[Issue 23142] New: Scope should not apply to unittests

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23142

          Issue ID: 23142
           Summary: Scope should not apply to unittests
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: alphaglosined at gmail.com

When declaring in a class or struct a unittest block should ignore any scope
attributes set due to not having a context pointer.

```d
void main()
{
}

struct Foo
{
    int x;

scope:
    void func()
    {
    }

    unittest
    {
    }
}
```

onlineapp.d(9): Error: function `onlineapp.Foo.__unittest_L9_C4` functions
cannot be `scope`

This error is not at all helpful and prevents a common use case for unittests
as documentation without writing scope on every method which is very
error-prone.

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