[NI] Make return type of !! operator definitely not-null

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/model/NewConstraintSystemImpl.kt

@@ -30,7 +30,6 @@ import org.jetbrains.kotlin.types.TypeConstructor
 import org.jetbrains.kotlin.types.UnwrappedType
 import org.jetbrains.kotlin.types.typeUtil.builtIns
 import org.jetbrains.kotlin.types.typeUtil.contains
-import org.jetbrains.kotlin.types.typeUtil.isTypeParameter
 import org.jetbrains.kotlin.utils.SmartList
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
@@ -45,6 +44,10 @@ class NewConstraintSystemImpl(
         KotlinConstraintSystemCompleter.Context,
         PostponedArgumentsAnalyzer.Context
 {
+    companion object {
+        private val TYPE_PARAMETER_FOR_EXCLXCL = "<TYPE-PARAMETER-FOR-EXCLEXCL-RESOLVE>" // TODO: Get this variable from ResolveConstruct
+    }
+
     private val storage = MutableConstraintStorage()
     private var state = State.BUILDING
     private val typeVariablesTransaction: MutableList<NewTypeVariable> = SmartList()
@@ -205,7 +208,7 @@ class NewConstraintSystemImpl(
     override fun fixVariable(variable: NewTypeVariable, resultType: UnwrappedType) {
         checkState(State.BUILDING, State.COMPLETION)
 
-        val actualResultType = eliminateSpecialIntersectionType(resultType) ?: resultType
+        val actualResultType = eliminateSpecialIntersectionType(variable, resultType) ?: resultType
         constraintInjector.addInitialEqualityConstraint(this, variable.defaultType, actualResultType, FixVariableConstraintPosition(variable))
         notFixedTypeVariables.remove(variable.freshTypeConstructor)
 
@@ -218,7 +221,9 @@ class NewConstraintSystemImpl(
         storage.fixedTypeVariables[variable.freshTypeConstructor] = actualResultType
     }
 
-    private fun eliminateSpecialIntersectionType(type: UnwrappedType): UnwrappedType? {
+    private fun eliminateSpecialIntersectionType(variable: NewTypeVariable, type: UnwrappedType): UnwrappedType? {
+        if (variable.shouldBeDefinitelyNotNull()) return null
+
         val constructor = type.constructor.safeAs<IntersectionTypeConstructor>() ?: return null
 
         if (constructor.supertypes.size != 2) return null
@@ -227,6 +232,13 @@ class NewConstraintSystemImpl(
         return actualType?.unwrap()
     }
 
+    private fun NewTypeVariable.shouldBeDefinitelyNotNull(): Boolean {
+        return when (this) {
+            is TypeVariableFromCallableDescriptor -> originalTypeParameter.name.asString() == TYPE_PARAMETER_FOR_EXCLXCL
+            is TypeVariableForLambdaReturnType -> false
+        }
+    }
+
     // KotlinConstraintSystemCompleter.Context, PostponedArgumentsAnalyzer.Context
     override fun canBeProper(type: UnwrappedType): Boolean {
         checkState(State.BUILDING, State.COMPLETION)

compiler/testData/codegen/box/regressions/nullableAfterExclExcl.kt

@@ -0,0 +1,13 @@
+interface Sample {
+    val callMe: Int
+}
+
+class Caller<out M : Sample?>(val member: M) {
+    fun test() {
+        member!!.callMe
+    }
+}
+
+fun box(): String {
+    return "OK"
+}

compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -17042,6 +17042,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             doTest(fileName);
         }
 
+        @TestMetadata("nullableAfterExclExcl.kt")
+        public void testNullableAfterExclExcl() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/nullableAfterExclExcl.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("objectCaptureOuterConstructorProperty.kt")
         public void testObjectCaptureOuterConstructorProperty() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/objectCaptureOuterConstructorProperty.kt");

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

@@ -17042,6 +17042,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("nullableAfterExclExcl.kt")
+        public void testNullableAfterExclExcl() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/nullableAfterExclExcl.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("objectCaptureOuterConstructorProperty.kt")
         public void testObjectCaptureOuterConstructorProperty() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/objectCaptureOuterConstructorProperty.kt");

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -17042,6 +17042,12 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             doTest(fileName);
         }
 
+        @TestMetadata("nullableAfterExclExcl.kt")
+        public void testNullableAfterExclExcl() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/nullableAfterExclExcl.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("objectCaptureOuterConstructorProperty.kt")
         public void testObjectCaptureOuterConstructorProperty() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/objectCaptureOuterConstructorProperty.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -20828,6 +20828,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             doTest(fileName);
         }
 
+        @TestMetadata("nullableAfterExclExcl.kt")
+        public void testNullableAfterExclExcl() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/nullableAfterExclExcl.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("objectCaptureOuterConstructorProperty.kt")
         public void testObjectCaptureOuterConstructorProperty() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/objectCaptureOuterConstructorProperty.kt");