IDEA-111450 false positive for "Redundant type cast" inspection

java/java-psi-api/src/com/intellij/psi/util/RedundantCastUtil.java

@@ -638,10 +638,21 @@ public class RedundantCastUtil {
   }
 
   private static boolean wrapperCastChangeSemantics(PsiExpression operand, PsiExpression otherOperand, PsiExpression toCast) {
-    boolean isPrimitiveComparisonWithCast = TypeConversionUtil.isPrimitiveAndNotNull(operand.getType()) ||
-                                            TypeConversionUtil.isPrimitiveAndNotNull(otherOperand.getType());
-    boolean isPrimitiveComparisonWithoutCast = TypeConversionUtil.isPrimitiveAndNotNull(toCast.getType()) ||
-                                               TypeConversionUtil.isPrimitiveAndNotNull(otherOperand.getType());
+    final boolean isPrimitiveComparisonWithCast;
+    final boolean isPrimitiveComparisonWithoutCast;
+
+    if (TypeConversionUtil.isPrimitiveAndNotNull(otherOperand.getType())) {
+      // IDEA-111450: A primitive comparison requires one primitive operand and one primitive or wrapper operand.
+      isPrimitiveComparisonWithCast = TypeConversionUtil.isPrimitiveAndNotNullOrWrapper(operand.getType());
+      isPrimitiveComparisonWithoutCast = TypeConversionUtil.isPrimitiveAndNotNullOrWrapper(toCast.getType());
+    }
+    else {
+      // We do not check whether `otherOperand` is a wrapper, because a reference-to-primitive cast has a
+      // side effect regardless of whether we end up doing a primitive or reference comparison.
+      isPrimitiveComparisonWithCast = TypeConversionUtil.isPrimitiveAndNotNull(operand.getType());
+      isPrimitiveComparisonWithoutCast = TypeConversionUtil.isPrimitiveAndNotNull(toCast.getType());
+    }
+
     // wrapper casted to primitive vs wrapper comparison
     return isPrimitiveComparisonWithCast != isPrimitiveComparisonWithoutCast;
   }
@@ -673,4 +684,4 @@ public class RedundantCastUtil {
     return method instanceof PsiMethod &&
            AnnotationUtil.isAnnotated((PsiMethod)method, CommonClassNames.JAVA_LANG_INVOKE_MH_POLYMORPHIC, false, true);
   }
-}
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting7/IDEA111450.java

@@ -0,0 +1,38 @@
+import java.lang.Character;
+import java.util.List;
+
+public class Test {
+  public static void test() {
+    Character c1 = '1';
+    Character c2 = '2';
+    Object o = '3';
+
+    // A cast on either operand is required to force a primitive comparison; not redundant.
+    System.out.println((char) c1 == c2);
+    System.out.println(c1 == (char) c2);
+
+    // If one operand is a primitive, and the other is a wrapper, the wrapper need not be cast.
+    System.out.println((<warning descr="Casting 'c1' to 'char' is redundant">char</warning>) c1 == '*');
+    System.out.println('*' == (<warning descr="Casting 'c1' to 'char' is redundant">char</warning>) c1);
+
+    // The cast on the Object is required to force a primitive comparison; not redundant.
+    System.out.println((char) o == '*');
+    System.out.println('*' == (char) o);
+
+    // The cast on the Object is required to force a primitive comparison; not redundant.
+    System.out.println((Character) o == '*');
+    System.out.println('*' == (Character) o);
+
+    // The cast on the Object triggers an implicit unboxing of the wrapper; not redundant.
+    System.out.println((char) o == c1);
+    System.out.println(c1 == (char) o);
+
+    // A cast on the Object is required for a primitive comparison, but the wrapper cast is redundant.
+    System.out.println((char) o == (<warning descr="Casting 'c1' to 'char' is redundant">char</warning>) c1);
+    System.out.println((<warning descr="Casting 'c1' to 'char' is redundant">char</warning>) c1 == (char) o);
+
+    // Although a reference comparison, the cast on the wrapper has a side effect; not redundant.
+    System.out.println(o == (char) c1);
+    System.out.println((char) c1 == o);
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingJdk7Test.java

@@ -179,4 +179,5 @@ public class LightAdvHighlightingJdk7Test extends LightDaemonAnalyzerTestCase {
   public void testIDEA62056() { doTest(false, false); }
   public void testIDEA78916() { doTest(false, false); }
   public void testIDEA111420() { doTest(false, false); }
+  public void testIDEA111450() { doTest(true, false); }
 }