False error: a boolean query (_ == true --> open(this)) in a class fails at its return #509

Problem. A boolean query in an ordinary class, a method whose return refinement relates its result to the state of this, fails when its body is checked:

import liquidjava.specification.*;

@StateSet({"unlocked", "locked"})
public class QueryShorthand {
    @StateRefinement(to = "locked(this)")
    public QueryShorthand() {}

    @Refinement("_ == true --> unlocked(this)")
    public boolean isUnlocked() {
        return true;
    }
}

Argument Mismatch Error: Argument '#ret_1' and its respective parameter of ghost 'QueryShorthand.state1' types are incompatible: expected QueryShorthand, got boolean

The same refinement works on an external spec (_ == true --> hasMore(this) on Scanner.hasNext()), whose methods have no body. When the return is checked, the state's argument seems to become the returned value instead of this.

Found while writing tests for #502.