Name lookups in D

[kdevel]

On Monday, 14 December 2020 at 16:21:56 UTC, Steven Schveighoffer 
wrote:
[...]
>> Just 'implemented' the following bug:
>> 
>> ~~~
>> import std.conv;
>> 
>> class B {
>> }
>> 
>> class D : B {
>>     string text;
>> }
>> 
>> void main ()
>> {
>>     B b = new D;
>>     string s = b.text;
>> }
>> ~~~
>> 
>> Due to UFCS std.conv.text grabs the object. Only a `static 
>> import`
>> or a selective import would reveal the problem during compile 
>> time.
>
> This is expected behavior.

Sure. In the original code the missing downcast was not that 
easily
discernible.

> B does not have a member named "text", and so it looks for a 
> UFCS function to call and finds one.
>
> Note that a static import means you have to use the FQN to call 
> text (but text is perfectly fine via UFCS). However, a 
> selective import would still call text as expected.

The original code accessed only std.conv.to. A selective import
of `to` would have complained and helped to spot the error:

q.d(13): Error: no property text for type q.B, perhaps import 
std.conv; is needed?

BTW: Most of the time dmd's guess is accurate.