do not replace diamonds without necessity (IDEA-87172)

java/java-tests/testData/refactoring/introduceParameter/afterPreserveDiamondOccurrences.java

@@ -0,0 +1,22 @@
+
+public class TestCompletion {
+
+    public static <T, V> ParallelPipeline<T, V> test(T base, V newStage, T upstream, final ParallelPipeline<T, V> anObject) {
+        if (base != null){
+            return anObject;
+        }
+        else {
+            return new ParallelPipeline<>(upstream, newStage);
+        }
+
+    }
+
+
+    void f() {
+        test(null, null, null, new ParallelPipeline<>(null, null));
+    }
+    private static class ParallelPipeline<T, V> {
+        public ParallelPipeline(T p0, V p1) {
+        }
+    }
+}

java/java-tests/testData/refactoring/introduceParameter/beforePreserveDiamondOccurrences.java

@@ -0,0 +1,22 @@
+
+public class TestCompletion {
+
+    public static <T, V> ParallelPipeline<T, V> test(T base, V newStage, T upstream) {
+        if (base != null){
+            return <selection>new ParallelPipeline<>(base, newStage)</selection>;
+        }
+        else {
+            return new ParallelPipeline<>(upstream, newStage);
+        }
+
+    }
+
+
+    void f() {
+        test(null, null, null);
+    }
+    private static class ParallelPipeline<T, V> {
+        public ParallelPipeline(T p0, V p1) {
+        }
+    }
+}

java/java-tests/testSrc/com/intellij/refactoring/IntroduceParameterTest.java

@@ -275,6 +275,10 @@ public class IntroduceParameterTest extends LightRefactoringTestCase  {
     doTest(IntroduceParameterRefactoring.REPLACE_FIELDS_WITH_GETTERS_ALL, true, false, true, false);
   }
 
+  public void testPreserveDiamondOccurrences() throws Exception {
+    doTest(IntroduceParameterRefactoring.REPLACE_FIELDS_WITH_GETTERS_ALL, true, false, true, false);
+  }
+
   public void testSubstituteTypeParams() throws Exception {
     doTest(IntroduceParameterRefactoring.REPLACE_FIELDS_WITH_GETTERS_ALL, true, false, true, false);
   }