Bug ID: JDK-8024809 javac, some lambda programs are rejected by flow analysis

Type: Bug
Component: tools
Sub-Component: javac
Affected Version: 8

Priority: P3
Status: Closed
Resolution: Fixed

Submitted: 2013-09-13
Updated: 2015-05-11
Resolved: 2013-10-19

JDK 8
8 b115Fixed

This compiles

public class Tmp
{
    final Runnable r1 = ()->System.out.println(r1);
}

This does NOT . . . . . . . . . . . . . . . . . . . . . . . . .

public class Tmp
{
    final Runnable r1;

    final Runnable r2 = ()-> System.out.println(r1); // Error: r1 not
initialized

    Tmp()
    {
        r1 = ()->System.out.println(r1);  // Error: r1 not initialized
    }
} 

This compiles . . . . . . . . . . . . . . . . . . . . . . . . .

public class Tmp
{
    final Object lock = new Object();

    final Runnable r2 = ()->{
        System.out.println(r2);
        synchronized (lock){
        }
    };
}

This does NOT . . . . . . . . . . . . . . . . . . . . . . . . .

public class Tmp
{
    final Object lock = new Object();

    final Runnable r2 = ()->{
        synchronized (lock){
            System.out.println(r2);  // Error: self-reference in initializer
        }
    };
}


reported by Zhong Yu in lambda-dev list.

The following code doesn't produce a compilation error if ran vs jdk b132: class Tmp { final Runnable notInitialized = () -> { Runnable simpleVariable = notInitialized; }; } and this produces: class Tmp { final Runnable notInitialized = () -> { System.out.println(notInitialized); }; } It seems to me that behavior in both cases should be similar, shouldn't it?
24-07-2014
The fix for this patch will break several JCK tests, this is expected, the affected tests will need to be modified.
19-10-2013
The fix for this bug can't be pushed till the fix for JDK-8026854 is in TL
18-10-2013
The current patch for this bug breaks the build: /home/vromero/openJDK/jdk8Flow/jdk/src/share/classes/java/time/temporal/TemporalQueries.java:101: error: self-reference in initializer return temporal.query(ZONE_ID); ^ /home/vromero/openJDK/jdk8Flow/jdk/src/share/classes/java/time/temporal/TemporalQueries.java:108: error: self-reference in initializer return temporal.query(CHRONO); ^ /home/vromero/openJDK/jdk8Flow/jdk/src/share/classes/java/time/temporal/TemporalQueries.java:115: error: self-reference in initializer return temporal.query(PRECISION); ^ /home/vromero/openJDK/jdk8Flow/jdk/src/share/classes/java/time/temporal/TemporalQueries.java:124: error: illegal forward reference return (zone != null ? zone : temporal.query(OFFSET)); This is the now offending code is: static final TemporalQuery<ZoneId> ZONE_ID = (temporal) -> { return temporal.query(ZONE_ID); }; static final TemporalQuery<Chronology> CHRONO = (temporal) -> { return temporal.query(CHRONO); }; static final TemporalQuery<TemporalUnit> PRECISION = (temporal) -> { return temporal.query(PRECISION); }; static final TemporalQuery<ZoneId> ZONE = (temporal) -> { ZoneId zone = temporal.query(ZONE_ID); return (zone != null ? zone : temporal.query(OFFSET)); };
15-10-2013
Two specified errors are intertwined here. #1, 8.3.2.3: First, a "use" of a field in a field initializer is generally prohibited if the use occurs before the field declaration. The spec is not very clear on this, but the intent has always been that "before" includes the field's own initializer. So "int x = x+1;" is not a valid field declaration. The rules carve out two exceptions: i) assignment to a field before its declaration is okay; ii) a use from inside of an anonymous class is okay. There is no exception for a use inside of a lambda expression, so "Runnable r1 = ()->System.out.println(r1);" is illegal. #2, Ch. 16: Second, a blank final field must be definitely assigned before its use. Per 16.9, a use of a blank final field in another field's initializer must be preceded by an assignment to that field in some other (preceding) initializer. This explains the two errors in example #2. --- Summary evaluation: every use of 'r1' or 'r2' in these examples should be treated as an error.
30-09-2013

Blocks :	JDK-8026854 - java.time.temporal.TemporalQueries doesn't compile after javac modification to lambda flow analysis
Relates :	JDK-8028059 - javac: illegal forward reference since b115
Relates :	JDK-8027677 - microbenchmarks failed with self-reference in initializer
Relates :	JDK-8053906 - javac is accepting a self-referencing variable initializer inside a lambda expression
Relates :	JDK-8027941 - javac fails with "self-reference in initializer" when referencing the static field from lambda
Relates :	JDK-8077667 - 'variable may not have been initialized' error for parameter in lambda function
Relates :	JDK-8026854 - java.time.temporal.TemporalQueries doesn't compile after javac modification to lambda flow analysis
Relates :	JDK-8025762 - 8.3.3: Clarify that a field cannot be referenced in its own initializer