r228792 - Add a warning for direct-list-initialization of a variable with a deduced type
Hans Wennborg
hans at chromium.org
Tue Feb 10 19:34:15 PST 2015
Merged in r228799.
Thanks,
Hans
On Tue, Feb 10, 2015 at 7:17 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> Hi Hans,
>
> I'd really like to ship this change as part of Clang 3.6: there's an
> upcoming change to our behavior that will cause us to reject or differently
> interpret some code in C++11 and C++14 modes, and this patch adds a warning
> for the affected cases with a fix-it hint.
>
> On Tue, Feb 10, 2015 at 6:41 PM, Richard Smith <richard-llvm at metafoo.co.uk>
> wrote:
>>
>> Author: rsmith
>> Date: Tue Feb 10 20:41:33 2015
>> New Revision: 228792
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=228792&view=rev
>> Log:
>> Add a warning for direct-list-initialization of a variable with a deduced
>> type
>> (or of a lambda init-capture, which is sort-of such a variable). The
>> semantics
>> of such constructs will change when we implement N3922, so we intend to
>> warn on
>> this in Clang 3.6 then change the semantics in Clang 3.7.
>>
>> Modified:
>> cfe/trunk/include/clang/Basic/DiagnosticGroups.td
>> cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td
>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> cfe/trunk/lib/Parse/ParseExprCXX.cpp
>> cfe/trunk/lib/Sema/SemaDecl.cpp
>> cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
>> cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp
>> cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm
>> cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
>>
>> Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
>> +++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Tue Feb 10 20:41:33
>> 2015
>> @@ -750,3 +750,6 @@ def SerializedDiagnostics : DiagGroup<"s
>> // A warning group for warnings about code that clang accepts when
>> // compiling CUDA C/C++ but which is not compatible with the CUDA spec.
>> def CudaCompat : DiagGroup<"cuda-compat">;
>> +
>> +// A warning group for things that will change semantics in the future.
>> +def FutureCompat : DiagGroup<"future-compat">;
>>
>> Modified: cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td (original)
>> +++ cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td Tue Feb 10
>> 20:41:33 2015
>> @@ -804,6 +804,10 @@ def warn_cxx98_compat_lambda : Warning<
>> def err_lambda_missing_parens : Error<
>> "lambda requires '()' before %select{'mutable'|return type|"
>> "attribute specifier}0">;
>> +def warn_init_capture_direct_list_init : Warning<
>> + "direct list initialization of a lambda init-capture will change
>> meaning in "
>> + "a future version of Clang; insert an '=' to avoid a change in
>> behavior">,
>> + InGroup<FutureCompat>;
>>
>> // Availability attribute
>> def err_expected_version : Error<
>>
>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Feb 10
>> 20:41:33 2015
>> @@ -1645,6 +1645,10 @@ def err_auto_var_init_multiple_expressio
>> def err_auto_var_init_paren_braces : Error<
>> "cannot deduce type for variable %0 with type %1 from "
>> "parenthesized initializer list">;
>> +def warn_auto_var_direct_list_init : Warning<
>> + "direct list initialization of a variable with a deduced type will
>> change "
>> + "meaning in a future version of Clang; insert an '=' to avoid a change
>> in "
>> + "behavior">, InGroup<FutureCompat>;
>> def err_auto_new_ctor_multiple_expressions : Error<
>> "new expression for type %0 contains multiple constructor arguments">;
>> def err_auto_missing_trailing_return : Error<
>>
>> Modified: cfe/trunk/lib/Parse/ParseExprCXX.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseExprCXX.cpp?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Parse/ParseExprCXX.cpp (original)
>> +++ cfe/trunk/lib/Parse/ParseExprCXX.cpp Tue Feb 10 20:41:33 2015
>> @@ -894,11 +894,16 @@ Optional<unsigned> Parser::ParseLambdaIn
>> // to save the necessary state, and restore it later.
>> EnterExpressionEvaluationContext EC(Actions,
>> Sema::PotentiallyEvaluated);
>> - TryConsumeToken(tok::equal);
>> + bool HadEquals = TryConsumeToken(tok::equal);
>>
>> - if (!SkippedInits)
>> + if (!SkippedInits) {
>> + // Warn on constructs that will change meaning when we
>> implement N3922
>> + if (!HadEquals && Tok.is(tok::l_brace)) {
>> + Diag(Tok, diag::warn_init_capture_direct_list_init)
>> + << FixItHint::CreateInsertion(Tok.getLocation(), "=");
>> + }
>> Init = ParseInitializer();
>> - else if (Tok.is(tok::l_brace)) {
>> + } else if (Tok.is(tok::l_brace)) {
>> BalancedDelimiterTracker Braces(*this, tok::l_brace);
>> Braces.consumeOpen();
>> Braces.skipToEnd();
>>
>> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Tue Feb 10 20:41:33 2015
>> @@ -8716,6 +8716,14 @@ void Sema::AddInitializerToDecl(Decl *Re
>> CheckVariableDeclarationType(VDecl);
>> if (VDecl->isInvalidDecl())
>> return;
>> +
>> + // If all looks well, warn if this is a case that will change meaning
>> when
>> + // we implement N3922.
