Fix overload ambiguity after smartcast to nullable Nothing

#KT-39544 Fixed

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java

@@ -21422,6 +21422,11 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirOldFronte
             runTest("compiler/testData/diagnostics/tests/smartCasts/smartcastOnSameFieldOfDifferentInstances.kt");
         }
 
+        @TestMetadata("smartcastToNothingAfterCheckingForNull.kt")
+        public void testSmartcastToNothingAfterCheckingForNull() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/smartCasts/smartcastToNothingAfterCheckingForNull.kt");
+        }
+
         @TestMetadata("thisWithLabel.kt")
         public void testThisWithLabel() throws Exception {
             runTest("compiler/testData/diagnostics/tests/smartCasts/thisWithLabel.kt");

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ArgumentsUtils.kt

@@ -32,6 +32,8 @@ import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValueWithSmartCastI
 import org.jetbrains.kotlin.types.UnwrappedType
 import org.jetbrains.kotlin.types.checker.intersectWrappedTypes
 import org.jetbrains.kotlin.types.checker.prepareArgumentTypeRegardingCaptureTypes
+import org.jetbrains.kotlin.types.typeUtil.isNullableNothing
+import org.jetbrains.kotlin.types.typeUtil.makeNullable
 import org.jetbrains.kotlin.utils.DFS
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
@@ -71,6 +73,13 @@ val ReceiverValueWithSmartCastInfo.stableType: UnwrappedType
          */
         val intersectionType = intersectWrappedTypes(allOriginalTypes)
 
+        // Intersection type of Nothing with any flexible types will be Nothing!.
+        // This is a bit incorrect as cast to Nothing? or Nothing can result only in Nothing? or Nothing,
+        // otherwise it'll be possible to pass null to some non-nullable type
+        if (intersectionType.isNullableNothing() && !intersectionType.isMarkedNullable) {
+            return intersectionType.makeNullable().unwrap()
+        }
+
         return prepareArgumentTypeRegardingCaptureTypes(intersectionType) ?: intersectionType
     }
 

compiler/testData/diagnostics/tests/smartCasts/alwaysNullWithJava.kt

@@ -11,7 +11,7 @@ public class My {
 fun test() {
     val my = My.create()
     if (my == null) {
-        <!OI;DEBUG_INFO_CONSTANT!>my<!><!OI;UNSAFE_CALL!>.<!>foo()
+        <!OI;DEBUG_INFO_CONSTANT!>my<!><!UNSAFE_CALL!>.<!>foo()
     }
 }
 

compiler/testData/diagnostics/tests/smartCasts/smartcastToNothingAfterCheckingForNull.fir.kt

@@ -0,0 +1,29 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: B.java
+
+public abstract class B<T> implements A<T> {}
+
+// FILE: test.kt
+
+interface A<T> {
+    val content: T
+}
+fun f(x: Any?) {}
+fun f(x: Byte) {}
+fun f(x: Char) {}
+
+fun g(i: Int) {}
+
+fun g(x: B<Int>) {
+    val y = x.content
+    if (y == null) {
+        f(y)
+        g(y)
+    }
+
+    if (y is Nothing?) {
+        <!AMBIGUITY!>f<!>(y)
+        <!AMBIGUITY!>g<!>(y)
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/smartcastToNothingAfterCheckingForNull.kt

@@ -0,0 +1,29 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: B.java
+
+public abstract class B<T> implements A<T> {}
+
+// FILE: test.kt
+
+interface A<T> {
+    val content: T
+}
+fun f(x: Any?) {}
+fun f(x: Byte) {}
+fun f(x: Char) {}
+
+fun g(i: Int) {}
+
+fun g(x: B<Int>) {
+    val y = x.content
+    if (y == null) {
+        f(<!DEBUG_INFO_CONSTANT!>y<!>)
+        <!NONE_APPLICABLE!>g<!>(<!DEBUG_INFO_CONSTANT!>y<!>)
+    }
+
+    if (y is Nothing?) {
+        f(y)
+        <!NONE_APPLICABLE!>g<!>(y)
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/smartcastToNothingAfterCheckingForNull.txt

@@ -0,0 +1,22 @@
+package
+
+public fun f(/*0*/ x: kotlin.Any?): kotlin.Unit
+public fun f(/*0*/ x: kotlin.Byte): kotlin.Unit
+public fun f(/*0*/ x: kotlin.Char): kotlin.Unit
+public fun g(/*0*/ x: B<kotlin.Int>): kotlin.Unit
+public fun g(/*0*/ i: kotlin.Int): kotlin.Unit
+
+public interface A</*0*/ T> {
+    public abstract val content: T
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class B</*0*/ T : kotlin.Any!> : A<T!> {
+    public constructor B</*0*/ T : kotlin.Any!>()
+    public abstract override /*1*/ /*fake_override*/ val content: T!
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -21499,6 +21499,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTestWithFirVali
                 runTest("compiler/testData/diagnostics/tests/smartCasts/smartcastOnSameFieldOfDifferentInstances.kt");
             }
 
+            @TestMetadata("smartcastToNothingAfterCheckingForNull.kt")
+            public void testSmartcastToNothingAfterCheckingForNull() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/smartcastToNothingAfterCheckingForNull.kt");
+            }
+
             @TestMetadata("thisWithLabel.kt")
             public void testThisWithLabel() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/smartCasts/thisWithLabel.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -21424,6 +21424,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/smartCasts/smartcastOnSameFieldOfDifferentInstances.kt");
             }
 
+            @TestMetadata("smartcastToNothingAfterCheckingForNull.kt")
+            public void testSmartcastToNothingAfterCheckingForNull() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/smartcastToNothingAfterCheckingForNull.kt");
+            }
+
             @TestMetadata("thisWithLabel.kt")
             public void testThisWithLabel() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/smartCasts/thisWithLabel.kt");