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Build/compilation issue with wildcard types #4059
Description
Following is some sample code to replicate the issue:
import java.util.List;
public class Tester {
<T extends List<? extends Entry<?, ?>>> Entry<?, ?> test(T input) {
return ConcreteEntry.from(input.get(0)); // Error here
}
public static void main(String[] args) {
Tester tester = new Tester();
System.out.println(tester.test(List.of(new ConcreteEntry<>("a", 1))));
}
}
interface Entry<K, V> {
K getKey();
V getValue();
}
class ConcreteEntry<K, V> implements Entry<K, V> {
private final K key;
private final V value;
public ConcreteEntry(K key, V value) {
this.key = key;
this.value = value;
}
public static <K, V> ConcreteEntry<K, V> from(Entry<K, V> entry) {
return new ConcreteEntry<>(entry.getKey(), entry.getValue());
}
@Override
public K getKey() {
return key;
}
@Override
public V getValue() {
return value;
}
@Override
public String toString() {
return this.key + "=" + this.value;
}
}The test method throws the error The method from(Entry<K,V>) in the type ConcreteEntry is not applicable for the arguments (capture#1-of ? extends Entry<?,?>) Java(67108979). The expected behaviour is correct compilation. However, enabling the "java.jdt.ls.javac.enabled" works, but is not an ideal solution.
This occurs with the latest Language Support for Java(TM) by Red Hat - v1.42.0.
Activity
anar-ibragimoff commentedon May 27, 2025
same as #4053
msohaill commentedon May 27, 2025
Strangely enough, I still get the issue when downgrading to v1.41.1. Perhaps it is an issue with the Eclipse Language Tools? Not sure if there's a pinned version or anything
rgrunber commentedon Jun 25, 2025
Looks like this was resolved recently according to #4053 (comment) ? It may have been an upstream bug that was fixed there. @msohaill can you confirm if this is resolved in the pre-release stream ?
msohaill commentedon Jun 25, 2025
Hi @rgrunber! It seems I still get the issue with
v1.43.2025062508. The error message remains the same. Let me know if you would require any more information!davidhay1969 commentedon Jul 2, 2025
Morning, also seeing a similar issue with versions of the extension post
v1.41.1including the current latest pre-release version: -Looking thorugh the linked issues / PRs, to check whether there's anything else about my environment ( macOS, VSCode, JDK etc. ) that's relevant ...
davidhay1969 commentedon Jul 2, 2025
Just got a new update on the pre-release channel: -
code --list-extensions --show-versions | grep redhat.javaalas the same problem 😿
rgrunber commentedon Jul 3, 2025
I tried with
1.32.0and still see the errors there as well, so likely this isn't something to recently regress. Seems similar to #3688 . This is looking like some kind of longer term limitation of ECJ compilation vs. Javac. See eclipse-jdt/eclipse.jdt.core#1053, eclipse-jdt/eclipse.jdt.core#366 .interrupt-routine commentedon Jan 29, 2026
As of v
1.52.0I hit the same bug with code samples as simple as this:Type mismatch: cannot convert from List<List<capture#1-of ?>> to List<List<Object>>Java(16777233)Compiles fine with
javac -Xlint:all