Fix NPE on goto to invalid method reference

[mbien]

• check if element is a record before listing components
• removed reflective method calls and updated logic
• added regression test

reproducer:

public class GoToInvalidMethodReferenceNPE {
    public static void main(String args[]) {
        ChangeListener listener = GoToInvalidMethodReferenceNPE::invalid;
        //                                                       ^^^^^^^ ctrl click (after parsing)
    }
}

fixes #8735

[mbien]

is this cast ok?

[lahodaj]

I think it mostly is OK. And it basically weakly suggests that peer.getEnclosingElement() == enclosing, which should be always true. (I probably would just do enclosing.getEnclosingElement(), though.)

I wonder if it is possible to write a test for this - I can try at some point if needed.

Otherwise - great cleanup, thanks for doing this!

[mbien]

(I probably would just do enclosing.getEnclosingElement(), though.)

you mean changing

    for (RecordComponentElement component : ((TypeElement)peer.getEnclosingElement()).getRecordComponents()) {

into

    for (RecordComponentElement component : ((TypeElement)enclosing).getRecordComponents()) {

good idea,

[mbien]

added regression test and updated the logic so that it breaks out of both loops instead of just the inner loop.

[mbien]

rebased, planning to merge once tests are green.

[mbien]

btw for future reference: this check basically is the fix for this issue. Without it, javac would throw a NPE a few lines later (see reproducer).

java.lang.NullPointerException: Cannot invoke "com.sun.tools.javac.code.Scope$WriteableScope.getSymbols(com.sun.tools.javac.code.Scope$LookupKind)" because the return value of "com.sun.tools.javac.code.Symbol$TypeSymbol.members()" is null
	at com.sun.tools.javac.code.Symbol$TypeSymbol.getEnclosedElements(Symbol.java:879)
	at com.sun.tools.javac.code.Symbol$TypeSymbol.getEnclosedElements(Symbol.java:818)
	at org.netbeans.modules.editor.java.GoToSupport.resolveContext(GoToSupport.java:481)