Quick fix "add !!" for SMARTCAST_IMPOSSIBLE in certain situations

idea/src/org/jetbrains/kotlin/idea/quickfix/ExclExclCallFixes.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.diagnostics.Diagnostic
+import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.idea.KotlinBundle
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
@@ -34,6 +35,7 @@ import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.types.TypeUtils
+import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlin.util.isValidOperator
 
@@ -106,6 +108,25 @@ class AddExclExclCallFix(val psiElement: PsiElement) : ExclExclCallFix() {
     }
 }
 
+object SmartCastImpossibleExclExclFixFactory: KotlinSingleIntentionActionFactory() {
+    override fun createAction(diagnostic: Diagnostic): IntentionAction? {
+        if (diagnostic.factory !== Errors.SMARTCAST_IMPOSSIBLE) return null
+        val element = diagnostic.psiElement as? KtExpression ?: return null
+
+        val analyze = element.analyze(BodyResolveMode.PARTIAL)
+        val type = analyze.getType(element)
+        if (type == null || !TypeUtils.isNullableType(type)) return null
+
+        val diagnosticWithParameters = Errors.SMARTCAST_IMPOSSIBLE.cast(diagnostic)
+        val expectedType = diagnosticWithParameters.a
+        if (TypeUtils.isNullableType(expectedType)) return null
+        val nullableExpectedType = TypeUtils.makeNullable(expectedType)
+        if (!type.isSubtypeOf(nullableExpectedType)) return null
+
+        return AddExclExclCallFix(element)
+    }
+}
+
 object MissingIteratorExclExclFixFactory : KotlinSingleIntentionActionFactory() {
     override fun createAction(diagnostic: Diagnostic): IntentionAction? {
         val element = diagnostic.psiElement

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -300,6 +300,7 @@ class QuickFixRegistrar : QuickFixContributor {
         NULL_FOR_NONNULL_TYPE.registerFactory(factoryForTypeMismatchError)
         CONSTANT_EXPECTED_TYPE_MISMATCH.registerFactory(factoryForTypeMismatchError)
 
+        SMARTCAST_IMPOSSIBLE.registerFactory(SmartCastImpossibleExclExclFixFactory)
         SMARTCAST_IMPOSSIBLE.registerFactory(CastExpressionFix.SmartCastImpossibleFactory)
 
         PLATFORM_CLASS_MAPPED_TO_KOTLIN.registerFactory(MapPlatformClassToKotlinFix)

idea/testData/quickfix/typeMismatch/addExclExclWhenSmartCastImpossible.kt

@@ -0,0 +1,17 @@
+// "Add non-null asserted (!!) call" "true"
+// ACTION: Cast expression 'a' to 'Foo'
+
+interface Foo {
+    fun bar()
+}
+
+open class MyClass {
+    open val a: Foo? = null
+
+    fun foo() {
+        if (a != null) {
+            <caret>a.bar()
+        }
+    }
+}
+

idea/testData/quickfix/typeMismatch/addExclExclWhenSmartCastImpossible.kt.after

@@ -0,0 +1,17 @@
+// "Add non-null asserted (!!) call" "true"
+// ACTION: Cast expression 'a' to 'Foo'
+
+interface Foo {
+    fun bar()
+}
+
+open class MyClass {
+    open val a: Foo? = null
+
+    fun foo() {
+        if (a != null) {
+            a!!.bar()
+        }
+    }
+}
+

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -7662,6 +7662,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
             doTest(fileName);
         }
 
+        @TestMetadata("addExclExclWhenSmartCastImpossible.kt")
+        public void testAddExclExclWhenSmartCastImpossible() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/typeMismatch/addExclExclWhenSmartCastImpossible.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("addIntArrayOf.kt")
         public void testAddIntArrayOf() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/typeMismatch/addIntArrayOf.kt");