[FE 1.0] Don't throw empty intersection exception, return empty intersection type instead

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

@@ -13670,6 +13670,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/inference/discardInapplicableCandidateWithNotSatisfyingSelfType.kt");
             }
 
+            @Test
+            @TestMetadata("dontThrowEmptyIntersectionException.kt")
+            public void testDontThrowEmptyIntersectionException() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inference/dontThrowEmptyIntersectionException.kt");
+            }
+
             @Test
             @TestMetadata("equalitySubstitutionInsideNonInvariantType.kt")
             public void testEqualitySubstitutionInsideNonInvariantType() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java

@@ -13670,6 +13670,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/inference/discardInapplicableCandidateWithNotSatisfyingSelfType.kt");
             }
 
+            @Test
+            @TestMetadata("dontThrowEmptyIntersectionException.kt")
+            public void testDontThrowEmptyIntersectionException() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inference/dontThrowEmptyIntersectionException.kt");
+            }
+
             @Test
             @TestMetadata("equalitySubstitutionInsideNonInvariantType.kt")
             public void testEqualitySubstitutionInsideNonInvariantType() throws Exception {

compiler/frontend/src/org/jetbrains/kotlin/types/TypeIntersector.java

@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl;
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker;
 import org.jetbrains.kotlin.types.error.ErrorTypeKind;
 import org.jetbrains.kotlin.types.error.ErrorUtils;
+import org.jetbrains.kotlin.types.typeUtil.TypeUtilsKt;
 
 import java.util.*;
 
@@ -124,7 +125,7 @@ public class TypeIntersector {
             }
 
             if (bestRepresentative == null) {
-                throw new AssertionError("Empty intersection for types " + types);
+                return null;
             }
             return TypeUtils.makeNullableAsSpecified(bestRepresentative, allNullable);
         }

compiler/testData/diagnostics/tests/inference/dontThrowEmptyIntersectionException.fir.kt

@@ -0,0 +1,22 @@
+// WITH_STDLIB
+
+// FILE: Test.java
+public interface Test<K> implements I<String> {}
+
+// FILE: Test2.java
+public interface Test2<K, M>
+
+// FILE: Test3.java
+public interface Test3<K> {}
+
+// FILE: I.java
+public interface I<K> {}
+
+// FILE: main.kt
+fun main(z: I<String>) {
+    z <!UNCHECKED_CAST!>as Test<Test2<Int, *>><!>
+    z <!UNCHECKED_CAST!>as Test<Test2<Int, <!UNRESOLVED_REFERENCE!>Foo<!>>><!>
+    z as Test<<!UNRESOLVED_REFERENCE!>Foo<!>>
+    z as <!UNRESOLVED_REFERENCE!>Any2<!>
+    println(z)
+}

compiler/testData/diagnostics/tests/inference/dontThrowEmptyIntersectionException.kt

@@ -0,0 +1,22 @@
+// WITH_STDLIB
+
+// FILE: Test.java
+public interface Test<K> implements I<String> {}
+
+// FILE: Test2.java
+public interface Test2<K, M>
+
+// FILE: Test3.java
+public interface Test3<K> {}
+
+// FILE: I.java
+public interface I<K> {}
+
+// FILE: main.kt
+fun main(z: I<String>) {
+    z <!UNCHECKED_CAST!>as Test<Test2<Int, *>><!>
+    z <!USELESS_CAST!>as Test<Test2<Int, <!UNRESOLVED_REFERENCE!>Foo<!>>><!>
+    z <!USELESS_CAST!>as Test<<!UNRESOLVED_REFERENCE!>Foo<!>><!>
+    z as <!UNRESOLVED_REFERENCE!>Any2<!>
+    println(z)
+}

compiler/testData/diagnostics/tests/inference/dontThrowEmptyIntersectionException.txt

@@ -0,0 +1,27 @@
+package
+
+public fun main(/*0*/ z: I<kotlin.String>): kotlin.Unit
+
+public interface I</*0*/ K : kotlin.Any!> {
+    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 interface Test</*0*/ K : kotlin.Any!> : I<kotlin.String!> {
+    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 interface Test2</*0*/ K : kotlin.Any!, /*1*/ M : kotlin.Any!> {
+    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 interface Test3</*0*/ K : kotlin.Any!> {
+    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-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -13676,6 +13676,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/inference/discardInapplicableCandidateWithNotSatisfyingSelfType.kt");
             }
 
+            @Test
+            @TestMetadata("dontThrowEmptyIntersectionException.kt")
+            public void testDontThrowEmptyIntersectionException() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inference/dontThrowEmptyIntersectionException.kt");
+            }
+
             @Test
             @TestMetadata("equalitySubstitutionInsideNonInvariantType.kt")
             public void testEqualitySubstitutionInsideNonInvariantType() throws Exception {