148046 – [compiler][1.5] should raise an incompatible types error when a given type variable cannot fulfill its bounds

Bug 148046 - [compiler][1.5] should raise an incompatible types error when a given type variable cannot fulfill its bounds

Summary: [compiler][1.5] should raise an incompatible types error when a given type va...

Status:	VERIFIED FIXED

Alias:	None

Product:	JDT
Classification:	Eclipse Project
Component:	Core (show other bugs)
Version:	3.2
Hardware:	PC All

Importance:	P3 normal (vote)
Target Milestone:	3.4 M3
Assignee:	Philipe Mulet
QA Contact:

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Reported:	2006-06-21 10:41 EDT by Maxime Daniel
Modified:	2007-10-29 08:36 EDT (History)
CC List:	0 users

See Also:

Attachments
Proposed patch (4.86 KB, patch) 2007-10-10 07:26 EDT, Philipe Mulet	no flags	Details \| Diff
Better patch (5.35 KB, patch) 2007-10-10 07:45 EDT, Philipe Mulet	no flags	Details \| Diff
Additional change (4.87 KB, patch) 2007-10-10 10:09 EDT, Philipe Mulet	no flags	Details \| Diff
Show Obsolete (1) View All Add an attachment (proposed patch, testcase, etc.)

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Description Maxime Daniel

2006-06-21 10:41:33 EDT

Version: 3.2.0
Build id: I20060614-0843

In GenericTypeTest#550, which is copied below for clarity, U must extend B and honor a lower bound of A. But B extends A, hence U cannot satisfy all its bounds, and javac 1.5.0_08 and 6.0 b86 both raise an error. Eclipse only raises an unchecked warning.

class A {}
class B extends A {}
public class X<T> {
	public <U extends B> void foo(X<? super A> param) {
		X<U> foo = (X<U>) param; // unchecked warning vs error
	}
}

Comment 1 Philipe Mulet

2006-10-08 10:24:46 EDT

Cast checks are spec'ed to tolerate such situations where both types are not provably distinct.

javac doesn't follow the spec here; but I admit their behavior is more helpful as statically the cast could be rejected based on bound constraints.

Need to decide whether we bet on spec to evolve in javac direction or we stick to the spec.

Comment 2 Philipe Mulet

2007-01-10 06:45:27 EST

Other symptoms in bug 120088.

Comment 3 Philipe Mulet

2007-01-10 06:45:50 EST

Also see bug 170064.

Comment 4 Philipe Mulet

2007-10-10 07:23:58 EDT

Added GenericTypeTest#test1193

Comment 5 Philipe Mulet

2007-10-10 07:26:02 EDT

Created attachment 80032 [details]
Proposed patch

Comment 6 Philipe Mulet

2007-10-10 07:28:33 EDT

Tuned GenericTypeTest#test0550

Comment 7 Philipe Mulet

2007-10-10 07:45:56 EDT

Created attachment 80034 [details]
Better patch

Comment 8 Philipe Mulet

2007-10-10 07:51:31 EDT

Released for 3.4M3.
Fixed

Comment 9 Philipe Mulet

2007-10-10 10:09:28 EDT

Created attachment 80043 [details]
Additional change

Required to avoid some regression in classlibs (java/lang/Class)

Comment 10 Philipe Mulet

2007-10-10 10:09:51 EDT

Released for 3.4M3.
Fixed

Comment 11 Maxime Daniel

2007-10-29 08:36:54 EDT

Verified for 3.4 M3 using build I20071029-0010.