[FIR] KT-57095: Allow X? -> * assignments in unification

^KT-57095 Fixed

Merge-request: KT-MR-9180
Merged-by: Nikolay Lunyak <Nikolay.Lunyak@jetbrains.com>

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -783,6 +783,18 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
             runTest("compiler/testData/diagnostics/tests/QualifiedExpressions.kt");
         }
 
+        @Test
+        @TestMetadata("rawCastToStarProjection_Fail.kt")
+        public void testRawCastToStarProjection_Fail() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Fail.kt");
+        }
+
+        @Test
+        @TestMetadata("rawCastToStarProjection_Ok.kt")
+        public void testRawCastToStarProjection_Ok() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Ok.kt");
+        }
+
         @Test
         @TestMetadata("RecursiveResolve.kt")
         public void testRecursiveResolve() throws Exception {

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

@@ -783,6 +783,18 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
             runTest("compiler/testData/diagnostics/tests/QualifiedExpressions.kt");
         }
 
+        @Test
+        @TestMetadata("rawCastToStarProjection_Fail.kt")
+        public void testRawCastToStarProjection_Fail() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Fail.kt");
+        }
+
+        @Test
+        @TestMetadata("rawCastToStarProjection_Ok.kt")
+        public void testRawCastToStarProjection_Ok() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Ok.kt");
+        }
+
         @Test
         @TestMetadata("RecursiveResolve.kt")
         public void testRecursiveResolve() throws Exception {

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

@@ -783,6 +783,18 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
             runTest("compiler/testData/diagnostics/tests/QualifiedExpressions.kt");
         }
 
+        @Test
+        @TestMetadata("rawCastToStarProjection_Fail.kt")
+        public void testRawCastToStarProjection_Fail() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Fail.kt");
+        }
+
+        @Test
+        @TestMetadata("rawCastToStarProjection_Ok.kt")
+        public void testRawCastToStarProjection_Ok() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Ok.kt");
+        }
+
         @Test
         @TestMetadata("RecursiveResolve.kt")
         public void testRecursiveResolve() throws Exception {

compiler/fir/providers/src/org/jetbrains/kotlin/fir/types/TypeUnification.kt

@@ -78,7 +78,11 @@ fun FirSession.doUnify(
     }
 
     // Foo ~ X? => fail
-    if (originalType?.nullability != ConeNullability.NULLABLE && typeWithParameters?.nullability == ConeNullability.NULLABLE) {
+    if (
+        originalTypeProjection !is ConeStarProjection &&
+        originalType?.nullability != ConeNullability.NULLABLE &&
+        typeWithParameters?.nullability == ConeNullability.NULLABLE
+    ) {
         return true
     }
 

compiler/testData/diagnostics/tests/rawCastToStarProjection_Fail.kt

@@ -0,0 +1,9 @@
+// FIR_IDENTICAL
+// ISSUE: KT-57095
+
+open class ValueType<T> {
+    class Optional<T>: ValueType<T?>()
+}
+private fun checkType(type: ValueType<*>) {
+    type as ValueType.Optional // K1: ok, K2: NO_TYPE_ARGUMENTS_ON_RHS
+}

compiler/testData/diagnostics/tests/rawCastToStarProjection_Ok.kt

@@ -0,0 +1,10 @@
+// FIR_IDENTICAL
+// ISSUE: KT-57095
+
+open class ValueType<T> {
+    class Optional<T>: ValueType<T?>()
+}
+
+private fun checkType(type: ValueType<out Any?>) {
+    type as ValueType.Optional // K1 & K2: ok
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -783,6 +783,18 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
             runTest("compiler/testData/diagnostics/tests/QualifiedExpressions.kt");
         }
 
+        @Test
+        @TestMetadata("rawCastToStarProjection_Fail.kt")
+        public void testRawCastToStarProjection_Fail() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Fail.kt");
+        }
+
+        @Test
+        @TestMetadata("rawCastToStarProjection_Ok.kt")
+        public void testRawCastToStarProjection_Ok() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/rawCastToStarProjection_Ok.kt");
+        }
+
         @Test
         @TestMetadata("RecursiveResolve.kt")
         public void testRecursiveResolve() throws Exception {