[Bug c++/79372] ICE on C++ code with illegal decomposition declaration on x86_64-linux-gnu: in tsubst_decomp_names, at cp/pt.c:15599

["dmalcolm at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79372

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-02-06
                 CC|                            |dmalcolm at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for filing this bug.

Confirmed.

The ICE began with r242377 (aka 9c8aeb661a9d6cc82186dde40839f7353188c187):

   Implement P0217R3 - C++17 structured bindings

where the reproducer transitions from (r242376):

test.cc:4:20: error: expected unqualified-id before ‘[’ token
   void f () { auto [x] = 0; }
                    ^
to (r242377):

test.cc:4:20: warning: decomposition declaration only available with -std=c++1z
or -std=gnu++1z
   void f () { auto [x] = 0; }
                    ^
test.cc:4:20: error: cannot decompose non-array non-class type ‘int’
   void f () { auto [x] = 0; }
                    ^~~
 int main() S<int> void S<T>::f() [with T = int]
test.cc: In instantiation of ‘void S<T>::f() [with T = int]’:
test.cc:10:8:   required from here
test.cc:4:20: internal compiler error: in tsubst_decomp_names, at cp/pt.c:15338
0x816413 tsubst_decomp_names
        ../../gcc/cp/pt.c:15338
0x817922 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/cp/pt.c:15512
0x818705 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/cp/pt.c:15618
0x83ac5b instantiate_decl(tree_node*, int, bool)
        ../../gcc/cp/pt.c:22536
0x83b5ef instantiate_pending_templates(int)
        ../../gcc/cp/pt.c:22655
0x8a27dd c_parse_final_cleanups()
        ../../gcc/cp/decl2.c:4509
0xabc798 c_common_parse_file()
        ../../gcc/c-family/c-opts.c:1113