GROOVY-11986

src/main/java/groovy/lang/MetaClassImpl.java

@@ -3333,7 +3333,11 @@ private void checkIfStdMethod(final MetaMethod metaMethod) {
             checkIfGroovyObjectMethod(metaMethod);
             break;
           case "get":
-            if (checkMatch(metaMethod, genericGetMethod, GETTER_MISSING_ARGS) && metaMethod.getReturnType() != Void.TYPE) {
+            // GROOVY-11986: parameter must be String exactly, not just assignable from String,
+            // to avoid hijacking unrelated single-arg get(X) methods (e.g. get(Serializable),
+            // get(Object)) as the generic property getter, which silently shadows propertyMissing
+            if (checkMatch(metaMethod, genericGetMethod, GETTER_MISSING_ARGS) && metaMethod.getReturnType() != Void.TYPE
+                    && metaMethod.getParameterTypes()[0].getTheClass() == String.class) {
                 genericGetMethod = metaMethod;
             }
             break;

src/test/groovy/bugs/Groovy11986.groovy

@@ -0,0 +1,93 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you 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
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  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 bugs
+
+import org.junit.jupiter.api.Test
+
+import static groovy.test.GroovyAssert.assertScript
+
+final class Groovy11986 {
+
+    // get(Serializable) is the GORM entity-by-ID lookup shape; it must not be
+    // registered as the genericGetMethod, otherwise dynamic property access on
+    // an instance hijacks propertyMissing(String).
+    @Test
+    void testInheritedGetSerializableDoesNotShadowPropertyMissing() {
+        assertScript '''
+            trait T {
+                Object get(Serializable id) { "by-id:$id".toString() }
+                Object propertyMissing(String name) { "missing:$name".toString() }
+            }
+            class C implements T {
+                String title
+            }
+
+            def c = new C(title: 'hello')
+            assert c.title == 'hello'        // bean property still wins
+            assert c.foo == 'missing:foo'    // dynamic access falls through to propertyMissing
+            assert c.get('foo') == 'by-id:foo' // direct call still hits get(Serializable)
+        '''
+    }
+
+    @Test
+    void testInheritedGetObjectDoesNotShadowPropertyMissing() {
+        assertScript '''
+            class Base {
+                Object get(Object key) { "by-key:$key".toString() }
+            }
+            class C extends Base {
+                Object propertyMissing(String name) { "missing:$name".toString() }
+            }
+
+            def c = new C()
+            assert c.foo == 'missing:foo'
+            assert c.get('foo') == 'by-key:foo'
+        '''
+    }
+
+    // Sanity: a real get(String) is still picked up as the generic getter.
+    @Test
+    void testGetStringStillRegistersAsGenericGetter() {
+        assertScript '''
+            class C {
+                def get(String name) { "value:$name".toString() }
+            }
+
+            def c = new C()
+            assert c.foo == 'value:foo'
+        '''
+    }
+
+    // Sanity: get(String) on a class that also inherits get(Serializable) wins
+    // as the generic getter (closer parameter match).
+    @Test
+    void testGetStringWinsOverInheritedGetSerializable() {
+        assertScript '''
+            trait T {
+                Object get(Serializable id) { "by-id:$id".toString() }
+            }
+            class C implements T {
+                Object get(String name) { "by-name:$name".toString() }
+            }
+
+            def c = new C()
+            assert c.foo == 'by-name:foo'
+        '''
+    }
+}