gccgo: internal compiler error in backend_numeric_constant_expression

[dvyukov]

gccgo crashes on the following program:

package a
const (
    d rune=0^V
    (=0
    V
)

go1: internal compiler error: in backend_numeric_constant_expression, at go/gofrontend/expressions.cc:460
0x5f2093 Expression::backend_numeric_constant_expression(Translate_context*, Numeric_constant*)
    ../../gcc/go/gofrontend/expressions.cc:460
0x5f2311 Integer_expression::do_get_backend(Translate_context*)
    ../../gcc/go/gofrontend/expressions.cc:1953
0x5f431d Const_expression::do_get_backend(Translate_context*)
    ../../gcc/go/gofrontend/expressions.cc:2864
0x619571 Named_constant::get_backend(Gogo*, Named_object*)
    ../../gcc/go/gofrontend/gogo.cc:6621
0x620726 Named_object::get_backend(Gogo*, std::vector<Bexpression*, std::allocator<Bexpression*> >&, std::vector<Btype*, std::allocator<Btype*> >&, std::vector<Bfunction*, std::allocator<Bfunction*> >&)
    ../../gcc/go/gofrontend/gogo.cc:7091
0x626912 Gogo::write_globals()
    ../../gcc/go/gofrontend/gogo.cc:1345

gcc version 6.0.0 2015070 (experimental) (GCC)

[dvyukov]

@paranoiacblack

[gopherbot]

CL https://golang.org/cl/13794 mentions this issue.