Bug 84345

Summary:

[1.5][compiler] Widening reference is possible when boxing in a cast expression

Product:

[Eclipse Project] JDT

Reporter:

Olivier Thomann <Olivier_Thomann>

Component:

Core

Assignee:

Philipe Mulet <philippe_mulet>

Status:

VERIFIED FIXED

QA Contact:

Severity:

normal

Priority:

Version:

3.1

Target Milestone:

3.1 M5

Hardware:

OS:

Windows XP

Whiteboard:

Attachments:

Description	Flags
Apply on HEAD	none

Description Olivier Thomann

2005-02-03 11:57:29 EST

In a cast expression, it is possible to cast a byte into Number.
byte b = 0;
Number n = (Number) b;

is legal. Right now we report an incompatible cast.

The test in Expression checks for == in case of boxing instead of
isCompatibleWith(...).

Comment 1 Olivier Thomann

2005-02-03 11:59:01 EST

Created attachment 17659 [details]
Apply on HEAD

I am running all the tests now.
With this patch, we report the cast as unnecessary. Indeed, if you remove the
cast, it compiles perfectly fine.

Comment 2 Olivier Thomann

2005-02-03 13:01:42 EST

With this patch, everything looks good for the cast expression, but there is a
side effect in the EqualExpression.
The following code doesn't report an error anymore:

public class X {
  public Object foo() {
    java.io.Serializable o = null;
    if (o == 0) return o;
    return this;
  }
}

The JLS3 don't require the types to be cast compatible anymore. They refer to
types that need to be convertible to numeric types. java.io.Serializable is not
convertible to a numeric types.
Check 5.1.8 section.

Comment 3 Olivier Thomann

2005-02-03 14:28:43 EST

Forget what I said in comment 2. This was wrong. In case of reference type, the
casting conversion still apply. I need to investigate what should be the fix in
the cast check to handle the equality expressions.

Comment 4 Philipe Mulet

2005-02-07 12:34:23 EST

I believe the spec is a bit unprecise. It does perform numeric comparison as
soon as any of the operand is a numeric type.
Adjusted the implementation along this idea.

Added AutoboxingTest#test089.
Fixed

Comment 5 Jerome Lanneluc

2005-02-15 09:00:42 EST

Verified in I20050214