[Bug c++/67692] New: [concepts] ICE when using requires in non-concept contexts

[ryan.burn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67692

            Bug ID: 67692
           Summary: [concepts] ICE when using requires in non-concept
                    contexts
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ryan.burn at gmail dot com
  Target Milestone: ---

The below code produces an ICE compiling with -std=c++1z:

////////////////////////////////////////
template<class T>
bool f(T x) {
  return requires(T x) {
    ++x;
  };
}

int main() {
  f(3);
  return 0;
}
////////////////////////////////////////

Stack trace:
main.cpp: In function ‘bool f(T) [with T = int]’:
main.cpp:5:3: internal compiler error: in gimplify_expr, at gimplify.c:8848
   };
   ^
0xa99c53 gimplify_expr(tree_node**, gimple_statement_base**,
gimple_statement_base**, bool (*)(tree_node*), int)
        ../../gcc/gcc/gimplify.c:8848
0xaa6bc0 gimplify_modify_expr
        ../../gcc/gcc/gimplify.c:4625
0xa979d2 gimplify_expr(tree_node**, gimple_statement_base**,
gimple_statement_base**, bool (*)(tree_node*), int)
        ../../gcc/gcc/gimplify.c:8116
0xa9bb96 gimplify_stmt(tree_node**, gimple_statement_base**)
        ../../gcc/gcc/gimplify.c:5526
0xa990d6 gimplify_and_add(tree_node*, gimple_statement_base**)
        ../../gcc/gcc/gimplify.c:398
0xa990d6 gimplify_return_expr
        ../../gcc/gcc/gimplify.c:1291
0xa990d6 gimplify_expr(tree_node**, gimple_statement_base**,
gimple_statement_base**, bool (*)(tree_node*), int)
        ../../gcc/gcc/gimplify.c:8363
0xa9bb96 gimplify_stmt(tree_node**, gimple_statement_base**)
        ../../gcc/gcc/gimplify.c:5526
0xa9d929 gimplify_body(tree_node*, bool)
        ../../gcc/gcc/gimplify.c:9250
0xa9df46 gimplify_function_tree(tree_node*)
        ../../gcc/gcc/gimplify.c:9408
0x92ccd7 cgraph_node::analyze()
        ../../gcc/gcc/cgraphunit.c:636
0x92fedb analyze_functions
        ../../gcc/gcc/cgraphunit.c:1028
0x930a68 symbol_table::finalize_compilation_unit()
        ../../gcc/gcc/cgraphunit.c:2477
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