[Issue 23988] New: Conditional Exp does not bring enums to correct common type if one leg is const

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23988

          Issue ID: 23988
           Summary: Conditional Exp does not bring enums to correct common
                    type if one leg is const
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: bugzilla at digitalmars.com

Consider:

    enum E : ubyte { A }

    pragma(msg, "test1 ", typeof(1 ? E.A : E.A));
    pragma(msg, "test2 ", typeof(1 ? E.A : cast(const)E.A));

which prints:

    test1 E
    test2 int

when it should print:

    test1 E
    test2 const(E)

The spec sez:

"If either the second or third expressions are of type void, then the resulting
type is void. Otherwise, the second and third expressions are implicitly
converted to a common type which becomes the result type of the conditional
expression."

https://dlang.org/spec/expression.html#conditional_expressions

Note that it doesn't exactly say what the common type is, but what the compiler
is doing is not expected. But the most obvious result should be const(E).

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