[Bug c++/68828] New: [concepts] ICE in fold with requires and function call around parameters

[jarrydb at cse dot unsw.edu.au]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68828

            Bug ID: 68828
           Summary: [concepts] ICE in fold with requires and function call
                    around parameters
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jarrydb at cse dot unsw.edu.au
  Target Milestone: ---

The following causes r231384 to ICE

template <typename... Types>
struct Var
{
};

struct A
{
};

template <typename T>
T
forward(T t)
{
  return static_cast<T>(t);
}

template <typename V, typename... Types, typename... Args>
bool requires_types_args(V&& v, Var<Types...>&, Args&&... args)
{
  return (true && ... &&
    requires (V&& v, Types type, Args... args) {
      foo(forward<V>(v), forward<Types>(type), 
        forward<Args>(args)...);
    }
  );
}

void bar()
{
  Var<int, char> v;
  requires_types_args(A(), v, 1, 'b');
}


Error is:

g++ -std=c++1z fold-ice3.cpp
fold-ice3.cpp: In instantiation of ‘bool requires_types_args(V&&, Var<Types
...>&, Args&& ...) [with V = A; Types = int, char; Args = {int, char}]’:
fold-ice3.cpp:31:37:   required from here
fold-ice3.cpp:22:10: error: ‘foo’ was not declared in this scope
       foo(forward<V>(v), forward<Types>(type),
       ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         forward<Args>(args)...);
         ~~~~~~~~~~~~~~~~~~~~~~~

fold-ice3.cpp:22:10: error: ‘foo’ was not declared in this scope, and no
declarations were found by argument-dependent lookup at the point of
instantiation [-fpermissive]
fold-ice3.cpp:22:10: note: ‘foo’ declared here, later in the translation unit
fold-ice3.cpp:26:1: internal compiler error: tree check: expected tree that
contains ‘typed’ structure, have ‘simple_req’ in cp_fold, at
cp/cp-gimplify.c:1948
 }
 ^

0xf62e24 tree_contains_struct_check_failed(tree_node const*,
tree_node_structure_enum, char const*, int, char const*)
        ../../../src/gcc-git/gcc/tree.c:9771
0x7f610c contains_struct_check(tree_node*, tree_node_structure_enum, char
const*, int, char const*)
        ../../../src/gcc-git/gcc/tree.h:3111
0x7f610c cp_fold
        ../../../src/gcc-git/gcc/cp/cp-gimplify.c:1948
0x7f6620 cp_fold_r
        ../../../src/gcc-git/gcc/cp/cp-gimplify.c:941
0xf85d82 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node*
(*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*,
hash_set<tree_node*, default_hash_traits<tree_node*> >*))
        ../../../src/gcc-git/gcc/tree.c:11492
0xf85ecd walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node*
(*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*,
hash_set<tree_node*, default_hash_traits<tree_node*> >*))
        ../../../src/gcc-git/gcc/tree.c:11539
0x79fb18 cp_walk_subtrees(tree_node**, int*, tree_node* (*)(tree_node**, int*,
void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)
        ../../../src/gcc-git/gcc/cp/tree.c:3895
0xf85df8 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node*
(*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*,
hash_set<tree_node*, default_hash_traits<tree_node*> >*))
        ../../../src/gcc-git/gcc/tree.c:11515
0xf861d6 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node*
(*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*,
hash_set<tree_node*, default_hash_traits<tree_node*> >*))
        ../../../src/gcc-git/gcc/tree.c:11809
0x612eaf finish_function(int)
        ../../../src/gcc-git/gcc/cp/decl.c:14589
0x641eaf instantiate_decl(tree_node*, int, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:21802
0x687c7b instantiate_pending_templates(int)
        ../../../src/gcc-git/gcc/cp/pt.c:21897
0x6c8ef1 c_parse_final_cleanups()
        ../../../src/gcc-git/gcc/cp/decl2.c:4579
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