[Bug c++/59759] internal compiler error: in unify, using std::enable_if on classes

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59759

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-invalid-code
   Last reconfirmed|2014-09-26 00:00:00         |2016-1-19
                 CC|                            |msebor at gcc dot gnu.org
      Known to fail|                            |6.0

--- Comment #15 from Martin Sebor <msebor at gcc dot gnu.org> ---
Today's trunk still crashes on the (invalid) test case in comment #7.  Below is
an ever so slightly more reduced test case that reproduces the failure.  The
patch from comment #11 still fixes the ICE and produces the following output:

u.c: In function ‘void f(A<T>*)’:
u.c:16:8: error: ‘class C<B<T>, int>::U’ resolves to ‘C<B<int>, int>::U {aka
int}’, which is is not a class type
   A<int>* map;
        ^

u.c:17:9: error: no matching function for call to ‘f(A<int>*&)’
   f (map);
         ^

u.c:15:6: note: candidate: template<class T> void f(A<T>*)
 void f (A<T>*) {
      ^

u.c:15:6: note:   template argument deduction/substitution failed:
u.c:17:9: note:   template argument ‘0’ does not match ‘x’
   f (map);
         ^


Slightly reduced test case:

$ cat u.c && /build/gcc-trunk/gcc/xgcc -B /build/gcc-trunk/gcc -S -Wall -Wextra
-Wpedantic -xc++ u.c
template <class T>
struct B { };

template <class, class T>
struct C {
  typedef T U;
};

const int x = 0;

template <class T, class C<B<T>, int>::U = x>
struct A;

template <class T>
void f (A<T>*) {
  A<int>* map;
  f (map);
}
u.c: In function ‘void f(A<T>*)’:
u.c:16:8: error: ‘class C<B<T>, int>::U’ resolves to ‘C<B<int>, int>::U {aka
int}’, which is is not a class type
   A<int>* map;
        ^

u.c: In substitution of ‘template<class T> void f(A<T>*) [with T = <missing>]’:
u.c:17:9:   required from here
u.c:17:9: internal compiler error: in unify, at cp/pt.c:19935
   f (map);
         ^

0x10440953 unify
        /src/gcc/trunk/gcc/cp/pt.c:19935
0x1043f30b unify
        /src/gcc/trunk/gcc/cp/pt.c:19768
0x104384a7 try_class_unification
        /src/gcc/trunk/gcc/cp/pt.c:18772
0x1043f803 unify
        /src/gcc/trunk/gcc/cp/pt.c:19806
0x1043eb77 unify
        /src/gcc/trunk/gcc/cp/pt.c:19672
0x10435643 unify_one_argument
        /src/gcc/trunk/gcc/cp/pt.c:18121
0x10435983 type_unification_real
        /src/gcc/trunk/gcc/cp/pt.c:18195
0x104334a7 fn_type_unification(tree_node*, tree_node*, tree_node*, tree_node*
const*, unsigned int, tree_node*, unification_kind_t, int, bool, bool)
        /src/gcc/trunk/gcc/cp/pt.c:17623
0x1032e533 add_template_candidate_real
        /src/gcc/trunk/gcc/cp/call.c:3091
0x1032ea8f add_template_candidate
        /src/gcc/trunk/gcc/cp/call.c:3169
0x10338b3f add_candidates
        /src/gcc/trunk/gcc/cp/call.c:5341
0x10332893 perform_overload_resolution
        /src/gcc/trunk/gcc/cp/call.c:4026
0x10332c1f build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, bool, int)
        /src/gcc/trunk/gcc/cp/call.c:4103
0x105f857b finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**,
bool, bool, int)
        /src/gcc/trunk/gcc/cp/semantics.c:2413
0x10500dbb cp_parser_postfix_expression
        /src/gcc/trunk/gcc/cp/parser.c:6884
0x10503d5f cp_parser_unary_expression
        /src/gcc/trunk/gcc/cp/parser.c:7964
0x1050516b cp_parser_cast_expression
        /src/gcc/trunk/gcc/cp/parser.c:8641
0x10505293 cp_parser_binary_expression
        /src/gcc/trunk/gcc/cp/parser.c:8743
0x105064a7 cp_parser_assignment_expression
        /src/gcc/trunk/gcc/cp/parser.c:9031
0x10506a2b cp_parser_expression
        /src/gcc/trunk/gcc/cp/parser.c:9198
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