[java-inspections] IDEA-353938 Report ignored object allocations inside method references

GitOrigin-RevId: 1261b9bdb64bec0269fe7d0ffb2ac634e1494e81

java/java-analysis-impl/resources/messages/InspectionGadgetsBundle.properties

@@ -148,6 +148,7 @@ octal.and.decimal.integers.in.same.array.display.name=Octal and decimal integers
 octal.and.decimal.integers.in.same.array.problem.descriptor=Octal and decimal integers in the same array initializer #loc
 result.of.object.allocation.ignored.display.name=Result of object allocation ignored
 result.of.object.allocation.ignored.problem.descriptor=Result of <code>new #ref()</code> is ignored #loc
+result.of.object.allocation.ignored.problem.descriptor.methodRef=Object allocated inside <code>#ref</code> is discarded #loc
 result.of.object.allocation.ignored.options.chooserTitle=Choose Class for Which Object Allocation Can Be Ignored
 result.of.object.allocation.fix.name=Ignore allocations of objects with type ''{0}''
 use.0index.in.jdbc.resultset.display.name=Use of index 0 in JDBC ResultSet

java/java-impl/src/com/siyeh/ig/bugs/IgnoreResultOfCallInspection.java

@@ -212,8 +212,8 @@ public final class IgnoreResultOfCallInspection extends BaseInspection {
     public void visitMethodReferenceExpression(@NotNull PsiMethodReferenceExpression expression) {
       if (PsiTypes.voidType().equals(LambdaUtil.getFunctionalInterfaceReturnType(expression))) {
         PsiElement resolve = expression.resolve();
-        if (resolve instanceof PsiMethod) {
-          visitCalledExpression(expression, (PsiMethod)resolve, null);
+        if (resolve instanceof PsiMethod method && !method.isConstructor()) {
+          visitCalledExpression(expression, method, null);
         }
       }
     }

java/java-impl/src/com/siyeh/ig/bugs/ResultOfObjectAllocationIgnoredInspection.java

@@ -63,6 +63,9 @@ public final class ResultOfObjectAllocationIgnoredInspection extends BaseInspect
 
   @Override
   public @NotNull String buildErrorString(Object... infos) {
+    if (infos[0] instanceof PsiMethodReferenceExpression) {
+      return InspectionGadgetsBundle.message("result.of.object.allocation.ignored.problem.descriptor.methodRef");
+    }
     return InspectionGadgetsBundle.message("result.of.object.allocation.ignored.problem.descriptor");
   }
 
@@ -73,6 +76,23 @@ public final class ResultOfObjectAllocationIgnoredInspection extends BaseInspect
 
   private class ResultOfObjectAllocationIgnoredVisitor extends BaseInspectionVisitor {
 
+    @Override
+    public void visitMethodReferenceExpression(@NotNull PsiMethodReferenceExpression expression) {
+      super.visitMethodReferenceExpression(expression);
+      if (PsiTypes.voidType().equals(LambdaUtil.getFunctionalInterfaceReturnType(expression))) {
+        if (expression.isConstructor()) {
+          PsiElement qualifier = expression.getQualifier();
+          if (qualifier instanceof PsiReferenceExpression ref && ref.resolve() instanceof PsiClass cls &&
+              !ignoredClasses.contains(cls.getQualifiedName())) {
+            registerError(expression, expression);
+          }
+          if (qualifier instanceof PsiTypeElement typeElement && typeElement.getType() instanceof PsiArrayType) {
+            registerError(expression, expression);
+          }
+        }
+      }
+    }
+
     @Override
     public void visitNewExpression(@NotNull PsiNewExpression expression) {
       super.visitNewExpression(expression);

java/java-tests/testData/ig/com/siyeh/igtest/bugs/result_of_object_allocation_ignored/ResultOfObjectAllocationIgnored.java

@@ -1,5 +1,7 @@
 package com.siyeh.igtest.bugs.result_of_object_allocation_ignored;
 
+import java.util.function.*;
+
 public class ResultOfObjectAllocationIgnored {
 
     private ResultOfObjectAllocationIgnored() {
@@ -25,4 +27,15 @@ public class ResultOfObjectAllocationIgnored {
             default -> new Throwable();
         };
     }
+    
+    void methodRef() {
+      Runnable simple = <warning descr="Object allocated inside 'Object::new' is discarded">Object::new</warning>;
+      Runnable impliciCtor = <warning descr="Object allocated inside 'Foo::new' is discarded">Foo::new</warning>;
+      Runnable qualified = <warning descr="Object allocated inside 'java.lang.Object::new' is discarded">java.lang.Object::new</warning>;
+      Runnable ignored = java.util.ArrayList::new;
+      IntConsumer primitiveArr = <warning descr="Object allocated inside 'int[]::new' is discarded">int[]::new</warning>;
+      IntConsumer objectArr = <warning descr="Object allocated inside 'Object[]::new' is discarded">Object[]::new</warning>;
+    }
+    
+    class Foo {}
 }

java/java-tests/testSrc/com/siyeh/ig/bugs/IgnoreResultOfCallInspectionTest.java

@@ -457,6 +457,7 @@ public class IgnoreResultOfCallInspectionTest extends LightJavaInspectionTestCas
           static {
             Runnable r = () -> Util./*Result of 'Util.util()' is ignored*/util/**/();
             Runnable r1 = Util::/*Result of 'Util.util()' is ignored*/util/**/;
+            Runnable r2 = Object::new; // Reported by ResultOfObjectAllocationIgnoredInspection
           }
         }
         """);

java/java-tests/testSrc/com/siyeh/ig/bugs/ResultOfObjectAllocationIgnoredInspectionTest.java

@@ -16,7 +16,9 @@
 package com.siyeh.ig.bugs;
 
 import com.intellij.codeInspection.InspectionProfileEntry;
+import com.intellij.testFramework.LightProjectDescriptor;
 import com.siyeh.ig.LightJavaInspectionTestCase;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -28,6 +30,11 @@ public class ResultOfObjectAllocationIgnoredInspectionTest extends LightJavaInsp
     doTest();
   }
 
+  @Override
+  protected @NotNull LightProjectDescriptor getProjectDescriptor() {
+    return JAVA_21;
+  }
+
   @Nullable
   @Override
   protected InspectionProfileEntry getInspection() {