Fix wrong checkcast for === on objects

#KT-6747 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/AsmUtil.java

@@ -527,10 +527,6 @@ public class AsmUtil {
             return StackValue.cmp(opToken, leftType, left, right);
         }
 
-        if (opToken == JetTokens.EQEQEQ || opToken == JetTokens.EXCLEQEQEQ) {
-            return StackValue.cmp(opToken, leftType, left, right);
-        }
-
         return StackValue.operation(Type.BOOLEAN_TYPE, new Function1<InstructionAdapter, Unit>() {
             @Override
             public Unit invoke(InstructionAdapter v) {

compiler/backend/src/org/jetbrains/kotlin/codegen/ExpressionCodegen.java

@@ -3056,7 +3056,16 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
             rightType = boxType(rightType);
         }
 
-        return genEqualsForExpressionsOnStack(opToken, genLazy(left, leftType), genLazy(right, rightType));
+        StackValue leftValue = genLazy(left, leftType);
+        StackValue rightValue = genLazy(right, rightType);
+
+        if (opToken == JetTokens.EQEQEQ || opToken == JetTokens.EXCLEQEQEQ) {
+            // TODO: always casting to the type of the left operand in case of primitives looks wrong
+            Type operandType = isPrimitive(leftType) ? leftType : OBJECT_TYPE;
+            return StackValue.cmp(opToken, operandType, leftValue, rightValue);
+        }
+
+        return genEqualsForExpressionsOnStack(opToken, leftValue, rightValue);
     }
 
     private boolean isIntZero(JetExpression expr, Type exprType) {

compiler/testData/codegen/box/binaryOp/kt6747_identityEquals.kt

@@ -0,0 +1,10 @@
+class Test {
+    fun check(a: Any?): String {
+        if (this === a) return "Fail 1"
+        if (!(this !== a)) return "Fail 2"
+        if (this.identityEquals(a)) return "Fail 3"
+        return "OK"
+    }
+}
+
+fun box(): String = Test().check("String")

compiler/testData/codegen/box/platformTypes/primitives/identityEquals.kt

@@ -17,4 +17,4 @@ fun box(): String {
     if (!y2) return "Fail (y2): $y"
 
     return "OK"
-}
+}

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxCodegenTestGenerated.java

@@ -282,6 +282,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt6747_identityEquals.kt")
+        public void testKt6747_identityEquals() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/binaryOp/kt6747_identityEquals.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("longOverflow.kt")
         public void testLongOverflow() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/binaryOp/longOverflow.kt");
@@ -5276,6 +5282,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("identityEquals.kt")
+            public void testIdentityEquals() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/platformTypes/primitives/identityEquals.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("inc.kt")
             public void testInc() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/platformTypes/primitives/inc.kt");
@@ -5342,12 +5354,6 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 doTest(fileName);
             }
 
-            @TestMetadata("udentityEquals.kt")
-            public void testUdentityEquals() throws Exception {
-                String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/platformTypes/primitives/udentityEquals.kt");
-                doTest(fileName);
-            }
-
             @TestMetadata("unaryMinus.kt")
             public void testUnaryMinus() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/platformTypes/primitives/unaryMinus.kt");