>> + if (DirectInit && !CXXDirectInit && isa<InitListExpr>(Init)) {
>> + Diag(Init->getLocStart(),
>> + diag::warn_auto_var_direct_list_init)
>> + << FixItHint::CreateInsertion(Init->getLocStart(), "=");
>> + }
>> }
>>
>> // dllimport cannot be used on variable definitions.
>>
>> Modified: cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
>> (original)
>> +++ cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp Tue Feb
>> 10 20:41:33 2015
>> @@ -48,7 +48,7 @@ auto bad_init_2 = [a(1, 2)] {}; // expec
>> auto bad_init_3 = [&a(void_fn())] {}; // expected-error {{cannot form a
>> reference to 'void'}}
>> auto bad_init_4 = [a(void_fn())] {}; // expected-error {{has incomplete
>> type 'void'}}
>> auto bad_init_5 = [a(overload_fn)] {}; // expected-error {{cannot deduce
>> type for lambda capture 'a' from initializer of type '<overloaded function}}
>> -auto bad_init_6 = [a{overload_fn}] {}; // expected-error {{cannot deduce
>> type for lambda capture 'a' from initializer list}}
>> +auto bad_init_6 = [a{overload_fn}] {}; // expected-error {{cannot deduce
>> type for lambda capture 'a' from initializer list}} expected-warning {{will
>> change meaning in a future version of Clang}}
>>
>> template<typename...T> void pack_1(T...t) { (void)[a(t...)] {}; } //
>> expected-error {{initializer missing for lambda capture 'a'}}
>> template void pack_1<>(); // expected-note {{instantiation of}}
>> @@ -61,7 +61,7 @@ auto a = [a(4), b = 5, &c = static_cast<
>> using T = decltype(c);
>> using T = const int &;
>> };
>> -auto b = [a{0}] {}; // expected-error {{include <initializer_list>}}
>> +auto b = [a{0}] {}; // expected-error {{include <initializer_list>}}
>> expected-warning {{will change meaning in a future version of Clang}}
>>
>> struct S { S(); S(S&&); };
>> template<typename T> struct remove_reference { typedef T type; };
>>
>> Modified: cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp (original)
>> +++ cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp Tue Feb 10 20:41:33
>> 2015
>> @@ -61,7 +61,7 @@ class C {
>> int z;
>> void init_capture() {
>> [n(0)] () mutable -> int { return ++n; }; //
>> expected-warning{{extension}}
>> - [n{0}] { return; }; // expected-error {{<initializer_list>}}
>> expected-warning{{extension}}
>> + [n{0}] { return; }; // expected-error {{<initializer_list>}}
>> expected-warning{{extension}} expected-warning{{will change meaning in a
>> future version}}
>> [n = 0] { return ++n; }; // expected-error {{captured by copy in a
>> non-mutable}} expected-warning{{extension}}
>> [n = {0}] { return; }; // expected-error {{<initializer_list>}}
>> expected-warning{{extension}}
>> [a([&b = z]{})](){}; // expected-warning 2{{extension}}
>>
>> Modified: cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm (original)
>> +++ cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm Tue Feb 10
>> 20:41:33 2015
>> @@ -21,7 +21,7 @@ class C {
>>
>> [foo(bar)] () {};
>> [foo = bar] () {};
>> - [foo{bar}] () {}; // expected-error {{<initializer_list>}}
>> + [foo{bar}] () {}; // expected-error {{<initializer_list>}}
>> expected-warning {{will change meaning}}
>> [foo = {bar}] () {}; // expected-error {{<initializer_list>}}
>>
>> [foo(bar) baz] () {}; // expected-error {{called object type 'int' is
>> not a function}}
>>
>> Modified: cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp?rev=228792&r1=228791&r2=228792&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp
>> (original)
>> +++ cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp Tue
>> Feb 10 20:41:33 2015
>> @@ -117,6 +117,7 @@ void argument_deduction() {
>>
>> void auto_deduction() {
>> auto l = {1, 2, 3, 4};
>> + auto l2 {1, 2, 3, 4}; // expected-warning {{will change meaning in a
>> future version of Clang}}
>> static_assert(same_type<decltype(l),
>> std::initializer_list<int>>::value, "");
>> auto bl = {1, 2.0}; // expected-error {{cannot deduce}}
>>
>>
>>
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