[Issue 20744] [The D Bug Tracker] UDAs on function parameters confuse std.traits.ParameterDefaults

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20744

Simen Kjaeraas <simen.kjaras at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |simen.kjaras at gmail.com

--- Comment #2 from Simen Kjaeraas <simen.kjaras at gmail.com> ---
Definitely a compiler issue. It seems UDAs are being looked up in the scope
where the result of `is(Func PT == __parameters)` is being used. Here's a very
reduced example:

module foo;

import bar;

struct S {}

void f(@S int = 3);

pragma(msg, ParameterDefaults!f.stringof);

-----

module bar;

//enum S = 3; // Uncomment to make things compile

template ParameterDefaults(func...) {
    static if (is(typeof(func[0]) PT == __parameters)) {
        enum ParameterDefaults = (PT[0..1] args) @trusted {
            return *&(args[0]);
        }();
    }
}

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