http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54875
--- Comment #4 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-11-16 15:20:11 UTC --- Author: dodji Date: Fri Nov 16 15:20:03 2012 New Revision: 193562 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=193562 Log: PR c++/54875 - Error with alias template that resolves to an enum Consider this short example: 1 template<typename T> 2 using AddConst = T const; 3 4 enum FwdEnum : int; 5 6 int main() { 7 AddConst<FwdEnum> *ptr = nullptr; 8 } At line 7, when we build the type for AddConst<FwdEnum> in lookup_template_class_1, the resulting type is the enum FwdEnum. This confuses lookup_template_class_1 near the if below, wrongly making it taking the branch and thus calling tsubst_enum while it shouldn't: if (TREE_CODE (t) == ENUMERAL_TYPE && !is_dependent_type) /* Now that the type has been registered on the instantiations list, we set up the enumerators. Because the enumeration constants may involve the enumeration type itself, we make sure to register the type first, and then create the constants. That way, doing tsubst_expr for the enumeration constants won't result in recursive calls here; we'll find the instantiation and exit above. */ tsubst_enum (template_type, t, arglist); Before the alias template feature, the only reason why TREE_CODE (t) == ENUMERAL_TYPE would be true is when lookup_template_class_1 is called for an enum that is a member of a class template. But that condition can be also true for an alias template instantiation. So I guess that condition should be changed to TREE_CODE (template_type) == ENUMERAL_TYPE, to specifically detect the member enum of a class template case. Note that for the alias template instantiation case above, template_type points to a TEMPLATE_TYPE_PARM which name is AddConst. This is what the patchlet below does. Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk. gcc/cp/ * pt.c (lookup_template_class_1): Look at the type of the potential member enum of class template to determine if we are actually substituting into a member enum of class template. gcc/testsuite/ * g++.dg/cpp0x/alias-decl-27.C: New test. Added: trunk/gcc/testsuite/g++.dg/cpp0x/alias-decl-27.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/pt.c trunk/gcc/testsuite/ChangeLog
