Index: include/clang/Basic/DiagnosticGroups.td =================================================================== --- include/clang/Basic/DiagnosticGroups.td +++ include/clang/Basic/DiagnosticGroups.td @@ -168,6 +168,9 @@ def CXXPre1zCompat : DiagGroup<"c++98-c++11-c++14-compat">; def CXXPre1zCompatPedantic : DiagGroup<"c++98-c++11-c++14-compat-pedantic", [CXXPre1zCompat]>; +def CXXPre2aCompat : DiagGroup<"c++98-c++11-c++14-c++17-compat">; +def CXXPre2aCompatPedantic : DiagGroup<"c++98-c++11-c++14-c++17-compat-pedantic", + [CXXPre2aCompat]>; def CXX98CompatBindToTemporaryCopy : DiagGroup<"c++98-compat-bind-to-temporary-copy">; @@ -784,6 +787,10 @@ // earlier C++ versions. def CXX17 : DiagGroup<"c++17-extensions">; +// A warning group for warnings about using C++2a features as extensions in +// earlier C++ versions. +def CXX2a : DiagGroup<"c++2a-extensions">; + def : DiagGroup<"c++0x-extensions", [CXX11]>; def : DiagGroup<"c++1y-extensions", [CXX14]>; def : DiagGroup<"c++1z-extensions", [CXX17]>; Index: include/clang/Basic/DiagnosticSemaKinds.td =================================================================== --- include/clang/Basic/DiagnosticSemaKinds.td +++ include/clang/Basic/DiagnosticSemaKinds.td @@ -6470,8 +6470,6 @@ "%0 can appear only once in a capture list">; def err_reference_capture_with_reference_default : Error< "'&' cannot precede a capture when the capture default is '&'">; - def err_this_capture_with_copy_default : Error< - "'this' cannot be explicitly captured when the capture default is '='">; def err_copy_capture_with_copy_default : Error< "'&' must precede a capture when the capture default is '='">; def err_capture_does_not_name_variable : Error< @@ -6544,6 +6542,14 @@ InGroup, DefaultIgnore; def ext_star_this_lambda_capture_cxx17 : ExtWarn< "capture of '*this' by copy is a C++17 extension">, InGroup; + + // C++2a [=, this] captures. + def warn_cxx17_compat_equals_this_lambda_capture : Warning< + "explicit capture of 'this' with a capture default of '=' is incompatible " + "with C++ standards before C++2a">, InGroup, DefaultIgnore; + def ext_equals_this_lambda_capture_cxx2a : ExtWarn< + "explicit capture of 'this' with a capture default of '=' " + "is a C++2a extension">, InGroup; } def err_return_in_captured_stmt : Error< Index: lib/Sema/SemaLambda.cpp =================================================================== --- lib/Sema/SemaLambda.cpp +++ lib/Sema/SemaLambda.cpp @@ -948,17 +948,15 @@ continue; } - // C++1z [expr.prim.lambda]p8: - // If a lambda-capture includes a capture-default that is =, each - // simple-capture of that lambda-capture shall be of the form "& - // identifier" or "* this". [ Note: The form [&,this] is redundant but - // accepted for compatibility with ISO C++14. --end note ] - if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis) { - Diag(C->Loc, diag::err_this_capture_with_copy_default) - << FixItHint::CreateRemoval( - SourceRange(getLocForEndOfToken(PrevCaptureLoc), C->Loc)); - continue; - } + // C++2a [expr.prim.lambda]p8: + // If a lambda-capture includes a capture-default that is =, + // each simple-capture of that lambda-capture shall be of the form + // "&identifier", "this", or "* this". [ Note: The form [&,this] is + // redundant but accepted for compatibility with ISO C++14. --end note ] + if (Intro.Default == LCD_ByCopy && C->Kind != LCK_StarThis) + Diag(C->Loc, !getLangOpts().CPlusPlus2a + ? diag::ext_equals_this_lambda_capture_cxx2a + : diag::warn_cxx17_compat_equals_this_lambda_capture); // C++11 [expr.prim.lambda]p12: // If this is captured by a local lambda expression, its nearest Index: test/CXX/expr/expr.prim/expr.prim.lambda/p8.cpp =================================================================== --- test/CXX/expr/expr.prim/expr.prim.lambda/p8.cpp +++ test/CXX/expr/expr.prim/expr.prim.lambda/p8.cpp @@ -8,7 +8,7 @@ (void)[this, this] () {}; // expected-error {{'this' can appear only once}} (void)[=, foo] () {}; // expected-error {{'&' must precede a capture when}} (void)[=, &foo] () {}; - (void)[=, this] () {}; // expected-error {{'this' cannot be explicitly captured}} + (void)[=, this] () {}; // expected-warning {{C++2a extension}} (void)[&, foo] () {}; (void)[&, &foo] () {}; // expected-error {{'&' cannot precede a capture when}} (void)[&, this] () {}; @@ -23,7 +23,7 @@ void S2::f(int i) { (void)[&, i]{ }; (void)[&, &i]{ }; // expected-error{{'&' cannot precede a capture when the capture default is '&'}} - (void)[=, this]{ }; // expected-error{{'this' cannot be explicitly captured}} + (void)[=, this]{ }; // expected-warning{{C++2a extension}} (void)[=]{ this->g(i); }; (void)[i, i]{ }; // expected-error{{'i' can appear only once in a capture list}} (void)[i(0), i(1)]{ }; // expected-error{{'i' can appear only once in a capture list}} Index: test/FixIt/fixit-cxx0x.cpp =================================================================== --- test/FixIt/fixit-cxx0x.cpp +++ test/FixIt/fixit-cxx0x.cpp @@ -54,7 +54,6 @@ void S2::f(int i) { (void)[&, &i, &i]{}; // expected-error 2{{'&' cannot precede a capture when the capture default is '&'}} - (void)[=, this]{ this->g(5); }; // expected-error{{'this' cannot be explicitly captured}} (void)[i, i]{ }; // expected-error{{'i' can appear only once in a capture list}} (void)[&, i, i]{ }; // expected-error{{'i' can appear only once in a capture list}} (void)[] mutable { }; // expected-error{{lambda requires '()' before 'mutable'}} Index: test/SemaCXX/cxx2a-lambda-equals-this.cpp =================================================================== --- test/SemaCXX/cxx2a-lambda-equals-this.cpp +++ test/SemaCXX/cxx2a-lambda-equals-this.cpp @@ -0,0 +1,15 @@ +// RUN: %clang_cc1 -std=c++2a -verify %s +// expected-no-diagnostics + +// This test does two things. +// Deleting the copy constructor ensures that an [=, this] capture doesn't copy the object. +// Accessing a member variable from the lambda ensures that the capture actually works. +class A { + A(const A &) = delete; + int i; + + void func() { + auto L = [=, this]() -> int { return i; }; + L(); + } +}; Index: www/cxx_status.html =================================================================== --- www/cxx_status.html +++ www/cxx_status.html @@ -777,13 +777,12 @@

C++2a implementation status

-

Clang does not yet support any of the proposed features of - +

Clang has experimental support for some proposed features of the C++ standard following C++17, provisionally named C++2a. Note that support for these features may change or be removed without notice, as the draft C++2a standard evolves. - +

You can use Clang in C++2a mode with the -std=c++2a option.

List of features and minimum Clang version with support @@ -808,7 +807,7 @@ Allow lambda-capture [=, this] P0409R2 - No + SVN __VA_OPT__ for preprocessor comma elision