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Inference crashes on a chained call whose lambda returns a capture of an F-bounded type argument

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#8,323 0 comments 0 reactions 1 assignee View on GitHub

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@smillst is already working on this.

Since Oct 6, 2026.

  • #8324 by @smillst — merged

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Description

crash
import java.util.List;
import java.util.function.Function;

public class FBoundedCaptureInChainedCall {
  interface FB<K, V extends Comparable<V>> {}

  interface Box<T> {
    <R> Box<R> map(Function<? super T, ? extends R> f);

    <S> S get(Getter<? super T, S> g);
  }

  interface Getter<T, S> {}

  static native <T> Getter<T, List<T>> toList();

  static native <P> FB<P, ? extends Integer> fbExtends(P p);

  static List<FB<?, ?>> m(Box<String> b) {
    // Crash: BugInCF "False bound for: Constraint: Object <: FB<? extends Object, ? extends Object>".
    return b.map(t -> fbExtends(t)).get(toList());
  }
}

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Java
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