[Bug c++/68826] New: [concepts] ICE in fold expression with requires

[jarrydb at cse dot unsw.edu.au]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68826

            Bug ID: 68826
           Summary: [concepts] ICE in fold expression with requires
           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: ---

r231384

ICE in the fold expression in the following code:

template <typename... Types>
bool requires_types(Types&&... types)
{
  return (true && ... &&
    requires { foo(types); });
}

void bar()
{
  requires_types('c', 1, "hi");
}


The error is:

g++ -std=c++1z fold-ice1.cpp -c
fold-ice1.cpp: In instantiation of ‘bool requires_types(Types&& ...) [with
Types = {char, int, const char (&)[3]}]’:
fold-ice1.cpp:10:30:   required from here
fold-ice1.cpp:5:19: internal compiler error: in tsubst_copy, at cp/pt.c:13729
     requires { foo(types); });
                ~~~^~~~~~~

0x64d155 tsubst_copy
        ../../../src/gcc-git/gcc/cp/pt.c:13729
0x64e560 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../../src/gcc-git/gcc/cp/pt.c:16822
0x650303 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../../src/gcc-git/gcc/cp/pt.c:16312
0x6451ac tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:15628
0x82133c tsubst_simple_requirement
        ../../../src/gcc-git/gcc/cp/constraint.cc:1580
0x82133c tsubst_requirement
        ../../../src/gcc-git/gcc/cp/constraint.cc:1636
0x82133c tsubst_requirement_body
        ../../../src/gcc-git/gcc/cp/constraint.cc:1659
0x82133c tsubst_requires_expr(tree_node*, tree_node*, int, tree_node*)
        ../../../src/gcc-git/gcc/cp/constraint.cc:1690
0x64f690 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../../src/gcc-git/gcc/cp/pt.c:16980
0x6451ac tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:15628
0x66176b gen_elem_of_pack_expansion_instantiation
        ../../../src/gcc-git/gcc/cp/pt.c:10514
0x66176b tsubst_pack_expansion(tree_node*, tree_node*, int, tree_node*)
        ../../../src/gcc-git/gcc/cp/pt.c:10944
0x64b69c tsubst_fold_expr_pack
        ../../../src/gcc-git/gcc/cp/pt.c:10604
0x64b69c tsubst_binary_left_fold
        ../../../src/gcc-git/gcc/cp/pt.c:10661
0x64b69c tsubst_copy
        ../../../src/gcc-git/gcc/cp/pt.c:14303
0x650248 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../../src/gcc-git/gcc/cp/pt.c:16058
0x6451ac tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:15628
0x644457 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:14940
0x644f9b tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:15116
0x641e06 instantiate_decl(tree_node*, int, bool)
        ../../../src/gcc-git/gcc/cp/pt.c:21780
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