Compilation error with Eclipse 4.39 not with javac or Eclipse 4.38

Improve the impl to cover one more issue
+ really make ivar-ivar dependencies bidirectional
+ also consider ivar-super bounds in ivar prioritization
  - but not so for same bounds

Also fix an NPE in debug logging

Fixes #4937

Author: stephan-herrmann

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/lookup/BoundSet.java

@@ -430,10 +430,16 @@ else if (boundNullBits != 0) // combine bits from both sources, even if this cre
 				// for a dependency between two IVs make a note about the inverse bound.
 				// this should be needed to determine IV dependencies independent of direction.
 				// TODO: so far no test could be identified which actually needs it ...
-				InferenceVariable rightIV = (InferenceVariable) bound.right.prototype();
-				three = this.boundsPerVariable.get(rightIV);
-				if (three == null)
-					this.boundsPerVariable.put(rightIV, (three = new ThreeSets()));
+				int relation = switch (bound.relation) {
+					case ReductionResult.SUBTYPE -> ReductionResult.SUPERTYPE;
+					case ReductionResult.SUPERTYPE -> ReductionResult.SUBTYPE;
+					default -> -1;
+				};
+				if (relation != -1) {
+					InferenceVariable rightIV = (InferenceVariable) bound.right.prototype();
+					three = this.boundsPerVariable.computeIfAbsent(rightIV, k -> new ThreeSets());
+					three.addBound(new TypeBound(rightIV, bound.left, relation));
+				}
 			}
 		}
 	}
@@ -722,7 +728,8 @@ protected TypeBinding getP(int i) {
 		if (InferenceContext18.DEBUG) {
 			if (!capturesToRemove.isEmpty()) {
 				for (ParameterizedTypeBinding toRemove : capturesToRemove) {
-					System.out.println("Removing capture bound " + //$NON-NLS-1$
+					if (this.captures.containsKey(toRemove))
+						System.out.println("Removing capture bound " + //$NON-NLS-1$
 							String.valueOf(toRemove.shortReadableName()) +
 							"=capture("+String.valueOf(this.captures.get(toRemove).shortReadableName())+")"); //$NON-NLS-1$ //$NON-NLS-2$
 				}
@@ -1073,8 +1080,7 @@ public int rankIVar(InferenceVariable ivar) {
 					if (!(bound.right instanceof InferenceVariable))
 						return 1;
 			if (three.superBounds != null)
-				for (TypeBound bound :three.superBounds)
-					if (!(bound.right instanceof InferenceVariable))
+				if (!three.superBounds.isEmpty())
 						return 2;
 		}
 		return 3;

org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/GenericsRegressionTest_9.java

@@ -2074,6 +2074,26 @@ TypeConverter<?> findCompatibleConverter(Class<?> clazz) {
 	});
 }
 
+public void testGH4937() {
+	runConformTest(new String[] {
+		"A.java",
+		"""
+		import java.util.List;
+
+		public class A {
+		    public static void foo() {
+		        System.out.println(List.of(BusinessExtractBuilder.create())); // Error here
+		    }
+		    public static class BusinessExtractBuilder<T> {
+		        public static <U extends BusinessExtractBuilder<U>> U create() {
+		            return null;
+		        }
+		    }
+		}
+		"""
+	});
+}
+
 public static Class<GenericsRegressionTest_9> testClass() {
 	return GenericsRegressionTest_9.class;
 }