Bug 223427

Summary:	[1.5][compiler] unnecessary warning when creating an array of varargs
Product:	[Eclipse Project] JDT	Reporter:	Rémi Forax <forax>
Component:	Core	Assignee:	Srikanth Sankaran <srikanth_sankaran>
Status:	VERIFIED WONTFIX	QA Contact:
Severity:	normal
Priority:	P3	CC:	jarthana, Olivier_Thomann, srikanth_sankaran
Version:	3.4
Target Milestone:	3.8 M5
Hardware:	PC
OS:	Linux
Whiteboard:

Description Rémi Forax

2008-03-20 17:19:31 EDT

Build ID: I20080207-1530

Steps To Reproduce:
1. compile the snippet

HashSet<Class<?>> constantClassSet=new HashSet<Class<?>>();
Collections.addAll(constantClassSet,
  String.class,       // utf8 symbols
  Integer.class, Float.class, Long.class, Double.class // primitive values
);

More information:
The warning reported by the compiler: 
Type safety : A generic array of Class<? extends Object> is created for a varargs parameter	AnonymousClassLoader.java	kijaro-properties/davinci/bootcp/java/dyn	line 229	Java Problem13

An array of parameterized type is unsafe because a parameterized
type is not a reified type. An array of wildcard type is safe.
The compiler infers Class<? extends Object> but doesn't 'see'
that Class<? extends Object> is equivalent to Class<?>.

Rémi

Comment 1 Rémi Forax

2008-04-21 08:50:41 EDT

Argh, the previous test case doesn't exhibit the problem.
Should be:

HashSet<Class<?>> constantClassSet=new HashSet<Class<?>>();
Collections.addAll(constantClassSet,
  String.class, Object.class
);

Comment 2 Philipe Mulet

2008-04-21 09:07:27 EDT

This equivalence is not accounted in the spec, hence the compiler diagnosis is accurate I believe.

I agree that the underlying bounds are equivalent, but Class<?> is unbound, and benefits from certain privileges wrt to reification where Class<? extends Object>. So unless the spec was to account for it, then we wouldn't be allowed to change this.

Note that javac exhibits the same behavior as we do.

Comment 3 Philipe Mulet

2008-04-21 09:19:52 EDT

Added VarargsTest#test061

Comment 4 Srikanth Sankaran

2012-01-11 03:23:29 EST

Rémi, As you are aware, SE7 adds linguistic support
for this via @SafeVarargs annotation. OK to close
as is for compliance < 1.7 ?

Comment 5 Rémi Forax

2012-01-11 08:45:15 EST

(In reply to comment #4)
> Rémi, As you are aware, SE7 adds linguistic support
> for this via @SafeVarargs annotation. OK to close
> as is for compliance < 1.7 ?

Ok to close.
Philippe was right and could have closed that bug.

cheers,
Rémi

Comment 6 Srikanth Sankaran

2012-01-11 19:49:46 EST

Closing as WONTFIX.

Comment 7 Jay Arthanareeswaran

2012-01-23 05:10:08 EST

Verified for 3.8M5