[Issue 11257] Allow whole implicit conversion if one or more overlapped field could.

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=11257

--- Comment #3 from Walter Bright <bugzilla at digitalmars.com> ---
I can't agree with this. A cast should be used to break out of const, and
should not be allowed in @safe code.

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