Description Ingo Hadan 2021-10-22 09:48:59 EDT

In a scenario with generic classes and variadic arguments the java editor marks a line as error that the command line (jdk) java compiler (javac) does compile. It looks similar to e.g. 481649 but seems to be triggered by variadic arguments.

The following Program reproduces the issue:

import java.util.function.Function;
import java.util.function.Predicate;

public class GenericsBug<S> {
	public static interface MyInterface<U> {}
	
	public static class SubClass<U,V> implements MyInterface<V>{
		public SubClass(Function<U,V> g, MyInterface<V>... i) { }
    }
	
	public static class OptSubClass<U> implements MyInterface<U> {
		public OptSubClass(String s, Predicate<U> p, MyInterface<U>... i) { }

	}
	
	public static class ParamClass<T> {
		public T    getU()    { return null;}
	}
	
	GenericsBug(MyInterface<S> in1, MyInterface<S> in2) { }
	
	
	public static class MySubClass extends SubClass<ParamClass<Boolean>,Boolean> {
		public MySubClass() {
			super(ParamClass::getU);
		}
	}
	
	public static void foo() {
		SubClass<ParamClass<Boolean>,Boolean> sc = new SubClass<>(ParamClass::getU);
	    new GenericsBug<>(new MySubClass(),
	    		          new OptSubClass<>("foo", t->t, sc));
	}
};

The instanciation of GenericsBug yields the error "Cannot infer type arguments for GenericsBug<>" It may also be reproduced with ecj standalone.

-- Configuration Details --
Product: Eclipse IDE 4.21.0.20210910-1200 (org.eclipse.epp.package.jee.product)Installed Features:
 org.eclipse.jdt 3.18.900.v20210906-0500
Versioning Plugin:
 org.eclipse.platform 4.21.0.v20210906-0842