The following invalid code snippet triggers an ICE since GCC 7.1.0:

===============================
template<int> struct A
{
  int i{};

  A();
  constexpr A(int) : A() {}
};

constexpr A<0> a{0};
===============================

bug.cc:9:19: error: 'constexpr A<<anonymous> >::A(int) [with int <anonymous> = 0]' called in a constant expression
    9 | constexpr A<0> a{0};
      |                   ^
bug.cc:6:13: note: 'constexpr A<<anonymous> >::A(int) [with int <anonymous> = 0]' is not usable as a 'constexpr' function because:
    6 |   constexpr A(int) : A() {}
      |             ^
bug.cc:6:13: internal compiler error: in build_data_member_initialization, at cp/constexpr.c:400
0x66cf30 build_data_member_initialization
	../../gcc/gcc/cp/constexpr.c:400
0x960432 build_constexpr_constructor_member_initializers
	../../gcc/gcc/cp/constexpr.c:612
0x960432 massage_constexpr_body
	../../gcc/gcc/cp/constexpr.c:738
0x96ce3d explain_invalid_constexpr_fn(tree_node*)
	../../gcc/gcc/cp/constexpr.c:982
0x9621e1 cxx_eval_call_expression
	../../gcc/gcc/cp/constexpr.c:2594
0x96543c cxx_eval_constant_expression
	../../gcc/gcc/cp/constexpr.c:6269
0x968cc4 cxx_eval_outermost_constant_expr
	../../gcc/gcc/cp/constexpr.c:7301
0x96da7e maybe_constant_init_1
	../../gcc/gcc/cp/constexpr.c:7756
0xb9902a store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, int)
	../../gcc/gcc/cp/typeck2.c:777
0x9b4cc6 check_initializer
	../../gcc/gcc/cp/decl.c:7185
0x9dab09 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
	../../gcc/gcc/cp/decl.c:8119
0xac5174 cp_parser_init_declarator
	../../gcc/gcc/cp/parser.c:22556
0xaa0773 cp_parser_simple_declaration
	../../gcc/gcc/cp/parser.c:15088
0xacfdb5 cp_parser_declaration
	../../gcc/gcc/cp/parser.c:14787
0xad078e cp_parser_toplevel_declaration
	../../gcc/gcc/cp/parser.c:14808
0xad078e cp_parser_translation_unit
	../../gcc/gcc/cp/parser.c:4978
0xad078e c_parse_file()
	../../gcc/gcc/cp/parser.c:46558
0xbf924d c_common_parse_file()
	../../gcc/gcc/c-family/c-opts.c:1223
Please submit a full bug report, [etc.]