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Note GCC had implemented such feature since GCC 12 <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100975>. This patch implements CWG 2397, allowing array of placeholder type to be valid. See also https://wg21.cmeerw.net/cwg/issue2397. Repository: rG LLVM Github Monorepo https://reviews.llvm.org/D147909 Files: clang/include/clang/Basic/DiagnosticSemaKinds.td clang/lib/Sema/SemaType.cpp clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/cwg2397.cpp clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp =================================================================== --- clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp +++ clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp @@ -2,6 +2,6 @@ void f() { int b[5]; - auto a[5] = b; // expected-error{{'a' declared as array of 'auto'}} - auto *c[5] = b; // expected-error{{'c' declared as array of 'auto *'}} + auto a[5] = b; // expected-error{{variable 'a' with type 'auto[5]' has incompatible initializer of type 'int[5]'}} + auto *c[5] = b; // expected-error{{variable 'c' with type 'auto *[5]' has incompatible initializer of type 'int[5]'}} } Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/cwg2397.cpp =================================================================== --- /dev/null +++ clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/cwg2397.cpp @@ -0,0 +1,20 @@ +// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++11 + +void foo() { + int a[5]; + + auto (&b)[5] = a; + auto (*c)[5] = &a; + + auto d[] = {0}; // expected-error{{cannot deduce actual type for variable 'd' with type 'auto[]' from initializer list}} +} + +void g() { + int a[5]; + auto (*b)[5] = &a; + auto (&c)[5] = a; + auto (&&d)[5] = static_cast<int(&&)[5]>(a); + static_assert(__is_same(decltype(b), int (*)[5]), ""); + static_assert(__is_same(decltype(c), int (&)[5]), ""); + static_assert(__is_same(decltype(d), int (&&)[5]), ""); +} Index: clang/lib/Sema/SemaType.cpp =================================================================== --- clang/lib/Sema/SemaType.cpp +++ clang/lib/Sema/SemaType.cpp @@ -5130,17 +5130,6 @@ D.setInvalidType(true); } } - const AutoType *AT = T->getContainedAutoType(); - // Allow arrays of auto if we are a generic lambda parameter. - // i.e. [](auto (&array)[5]) { return array[0]; }; OK - if (AT && D.getContext() != DeclaratorContext::LambdaExprParameter) { - // We've already diagnosed this for decltype(auto). - if (!AT->isDecltypeAuto()) - S.Diag(DeclType.Loc, diag::err_illegal_decl_array_of_auto) - << getPrintableNameForEntity(Name) << T; - T = QualType(); - break; - } // Array parameters can be marked nullable as well, although it's not // necessary if they're marked 'static'. Index: clang/include/clang/Basic/DiagnosticSemaKinds.td =================================================================== --- clang/include/clang/Basic/DiagnosticSemaKinds.td +++ clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -2314,8 +2314,6 @@ def err_binding_cannot_appear_in_own_initializer : Error< "binding %0 cannot appear in the initializer of its own " "decomposition declaration">; -def err_illegal_decl_array_of_auto : Error< - "'%0' declared as array of %1">; def err_new_array_of_auto : Error< "cannot allocate array of 'auto'">; def err_auto_not_allowed : Error<
Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp =================================================================== --- clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp +++ clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/p1-cxx0x.cpp @@ -2,6 +2,6 @@ void f() { int b[5]; - auto a[5] = b; // expected-error{{'a' declared as array of 'auto'}} - auto *c[5] = b; // expected-error{{'c' declared as array of 'auto *'}} + auto a[5] = b; // expected-error{{variable 'a' with type 'auto[5]' has incompatible initializer of type 'int[5]'}} + auto *c[5] = b; // expected-error{{variable 'c' with type 'auto *[5]' has incompatible initializer of type 'int[5]'}} } Index: clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/cwg2397.cpp =================================================================== --- /dev/null +++ clang/test/CXX/dcl.decl/dcl.meaning/dcl.array/cwg2397.cpp @@ -0,0 +1,20 @@ +// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++11 + +void foo() { + int a[5]; + + auto (&b)[5] = a; + auto (*c)[5] = &a; + + auto d[] = {0}; // expected-error{{cannot deduce actual type for variable 'd' with type 'auto[]' from initializer list}} +} + +void g() { + int a[5]; + auto (*b)[5] = &a; + auto (&c)[5] = a; + auto (&&d)[5] = static_cast<int(&&)[5]>(a); + static_assert(__is_same(decltype(b), int (*)[5]), ""); + static_assert(__is_same(decltype(c), int (&)[5]), ""); + static_assert(__is_same(decltype(d), int (&&)[5]), ""); +} Index: clang/lib/Sema/SemaType.cpp =================================================================== --- clang/lib/Sema/SemaType.cpp +++ clang/lib/Sema/SemaType.cpp @@ -5130,17 +5130,6 @@ D.setInvalidType(true); } } - const AutoType *AT = T->getContainedAutoType(); - // Allow arrays of auto if we are a generic lambda parameter. - // i.e. [](auto (&array)[5]) { return array[0]; }; OK - if (AT && D.getContext() != DeclaratorContext::LambdaExprParameter) { - // We've already diagnosed this for decltype(auto). - if (!AT->isDecltypeAuto()) - S.Diag(DeclType.Loc, diag::err_illegal_decl_array_of_auto) - << getPrintableNameForEntity(Name) << T; - T = QualType(); - break; - } // Array parameters can be marked nullable as well, although it's not // necessary if they're marked 'static'. Index: clang/include/clang/Basic/DiagnosticSemaKinds.td =================================================================== --- clang/include/clang/Basic/DiagnosticSemaKinds.td +++ clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -2314,8 +2314,6 @@ def err_binding_cannot_appear_in_own_initializer : Error< "binding %0 cannot appear in the initializer of its own " "decomposition declaration">; -def err_illegal_decl_array_of_auto : Error< - "'%0' declared as array of %1">; def err_new_array_of_auto : Error< "cannot allocate array of 'auto'">; def err_auto_not_allowed : Error<
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