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[Clang] Fix parsing of (auto(x)).

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Allow auto(x) to appear in a parenthesis
expression.

The pattern (auto( can appear as part of a declarator,
so the parser is modified to avoid the ambiguity,
in a way consistent with the proposed resolution to CWG1223.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D149276
This commit is contained in:
Corentin Jabot 2023-04-26 20:09:13 +02:00
parent 55acb70b21
commit 1b0ba1c12f
9 changed files with 203 additions and 30 deletions
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2
clang/docs/ReleaseNotes.rst
View File

@ -468,6 +468,8 @@ Bug Fixes to C++ Support
- Some predefined expressions are now treated as string literals in MSVC
compatibility mode.
(`#114 <https://github.com/llvm/llvm-project/issues/114>`_)
- Fix parsing of `auto(x)`, when it is surrounded by parentheses.
(`#62494 <https://github.com/llvm/llvm-project/issues/62494>`_)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^

12
clang/include/clang/Parse/Parser.h
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@ -2523,10 +2523,10 @@ private:
enum TentativeCXXTypeIdContext {
TypeIdInParens,
TypeIdUnambiguous,
TypeIdAsTemplateArgument
TypeIdAsTemplateArgument,
TypeIdInTrailingReturnType,
};
/// isTypeIdInParens - Assumes that a '(' was parsed and now we want to know
/// whether the parens contain an expression or a type-id.
/// Returns true for a type-id and false for an expression.
@ -2654,14 +2654,16 @@ private:
TPResult TryParseProtocolQualifiers();
TPResult TryParsePtrOperatorSeq();
TPResult TryParseOperatorId();
TPResult TryParseInitDeclaratorList();
TPResult TryParseInitDeclaratorList(bool MayHaveTrailingReturnType = false);
TPResult TryParseDeclarator(bool mayBeAbstract, bool mayHaveIdentifier = true,
bool mayHaveDirectInit = false);
bool mayHaveDirectInit = false,
bool mayHaveTrailingReturnType = false);
TPResult TryParseParameterDeclarationClause(
bool *InvalidAsDeclaration = nullptr, bool VersusTemplateArg = false,
ImplicitTypenameContext AllowImplicitTypename =
ImplicitTypenameContext::No);
TPResult TryParseFunctionDeclarator();
TPResult TryParseFunctionDeclarator(bool MayHaveTrailingReturnType = false);
bool NameAfterArrowIsNonType();
TPResult TryParseBracketDeclarator();
TPResult TryConsumeDeclarationSpecifier();

3
clang/lib/Parse/ParseDecl.cpp
View File

@ -6502,7 +6502,8 @@ void Parser::ParseDirectDeclarator(Declarator &D) {
// that it's an initializer instead.
if (D.mayOmitIdentifier() && D.mayBeFollowedByCXXDirectInit()) {
RevertingTentativeParsingAction PA(*this);
if (TryParseDeclarator(true, D.mayHaveIdentifier(), true) ==
if (TryParseDeclarator(true, D.mayHaveIdentifier(), true,
D.getDeclSpec().getTypeSpecType() == TST_auto) ==
TPResult::False) {
D.SetIdentifier(nullptr, Tok.getLocation());
goto PastIdentifier;

