[Issue 20001] New: Error: a struct is not a valid initializer for a _error_

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20001

          Issue ID: 20001
           Summary: Error: a struct is not a valid initializer for a
                    _error_
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: elpenguino+D at gmail.com

Very easy to reproduce:
```
X x = {};
```

This gives us a useful "undefined identifier X" error and the useless error
mentioned in the title. The second error should not be printed in this case.

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