft
case tok::kw___declspec:
case tok::kw___cdecl:
case tok::kw___stdcall:
case tok::kw___fastcall:
case tok::kw___thiscall:
case tok::kw___regcall:
case tok::kw___vectorcall:
case tok::kw___w64:
case tok::kw___sptr:
case tok::kw___uptr:
case tok::kw___ptr64:
case tok::kw___ptr32:
case tok::kw___forceinline:
case tok::kw___unaligned:
case tok::kw__Nonnull:
case tok::kw__Nullable:
case tok::kw__Nullable_result:
case tok::kw__Null_unspecified:
case tok::kw___kindof:
return TPResult::True;
// Borland
case tok::kw___pascal:
return TPResult::True;
// AltiVec
case tok::kw___vector:
return TPResult::True;
case tok::annot_template_id: {
TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
// If lookup for the template-name found nothing, don't assume we have a
// definitive disambiguation result yet.
if ((TemplateId->hasInvalidName() ||
TemplateId->Kind == TNK_Undeclared_template) &&
InvalidAsDeclSpec) {
// 'template-id(' can be a valid expression but not a valid decl spec if
// the template-name is not declared, but we don't consider this to be a
// definitive disambiguation. In any other context, it's an error either
// way.
*InvalidAsDeclSpec = NextToken().is(tok::l_paren);
return TPResult::Ambiguous;
}
if (TemplateId->hasInvalidName())
return TPResult::Error;
if (IsPlaceholderSpecifier(TemplateId, /*Lookahead=*/0))
return TPResult::True;
if (TemplateId->Kind != TNK_Type_template)
return TPResult::False;
CXXScopeSpec SS;
AnnotateTemplateIdTokenAsType(SS);
assert(Tok.is(tok::annot_typename));
goto case_typename;
}
case tok::annot_cxxscope: // foo::bar or ::foo::bar, but already parsed
// We've already annotated a scope; try to annotate a type.
if (TryAnnotateTypeOrScopeToken())
return TPResult::Error;
if (!Tok.is(tok::annot_typename)) {
if (Tok.is(tok::annot_cxxscope) &&
NextToken().is(tok::annot_template_id)) {
TemplateIdAnnotation *TemplateId =
takeTemplateIdAnnotation(NextToken());
if (TemplateId->hasInvalidName()) {
if (InvalidAsDeclSpec) {
*InvalidAsDeclSpec = NextToken().is(tok::l_paren);
return TPResult::Ambiguous;
}
return TPResult::Error;
}
if (IsPlaceholderSpecifier(TemplateId, /*Lookahead=*/1))
return TPResult::True;
}
// If the next token is an identifier or a type qualifier, then this
// can't possibly be a valid expression either.
if (Tok.is(tok::annot_cxxscope) && NextToken().is(tok::identifier)) {
CXXScopeSpec SS;
Actions.RestoreNestedNameSpecifierAnnotation(Tok.getAnnotationValue(),
Tok.getAnnotationRange(),
SS);
if (SS.getScopeRep() && SS.getScopeRep()->isDependent()) {
RevertingTentativeParsingAction PA(*this);
ConsumeAnnotationToken();
ConsumeToken();
bool isIdentifier = Tok.is(tok::identifier);
TPResult TPR = TPResult::False;
if (!isIdentifier)
TPR = isCXXDeclarationSpecifier(BracedCastResult,
InvalidAsDeclSpec);
if (isIdentifier ||
TPR == TPResult::True || TPR == TPResult::Error)
return TPResult::Error;
if (InvalidAsDeclSpec) {
// We can't tell whether this is a missing 'typename' or a valid
// expression.
*InvalidAsDeclSpec = true;
return TPResult::Ambiguous;
} else {
// In MS mode, if InvalidAsDeclSpec is not provided, and the tokens
// are or the form *) or &) *> or &> &&>, this can't be an expression.
