[Mono-bugs] [Bug 74885][Nor] New - ECMA 14.9.6 violation

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Changed by robertj@gmx.net.

http://bugzilla.ximian.com/show_bug.cgi?id=74885

--- shadow/74885	2005-05-09 14:53:57.000000000 -0400
+++ shadow/74885.tmp.7538	2005-05-09 14:53:57.000000000 -0400
@@ -0,0 +1,78 @@
+Bug#: 74885
+Product: Mono: Compilers
+Version: 1.1
+OS: All
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Normal
+Component: C#
+AssignedTo: mono-bugs@ximian.com                            
+ReportedBy: robertj@gmx.net               
+QAContact: mono-bugs@ximian.com
+TargetMilestone: ---
+URL: 
+Summary: ECMA 14.9.6 violation
+
+ECMA 14.9.6 states that the predefined operator "=="
+must fail on value types. Both mcs and gmcs (from SVN)
+violate the rule when a user-defined implicit convertion
+for a numeric type is implemented by a value type:
+
+using System;
+
+struct S {
+    int v;
+
+    public S(int i) {
+        this.v = i;
+    }
+
+    public static implicit operator int(S s) {
+        return s.v;
+    }
+}
+
+class T {
+    static void Main() {
+        S a = new S(1);
+        S b = new S(1);
+        // should fail with error CS0019
+        Console.WriteLine(a == b);
+    }
+}
+
+
+I guess that the problem can be find in [g]mcs/expression.cs,
+method Binary.ResolveOperator(), that doesn't handle the case
+(l.IsValueType && r.IsValueType).
+Therefore the DoNumericPromotions()-call from ResolveOperator()
+promotes the operands to Int32 and the "=="-operator succeeds.
+
+Note that MSFT's CSC 1.0 & 1.1 have the same glitch!
+
+Beside the problem with the user-defined implicit convertion
+for numeric types, CSC 2.0b2 gets fooled by a user-defined
+string convertion as well:
+
+struct S {
+    int v;
+
+    public S(int i) {
+        this.v = i;
+    }
+
+    public static implicit operator string(S s) {
+        return s.v.ToString();
+    }
+}
+
+class T {
+    static void Main() {
+        S a = new S(1);
+        S b = new S(1);
+        // should fail with error CS0019
+        Console.WriteLine(a == b);
+    }
+}