[Mono-bugs] [Bug 610240] New: Nested classes with generics: type parameters not considered equal (from same bindings)

bugzilla_noreply at novell.com bugzilla_noreply at novell.com
Sun May 30 23:34:54 EDT 2010



           Summary: Nested classes with generics: type parameters not
                    considered equal (from same bindings)
    Classification: Mono
           Product: Mono: Compilers
           Version: SVN
          Platform: i386
        OS/Version: Ubuntu
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: C#
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: chadwick at ccs.neu.edu
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---
           Blocker: ---

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:
Gecko/20100410 Ubuntu/9.10 (karmic) Firefox/3.5.9

Nested classes that share a parent's type parameter are not considered equal...

Here's a minimized test-case, ("Gen.cs"):

  // ---------------  Gen.cs  ------------------------
     public class List<X>{
         public class Comp<Y>{
             public List<Y>.Comp<X> flip(Y y, X x){
                 return new Flip<Y>(this);
         public class Flip<Z> : List<Z>.Comp<X>{
             Comp<Z> c;
             public Flip(Comp<Z> cc){ c = cc; }
  // -----------------------------------------------

The nested classes refer to the same binding of the type parameter X. Yet the
call to the constructor of List<X>.Flip<Y> inside of List<X>.Comp<Y> is flagged
as not matching the constructor's parameter type (once renamed) of
List<X>.Comp<Y>, even though X and Y in both cases share bindings.

Fully expanding all types in the source (i.e., prefixing with List<X>) doesn't
affect the result.

Errors are:
   Gen.cs(4,37): error CS1502: The best overloaded method match for
`List<X>.Flip<Y>.Flip(List<X>.Comp<Y>)' has some invalid arguments
   Gen.cs(4,37): error CS1503: Argument `#1' cannot convert `List<X>.Comp<Y>'
expression to type `List<X>.Comp<Y>'

With a mention of:
   Gen.cs(4,37): (equally named types possibly from different assemblies in
previous error)

Using a build from daily source:

If this is the expected behavior a suggestion for achieving this kind of
'equality' would be greatly appreciated.

Reproducible: Always

Steps to Reproduce:
1. Compile the test file GMCS
Actual Results:  
Compile Errors

Expected Results:  
Successful Compile

Older version (gmcs 2.4.3) was not so strict, not requiring the List<Y> and
List<Z> prefixes on lines 3 and 7, which were caught by Microsoft CSC.

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