Fix Bugzilla Issue 24687 - [REG2.110] Cannot cast string-imports to select overload anymore

[RazvanN7]

When checking if an expression is implicitly convertible to a type the current implementation of hexstring assumes that the match is convert irrespective of what the actual types are. Fix this by considering the case where the types are identical.

cc @dkorpel as the original author.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	24687	regression	[REG2.110] Cannot cast string-imports to select overload anymore

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#16770"

[RazvanN7]

This could also be expressed as a separate condition at the beginning of this function:

if (e.type == t)
    return MATCH.exact;

However, I wanted it to be localized to the actual code that introduced the regression. Arguably, this condition should be first executed by the implicitConvTo function, however, I believe that when it was implemented the expectation was that this would be checked at the call site before actually calling implicitConvTo.

[dkorpel]

Nice! I was a bit puzzled by the issue, and was afraid it would require another match level to fix, but you found a straightforward fix