// The typename must be missing.
if (getLangOpts().MSVCCompat) {
if (((Tok.is(tok::amp) || Tok.is(tok::star)) &&
(NextToken().is(tok::r_paren) ||
NextToken().is(tok::greater))) ||
(Tok.is(tok::ampamp) && NextToken().is(tok::greater)))
return TPResult::True;
}
}
} else {
// Try to resolve the name. If it doesn't exist, assume it was
// intended to name a type and keep disambiguating.
switch (TryAnnotateName()) {
case ANK_Error:
return TPResult::Error;
case ANK_TentativeDecl:
return TPResult::False;
case ANK_TemplateName:
// In C++17, this could be a type template for class template
// argument deduction.
if (getLangOpts().CPlusPlus17) {
if (TryAnnotateTypeOrScopeToken())
return TPResult::Error;
if (Tok.isNot(tok::identifier))
break;
}
// A bare type template-name which can't be a template template
// argument is an error, and was probably intended to be a type.
// In C++17, this could be class template argument deduction.
return (getLangOpts().CPlusPlus17 || GreaterThanIsOperator)
? TPResult::True
: TPResult::False;
case ANK_Unresolved:
return InvalidAsDeclSpec ? TPResult::Ambiguous : TPResult::False;
case ANK_Success:
break;
}
// Annotated it, check again.
assert(Tok.isNot(tok::annot_cxxscope) ||
NextToken().isNot(tok::identifier));
return isCXXDeclarationSpecifier(BracedCastResult, InvalidAsDeclSpec);
}
}
return TPResult::False;
}
// If that succeeded, fallthrough into the generic simple-type-id case.
LLVM_FALLTHROUGH;
// The ambiguity resides in a simple-type-specifier/typename-specifier
// followed by a '('. The '(' could either be the start of:
//
// direct-declarator:
// '(' declarator ')'
//
// direct-abstract-declarator:
// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
// exception-specification[opt]
// '(' abstract-declarator ')'
//
// or part of a function-style cast expression:
//
// simple-type-specifier '(' expression-list[opt] ')'
//
// simple-type-specifier:
case tok::annot_typename:
case_typename:
// In Objective-C, we might have a protocol-qualified type.
if (getLangOpts().ObjC && NextToken().is(tok::less)) {
// Tentatively parse the protocol qualifiers.
RevertingTentativeParsingAction PA(*this);
ConsumeAnyToken(); // The type token
TPResult TPR = TryParseProtocolQualifiers();
bool isFollowedByParen = Tok.is(tok::l_paren);
bool isFollowedByBrace = Tok.is(tok::l_brace);
if (TPR == TPResult::Error)
return TPResult::Error;
if (isFollowedByParen)
return TPResult::Ambiguous;
if (getLangOpts().CPlusPlus11 && isFollowedByBrace)
return BracedCastResult;
return TPResult::True;
}
LLVM_FALLTHROUGH;
case tok::kw_char:
case tok::kw_wchar_t:
case tok::kw_char8_t:
case tok::kw_char16_t:
case tok::kw_char32_t:
case tok::kw_bool:
case tok::kw_short:
case tok::kw_int:
case tok::kw_long:
case tok::kw___int64:
case tok::kw___int128:
case tok::kw_signed:
case tok::kw_unsigned:
case tok::kw_half:
case tok::kw_float:
case tok::kw_double:
case tok::kw___bf16:
case tok::kw__Float16:
case tok::kw___float128:
case tok::kw_void:
case tok::annot_decltype:
#define GENERIC_IMAGE_TYPE(ImgType, Id) case tok::kw_##ImgType##_t:
#include "clang/Basic/OpenCLImageTypes.def"
if (NextToken().is(tok::l_paren))
return TPResult::Ambiguous;
// This is a function-style cast in all cases we disambiguate other than
// one:
// struct S {
// enum E : int { a = 4 }; // enum
// enum E : int { 4 }; // bit-field
// };
if (getLangOpts().CPlusPlus11 && NextToken().is(tok::l_brace))
return BracedCastResult;
if (isStartOfObjCClassMessageMissingOpenBracket())
return TPResult::False;
return TPResult::True;
// GNU typeof support.
