@ptrToInt fails at comptime if expression result is a variable

[Snektron]

The following snippet fails to compile:

export fn a() usize {
    return comptime blk: {
        const b: u8 = 1;
        const c = @ptrToInt(&b);
        break :blk c;
    };
}

<source>:4:19: error: cannot store runtime value in compile time variable
        const c = @ptrToInt(&b);
                  ^

but if the temporary c is left out:

export fn a() usize {
    return comptime blk: {
        const b: u8 = 1;
        break :blk @ptrToInt(&b);
    };
}

compilation is successful. Note that it does not matter whether c is designated as comptime variable, it yields the same error. Same with assigning an expression to c which is dependent on @ptrToInt(&b).