https://github.com/Endilll created https://github.com/llvm/llvm-project/pull/78103
C++14 introduced deduced return type for regular functions, but shortly after [CWG1878](https://wg21.link/cwg1878) was filed and resolved to disallow deduced return types in conversion function templates. So this patch diagnoses such usage of deduced return type in C++14 mode onwards. Fixes #51776 >From 522c7dff31a6f63995877674f9f4282ae60f7aaa Mon Sep 17 00:00:00 2001 From: Vlad Serebrennikov <serebrennikov.vladis...@gmail.com> Date: Sun, 14 Jan 2024 19:45:04 +0300 Subject: [PATCH] [clang] Implement CWG1878 "`operator auto` template" C++14 introduced deduced return type for regular functions, but shortly after [CWG1878](https://wg21.link/cwg1878) was filed and resolved to disallow deduced return types in conversion function templates. So this patch diagnoses such usage of deduced return type in C++14 mode onwards. --- clang/docs/ReleaseNotes.rst | 2 ++ .../clang/Basic/DiagnosticSemaKinds.td | 3 +- clang/lib/Sema/SemaDeclCXX.cpp | 10 ++++++- clang/test/CXX/drs/dr18xx.cpp | 26 +++++++++++++---- .../SemaCXX/deduced-return-type-cxx14.cpp | 28 +++++++++++++++---- clang/www/cxx_dr_status.html | 2 +- 6 files changed, 57 insertions(+), 14 deletions(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 3cbce1be159437..271e641a5ccce0 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -560,6 +560,8 @@ Improvements to Clang's diagnostics - Clang now diagnoses unexpanded packs within the template argument lists of function template specializations. - Clang now diagnoses attempts to bind a bitfield to an NTTP of a reference type as erroneous converted constant expression and not as a reference to subobject. +- Clang now diagnoses ``auto`` and ``decltype(auto)`` in declarations of conversion function template + (`CWG1878: <https://cplusplus.github.io/CWG/issues/1878.html>`_) Improvements to Clang's time-trace diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 1a79892e40030a..de99d753a13a6c 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -2411,7 +2411,8 @@ def err_auto_not_allowed : Error< "|in type allocated by 'new'|in K&R-style function parameter" "|in template parameter|in friend declaration|in function prototype that is " "not a function declaration|in requires expression parameter" - "|in array declaration}1">; + "|in array declaration" + "|in declaration of conversion function template}1">; def err_dependent_deduced_tst : Error< "typename specifier refers to " "%select{class template|function template|variable template|alias template|" diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp index 36e53c684ac4dc..613dccbf445f91 100644 --- a/clang/lib/Sema/SemaDeclCXX.cpp +++ b/clang/lib/Sema/SemaDeclCXX.cpp @@ -11323,8 +11323,16 @@ Decl *Sema::ActOnConversionDeclarator(CXXConversionDecl *Conversion) { } if (FunctionTemplateDecl *ConversionTemplate - = Conversion->getDescribedFunctionTemplate()) + = Conversion->getDescribedFunctionTemplate()) { + if (ConvType->isUndeducedAutoType()) { + Diag(Conversion->getTypeSpecStartLoc(), diag::err_auto_not_allowed) + << Conversion->getTypeSourceInfo()->getTypeLoc().getContainedAutoTypeLoc().getSourceRange() + << llvm::to_underlying(Conversion->getConversionType()->getAs<AutoType>()->getKeyword()) + << /* in declaration of conversion function template */ 24; + } + return ConversionTemplate; + } return Conversion; } diff --git a/clang/test/CXX/drs/dr18xx.cpp b/clang/test/CXX/drs/dr18xx.cpp index 175c39e8b73abb..8be94ed49e639d 100644 --- a/clang/test/CXX/drs/dr18xx.cpp +++ b/clang/test/CXX/drs/dr18xx.cpp @@ -1,10 +1,10 @@ // RUN: %clang_cc1 -std=c++98 -triple x86_64-unknown-unknown %s -verify=expected,cxx98-14,cxx98 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors // RUN: %clang_cc1 -std=c++11 -triple x86_64-unknown-unknown %s -verify=expected,cxx98-14,cxx11-17,since-cxx11 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors -// RUN: %clang_cc1 -std=c++14 -triple x86_64-unknown-unknown %s -verify=expected,cxx98-14,cxx11-17,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors -// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx17,cxx11-17,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors -// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx17,since-cxx20,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors -// RUN: %clang_cc1 -std=c++23 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx17,since-cxx20,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors -// RUN: %clang_cc1 -std=c++2c -triple x86_64-unknown-unknown %s -verify=expected,since-cxx17,since-cxx20,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors +// RUN: %clang_cc1 -std=c++14 