99
clang/lib/Parse/ParseTentative.cpp
View File

@ -262,6 +262,7 @@ Parser::TPResult Parser::TryConsumeDeclarationSpecifier() {
/// attribute-specifier-seqopt type-specifier-seq declarator
///
Parser::TPResult Parser::TryParseSimpleDeclaration(bool AllowForRangeDecl) {
bool DeclSpecifierIsAuto = Tok.is(tok::kw_auto);
if (TryConsumeDeclarationSpecifier() == TPResult::Error)
return TPResult::Error;
@ -277,7 +278,8 @@ Parser::TPResult Parser::TryParseSimpleDeclaration(bool AllowForRangeDecl) {
assert(TPR == TPResult::False);
}
TPResult TPR = TryParseInitDeclaratorList();
TPResult TPR = TryParseInitDeclaratorList(
/*mayHaveTrailingReturnType=*/DeclSpecifierIsAuto);
if (TPR != TPResult::Ambiguous)
return TPR;
@ -314,10 +316,15 @@ Parser::TPResult Parser::TryParseSimpleDeclaration(bool AllowForRangeDecl) {
/// '{' initializer-list ','[opt] '}'
/// '{' '}'
///
Parser::TPResult Parser::TryParseInitDeclaratorList() {
Parser::TPResult
Parser::TryParseInitDeclaratorList(bool MayHaveTrailingReturnType) {
while (true) {
// declarator
TPResult TPR = TryParseDeclarator(false/*mayBeAbstract*/);
TPResult TPR = TryParseDeclarator(
/*mayBeAbstract=*/false,
/*mayHaveIdentifier=*/true,
/*mayHaveDirectInit=*/false,
/*mayHaveTrailingReturnType=*/MayHaveTrailingReturnType);
if (TPR != TPResult::Ambiguous)
return TPR;
@ -532,13 +539,18 @@ Parser::isCXXConditionDeclarationOrInitStatement(bool CanBeInitStatement,
RevertingTentativeParsingAction PA(*this);
// FIXME: A tag definition unambiguously tells us this is an init-statement.
bool MayHaveTrailingReturnType = Tok.is(tok::kw_auto);
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*/)))
if (State.update(TryParseDeclarator(
/*mayBeAbstract=*/false,
/*mayHaveIdentifier=*/true,
/*mayHaveDirectInit=*/false,
/*mayHaveTrailingReturnType=*/MayHaveTrailingReturnType)))
return State.result();
// Attributes, asm label, or an initializer imply this is not an expression.
@ -623,13 +635,16 @@ bool Parser::isCXXTypeId(TentativeCXXTypeIdContext Context, bool &isAmbiguous) {
// We need tentative parsing...
RevertingTentativeParsingAction PA(*this);
bool MayHaveTrailingReturnType = Tok.is(tok::kw_auto);
// type-specifier-seq
TryConsumeDeclarationSpecifier();
assert(Tok.is(tok::l_paren) && "Expected '('");
// declarator
TPR = TryParseDeclarator(true/*mayBeAbstract*/, false/*mayHaveIdentifier*/);
TPR = TryParseDeclarator(true /*mayBeAbstract*/, false /*mayHaveIdentifier*/,
/*mayHaveDirectInit=*/false,
MayHaveTrailingReturnType);
// In case of an error, let the declaration parsing code handle it.
if (TPR == TPResult::Error)
@ -658,6 +673,9 @@ bool Parser::isCXXTypeId(TentativeCXXTypeIdContext Context, bool &isAmbiguous) {
TPR = TPResult::True;
isAmbiguous = true;
} else if (Context == TypeIdInTrailingReturnType) {
TPR = TPResult::True;
isAmbiguous = true;
} else
TPR = TPResult::False;
}
@ -1042,7 +1060,8 @@ Parser::TPResult Parser::TryParseOperatorId() {
///
Parser::TPResult Parser::TryParseDeclarator(bool mayBeAbstract,
bool mayHaveIdentifier,
bool mayHaveDirectInit) {
bool mayHaveDirectInit,
bool mayHaveTrailingReturnType) {
// declarator:
// direct-declarator
// ptr-operator declarator
@ -1084,7 +1103,7 @@ Parser::TPResult Parser::TryParseDeclarator(bool mayBeAbstract,
ImplicitTypenameContext::No))) { // 'int(int)' is a function.
// '(' parameter-declaration-clause ')' cv-qualifier-seq[opt]
// exception-specification[opt]
TPResult TPR = TryParseFunctionDeclarator();
TPResult TPR = TryParseFunctionDeclarator(mayHaveTrailingReturnType);
if (TPR != TPResult::Ambiguous)
return TPR;
} else {
