result can't be used in expressions when not initialized

[echebbi]

Bug description

Using result in an expression leads to a runtime error during interpretation. For example, the following code produces an error during the evaluation of the if's condition:

class A {

    def boolean isX() {
        if (result) {
           
        }
        result := false;
    }

}

The error is "Couldn't find the 'result' variable".

Expected behavior

Not sure. One of the following:

• result is set a default value,
• it is explicitely forbidden to use result without initializing it first and this is enforced by an error marker in the editor.

How to reproduce

Steps to reproduce the behavior:

1. Create an ALE project
2. Write a semantics that uses result in an expression as shown above
3. Run the interpreter

Additional context

• ALE version: master @ a1a0bf8

Issue caused by the following line:

ale-lang/plugins/org.eclipse.emf.ecoretools.ale.core/src/org/eclipse/emf/ecoretools/ale/core/interpreter/internal/MethodEvaluator.java

Line 688 in a1a0bf8

result = aqlEngine.eval(dummyAstResult, scopes.getCurrent().getVariableValues());

Since result has not been initialized yet, the map returned by scopes.getCurrent().getVariableValues() won't contain it. The appropriate fix depends on the chosen solution.