[GROOVY-3578] Ordering of files passed to compiler affects whether some (invalid) generics errors get reported

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 1.6.5, 1.7-beta-2
• Component/s: Compiler
• Environment: Windows 7
• Assignee: Jochen Theodorou
• Reporter: Andy Clement
• Created: 11/Jun/09 12:03
• Updated: 30/Sep/09 10:17
• Resolved: 30/Sep/09 10:00

Description

I have two files:

— A.groovy

package p;

public class A<T> {
}

—

— B.groovy

package p;

class B extends A<String> {
}

—

Depending on the order in which they are passed to groovyc, I may get an error:

> groovyc A.groovy B.groovy

works fine.

> groovyc B.groovy A.groovy

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup
failed, B.groovy: 3: The type String is not a valid substitute for the
bounded parameter <T>
@ line 3, column 17.
class B extends A<String> {
^
1 error

This happens because the generics checking is done as part of the resolution phase. From CompilationUnit:

private final SourceUnitOperation resolve = new SourceUnitOperation() {
        public void call(SourceUnit source) throws CompilationFailedException {
            List classes = source.ast.getClasses();
            for (Iterator it = classes.iterator(); it.hasNext();) {
                ClassNode node = (ClassNode) it.next();

                VariableScopeVisitor scopeVisitor = new VariableScopeVisitor(source);
                scopeVisitor.visitClass(node);

                resolveVisitor.startResolving(node, source);

                GenericsVisitor genericsVisitor = new GenericsVisitor(source);
                genericsVisitor.visitClass(node);
            }

        }
    };

if the generics check is performed before the types involved (like A) are resolved, you get this problem. The solution is to break that into two phases: resolution and then generics checking (take the last two lines from the resolution phase and move them into a new phase, done after resolution):

    /**
     * Check generics usage
     */
    private final SourceUnitOperation checkGenerics = new SourceUnitOperation() {
        public void call(SourceUnit source) throws CompilationFailedException {
            List classes = source.ast.getClasses();
            for (Iterator it = classes.iterator(); it.hasNext();) {
                ClassNode node = (ClassNode) it.next();

                GenericsVisitor genericsVisitor = new GenericsVisitor(source);
                genericsVisitor.visitClass(node);
            }

        }
    };

then the order doesn't matter.