Zig: Slice length does not cast correctly

[dimenus]

test "slice len bug" {
    var list = [_]i32{ 1, 2, 3, 4 };
    const slice = list[0..];
    var baz: usize = 42;
    var bar: u32 = @as(u32, baz);
    var foo: u32 = @as(u32, slice.len);
}

generates test.zig:5:20: error: expected type 'u32', found 'usize' instead of compiling

Edit: Looks like this probably shouldn't compile. Just not a terribly helpful error.

[daurnimator]

This is expected behaviour: a usize can not (on your target at least) fit into a u32. See @intCast or @truncate.

[andrewrk]

Edit: Looks like this probably shouldn't compile. Just not a terribly helpful error.

What would a helpful error look like?

[dimenus]

Edit: Looks like this probably shouldn't compile. Just not a terribly helpful error.

What would a helpful error look like?

Something about as not being able to coerce a type into a type of a smaller size.

[JesseRMeyer]

Something about as not being able to coerce a type into a type of a smaller size.

test.zig:5:20: error: expected type 'u32', found 'usize'. Cannot safety type coerce usize to u32.
Did you mean: var bar: u32 = @intCast(u32, baz); ?

We should probably start a proposal for compiler error improvements. It's an enormous task.

[andrewrk]

Here's what it looks like to add a hint for failed type coercion: 8ecd6c4d8c021f7778b4959bdf75204dfd2d1946

@dimenus's test case now gives:

/home/andy/dev/zig/build/test.zig:5:20: error: expected type 'u32', found 'usize'
    var bar: u32 = @as(u32, baz);
                   ^
/home/andy/dev/zig/build/test.zig:5:20: note: unsigned 32-bit int cannot represent all possible unsigned 64-bit values
    var bar: u32 = @as(u32, baz);
                   ^