[Mono-bugs] [Bug 46502][Nor] New - Interface constraint on class affects overloading resolution for indexers

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Changed by sestoft@dina.kvl.dk.

http://bugzilla.ximian.com/show_bug.cgi?id=46502

--- shadow/46502	Thu Jul 17 04:09:15 2003
+++ shadow/46502.tmp.24091	Thu Jul 17 04:09:15 2003
@@ -0,0 +1,76 @@
+Bug#: 46502
+Product: Mono/MCS
+Version: unspecified
+OS: 
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Normal
+Component: Misc
+AssignedTo: mono-bugs@ximian.com                            
+ReportedBy: sestoft@dina.kvl.dk               
+QAContact: mono-bugs@ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: Interface constraint on class affects overloading resolution for indexers
+
+Description of Problem:
+
+Adding an interface constraint Seq : ISeq on class Seq changes overloading
+resolution for indexers, even in an expression where the interface is not used.
+
+Steps to reproduce the problem:
+1. Compile the program below
+
+using System;
+
+class Seq : ISeq {
+  public int this[int i] {
+    get { return i; }
+  }
+
+  public int[] this[params int[] ii] {
+    get { return new int[] { this[1], this[2], this[ii.Length] }; }
+  }
+}
+
+class TestSeq {
+  public static void Main(String[] args) {
+    Seq s4 = new Seq();
+    Console.WriteLine(s4[1]);			// 1
+    int[] r = s4[2, 2, 1, 2, 0];
+    for (int i=0, stop=r.Length; i<stop; i++)	// 1 2 5
+      Console.Write(r[i] + " ");        
+    Console.WriteLine();
+  }
+}
+
+interface ISeq { 
+  int this[int i] { get; }
+  int[] this[params int[] ii] { get; }
+}
+
+Actual Results:
+
+Bug7.cs(34) error CS0121: Ambiguous call when selecting function due to
+implicit casts
+Bug7.cs(34) error CS1501: No Overload for method `this' takes `5' arguments
+Compilation failed: 2 error(s), 0 warnings
+
+Expected Results:
+
+Should compile without problems; does with MS csc 1.1.
+
+How often does this happen? 
+
+Always in mono 0.25.  
+
+Additional Information:
+
+If the interface constraint ISeq is removed, everything is OK.  The
+bytecode generated by MS csc 1.1 executes fine with mono 0.25, so the
+problem is in mcs.  The process of interface mapping in mcs must have some
+weird side effect.  There is no problem if only the int this[int] indexer
+is defined in Seq and ISeq.