Author: Younan Zhang Date: 2024-12-13T15:50:41+08:00 New Revision: 28c3bf5c6dad0974f9f15b58afd0935c0c6cb3e4
URL: https://github.com/llvm/llvm-project/commit/28c3bf5c6dad0974f9f15b58afd0935c0c6cb3e4 DIFF: https://github.com/llvm/llvm-project/commit/28c3bf5c6dad0974f9f15b58afd0935c0c6cb3e4.diff LOG: [Clang][Parser] Add a warning to ambiguous uses of T...[N] types (#116332) `void f(T... [N])` is no longer treated as a function with a parameter of pack expansion type after the implementation of the pack indexing feature. This patch introduces a warning to clarify such cases while maintaining it as a pack indexing type in all language modes. Closes https://github.com/llvm/llvm-project/issues/115222 Added: Modified: clang/include/clang/Basic/DiagnosticParseKinds.td clang/lib/Parse/ParseExprCXX.cpp clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp clang/test/Parser/cxx0x-decl.cpp clang/test/Parser/cxx2c-pack-indexing.cpp clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp Removed: ################################################################################ diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td index 9fa8d5901bd0a5..86fcae209c40db 100644 --- a/clang/include/clang/Basic/DiagnosticParseKinds.td +++ b/clang/include/clang/Basic/DiagnosticParseKinds.td @@ -721,6 +721,9 @@ def warn_empty_init_statement : Warning< "has no effect">, InGroup<EmptyInitStatement>, DefaultIgnore; def err_keyword_as_parameter : Error < "invalid parameter name: '%0' is a keyword">; +def warn_pre_cxx26_ambiguous_pack_indexing_type : Warning< + "%0 is no longer a pack expansion but a pack " + "indexing type; add a name to specify a pack expansion">, InGroup<CXXPre26Compat>; // C++ derived classes def err_dup_virtual : Error<"duplicate 'virtual' in base specifier">; diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp index 03a58048e53a94..33a90e0cb8a42a 100644 --- a/clang/lib/Parse/ParseExprCXX.cpp +++ b/clang/lib/Parse/ParseExprCXX.cpp @@ -238,7 +238,8 @@ bool Parser::ParseOptionalCXXScopeSpecifier( else if (!HasScopeSpecifier && Tok.is(tok::identifier) && GetLookAheadToken(1).is(tok::ellipsis) && - GetLookAheadToken(2).is(tok::l_square)) { + GetLookAheadToken(2).is(tok::l_square) && + !GetLookAheadToken(3).is(tok::r_square)) { SourceLocation Start = Tok.getLocation(); DeclSpec DS(AttrFactory); SourceLocation CCLoc; @@ -253,6 +254,19 @@ bool Parser::ParseOptionalCXXScopeSpecifier( if (Type.isNull()) return false; + // C++ [cpp23.dcl.dcl-2]: + // Previously, T...[n] would declare a pack of function parameters. + // T...[n] is now a pack-index-specifier. [...] Valid C++ 2023 code that + // declares a pack of parameters without specifying a declarator-id + // becomes ill-formed. + // + // However, we still treat it as a pack indexing type because the use case + // is fairly rare, to ensure semantic consistency given that we have + // backported this feature to pre-C++26 modes. + if (!Tok.is(tok::coloncolon) && !getLangOpts().CPlusPlus26 && + getCurScope()->isFunctionDeclarationScope()) + Diag(Start, diag::warn_pre_cxx26_ambiguous_pack_indexing_type) << Type; + if (!TryConsumeToken(tok::coloncolon, CCLoc)) { AnnotateExistingIndexedTypeNamePack(ParsedType::make(Type), Start, EndLoc); diff --git a/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp b/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp index dbb6e60d9b93d7..a633c108bc22cd 100644 --- a/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp +++ b/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp @@ -57,9 +57,11 @@ template<typename T> void b(T[] ...); template<typename T> -void c(T ... []); // expected-error {{expected expression}} \ - // expected-error {{'T' does not refer to the name of a parameter pack}} \ - // expected-warning {{pack indexing is a C++2c extension}} +void c(T ... []); // expected-error {{type 'T[]' of function parameter pack does not contain any unexpanded parameter packs}} + +// A function that takes pointers to each type T as arguments, after any decay. +template <typename ...T> +void g(T...