76434 – [1.5] Generics, assign error despite equal types

Bug 76434 - [1.5] Generics, assign error despite equal types

Summary: [1.5] Generics, assign error despite equal types

Status:	VERIFIED FIXED

Alias:	None

Product:	JDT
Classification:	Eclipse Project
Component:	Core (show other bugs)
Version:	3.1
Hardware:	PC Windows XP

Importance:	P3 normal with 1 vote (vote)
Target Milestone:	3.1 M3
Assignee:	Philipe Mulet
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Reported:	2004-10-16 21:56 EDT by Heri
Modified:	2005-01-03 09:41 EST (History)
CC List:	0 users

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Description Heri

2004-10-16 21:56:00 EDT

Build 200410130800

I get the following compile error:

Type mismatch: cannot convert from Set<Map.Entry<Integer,?>> to
Set<Map.Entry<Integer,?>>

with this class:

public class Test 
{
  private Set<Map.Entry<Integer, ?>> m_values;
  
  Test(Map<Integer, ?> values)
  {
    m_values = values.entrySet();
  }
}

Comment 1 Guillaume Pothier

2004-10-27 22:34:04 EDT

I've had several of these errors with M2 and latest integration build (I20041026).
I have been able to use a cast as a workaround. Interestingly enough, the
compiler reports a warning about useless cast.
It never happened with "top-level" generics, bu only with "nested" generics, ie.
X<A<B>>.

Comment 2 Guillaume Pothier

2004-10-27 22:36:43 EDT

Thinking about it, it might have to do with inner classes.

Comment 3 Philipe Mulet

2004-10-29 09:54:12 EDT

Reproduced

Comment 4 Philipe Mulet

2004-10-29 10:24:12 EDT

Problem comes from a mismatch in wildcards, due to capture mechanism.
We are comparing 
    Set<Map.Entry<Integer, ? denoting: V from Map) 
with 
    Set<Map.Entry<Integer, ? denoting: V from Map$Entry)

Comment 5 Philipe Mulet

2004-11-02 10:48:31 EST

Ensured wildcards are properly relocated when passed around.
Added regression test: GenericTypeTest#test363
Fixed

Comment 6 Frederic Fusier

2004-11-04 11:41:44 EST

Verified for 3.1 M3 with build I200411040800

Comment 7 Philipe Mulet

2005-01-03 09:41:35 EST

Actually, reverting previous behavior which was the proper one. 
Javac does actually also reject this code.

The 2 wildcard occurrences could denote different types. One is relative to
Entry, and one is relative to Map; as said before.