Compiler Seg faults when using a switch on an undefined u0 works with u1

[winksaville]

Here is with u0:

/// Compiler Seg faults:
/// #0  0x00007f4479d32bf0 in llvm::Value::getContext() const () from /usr/lib/libLLVM-6.0.so
/// #1  0x00007f4479cd07f0 in llvm::SwitchInst::SwitchInst(llvm::Value*, llvm::BasicBlock*, unsigned int, llvm::Instruction*) () from /usr/lib/libLLVM-6.0.so
/// #2  0x00007f4479c61845 in LLVMBuildSwitch () from /usr/lib/libLLVM-6.0.so
/// #3  0x000055e869c63221 in ir_render_switch_br (g=0x55e86ad49660, executable=0x55e86adbe0f0, instruction=0x55e86afb4380) at ../src/codegen.cpp:3872
/// #4  0x000055e869c68ef8 in ir_render_instruction (g=0x55e86ad49660, executable=0x55e86adbe0f0, instruction=0x55e86afb4380) at ../src/codegen.cpp:5245
/// #5  0x000055e869c696d1 in ir_render (g=0x55e86ad49660, fn_entry=0x55e86adbdf90) at ../src/codegen.cpp:5380
/// #6  0x000055e869c6db70 in do_code_gen (g=0x55e86ad49660) at ../src/codegen.cpp:6376
/// #7  0x000055e869c7441d in codegen_build_and_link (g=0x55e86ad49660) at ../src/codegen.cpp:8229
/// #8  0x000055e869ce5739 in main (argc=4, argv=0x7fffdaaa5ee8) at ../src/main.cpp:972
test "undefined.u0" {
    var val: u0 = undefined;
    switch (val) {
        0 => assert(val == 0),
    }
}

Here is u1 that works:

test "undefined.u1.assert.truncate" {
    var val: u1 = undefined;
    switch (val) {
        0 => assert(val == 0),
        else => assert(@truncate(u1, val) == 1),
    }
}

[winksaville]

The code is at zig-ux-semantics.

[winksaville]

Here is a slightly simpler case which Seg faults:

test "switch.u0" {
    var val: u0 = 0;
    switch (val) {
        0 => assert(val == 0),
    }
}