Nullness Checker: spurious return.type.incompatible for a local array returned from an implicit lambda inside a generic method call #2134

The Nullness Checker reports a false-positive return.type.incompatible on a block-bodied lambda that assigns a local variable and returns it, when the lambda is passed as an argument to a generic method whose type argument is inferred. javac alone compiles it.

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

class H2Local {
    static <A, R> R of(A a, Function<A, R> f) {
        throw new Error();
    }

    Object[] localVar(List<String> list) {
        return of(
                list,
                l -> {
                    Object[] x = new Object[0];
                    return x;
                });
    }
}

javac -processor nullness H2Local.java

error: [return.type.incompatible] incompatible types in return.
        return of(
                 ^
  type of expression: @NonNull Object @Nullable []
  method return type: @NonNull Object @NonNull []
1 error

The lambda parameter l is not used in the body at all, so this is not related to #2084. x is a fresh, non-null array (new Object[0]), so the refined type of x at the return x; statement should be @NonNull Object @NonNull [], not @Nullable.

So the false positive appears specific to a lambda's block body being checked while it's the argument to a generic method invocation with its own type argument inference, not to block-bodied lambdas returning locals in general.

Expected: no error.

Environment: master 3591d45bec, JDK 25. Confirmed present identically on both master and the #2084 fix branch (unaffected by that fix).