case tok::kw_typeof: {
if (NextToken().isNot(tok::l_paren))
return TPResult::True;
RevertingTentativeParsingAction PA(*this);
TPResult TPR = TryParseTypeofSpecifier();
bool isFollowedByParen = Tok.is(tok::l_paren);
bool isFollowedByBrace = Tok.is(tok::l_brace);
if (TPR == TPResult::Error)
return TPResult::Error;
if (isFollowedByParen)
return TPResult::Ambiguous;
if (getLangOpts().CPlusPlus11 && isFollowedByBrace)
return BracedCastResult;
return TPResult::True;
}
// C++0x type traits support
case tok::kw___underlying_type:
return TPResult::True;
// C11 _Atomic
case tok::kw__Atomic:
return TPResult::True;
case tok::kw__ExtInt: {
if (NextToken().isNot(tok::l_paren))
return TPResult::Error;
RevertingTentativeParsingAction PA(*this);
ConsumeToken();
ConsumeParen();
if (!SkipUntil(tok::r_paren, StopAtSemi))
return TPResult::Error;
if (Tok.is(tok::l_paren))
return TPResult::Ambiguous;
if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace))
return BracedCastResult;
return TPResult::True;
}
default:
return TPResult::False;
}
}
bool Parser::isCXXDeclarationSpecifierAType() {
switch (Tok.getKind()) {
// typename-specifier
case tok::annot_decltype:
case tok::annot_template_id:
case tok::annot_typename:
case tok::kw_typeof:
case tok::kw___underlying_type:
return true;
// elaborated-type-specifier
case tok::kw_class:
case tok::kw_struct:
case tok::kw_union:
case tok::kw___interface:
case tok::kw_enum:
return true;
// simple-type-specifier
case tok::kw_char:
case tok::kw_wchar_t:
case tok::kw_char8_t:
case tok::kw_char16_t:
case tok::kw_char32_t:
case tok::kw_bool:
case tok::kw_short:
case tok::kw_int:
case tok::kw__ExtInt:
case tok::kw_long:
case tok::kw___int64:
case tok::kw___int128:
case tok::kw_signed:
case tok::kw_unsigned:
case tok::kw_half:
case tok::kw_float:
case tok::kw_double:
case tok::kw___bf16:
case tok::kw__Float16:
case tok::kw___float128:
case tok::kw_void:
case tok::kw___unknown_anytype:
case tok::kw___auto_type:
#define GENERIC_IMAGE_TYPE(ImgType, Id) case tok::kw_##ImgType##_t:
#include "clang/Basic/OpenCLImageTypes.def"
return true;
case tok::kw_auto:
return getLangOpts().CPlusPlus11;
case tok::kw__Atomic:
// "_Atomic foo"
return NextToken().is(tok::l_paren);
default:
return false;
}
}
/// [GNU] typeof-specifier:
/// 'typeof' '(' expressions ')'
/// 'typeof' '(' type-name ')'
///
Parser::TPResult Parser::TryParseTypeofSpecifier() {
assert(Tok.is(tok::kw_typeof) && "Expected 'typeof'!");
ConsumeToken();
assert(Tok.is(tok::l_paren) && "Expected '('");
// Parse through the parens after 'typeof'.
ConsumeParen();
if (!SkipUntil(tok::r_paren, StopAtSemi))
return TPResult::Error;
return TPResult::Ambiguous;
}
/// [ObjC] protocol-qualifiers:
//// '<' identifier-list '>'
Parser::TPResult Parser::TryParseProtocolQualifiers() {
assert(Tok.is(tok::less) && "Expected '<' for qualifier list");
ConsumeToken();
do {
if (Tok.isNot(tok::identifier))
return TPResult::Error;
ConsumeToken();
if (Tok.is(tok::comma)) {
ConsumeToken();
continue;
}
if (Tok.is(tok::greater)) {
ConsumeToken();
return TPResult::Ambiguous;
}
} while (false);
return TPResult::Error;
}
/// isCXXFunctionDeclarator - Disambiguates between a function declarator or
/// a constructor-style initializer, when parsing declaration statements.
/// Returns true for function declarator and false for constructor-style
/// initializer.
/// If during the disambiguation process a parsing error is encountered,
/// the function returns true to let the declaration parsing code handle it.
