unexpected truncation behavior with comptime_int larger than u64 range

[leesongun]

Trying to compile the following code

comptime {
    var a : u8 = @truncate(u1, 1 << 64);
}

results in (the value 139978047751248 changes every time)

./main.zig:2:18: error: integer value 139978047751248 cannot be coerced to type 'u8'
    var a : u8 = @truncate(u1, 1 << 64);
                 ^

This seems to be reason behind the following problems :

1. The following code reaches unreachable.

test "large comptime_int truncation" {
    if (@truncate(u1, 0x1_0000_0000_0000_0000) != 0)
        unreachable;
}

2. The following code prints 0.

const print = @import("std").debug.print;
test "print large comptime_int truncation" {
    print("{}", .{@truncate(u1, 0x1_0000_0000_0000_0001)});
}