std.builtin.FnArg should be comptime?

[SrMordred]

fn f1() void {}
fn f2(x:u32) u32 { return x; }

fn main() void {
    //fine
    const T = @typeInfo( @TypeOf(f1) ); 
    print("{any}", .{T});

    //values of type 'std.builtin.FnArg' must be comptime known, but index value is runtime known
    const T = @typeInfo( @TypeOf(f2) );
    print("{any}", .{T});
}

[SpexGuy]

This is a bug in std.fmt, it has failed to recognize that a value is comptime only and is trying to format it at runtime.