///
/// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
/// exception-specification[opt]
///
bool Parser::isCXXFunctionDeclarator(bool *IsAmbiguous) {
// C++ 8.2p1:
// The ambiguity arising from the similarity between a function-style cast and
// a declaration mentioned in 6.8 can also occur in the context of a
// declaration. In that context, the choice is between a function declaration
// with a redundant set of parentheses around a parameter name and an object
// declaration with a function-style cast as the initializer. Just as for the
// ambiguities mentioned in 6.8, the resolution is to consider any construct
// that could possibly be a declaration a declaration.
RevertingTentativeParsingAction PA(*this);
ConsumeParen();
bool InvalidAsDeclaration = false;
TPResult TPR = TryParseParameterDeclarationClause(&InvalidAsDeclaration);
if (TPR == TPResult::Ambiguous) {
if (Tok.isNot(tok::r_paren))
TPR = TPResult::False;
else {
const Token &Next = NextToken();
if (Next.isOneOf(tok::amp, tok::ampamp, tok::kw_const, tok::kw_volatile,
tok::kw_throw, tok::kw_noexcept, tok::l_square,
tok::l_brace, tok::kw_try, tok::equal, tok::arrow) ||
isCXX11VirtSpecifier(Next))
// The next token cannot appear after a constructor-style initializer,
// and can appear next in a function definition. This must be a function
// declarator.
TPR = TPResult::True;
else if (InvalidAsDeclaration)
// Use the absence of 'typename' as a tie-breaker.
TPR = TPResult::False;
}
}
if (IsAmbiguous && TPR == TPResult::Ambiguous)
*IsAmbiguous = true;
// In case of an error, let the declaration parsing code handle it.
return TPR != TPResult::False;
}
/// parameter-declaration-clause:
/// parameter-declaration-list[opt] '...'[opt]
/// parameter-declaration-list ',' '...'
///
/// parameter-declaration-list:
/// parameter-declaration
/// parameter-declaration-list ',' parameter-declaration
///
/// parameter-declaration:
/// attribute-specifier-seq[opt] decl-specifier-seq declarator attributes[opt]
/// attribute-specifier-seq[opt] decl-specifier-seq declarator attributes[opt]
/// '=' assignment-expression
/// attribute-specifier-seq[opt] decl-specifier-seq abstract-declarator[opt]
/// attributes[opt]
/// attribute-specifier-seq[opt] decl-specifier-seq abstract-declarator[opt]
/// attributes[opt] '=' assignment-expression
///
Parser::TPResult
Parser::TryParseParameterDeclarationClause(bool *InvalidAsDeclaration,
bool VersusTemplateArgument) {
if (Tok.is(tok::r_paren))
return TPResult::Ambiguous;
// parameter-declaration-list[opt] '...'[opt]
// parameter-declaration-list ',' '...'
//
// parameter-declaration-list:
// parameter-declaration
// parameter-declaration-list ',' parameter-declaration
//
while (1) {
// '...'[opt]
if (Tok.is(tok::ellipsis)) {
ConsumeToken();
if (Tok.is(tok::r_paren))
return TPResult::True; // '...)' is a sign of a function declarator.
else
return TPResult::False;
}
// An attribute-specifier-seq here is a sign of a function declarator.
if (isCXX11AttributeSpecifier(/*Disambiguate*/false,
/*OuterMightBeMessageSend*/true))
return TPResult::True;
ParsedAttributes attrs(AttrFactory);
MaybeParseMicrosoftAttributes(attrs);
// decl-specifier-seq
// A parameter-declaration's initializer must be preceded by an '=', so
// decl-specifier-seq '{' is not a parameter in C++11.
TPResult TPR = isCXXDeclarationSpecifier(TPResult::False,
InvalidAsDeclaration);
// A declaration-specifier (not followed by '(' or '{') means this can't be
// an expression, but it could still be a template argument.
if (TPR != TPResult::Ambiguous &&
!(VersusTemplateArgument && TPR == TPResult::True))
return TPR;
bool SeenType = false;
do {
SeenType |= isCXXDeclarationSpecifierAType();
if (TryConsumeDeclarationSpecifier() == TPResult::Error)
return TPResult::Error;
// If we see a parameter name, this can't be a template argument.