@ -1123,7 +1142,7 @@ Parser::TPResult Parser::TryParseDeclarator(bool mayBeAbstract,
// direct-declarator '(' parameter-declaration-clause ')'
// cv-qualifier-seq[opt] exception-specification[opt]
ConsumeParen();
TPR = TryParseFunctionDeclarator();
TPR = TryParseFunctionDeclarator(mayHaveTrailingReturnType);
} else if (Tok.is(tok::l_square)) {
// direct-declarator '[' constant-expression[opt] ']'
// direct-abstract-declarator[opt] '[' constant-expression[opt] ']'
@ -1390,6 +1409,16 @@ Parser::isCXXDeclarationSpecifier(ImplicitTypenameContext AllowImplicitTypename,
return isCXXDeclarationSpecifier(ImplicitTypenameContext::Yes,
BracedCastResult, InvalidAsDeclSpec);
case tok::kw_auto: {
if (!getLangOpts().CPlusPlus23)
return TPResult::True;
if (NextToken().is(tok::l_brace))
return TPResult::False;
if (NextToken().is(tok::l_paren))
return TPResult::Ambiguous;
return TPResult::True;
}
case tok::coloncolon: { // ::foo::bar
const Token &Next = NextToken();
if (Next.isOneOf(tok::kw_new, // ::new
@ -1423,7 +1452,6 @@ Parser::isCXXDeclarationSpecifier(ImplicitTypenameContext AllowImplicitTypename,
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:
@ -2002,6 +2030,7 @@ Parser::TPResult Parser::TryParseParameterDeclarationClause(
return TPR;
bool SeenType = false;
bool DeclarationSpecifierIsAuto = Tok.is(tok::kw_auto);
do {
SeenType |= isCXXDeclarationSpecifierAType();
if (TryConsumeDeclarationSpecifier() == TPResult::Error)
@ -2023,7 +2052,11 @@ Parser::TPResult Parser::TryParseParameterDeclarationClause(
// declarator
// abstract-declarator[opt]
TPR = TryParseDeclarator(true/*mayBeAbstract*/);
TPR = TryParseDeclarator(
/*mayBeAbstract=*/true,
/*mayHaveIdentifier=*/true,
/*mayHaveDirectInit=*/false,
/*mayHaveTrailingReturnType=*/DeclarationSpecifierIsAuto);
if (TPR != TPResult::Ambiguous)
return TPR;
@ -2077,7 +2110,8 @@ Parser::TPResult Parser::TryParseParameterDeclarationClause(
/// exception-specification:
/// 'throw' '(' type-id-list[opt] ')'
///
Parser::TPResult Parser::TryParseFunctionDeclarator() {
Parser::TPResult
Parser::TryParseFunctionDeclarator(bool MayHaveTrailingReturnType) {
// The '(' is already parsed.
TPResult TPR = TryParseParameterDeclarationClause();
@ -2122,7 +2156,50 @@ Parser::TPResult Parser::TryParseFunctionDeclarator() {
}
}
// attribute-specifier-seq
if (!TrySkipAttributes())
return TPResult::Ambiguous;
// trailing-return-type
if (Tok.is(tok::arrow) && MayHaveTrailingReturnType) {
if (TPR == TPResult::True)
return TPR;
ConsumeToken();
if (Tok.is(tok::identifier) && NameAfterArrowIsNonType()) {
return TPResult::False;
}
if (isCXXTypeId(TentativeCXXTypeIdContext::TypeIdInTrailingReturnType))
return TPResult::True;
}
return TPResult::Ambiguous;
}
// When parsing an identifier after an arrow it may be a member expression,
// in which case we should not annotate it as an independant expression
// so we just lookup that name, if it's not a type the construct is not
// a function declaration.
bool Parser::NameAfterArrowIsNonType() {
assert(Tok.is(tok::identifier));
Token Next = NextToken();
if (Next.is(tok::coloncolon))
return false;
IdentifierInfo *Name = Tok.getIdentifierInfo();
SourceLocation NameLoc = Tok.getLocation();
CXXScopeSpec SS;
TentativeParseCCC CCC(Next);
Sema::NameClassification Classification =
Actions.ClassifyName(getCurScope(), SS, Name, NameLoc, Next, &CCC);
switch (Classification.getKind()) {
case Sema::NC_OverloadSet:
case Sema::NC_NonType:
case Sema::NC_VarTemplate:
case Sema::NC_FunctionTemplate:
return true;
default:
break;
}
return false;
}
/// '[' constant-expression[opt] ']'

