Deparenthesize 'null' before checking the constant expression

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetPsiUtil.java

@@ -25,6 +25,7 @@ import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.jet.JetNodeTypes;
 import org.jetbrains.jet.lang.resolve.ImportPath;
 import org.jetbrains.jet.lang.resolve.name.FqName;
 import org.jetbrains.jet.lang.resolve.name.Name;
@@ -412,4 +413,9 @@ public class JetPsiUtil {
 
         return result;
     }
+
+    public static boolean isNullConstant(@NotNull JetExpression expression) {
+        JetExpression deparenthesized = deparenthesize(expression);
+        return deparenthesized instanceof JetConstantExpression && deparenthesized.getNode().getElementType() == JetNodeTypes.NULL;
+    }
 }

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/BasicExpressionTypingVisitor.java

@@ -1101,10 +1101,10 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
 
     private void checkSenselessComparisonWithNull(@NotNull JetBinaryExpression expression, @NotNull JetExpression left, @NotNull JetExpression right, @NotNull ExpressionTypingContext context) {
         JetExpression expr;
-        if (left instanceof JetConstantExpression && left.getNode().getElementType() == JetNodeTypes.NULL) {
+        if (JetPsiUtil.isNullConstant(left)) {
             expr = right;
         }
-        else if (right instanceof JetConstantExpression && right.getNode().getElementType() == JetNodeTypes.NULL) {
+        else if (JetPsiUtil.isNullConstant(right)) {
             expr = left;
         }
         else return;

compiler/testData/diagnostics/tests/senselessComparison/parenthesized.kt

@@ -0,0 +1,31 @@
+fun testEquals(x: Int) {
+    if (<!SENSELESS_COMPARISON!>x == null<!>) {}
+    if (<!SENSELESS_COMPARISON!>x == (null)<!>) {}
+    if (<!SENSELESS_COMPARISON!>x == null: Nothing?<!>) {}
+    if (<!SENSELESS_COMPARISON!>x == null: Nothing?<!>) {}
+    if (<!SENSELESS_COMPARISON!>x == @foo null<!>) {}
+}
+
+fun testEqualsFlipped(x: Int) {
+    if (<!SENSELESS_COMPARISON!>null == x<!>) {}
+    if (<!SENSELESS_COMPARISON!>(null) == x<!>) {}
+    if (<!SENSELESS_COMPARISON!>null: Nothing? == x<!>) {}
+    if (<!SENSELESS_COMPARISON!>null: Nothing? == x<!>) {}
+    if (<!SENSELESS_COMPARISON!>@foo null == x<!>) {}
+}
+
+fun testNotEquals(x: Int) {
+    if (<!SENSELESS_COMPARISON!>x != null<!>) {}
+    if (<!SENSELESS_COMPARISON!>x != (null)<!>) {}
+    if (<!SENSELESS_COMPARISON!>x != null: Nothing?<!>) {}
+    if (<!SENSELESS_COMPARISON!>x != null: Nothing?<!>) {}
+    if (<!SENSELESS_COMPARISON!>x != @foo null<!>) {}
+}
+
+fun testNotEqualsFlipped(x: Int) {
+    if (<!SENSELESS_COMPARISON!>null != x<!>) {}
+    if (<!SENSELESS_COMPARISON!>(null) != x<!>) {}
+    if (<!SENSELESS_COMPARISON!>null: Nothing? != x<!>) {}
+    if (<!SENSELESS_COMPARISON!>null: Nothing? != x<!>) {}
+    if (<!SENSELESS_COMPARISON!>@foo null != x<!>) {}
+}

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -15,19 +15,22 @@
  */
 package org.jetbrains.jet.checkers;
 
+import junit.framework.Assert;
 import junit.framework.Test;
 import junit.framework.TestSuite;
+
+import java.io.File;
 import org.jetbrains.jet.JetTestUtils;
 import org.jetbrains.jet.test.InnerTestClasses;
 import org.jetbrains.jet.test.TestMetadata;
 
-import java.io.File;
+import org.jetbrains.jet.checkers.AbstractDiagnosticsTestWithEagerResolve;
 