if (SeenType && Tok.is(tok::identifier))
return TPResult::True;
TPR = isCXXDeclarationSpecifier(TPResult::False,
InvalidAsDeclaration);
if (TPR == TPResult::Error)
return TPR;
// Two declaration-specifiers means this can't be an expression.
if (TPR == TPResult::True && !VersusTemplateArgument)
return TPR;
} while (TPR != TPResult::False);
// declarator
// abstract-declarator[opt]
TPR = TryParseDeclarator(true/*mayBeAbstract*/);
if (TPR != TPResult::Ambiguous)
return TPR;
// [GNU] attributes[opt]
if (Tok.is(tok::kw___attribute))
return TPResult::True;
// If we're disambiguating a template argument in a default argument in
// a class definition versus a parameter declaration, an '=' here
// disambiguates the parse one way or the other.
// If this is a parameter, it must have a default argument because
// (a) the previous parameter did, and
// (b) this must be the first declaration of the function, so we can't
// inherit any default arguments from elsewhere.
// FIXME: If we reach a ')' without consuming any '>'s, then this must
// also be a function parameter (that's missing its default argument).
if (VersusTemplateArgument)
return Tok.is(tok::equal) ? TPResult::True : TPResult::False;
if (Tok.is(tok::equal)) {
// '=' assignment-expression
// Parse through assignment-expression.
if (!SkipUntil(tok::comma, tok::r_paren, StopAtSemi | StopBeforeMatch))
return TPResult::Error;
}
if (Tok.is(tok::ellipsis)) {
ConsumeToken();
if (Tok.is(tok::r_paren))
return TPResult::True; // '...)' is a sign of a function declarator.
else
return TPResult::False;
}
if (!TryConsumeToken(tok::comma))
break;
}
return TPResult::Ambiguous;
}
/// TryParseFunctionDeclarator - We parsed a '(' and we want to try to continue
/// parsing as a function declarator.
/// If TryParseFunctionDeclarator fully parsed the function declarator, it will
/// return TPResult::Ambiguous, otherwise it will return either False() or
/// Error().
///
/// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
/// exception-specification[opt]
///
/// exception-specification:
/// 'throw' '(' type-id-list[opt] ')'
///
Parser::TPResult Parser::TryParseFunctionDeclarator() {
// The '(' is already parsed.
TPResult TPR = TryParseParameterDeclarationClause();
if (TPR == TPResult::Ambiguous && Tok.isNot(tok::r_paren))
TPR = TPResult::False;
if (TPR == TPResult::False || TPR == TPResult::Error)
return TPR;
// Parse through the parens.
if (!SkipUntil(tok::r_paren, StopAtSemi))
return TPResult::Error;
// cv-qualifier-seq
while (Tok.isOneOf(tok::kw_const, tok::kw_volatile, tok::kw___unaligned,
tok::kw_restrict))
ConsumeToken();
// ref-qualifier[opt]
if (Tok.isOneOf(tok::amp, tok::ampamp))
ConsumeToken();
// exception-specification
if (Tok.is(tok::kw_throw)) {
ConsumeToken();
if (Tok.isNot(tok::l_paren))
return TPResult::Error;
// Parse through the parens after 'throw'.
ConsumeParen();
if (!SkipUntil(tok::r_paren, StopAtSemi))
return TPResult::Error;
}
if (Tok.is(tok::kw_noexcept)) {
ConsumeToken();
// Possibly an expression as well.
if (Tok.is(tok::l_paren)) {
// Find the matching rparen.
ConsumeParen();
if (!SkipUntil(tok::r_paren, StopAtSemi))
return TPResult::Error;
}
}
return TPResult::Ambiguous;
}
/// '[' constant-expression[opt] ']'
///
Parser::TPResult Parser::TryParseBracketDeclarator() {
ConsumeBracket();
// A constant-expression cannot begin with a '{', but the
// expr-or-braced-init-list of a postfix-expression can.
if (Tok.is(tok::l_brace))
return TPResult::False;
if (!SkipUntil(tok::r_square, tok::comma, StopAtSemi | StopBeforeMatch))
return TPResult::Error;
// If we hit a comma before the ']', this is not a constant-expression,
// but might still be the expr-or-braced-init-list of a postfix-expression.
if (Tok.isNot(tok::r_square))
return TPResult::False;
ConsumeBracket();
return TPResult::Ambiguous;
}
/// Determine whether we might be looking at the '<' template-argument-list '>'
/// of a template-id or simple-template-id, rather than a less-than comparison.
