ConstructorCallChecker.java

package polyglot.visit;

import java.util.HashMap;
import java.util.Map;

import polyglot.ast.ConstructorCall;
import polyglot.ast.Node;
import polyglot.ast.NodeFactory;
import polyglot.frontend.Job;
import polyglot.types.ConstructorInstance;
import polyglot.types.Context;
import polyglot.types.SemanticException;
import polyglot.types.TypeSystem;
import polyglot.util.InternalCompilerError;

/** Visitor which ensures that constructor calls are not recursive. */
public class ConstructorCallChecker extends ContextVisitor
{
    public ConstructorCallChecker(Job job, TypeSystem ts, NodeFactory nf) {
	super(job, ts, nf);
    }

    protected Map constructorInvocations = new HashMap();
    
    protected NodeVisitor enterCall(Node n) throws SemanticException {
        if (n instanceof ConstructorCall) {
            ConstructorCall cc = (ConstructorCall)n;
            if (cc.kind() == ConstructorCall.THIS) {
                // the constructor calls another constructor in the same class
                Context ctxt = context();

                if (!(ctxt.currentCode() instanceof ConstructorInstance)) {
                    throw new InternalCompilerError("Constructor call " +
                        "occurring in a non-constructor.", cc.position());
                }
                ConstructorInstance srcCI = (ConstructorInstance)ctxt.currentCode();
                ConstructorInstance destCI = cc.constructorInstance();
                
                constructorInvocations.put(srcCI, destCI);
                while (destCI != null) {
                    destCI = (ConstructorInstance)constructorInvocations.get(destCI);
                    if (destCI != null && srcCI.equals(destCI)) {
                        // loop in the constructor invocations!
                        throw new SemanticException("Recursive constructor " +
                            "invocation.", cc.position());
                    }
                }
            }
        }
        return this;        
    }
}