[nem-bug] [Nemerle 0000846]: Do not allow to cast array[T] to array[S], if T is not known to be a reference type

[feedback at nemerle.org]

A NOTE has been added to this issue.
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<http://nemerle.org/bugs/view.php?id=846> 
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Reported By:                nikov
Assigned To:                
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Project:                    Nemerle
Issue ID:                   846
Category:                   Code Completion Engine
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
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Date Submitted:             01-28-2007 10:03 CET
Last Modified:              01-28-2007 10:23 CET
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Summary:                    Do not allow to cast array[T] to array[S], if T is
not known to be a reference type
Description: 
Do not allow to cast array[T] to array[S], if T is not known to be a
reference type (and T, S are different types). Consider the following
code:

using System.Collections.Generic;

module A {
	Foo[T,S](x : array[T]) : array[S] where T : S {
		x :> array[S]
	}
	Main() : void {
		_ = Foo.[int,object](array[1,2,3]);
	}
}

Ncc compiles this successfully, but the program fails at runtime. This
could be prevented at compile time, if Nemerle required T to be known to
be a reference type in order to allow cast between arrays (as, for
instance, C# does).

using System.Collections.Generic;

module A {
	Foo[T,S](x : array[T]) : array[S] where T : class, S {
		x :> array[S]
	}
}


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----------------------------------------------------------------------
 nikov - 01-28-07 10:23 
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Sorry, category should be '[Nemerle] Compiler', not 'Completion Engine'.

Issue History
Date Modified  Username       Field                    Change              
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01-28-07 10:03 nikov          New Issue                                    
01-28-07 10:23 nikov          Note Added: 0001653                          
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