K2: Handle DNN types properly during type aliases expansion

^KT-68383 Fixed
^KT-68497 Related

Author: dzharkov

compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/TypeExpansionUtils.kt

@@ -136,18 +136,19 @@ private fun mapTypeAliasArguments(
 
         override fun substituteArgument(projection: ConeTypeProjection, index: Int): ConeTypeProjection? {
             val type = (projection as? ConeKotlinTypeProjection)?.type ?: return null
-            val symbol = (type as? ConeTypeParameterType)?.lookupTag?.symbol ?: return super.substituteArgument(
-                projection,
-                index
-            )
+            // TODO: Consider making code more generic and "ready" to any kind of types (KT-68497)
+            val symbol =
+                (type.unwrapFlexibleAndDefinitelyNotNull() as? ConeTypeParameterType)?.lookupTag?.symbol
+                    ?: return super.substituteArgument(projection, index)
             val mappedProjection = typeAliasMap[symbol] ?: return super.substituteArgument(projection, index)
             var mappedType = (mappedProjection as? ConeKotlinTypeProjection)?.type.updateNullabilityIfNeeded(type)
             mappedType = when (mappedType) {
                 is ConeErrorType,
                 is ConeClassLikeTypeImpl,
                 is ConeDefinitelyNotNullType,
                 is ConeTypeParameterTypeImpl,
-                is ConeFlexibleType -> {
+                is ConeFlexibleType,
+                -> {
                     mappedType.withAttributes(type.attributes.add(mappedType.attributes))
                 }
                 null -> return mappedProjection

compiler/testData/diagnostics/tests/typealias/expansionDnnTypeArgument.fir.kt

@@ -6,16 +6,16 @@ interface Inv2<K, V> {
 typealias Inv1<T> = Inv2<String, T & Any>
 
 fun test1(inv: Inv1<String>) {
-    expectMap(<!ARGUMENT_TYPE_MISMATCH!>inv<!>)
+    expectMap(inv)
     val x = inv.get("")
-    x.<!UNRESOLVED_REFERENCE!>length<!>
+    x.length
 }
 
 fun test2(map: Inv1<String?>) {
     // Well, this K1 behavior doesn't look really correct, but we're not going to change it anymore
-    expectMap(<!ARGUMENT_TYPE_MISMATCH!>map<!>)
+    expectMap(map)
     val x = map.get("")
-    x.<!UNRESOLVED_REFERENCE!>length<!>
+    x.length
 }
 
 fun expectMap(x: Inv2<String, String>) {}