 /** This class is generated by {@link org.jetbrains.jet.checkers.AbstractDiagnosticsTestWithEagerResolve}. DO NOT MODIFY MANUALLY */
 @InnerTestClasses({JetDiagnosticsTestGenerated.Tests.class, JetDiagnosticsTestGenerated.Script.class})
 public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEagerResolve {
     @TestMetadata("compiler/testData/diagnostics/tests")
-    @InnerTestClasses({Tests.Annotations.class, Tests.BackingField.class, Tests.Cast.class, Tests.CheckArguments.class, Tests.ControlFlowAnalysis.class, Tests.ControlStructures.class, Tests.DataClasses.class, Tests.DataFlow.class, Tests.DataFlowInfoTraversal.class, Tests.DeclarationChecks.class, Tests.Enum.class, Tests.Extensions.class, Tests.FunctionLiterals.class, Tests.Generics.class, Tests.IncompleteCode.class, Tests.Inference.class, Tests.Infos.class, Tests.J_k.class, Tests.Jdk_annotations.class, Tests.Library.class, Tests.NullabilityAndAutoCasts.class, Tests.NullableTypes.class, Tests.Objects.class, Tests.OperatorsOverloading.class, Tests.Overload.class, Tests.Override.class, Tests.Redeclarations.class, Tests.Regressions.class, Tests.Scopes.class, Tests.Shadowing.class, Tests.Substitutions.class, Tests.Subtyping.class, Tests.Tuples.class, Tests.Varargs.class})
+    @InnerTestClasses({Tests.Annotations.class, Tests.BackingField.class, Tests.Cast.class, Tests.CheckArguments.class, Tests.ControlFlowAnalysis.class, Tests.ControlStructures.class, Tests.DataClasses.class, Tests.DataFlow.class, Tests.DataFlowInfoTraversal.class, Tests.DeclarationChecks.class, Tests.Enum.class, Tests.Extensions.class, Tests.FunctionLiterals.class, Tests.Generics.class, Tests.IncompleteCode.class, Tests.Inference.class, Tests.Infos.class, Tests.J_k.class, Tests.Jdk_annotations.class, Tests.Library.class, Tests.NullabilityAndAutoCasts.class, Tests.NullableTypes.class, Tests.Objects.class, Tests.OperatorsOverloading.class, Tests.Overload.class, Tests.Override.class, Tests.Redeclarations.class, Tests.Regressions.class, Tests.Scopes.class, Tests.SenselessComparison.class, Tests.Shadowing.class, Tests.Substitutions.class, Tests.Subtyping.class, Tests.Tuples.class, Tests.Varargs.class})
     public static class Tests extends AbstractDiagnosticsTestWithEagerResolve {
         @TestMetadata("Abstract.kt")
         public void testAbstract() throws Exception {
@@ -3349,6 +3352,19 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
             
         }
         
+        @TestMetadata("compiler/testData/diagnostics/tests/senselessComparison")
+        public static class SenselessComparison extends AbstractDiagnosticsTestWithEagerResolve {
+            public void testAllFilesPresentInSenselessComparison() throws Exception {
+                JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), "org.jetbrains.jet.checkers.AbstractDiagnosticsTestWithEagerResolve", new File("compiler/testData/diagnostics/tests/senselessComparison"), "kt", true);
+            }
+            
+            @TestMetadata("parenthesized.kt")
+            public void testParenthesized() throws Exception {
+                doTest("compiler/testData/diagnostics/tests/senselessComparison/parenthesized.kt");
+            }
+            
+        }
+        
         @TestMetadata("compiler/testData/diagnostics/tests/shadowing")
         public static class Shadowing extends AbstractDiagnosticsTestWithEagerResolve {
             public void testAllFilesPresentInShadowing() throws Exception {
@@ -3551,6 +3567,7 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
             suite.addTestSuite(Redeclarations.class);
             suite.addTestSuite(Regressions.class);
             suite.addTestSuite(Scopes.class);
+            suite.addTestSuite(SenselessComparison.class);
             suite.addTestSuite(Shadowing.class);
             suite.addTestSuite(Substitutions.class);
             suite.addTestSuite(Subtyping.class);