generate CHECK_CAST for smartcasted 'this'

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

@@ -293,7 +293,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
 
     @Override
     public StackValue visitSuperExpression(@NotNull JetSuperExpression expression, StackValue data) {
-        return StackValue.thisOrOuter(this, getSuperCallLabelTarget(expression), true);
+        return StackValue.thisOrOuter(this, getSuperCallLabelTarget(expression), true, true);
     }
 
     private ClassDescriptor getSuperCallLabelTarget(JetSuperExpression expression) {
@@ -1720,7 +1720,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
             Type scriptClassType = asmTypeForScriptDescriptor(bindingContext, scriptDescriptor);
             ValueParameterDescriptor valueParameterDescriptor = (ValueParameterDescriptor) descriptor;
             ClassDescriptor scriptClass = bindingContext.get(CLASS_FOR_SCRIPT, scriptDescriptor);
-            StackValue script = StackValue.thisOrOuter(this, scriptClass, false);
+            StackValue script = StackValue.thisOrOuter(this, scriptClass, false, false);
             script.put(script.type, v);
             Type fieldType = typeMapper.mapType(valueParameterDescriptor);
             return StackValue.field(fieldType, scriptClassType, valueParameterDescriptor.getName().getIdentifier(), false);
@@ -2152,7 +2152,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
                 StackValue.onStack(exprType).put(type, v);
             }
             else {
-                StackValue.thisOrOuter(this, classReceiverDeclarationDescriptor, false).put(type, v);
+                StackValue.thisOrOuter(this, classReceiverDeclarationDescriptor, false, false).put(type, v);
             }
         }
         else if (descriptor instanceof ScriptReceiver) {
@@ -3418,7 +3418,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
     public StackValue visitThisExpression(@NotNull JetThisExpression expression, StackValue receiver) {
         DeclarationDescriptor descriptor = bindingContext.get(BindingContext.REFERENCE_TARGET, expression.getInstanceReference());
         if (descriptor instanceof ClassDescriptor) {
-            return StackValue.thisOrOuter(this, (ClassDescriptor) descriptor, false);
+            return StackValue.thisOrOuter(this, (ClassDescriptor) descriptor, false, true);
         }
         else {
             if (descriptor instanceof CallableDescriptor) {

compiler/backend/src/org/jetbrains/jet/codegen/StackValue.java

@@ -309,10 +309,11 @@ public abstract class StackValue {
         return new Composed(prefix, suffix);
     }
 
-    public static StackValue thisOrOuter(ExpressionCodegen codegen, ClassDescriptor descriptor, boolean isSuper) {
-        // Coerce this/super for traits to support traits with required classes
-        // Do not coerce for other classes due to the 'protected' access issues (JVMS 7, 4.9.2 Structural Constraints)
-        boolean coerceType = descriptor.getKind() == ClassKind.TRAIT;
+    public static StackValue thisOrOuter(ExpressionCodegen codegen, ClassDescriptor descriptor, boolean isSuper, boolean isExplicit) {
+        // Coerce this/super for traits to support traits with required classes.
+        // Coerce explicit 'this' for the case when it is smartcasted.
+        // Do not coerce for other classes due to the 'protected' access issues (JVMS 7, 4.9.2 Structural Constraints).
+        boolean coerceType = descriptor.getKind() == ClassKind.TRAIT || (isExplicit && !isSuper);
         return new ThisOuter(codegen, descriptor, isSuper, coerceType);
     }
 

compiler/testData/codegen/box/typeInfo/implicitSmartCastedThis.kt

@@ -0,0 +1,13 @@
+open class A
+
+class B : A() {
+    fun foo(i: Int) = i
+}
+
+fun A.test() = if (this is B) foo(42) else 0
+
+fun box(): String {
+    if (B().test() != 42) return "fail1"
+    if (A().test() != 0) return "fail2"
+    return "OK"
+}

compiler/testData/codegen/box/typeInfo/smartCastedThis.kt

@@ -0,0 +1,11 @@
+package h
+
+open class A {
+    fun bar() = if (this is B) this.foo() else "fail"
+}
+
+class B() : A() {
+    fun foo() = "OK"
+}
+
+fun box() = B().bar()

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

@@ -4979,6 +4979,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest("compiler/testData/codegen/box/typeInfo/asInLoop.kt");
         }
         
+        @TestMetadata("implicitSmartCastedThis.kt")
+        public void testImplicitSmartCastedThis() throws Exception {
+            doTest("compiler/testData/codegen/box/typeInfo/implicitSmartCastedThis.kt");
+        }
+        
         @TestMetadata("inheritance.kt")
         public void testInheritance() throws Exception {
             doTest("compiler/testData/codegen/box/typeInfo/inheritance.kt");
@@ -4999,6 +5004,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest("compiler/testData/codegen/box/typeInfo/primitiveTypeInfo.kt");
         }
         
+        @TestMetadata("smartCastedThis.kt")
+        public void testSmartCastedThis() throws Exception {
+            doTest("compiler/testData/codegen/box/typeInfo/smartCastedThis.kt");
+        }
+        
     }
     
     @TestMetadata("compiler/testData/codegen/box/typeMapping")