Casting from int to float in zig

Question

I'm trying to cast to float by calling @as on my variable, this works correctly if the variable is constant, but throws a compile error otherwise. How to correctly perform casting from int to float in zig?

pub fn main() void {
    var foo: u32 = 3;
    const bar: f32 = @as(f32, foo) / 5;
    foo = 42;
    std.debug.print("{d}", .{bar});
}

error: expected type 'f32', found 'u32'
    const bar: f32 = @as(f32, foo) / 5;
                              ^~~