NPE when variable is initialized using a method with the same name in features calling "thrown()"

[rieske]

Issue description

A variable initialized using a method with the same name, as in def foo = foo() throws a NullPointerException when used in a feature method that calls thrown() in then: block.

How to reproduce

class SomeSpec extends spock.lang.Specification {
    def "foo test"() { // fails
        when:
        def foo = foo() // fails here
        println(foo)
        throw new IllegalStateException()

        then:
        thrown IllegalStateException
    }

    def "bar test"() { // passes
        when:
        def bar = foo()
        println(bar)
        throw new IllegalStateException()

        then:
        thrown IllegalStateException
    }

    String foo() {
        return "foo"
    }
}

foo test fails when running this test class (only tried with Gradle):

Expected exception of type 'java.lang.IllegalStateException', but got 'java.lang.NullPointerException'
	at org.spockframework.lang.SpecInternals.checkExceptionThrown(SpecInternals.java:81)
	at org.spockframework.lang.SpecInternals.thrownImpl(SpecInternals.java:68)
	at SomeSpec.foo test(SomeSpec.groovy:9)
Caused by: java.lang.NullPointerException: Cannot invoke method call() on null object
	at SomeSpec.foo test(SomeSpec.groovy:4)

Additional Environment information

Java/JDK

java -version

openjdk version "11.0.8" 2020-07-14
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.8+10)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.8+10, mixed mode)

Build-tool dependencies used

Gradle 6.8.1

Fails with: testImplementation("org.spockframework:spock-core:2.0-M4-groovy-2.5") and testImplementation("org.spockframework:spock-core:2.0-M4-groovy-3.0")

Works with: testImplementation("org.spockframework:spock-core:1.3-groovy-2.5")

[leonard84]

Hm, this might be a bit tricky to fix.

This happens because Spock transforms the when block above thrown into

        java.lang.Object foo 
        this.getSpecificationContext().setThrownException(null)
        try {
            foo = foo.call()
            this.println(foo)
            throw new java.lang.IllegalStateException()
        } 
        catch (java.lang.Throwable $spock_ex) {
            this.getSpecificationContext().setThrownException($spock_ex)
        } 

as you can see declaration and assignment are now split.

It is basically the same as

class Other {

   void bar() {
        def foo = null
        foo = foo() // fails here
   }


    String foo() {
        return "foo"
    }
}

I'm pretty sure that is some groovy heuristic that turns this.foo() into foo.call() when foo is declared as a local variable, but this needs further investigation. Probably the VariableScopeVisitor again.