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx14,cxx98-14,cxx11-17,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors +// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx14,since-cxx17,cxx11-17,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors +// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx14,since-cxx17,since-cxx20,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors +// RUN: %clang_cc1 -std=c++23 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx14,since-cxx17,since-cxx20,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors +// RUN: %clang_cc1 -std=c++2c -triple x86_64-unknown-unknown %s -verify=expected,since-cxx14,since-cxx17,since-cxx20,since-cxx11,since-cxx14 -fexceptions -Wno-deprecated-builtins -fcxx-exceptions -pedantic-errors #if __cplusplus == 199711L #define static_assert(...) __extension__ _Static_assert(__VA_ARGS__) @@ -317,6 +317,22 @@ namespace dr1872 { // dr1872: 9 #endif } +namespace dr1878 { // dr1878: 18 +#if __cplusplus >= 201402L +struct S { + template <typename T> + operator auto() const { return short(); } + // since-cxx14-error@-1 {{'auto' not allowed in declaration of conversion function template}} + template <typename T> + operator const auto() const { return int(); } + // since-cxx14-error@-1 {{'auto' not allowed in declaration of conversion function template}} + template <typename T> + operator decltype(auto)() const { return unsigned(); } + // since-cxx14-error@-1 {{'decltype(auto)' not allowed in declaration of conversion function template}} +}; +#endif +} + namespace dr1881 { // dr1881: 7 struct A { int a : 4; }; struct B : A { int b : 3; }; diff --git a/clang/test/SemaCXX/deduced-return-type-cxx14.cpp b/clang/test/SemaCXX/deduced-return-type-cxx14.cpp index eac9c587869f55..6533a9e561f248 100644 --- a/clang/test/SemaCXX/deduced-return-type-cxx14.cpp +++ b/clang/test/SemaCXX/deduced-return-type-cxx14.cpp @@ -1,11 +1,11 @@ -// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected,cxx20_23,cxx23 %s -// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected,cxx20_23,cxx23 %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING +// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected,since-cxx14,cxx20_23,cxx23 %s +// RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected,since-cxx14,cxx20_23,cxx23 %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING -// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20,cxx20_23 %s -// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20,cxx20_23 %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING +// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,since-cxx14,cxx14_20,cxx20_23 %s +// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,since-cxx14,cxx14_20,cxx20_23 %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING -// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20,cxx14 %s -// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20,cxx14 %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING +// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,since-cxx14,cxx14_20,cxx14 %s +// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,since-cxx14,cxx14_20,cxx14 %s -fdelayed-template-parsing -DDELAYED_TEMPLATE_PARSING auto f(); // expected-note {{previous}} int f(); // expected-error {{differ only in their return type}} @@ -686,3 +686,19 @@ auto f(auto x) { // cxx14-error {{'auto' not allowed in function prototype}} } } + +struct DeducedTargetTypeOfConversionFunction { + operator auto() const { return char(); } + operator const auto() const { return float(); } + operator decltype(auto)() const { return double(0); } + + template <typename T> + operator auto() const { return short(); } + // since-cxx14-error@-1 {{'auto' not allowed in declaration of conversion function template}} + template <typename T> + operator const auto() const { return int(); } + // since-cxx14-error@-1 {{'auto' not allowed in declaration of conversion function template}} + template <typename T> + operator decltype(auto)() const { return unsigned(); } + // since-cxx14-error@-1 {{'decltype(auto)' not allowed in declaration of conversion function template}} +}; diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html index 397bf1357d3cb3..c0b48193694230 100755 --- a/clang/www/cxx_dr_status.html +++ b/clang/www/cxx_dr_status.html @@ -11076,7 +11076,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2> <td><a href="https://cplusplus.github.io/CWG/issues/1878.html";>1878</a></td> <td>CD4</td> <td><TT>operator auto</TT> template</td> - <td class="unknown" align="center">Unknown</td> + <td class="unreleased" align="center">Clang 18</td> </tr> <tr id="1879"> <td><a href="https://cplusplus.github.io/CWG/issues/1879.html";>1879</a></td> _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