/// This will often fail and produce an ambiguity, but should never be wrong
/// if it returns True or False.
Parser::TPResult Parser::isTemplateArgumentList(unsigned TokensToSkip) {
if (!TokensToSkip) {
if (Tok.isNot(tok::less))
return TPResult::False;
if (NextToken().is(tok::greater))
return TPResult::True;
}
RevertingTentativeParsingAction PA(*this);
while (TokensToSkip) {
ConsumeAnyToken();
--TokensToSkip;
}
if (!TryConsumeToken(tok::less))
return TPResult::False;
// We can't do much to tell an expression apart from a template-argument,
// but one good distinguishing factor is that a "decl-specifier" not
// followed by '(' or '{' can't appear in an expression.
bool InvalidAsTemplateArgumentList = false;
if (isCXXDeclarationSpecifier(TPResult::False,
&InvalidAsTemplateArgumentList) ==
TPResult::True)
return TPResult::True;
if (InvalidAsTemplateArgumentList)
return TPResult::False;
// FIXME: In many contexts, X<thing1, Type> can only be a
// template-argument-list. But that's not true in general:
//
// using b = int;
// void f() {
// int a = A<B, b, c = C>D; // OK, declares b, not a template-id.
//
// X<Y<0, int> // ', int>' might be end of X's template argument list
//
// We might be able to disambiguate a few more cases if we're careful.
// A template-argument-list must be terminated by a '>'.
if (SkipUntil({tok::greater, tok::greatergreater, tok::greatergreatergreater},
StopAtSemi | StopBeforeMatch))
return TPResult::Ambiguous;
return TPResult::False;
}
/// Determine whether we might be looking at the '(' of a C++20 explicit(bool)
/// in an earlier language mode.
Parser::TPResult Parser::isExplicitBool() {
assert(Tok.is(tok::l_paren) && "expected to be looking at a '(' token");
RevertingTentativeParsingAction PA(*this);
ConsumeParen();
// We can only have 'explicit' on a constructor, conversion function, or
// deduction guide. The declarator of a deduction guide cannot be
// parenthesized, so we know this isn't a deduction guide. So the only
// thing we need to check for is some number of parens followed by either
// the current class name or 'operator'.
while (Tok.is(tok::l_paren))
ConsumeParen();
if (TryAnnotateOptionalCXXScopeToken())
return TPResult::Error;
// Class-scope constructor and conversion function names can't really be
// qualified, but we get better diagnostics if we assume they can be.
CXXScopeSpec SS;
if (Tok.is(tok::annot_cxxscope)) {
Actions.RestoreNestedNameSpecifierAnnotation(Tok.getAnnotationValue(),
Tok.getAnnotationRange(),
SS);
ConsumeAnnotationToken();
}
// 'explicit(operator' might be explicit(bool) or the declaration of a
// conversion function, but it's probably a conversion function.
if (Tok.is(tok::kw_operator))
return TPResult::Ambiguous;
// If this can't be a constructor name, it can only be explicit(bool).
if (Tok.isNot(tok::identifier) && Tok.isNot(tok::annot_template_id))
return TPResult::True;
if (!Actions.isCurrentClassName(Tok.is(tok::identifier)
? *Tok.getIdentifierInfo()
: *takeTemplateIdAnnotation(Tok)->Name,
getCurScope(), &SS))
return TPResult::True;
// Formally, we must have a right-paren after the constructor name to match
// the grammar for a constructor. But clang permits a parenthesized
// constructor declarator, so also allow a constructor declarator to follow
// with no ')' token after the constructor name.
if (!NextToken().is(tok::r_paren) &&
!isConstructorDeclarator(/*Unqualified=*/SS.isEmpty(),
/*DeductionGuide=*/false))
return TPResult::True;
// Might be explicit(bool) or a parenthesized constructor name.
return TPResult::Ambiguous;
}