[Mono-bugs] [Bug 415375] New: CS0019 erroneously reported for equality comparison between object type value and generic type value with "class" reference constraint

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=415375


           Summary: CS0019 erroneously reported for equality comparison
                    between object type value and generic type value with
                    "class" reference constraint
           Product: Mono: Compilers
           Version: 2.0
          Platform: x86-64
        OS/Version: openSUSE 10.3
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: C#
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: other+novell at bluecherry.net
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---


Given the following code:

  public class Inner<T> where T : class {
    public static void Compare(object obj, T value) {
      if (obj != value) { }
    }
  }

Actual result:
error CS0019: Operator `!=' cannot be applied to operands of type `object' and
`T'

Expected result:
Compiles successfully

Supporting evidence:
csc.exe compiles with no error

(ECMA reference pulled from another bug)
ECMA 334 section 14.9.6 (Reference type equality operators)

"Otherwise, if either A or B is a type parameter that is not known to be a
reference type (§25.7), then no reference type equality operator is
applicable."

This appears to be applicable, and since T has the class constraint, it is
known to be a reference type.

Also, this doesn't even work which seems even stranger since both the arguments
are theoretically the same:
  public class ThisClass {}
  public class Inner<T> where T : ThisClass {
    public static void Compare(ThisClass obj, T value) {
      if (obj != value) { }
    }
  }


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