ECJ 2025-12 fails inference with lower bounded wildcard while javac succeeds

[coehlrich]

With this:

public class Test {

	public static void main(String[] args) {
		Z<B> z = new Z<>(List.of(
				new Y<>(new A()),
				new Y<>(new B()),
				new Y<>(new C())));
	}
	
	public static record Z<T>(List<? extends X<? super T>> l) {}
	public static record Y<T>(T t) implements X<T> {}
	public static interface X<T> {}
	
	public static class A {}
	public static class B extends A {}
	public static class C extends B {}
}

ECJ fails to compile with Cannot infer type arguments for Z<> whilst Javac succeeds

While debugging this I noticed I noticed that <Z#0-T'#5 extends Z#1-T'#0> <: <Z#2-T'#1> (the upper bounds of Z#0-T'#5 are Z#1-T'#0, Z#2-T'#1, Z#3-T'#2) is reduced to false since isSubtypeOf isn't overriden by CaptureBinding18 so only the first bound is checked and that test2.Test.Y<Z#1-T'#0> <: test2.Test.X<? super Z#1-T'#0&Z#2-T'#1&Z#3-T'#2> is also reduced to false since currently TypeBinding.isTypeArgumentContainedBy only checks the lower bound.

With those 2 issues fixed ECJ then resolves E#4 to Test.Y<? extends java.lang.Object> since there is no ? super wildcard in the lower bounds for JLS §4.10.4 to output a ? super wildcard and without the z captures ECJ resolves E#4 to have a lower bound of Test.Y<? extends Test.A> for the same reason.

@stephan-herrmann

[iloveeclipse]

@coehlrich : is this a regression? Can you pish a PR with proposed fix?

[stephan-herrmann]

This issue can be reproduced all the way back to 4.20, the first release that supported records.

[coehlrich]

I intended to put 2026-03 in the title since I tested it on the latest commit but instead put 2025-12.

[stephan-herrmann]

since isSubtypeOf isn't overriden by CaptureBinding18 so only the first bound is checked

Here the implementation from TypeVariableBinding kicks in, which checks firstBound, superclass and superInterfaces. What else should it check?

... since currently TypeBinding.isTypeArgumentContainedBy only checks the lower bound

Can you pin-point an item from 4.5.1. that we fail to consider? I can see several uses of capture.lowerBound, so in which arm of that method do you see a gap?