[cfe-commits] r148210 - in /cfe/trunk: lib/AST/Type.cpp test/SemaCXX/decltype.cpp

[Eli Friedman]

On Sat, Jan 14, 2012 at 10:50 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> On Sat, Jan 14, 2012 at 10:24 PM, Richard Smith
> <richard-llvm at metafoo.co.uk> wrote:
>> Author: rsmith
>> Date: Sun Jan 15 00:24:57 2012
>> New Revision: 148210
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=148210&view=rev
>> Log:
>> decltype(e) is type-dependent if e is instantiation-dependent. Scary but true.
>> Don't consider decltype(e) for an instantiation-dependent, but not
>> type-dependent, e to be non-type-dependent but canonical(!).
>>
>> Modified:
>>    cfe/trunk/lib/AST/Type.cpp
>>    cfe/trunk/test/SemaCXX/decltype.cpp
>>
>> Modified: cfe/trunk/lib/AST/Type.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Type.cpp?rev=148210&r1=148209&r2=148210&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/AST/Type.cpp (original)
>> +++ cfe/trunk/lib/AST/Type.cpp Sun Jan 15 00:24:57 2012
>> @@ -1739,7 +1739,10 @@
>>  }
>>
>>  DecltypeType::DecltypeType(Expr *E, QualType underlyingType, QualType can)
>> -  : Type(Decltype, can, E->isTypeDependent(),
>> +  // C++11 [temp.type]p2: "If an expression e involves a template parameter,
>> +  // decltype(e) denotes a unique dependent type." Hence a decltype type is
>> +  // type-dependent even if its expression is only instantiation-dependent.
>> +  : Type(Decltype, can, E->isInstantiationDependent(),
>>          E->isInstantiationDependent(),
>>          E->getType()->isVariablyModifiedType(),
>>          E->containsUnexpandedParameterPack()),
>>
>> Modified: cfe/trunk/test/SemaCXX/decltype.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/decltype.cpp?rev=148210&r1=148209&r2=148210&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/decltype.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/decltype.cpp Sun Jan 15 00:24:57 2012
>> @@ -20,4 +20,11 @@
>>   class A{
>>       A(decltype(nullptr) param);
>>   };
>> -}
>> \ No newline at end of file
>> +}
>> +
>> +template<typename T> struct S {};
>> +template<typename T> auto f(T t) -> decltype(S<int>(t)) {
>> +  using U = decltype(S<int>(t));
>> +  using U = S<int>;
>> +  return S<int>(t);
>> +}
>
> This testcase isn't valid C++ as far as I can tell; what are you
> trying to show with it?

Err, wait, nevermind, it is; not sure what I was thinking.  GIven that
decltype(S<int>(t)) is always S<int>, no matter what t is, I'm not
sure why we can't analyze this correctly without marking it dependent,
though.

-Eli