gccgo: internal compiler error in do_determine_type

[dvyukov]

gccgo crashes on the following input:

package a
var _[t]

go1: internal compiler error: in do_determine_type, at go/gofrontend/expressions.h:1182
0x5fffd7 Parser_expression::do_determine_type(Type_context const*)
    ../../gcc/go/gofrontend/expressions.h:1182

0x6697dc Array_type::verify_length()
    ../../gcc/go/gofrontend/types.cc:5721
0x669a38 Array_type::do_verify()
    ../../gcc/go/gofrontend/types.cc:5784
0x617004 Type::verify()
    ../../gcc/go/gofrontend/types.h:580
0x617004 Gogo::verify_types()
    ../../gcc/go/gofrontend/gogo.cc:2548
0x610544 go_parse_input_files(char const**, unsigned int, bool, bool)
    ../../gcc/go/gofrontend/go.cc:102
0x60c32f go_langhook_parse_file
    ../../gcc/go/go-lang.c:304

gcc version 6.0.0 2015070 (experimental) (GCC)

[dvyukov]

@paranoiacblack

[gopherbot]

CL https://golang.org/cl/13795 mentions this issue.