2
clang/lib/Parse/Parser.cpp
View File

@ -1947,7 +1947,7 @@ bool Parser::TryAnnotateTypeOrScopeToken(
assert((Tok.is(tok::identifier) || Tok.is(tok::coloncolon) ||
Tok.is(tok::kw_typename) || Tok.is(tok::annot_cxxscope) ||
Tok.is(tok::kw_decltype) || Tok.is(tok::annot_template_id) ||
Tok.is(tok::kw___super)) &&
Tok.is(tok::kw___super) || Tok.is(tok::kw_auto)) &&
"Cannot be a type or scope token!");
if (Tok.is(tok::kw_typename)) {

49
clang/test/CXX/drs/dr12xx.cpp
View File

@ -31,6 +31,55 @@ namespace dr1213 { // dr1213: 7
#endif
}
#if __cplusplus >= 201103L
namespace dr1223 { // dr1227: yes open
struct M;
template <typename T>
struct V;
struct S {
S* operator()();
int N;
int M;
#if __cplusplus > 202002L
template <typename T>
static constexpr auto V = 0;
void f(char);
void f(int);
void mem(S s) {
auto(s)()->M; //expected-warning {{expression result unused}}
auto(s)()->V<int>; //expected-warning {{expression result unused}}
auto(s)()->f(0);
}
#endif
};
void f(S s) {
{
#if __cplusplus > 202002L
auto(s)()->N; //expected-warning {{expression result unused}}
#endif
auto(s)()->M;
}
{
S(s)()->N; //expected-warning {{expression result unused}}
S(s)()->M; //expected-warning {{expression result unused}}
}
}
struct A {
A(int*);
A *operator()();
};
typedef struct BB { int C[2]; } *B, C;
void g() {
A a(B ()->C);
A b(auto ()->C);
static_assert(sizeof(B ()->C[1] == sizeof(int)), "");
sizeof(auto () -> C[1]); // expected-error{{function cannot return array type 'C[1]'}}
}
}
#endif
#if __cplusplus >= 201103L
namespace dr1227 { // dr1227: yes
template <class T> struct A { using X = typename T::X; }; // expected-error {{type 'int' cannot be used prior to '::' because it has no members}}

8
clang/test/Parser/cxx-ambig-decl-expr.cpp
View File

@ -42,3 +42,11 @@ void arr() {
int (*_Atomic atomic_ptr_to_int);
*atomic_ptr_to_int = 42;
}
namespace function_with_trailing {
struct Foo {
Foo(int);
};
template <typename T> void bar()
{ Foo _(T::method()->mem()); }
}

