[FIR] Fix substitution of anonymous type's supertypes, ^KT-51418 Fixed

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

@@ -411,16 +411,42 @@ private fun ConeKotlinType.approximateToOnlySupertype(session: FirSession): Cone
         return null
     }
     val result = superType.type.withNullability(nullability, session.typeContext)
-    val resultTypeArguments = result.typeArguments
+    if (typeArguments.isNotEmpty()) {
-    if (resultTypeArguments.isNotEmpty() && resultTypeArguments.size == typeArguments.size) {
         val substitution = mutableMapOf<FirTypeParameterSymbol, ConeKotlinType>()
-        for (index in resultTypeArguments.indices) {
+
-            // TODO: this is not correct (should use firClass' arguments as keys); see comment in KT-51418
+        var index = 0
-            val key = resultTypeArguments[index]
+        fun addSubstitution(projection: ConeTypeProjection): Boolean {
-            val value = typeArguments[index]
+            when (projection) {
-            val symbol = (key as? ConeTypeParameterType)?.lookupTag?.typeParameterSymbol ?: continue
+                is ConeTypeParameterType -> {
-            substitution[symbol] = value.type!!
+                    val symbol = projection.lookupTag.typeParameterSymbol
+                    if (!substitution.containsKey(symbol)) {
+                        substitution[symbol] = typeArguments[index].type!!
+                        index++
+                    }
+                }
+                is ConeErrorType -> {
+                    return false
+                }
+                is ConeClassLikeType -> {
+                    for (typeArgument in projection.typeArguments) {
+                        if (!addSubstitution(typeArgument)) {
+                            return false
+                        }
+                    }
+                }
+                is ConeKotlinTypeProjection -> {
+                    if (!addSubstitution(projection.type)) {
+                        return false
+                    }
+                }
+                is ConeStarProjection -> {
+                    index++
+                }
+            }
+            return true
         }
+
+        addSubstitution(result)
         return ConeSubstitutorByMap(substitution, session).substituteOrSelf(result)
     }
     return result

compiler/testData/diagnostics/tests/inference/substitutions/hideLocalTypeForReturnTypeOfSingleExpressionFunction.kt

@@ -28,3 +28,16 @@ class FieldTest {
     private val ttt = test.bar()
     private val qqq = ttt.qux()
 }
+
+interface I<T>
+interface I2<A, B>
+
+private fun <V> f(x: V) = object : I<I<V>> {}
+private fun <V> f1(x: V) = object : I<I<in V>> {}
+private fun <V> f2(x: V) = object : I2<V, V> {}
+private fun <V, W> f3(x: V, y: W) = object : I<I2<*, W>> {}
+
+fun g() = f("f")
+fun g1() = f("f1")
+fun g2() = f2("f2")
+fun g3() = f3("f3", 3)

compiler/testData/diagnostics/tests/inference/substitutions/hideLocalTypeForReturnTypeOfSingleExpressionFunction.txt

@@ -1,7 +1,15 @@
 package
 
+private fun </*0*/ V> f(/*0*/ x: V): f.`<no name provided>`<V>
+private fun </*0*/ V> f1(/*0*/ x: V): f1.`<no name provided>`<V>
+private fun </*0*/ V> f2(/*0*/ x: V): f2.`<no name provided>`<V>
+private fun </*0*/ V, /*1*/ W> f3(/*0*/ x: V, /*1*/ y: W): f3.`<no name provided>`<V, W>
 private fun fPrivate(): test.`<no name provided>`<kotlin.String>
 public fun fPublic(): A<kotlin.String>
+public fun g(): I<I<kotlin.String>>
+public fun g1(): I<I<kotlin.String>>
+public fun g2(): I2<kotlin.String, kotlin.String>
+public fun g3(): I<I2<*, kotlin.Int>>
 public fun main(): kotlin.Unit
 private fun </*0*/ T> test(/*0*/ t: T): test.`<no name provided>`<T>
 
@@ -23,3 +31,15 @@ public final class FieldTest {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
+public interface I</*0*/ 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 interface I2</*0*/ A, /*1*/ B> {
+    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
+}
+