[]); template<typename T> void d(T ... x[]); // expected-error{{type 'T[]' of function parameter pack does not contain any unexpanded parameter packs}} diff --git a/clang/test/Parser/cxx0x-decl.cpp b/clang/test/Parser/cxx0x-decl.cpp index a0b3266c738ff5..6d4f16c6f533e8 100644 --- a/clang/test/Parser/cxx0x-decl.cpp +++ b/clang/test/Parser/cxx0x-decl.cpp @@ -214,6 +214,7 @@ struct MemberComponentOrder : Base { void NoMissingSemicolonHere(struct S [3]); template<int ...N> void NoMissingSemicolonHereEither(struct S... [N]); +// expected-warning@-1 {{'S...[N]' is no longer a pack expansion but a pack indexing type; add a name to specify a pack expansion}} \ // expected-error@-1 {{'S' does not refer to the name of a parameter pack}} \ // expected-error@-1 {{declaration of anonymous struct must be a definition}} \ // expected-error@-1 {{expected parameter declarator}} \ diff --git a/clang/test/Parser/cxx2c-pack-indexing.cpp b/clang/test/Parser/cxx2c-pack-indexing.cpp index 99347a2f8f1571..72e286322fa976 100644 --- a/clang/test/Parser/cxx2c-pack-indexing.cpp +++ b/clang/test/Parser/cxx2c-pack-indexing.cpp @@ -12,8 +12,7 @@ struct S { // expected-note {{to match this '['}} \ // expected-warning{{declaration does not declare anything}} - T...[]; // expected-error{{expected expression}} \ - // expected-warning{{declaration does not declare anything}} + T...[]; // expected-error{{expected member name or ';' after declaration specifiers}} void f(auto... v) { decltype(v...[1]) a = v...[1]; @@ -65,7 +64,7 @@ int main() { } -namespace GH11460 { +namespace GH111460 { template <typename... T> requires( ); // expected-error {{expected expression}} struct SS { diff --git a/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp b/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp index 80dfeb9b6a8bf5..118af8e867f5f6 100644 --- a/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp +++ b/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp @@ -19,3 +19,35 @@ void f(T... t) { // cxx11-warning@+1 {{pack indexing is a C++2c extension}} T...[0] c; } + +template <typename... T> +void g(T... [1]); // cxx11-warning {{'T...[1]' is no longer a pack expansion but a pack indexing type; add a name to specify a pack expansion}} \ + // cxx11-warning {{pack indexing is a C++2c extension}} \ + // cxx11-note {{candidate function template not viable}} \ + // cxx26-warning {{pack indexing is incompatible with C++ standards before C++2c}} \ + // cxx26-note {{candidate function template not viable}} + +template <typename... T> +void h(T... param[1]); + +template <class T> +struct S { + using type = T; +}; + +template <typename... T> +void h(typename T... [1]::type); // cxx11-warning {{pack indexing is a C++2c extension}} \ + // cxx26-warning {{pack indexing is incompatible with C++ standards before C++2c}} + +template <typename... T> +void x(T... [0]); // cxx11-warning {{'T...[0]' is no longer a pack expansion but a pack indexing type; add a name to specify a pack expansion}} \ + // cxx11-warning {{pack indexing is a C++2c extension}} \ + // cxx26-warning {{pack indexing is incompatible with C++ standards before C++2c}} + +void call() { + g<int, double>(nullptr, nullptr); // cxx26-error {{no matching function for call to 'g'}} \ + // cxx11-error {{no matching function for call to 'g'}} + h<int, double>(nullptr, nullptr); + h<S<int>, S<const char *>>("hello"); + x<int*>(nullptr); +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
