ECJ compile error: "Bound mismatch: The generic method ... is not applicable for the arguments" (eclipse-jdt#4041)

always "normalize" `? extends capture#1-of ? extends X` to `? extends X`

Fixes eclipse-jdt#4033

Author: stephan-herrmann

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

@@ -1473,6 +1473,7 @@ public RawTypeBinding createRawType(ReferenceBinding genericType, ReferenceBindi
 }
 
 public WildcardBinding createWildcard(ReferenceBinding genericType, int rank, TypeBinding bound, TypeBinding[] otherBounds, int boundKind) {
+	bound = normalizeWildcardBound(bound, boundKind);
 	if (genericType != null) {
 		AnnotationBinding[] annotations = genericType.typeAnnotations;
 		if (annotations != Binding.NO_ANNOTATIONS)
@@ -1486,9 +1487,19 @@ public CaptureBinding createCapturedWildcard(WildcardBinding wildcard, Reference
 }
 
 public WildcardBinding createWildcard(ReferenceBinding genericType, int rank, TypeBinding bound, TypeBinding[] otherBounds, int boundKind, AnnotationBinding [] annotations) {
+	bound = normalizeWildcardBound(bound, boundKind);
 	return this.typeSystem.getWildcard(genericType, rank, bound, otherBounds, boundKind, annotations);
 }
 
+private TypeBinding normalizeWildcardBound(TypeBinding bound, int boundKind) {
+	if (boundKind == Wildcard.EXTENDS && bound.getClass() == CaptureBinding.class) {
+		CaptureBinding capture = (CaptureBinding) bound;
+		if (capture.firstBound != null && capture.otherUpperBounds() == Binding.NO_TYPES && capture.wildcard.boundKind() == Wildcard.EXTENDS)
+			return capture.firstBound;
+	}
+	return bound;
+}
+
 /**
  * Returns the access restriction associated to a given type, or null if none
  */

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

@@ -1186,6 +1186,31 @@ public Set<String> getAllLabels(FluentIterable<TaskDefinition> from) {
 			"""
 		});
 }
+public void testGH4033() {
+	runConformTest(new String[] {
+			"Snippet.java",
+			"""
+			import java.util.Collection;
+			import java.util.Iterator;
+			
+			public class Snippet {
+				interface Apple {}
+				interface Banana<T1, T2> {}
+				interface Smoothie<T extends Apple, M extends Apple> extends Banana<T, String> {}
+			
+				public static void main(String[] args) {
+					Collection<Smoothie<? extends Apple, ? extends Apple>> c = null;
+					method(c);
+				}
+			
+				static final <S extends Banana<? extends T, ?>, T> Iterator<T> method(
+						Collection<S> c) {
+					return null;
+				}
+			}
+			"""
+		});
+}
 public static Class<GenericsRegressionTest_9> testClass() {
 	return GenericsRegressionTest_9.class;
 }