18
clang/test/Parser/cxx1z-decomposition.cpp
View File

@ -1,4 +1,5 @@
// RUN: %clang_cc1 -std=c++17 %s -verify -fcxx-exceptions
// RUN: %clang_cc1 -std=c++17 %s -verify=expected,cxx17 -fcxx-exceptions
// RUN: %clang_cc1 -std=c++2b %s -verify=expected,cxx2b -fcxx-exceptions
// RUN: not %clang_cc1 -std=c++17 %s -emit-llvm-only -fcxx-exceptions
struct S { int a, b, c; };
@ -30,7 +31,7 @@ namespace ForRangeDecl {
namespace OtherDecl {
// A parameter-declaration is not a simple-declaration.
// This parses as an array declaration.
void f(auto [a, b, c]); // expected-error {{'auto' not allowed in function prototype}} expected-error {{'a'}}
void f(auto [a, b, c]); // cxx17-error {{'auto' not allowed in function prototype}} expected-error {{'a'}}
void g() {
// A condition is allowed as a Clang extension.
@ -57,7 +58,7 @@ namespace OtherDecl {
namespace GoodSpecifiers {
void f() {
int n[1];
const volatile auto &[a] = n;
const volatile auto &[a] = n; // cxx2b-warning {{volatile qualifier in structured binding declaration is deprecated}}
}
}
@ -67,8 +68,8 @@ namespace BadSpecifiers {
struct S { int n; } s;
void f() {
// storage-class-specifiers
static auto &[a] = n; // expected-warning {{declared 'static' is a C++20 extension}}
thread_local auto &[b] = n; // expected-warning {{declared 'thread_local' is a C++20 extension}}
static auto &[a] = n; // cxx17-warning {{declared 'static' is a C++20 extension}}
thread_local auto &[b] = n; // cxx17-warning {{declared 'thread_local' is a C++20 extension}}
extern auto &[c] = n; // expected-error {{cannot be declared 'extern'}} expected-error {{declaration of block scope identifier with linkage cannot have an initializer}}
struct S {
mutable auto &[d] = n; // expected-error {{not permitted in this context}}
@ -85,16 +86,19 @@ namespace BadSpecifiers {
}
static constexpr inline thread_local auto &[j1] = n; // expected-error {{cannot be declared with 'constexpr inline' specifiers}}
static thread_local auto &[j2] = n; // expected-warning {{declared with 'static thread_local' specifiers is a C++20 extension}}
static thread_local auto &[j2] = n; // cxx17-warning {{declared with 'static thread_local' specifiers is a C++20 extension}}
inline auto &[k] = n; // expected-error {{cannot be declared 'inline'}}
const int K = 5;
auto ([c]) = s; // expected-error {{decomposition declaration cannot be declared with parentheses}}
void g() {
// defining-type-specifiers other than cv-qualifiers and 'auto'
S [a] = s; // expected-error {{cannot be declared with type 'S'}}
decltype(auto) [b] = s; // expected-error {{cannot be declared with type 'decltype(auto)'}}
auto ([c]) = s; // expected-error {{cannot be declared with parentheses}}
auto ([c2]) = s; // cxx17-error {{decomposition declaration cannot be declared with parenthese}} \
// cxx2b-error {{use of undeclared identifier 'c2'}} \
// cxx2b-error {{expected body of lambda expression}} \
// FIXME: This error is not very good.
auto [d]() = s; // expected-error {{expected ';'}} expected-error {{expected expression}}

38
clang/test/Parser/cxx2b-auto-x.cpp
View File

@ -18,7 +18,37 @@ struct looks_like_declaration {
using T = looks_like_declaration *;
void f() { T(&a)->n = 1; }
// FIXME: They should be deemed expressions without breaking function pointer
// parameter declarations with trailing return types.
// void g() { auto(&a)->n = 0; }
// void h() { auto{&a}->n = 0; }
void g() { auto(&a)->n = 0; } // cxx23-warning {{before C++23}} \
// cxx20-error {{declaration of variable 'a' with deduced type 'auto (&)' requires an initializer}} \
// cxx20-error {{expected ';' at end of declaration}}
void h() { auto{&a}->n = 0; } // cxx23-warning {{before C++23}} \
// cxx20-error {{expected unqualified-id}} \
// cxx20-error {{expected expression}}
void e(auto (*p)(int y) -> decltype(y)) {}
struct M;
struct S{
S operator()();
S* operator->();
int N;
int M;
} s; // expected-note {{here}}
void test() {
auto(s)()->N; // cxx23-warning {{expression result unused}} \
// cxx23-warning {{before C++23}} \
// cxx20-error {{unknown type name 'N'}}
auto(s)()->M; // expected-error {{redefinition of 's' as different kind of symbol}}
}
void test_paren() {
int a = (auto(0)); // cxx23-warning {{before C++23}} \
// cxx20-error {{expected expression}} \
// cxx20-error {{expected ')'}} \
// cxx20-note {{to match this '('}}
int b = (auto{0}); // cxx23-warning {{before C++23}} \
// cxx20-error {{expected expression}} \
// cxx20-error {{expected ')'}} \
// cxx20-note {{to match this '('}}
}