Support Groovy method pointers and array constructor method references (#5782)

Author: jevanlingen

rewrite-groovy/src/main/java/org/openrewrite/groovy/GroovyParserVisitor.java

@@ -955,8 +955,12 @@ public boolean endsWithClosures(List<org.codehaus.groovy.ast.expr.Expression> li
 
         @Override
         public void visitClassExpression(ClassExpression clazz) {
-            Space prefix = whitespace();
             ClassNode type = clazz.getType();
+            if (type.isArray()) {
+                queue.add(arrayType(type));
+                return;
+            }
+            Space prefix = whitespace();
             String name = type.getNameWithoutPackage().replace('$', '.');
             if (!source.startsWith(name, cursor)) {
                 name = type.getUnresolvedName().replace('$', '.');
@@ -2004,21 +2008,18 @@ public void visitStaticMethodCallExpression(StaticMethodCallExpression call) {
 
         @Override
         public void visitMethodPointerExpression(MethodPointerExpression ref) {
-            String referenceName = null;
-            if (ref.getMethodName() instanceof ConstantExpression) {
-                referenceName = ((ConstantExpression) ref.getMethodName()).getValue().toString();
-            }
-
+            boolean isMethodRef = ref instanceof MethodReferenceExpression;
+            String name = ref.getMethodName().getText();
             queue.add(new J.MemberReference(randomId(),
                     whitespace(),
-                    Markers.EMPTY,
-                    padRight(visit(ref.getExpression()), sourceBefore("::")),
+                    isMethodRef ? Markers.EMPTY : Markers.build(singleton(new MethodPointer(randomId()))),
+                    padRight(visit(ref.getExpression()), sourceBefore(isMethodRef ? "::" : ".&")),
                     null, // not supported by Groovy
                     padLeft(whitespace(), new J.Identifier(randomId(),
-                            sourceBefore(referenceName),
+                            sourceBefore(name),
                             Markers.EMPTY,
                             emptyList(),
-                            referenceName,
+                            name,
                             null, null)),
                     typeMapping.type(ref.getType()),
                     null, // not enough information in the AST

rewrite-groovy/src/main/java/org/openrewrite/groovy/GroovyPrinter.java

@@ -358,6 +358,21 @@ public J visitLambda(J.Lambda lambda, PrintOutputCapture<P> p) {
             return lambda;
         }
 
+        @Override
+        public J visitMemberReference(J.MemberReference memberRef, PrintOutputCapture<P> p) {
+            beforeSyntax(memberRef, Space.Location.MEMBER_REFERENCE_PREFIX, p);
+            visitRightPadded(memberRef.getPadding().getContaining(), JRightPadded.Location.MEMBER_REFERENCE_CONTAINING, p);
+            if (memberRef.getMarkers().findFirst(MethodPointer.class).isPresent()) {
+                p.append(".&");
+            } else {
+                p.append("::");
+            }
+            visitContainer("<", memberRef.getPadding().getTypeParameters(), JContainer.Location.TYPE_PARAMETERS, ",", ">", p);
+            visitLeftPadded("", memberRef.getPadding().getReference(), JLeftPadded.Location.MEMBER_REFERENCE_NAME, p);
+            afterSyntax(memberRef, p);
+            return memberRef;
+        }
+
         @Override
         public J visitFieldAccess(J.FieldAccess fieldAccess, PrintOutputCapture<P> p) {
             beforeSyntax(fieldAccess, Space.Location.FIELD_ACCESS_PREFIX, p);

rewrite-groovy/src/main/java/org/openrewrite/groovy/marker/MethodPointer.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.groovy.marker;
+
+import lombok.Value;
+import lombok.With;
+import org.openrewrite.marker.Marker;
+
+import java.util.UUID;
+
+@Value
+@With
+public class MethodPointer implements Marker {
+    UUID id;
+}

rewrite-groovy/src/test/java/org/openrewrite/groovy/tree/MethodInvocationTest.java

@@ -211,6 +211,17 @@ def xMethod() {}
         );
     }
 
+    @Test
+    void staticMethodPointer() {
+        rewriteRun(
+          groovy(
+            """
+              Integer.&parseInt
+              """
+          )
+        );
+    }
+
     @Test
     void staticMethodReference() {
         rewriteRun(
@@ -222,6 +233,17 @@ void staticMethodReference() {
         );
     }
 
+    @Test
+    void instanceMethodPointer() {
+        rewriteRun(
+          groovy(
+            """
+              ["a", "b", "c"].forEach(System.out.&println)
+              """
+          )
+        );
+    }
+
     @Test
     void instanceMethodReference() {
         rewriteRun(
@@ -233,6 +255,17 @@ void instanceMethodReference() {
         );
     }
 
+    @Test
+    void constructorMethodPointer() {
+        rewriteRun(
+          groovy(
+            """
+              ArrayList.&new
+              """
+          )
+        );
+    }
+
     @Test
     void constructorMethodReference() {
         rewriteRun(
@@ -244,6 +277,17 @@ void constructorMethodReference() {
         );
     }
 
+    @Test
+    void arrayConstructorMethodReference() {
+        rewriteRun(
+          groovy(
+            """
+              [1, 2, 3].stream().toArray(Integer[]::new)
+              """
+          )
+        );
+    }
+
     @SuppressWarnings("GroovyAssignabilityCheck")
     @Test
     void closureWithImplicitParameter() {