TypeBinding: What happens without custom hash()?

Jenkinsfile

@@ -27,9 +27,7 @@ pipeline {
 					# The max heap should be specified for tycho explicitly
 					# via configuration/argLine property in pom.xml
 					# export MAVEN_OPTS="-Xmx2G"
-
-					mvn clean install -f org.eclipse.jdt.core.compiler.batch -DlocalEcjVersion=99.99 -Dmaven.repo.local=$WORKSPACE/.m2/repository -DcompilerBaselineMode=disable -DcompilerBaselineReplace=none
-
+
 					mvn -U clean verify --batch-mode --fail-at-end -Dmaven.repo.local=$WORKSPACE/.m2/repository \
 						-Ptest-on-javase-23 -Pbree-libs -Papi-check -Pjavadoc -Pp2-repo \
 						-Dmaven.test.failure.ignore=true \
@@ -39,7 +37,6 @@ pipeline {
 						-DDetectVMInstallationsJob.disabled=true \
 						-Dtycho.apitools.debug \
 						-Dtycho.debug.artifactcomparator \
-						-Dcbi-ecj-version=99.99
 					"""
 			}
 			post {

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

@@ -258,11 +258,6 @@ public PackageBinding getPackage() {
 	return this.leafComponentType.getPackage();
 }
 
-@Override
-public int hashCode() {
-	return this.leafComponentType == null ? super.hashCode() : this.leafComponentType.hashCode();
-}
-
 /* Answer true if the receiver type can be assigned to the argument type (right)
 */
 @Override

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

@@ -165,10 +165,6 @@ public TypeBinding clone(TypeBinding outerType) {
 	return copy;
 }
 
-@Override
-public int hashCode() {
-	return this.enclosingType.hashCode();
-}
 /*
  * Overriden for code assist. In this case, the constantPoolName() has not been computed yet.
  * Slam the source name so that the signature is syntactically correct.

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

@@ -1204,15 +1204,6 @@ public TypeVariableBinding getTypeVariable(char[] variableName) {
 	return null;
 }
 
-@Override
-public int hashCode() {
-	// ensure ReferenceBindings hash to the same position as UnresolvedReferenceBindings so they can be replaced without rehashing
-	// ALL ReferenceBindings are unique when created so equals() is the same as ==
-	return (this.compoundName == null || this.compoundName.length == 0)
-		? super.hashCode()
-		: CharOperation.hashCode(this.compoundName[this.compoundName.length - 1]);
-}
-
 final int identityHashCode() {
 	return super.hashCode();
 }

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

@@ -19,7 +19,9 @@
  *******************************************************************************/
 package org.eclipse.jdt.internal.compiler.lookup;
 
+import java.util.Arrays;
 import java.util.HashMap;
+import java.util.Objects;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 import org.eclipse.jdt.internal.compiler.ast.ASTNode;
@@ -133,25 +135,9 @@ public boolean equals(Object other) {
 				PTBKey that = (PTBKey) other;  // homogeneous container.
 				return this.type == that.type && this.enclosingType == that.enclosingType && Util.effectivelyEqual(this.arguments, that.arguments); //$IDENTITY-COMPARISON$
 			}
-			final int hash(TypeBinding b) {
-				if(b instanceof WildcardBinding || b instanceof TypeVariableBinding || b.getClass() == ParameterizedTypeBinding.class) {
-					return System.identityHashCode(b);
-				}
-				return b.hashCode();
-			}
 			@Override
 			public int hashCode() {
-				final int prime=31;
-				int hashCode = 1 + hash(this.type);
-				if (this.enclosingType != null && this.enclosingType.getClass() == ParameterizedTypeBinding.class) {
-					// Note: this works as in swapUnresolved, a null enclosingType is never replaced by a
-					// ParameterizedTypeBinding (just by a non-generic or RawTypeBinding)
-					hashCode = hashCode * prime + System.identityHashCode(this.enclosingType);
-				}
-				for (int i = 0, length = this.arguments == null ? 0 : this.arguments.length; i < length; i++) {
-					hashCode = hashCode * prime + hash(this.arguments[i]);
-				}
-				return hashCode;
+				return Objects.hash(this.type, this.enclosingType, Arrays.hashCode(this.arguments));
 			}
 		}
 

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

@@ -614,11 +614,6 @@ public char[] genericTypeSignature() {
         return this.genericSignature;
     }
 
-	@Override
-	public int hashCode() {
-		return this.genericType.hashCode();
-	}
-
 	@Override
 	public boolean hasTypeBit(int bit) {
 		if (this.typeBits == TypeIds.BitUninitialized) {