Introduce PossiblyInnerType class

Use it when rendering inner types, similar logic will be used in different subsystems

core/descriptors/src/org/jetbrains/kotlin/descriptors/typeParameterUtils.kt

@@ -16,6 +16,9 @@
 
 package org.jetbrains.kotlin.descriptors
 
+import org.jetbrains.kotlin.types.KotlinType
+import org.jetbrains.kotlin.types.TypeProjection
+
 fun ClassDescriptor.computeConstructorTypeParameters(): List<TypeParameterDescriptor> {
     val declaredParameters = declaredTypeParameters
 
@@ -44,3 +47,30 @@ private class CapturedTypeParameterDescriptor(
     override fun getIndex() = declaredTypeParametersCount + originalDescriptor.index
     override fun toString() = originalDescriptor.toString() + "[inner-copy]"
 }
+
+class PossiblyInnerType(
+        val classDescriptor: ClassDescriptor,
+        val arguments: List<TypeProjection>,
+        val outerType: PossiblyInnerType?) {
+    fun segments(): List<PossiblyInnerType> = outerType?.segments().orEmpty() + this
+}
+
+fun KotlinType.buildPossiblyInnerType(): PossiblyInnerType?
+        = buildPossiblyInnerType(constructor.declarationDescriptor as? ClassDescriptor, 0)
+
+private fun KotlinType.buildPossiblyInnerType(classDescriptor: ClassDescriptor?, index: Int): PossiblyInnerType? {
+    if (classDescriptor == null) return null
+
+    val toIndex = classDescriptor.declaredTypeParameters.size + index
+    val argumentsSubList = arguments.subList(index, toIndex)
+
+    if (!classDescriptor.isInner) {
+        assert(toIndex == arguments.size) { "${arguments.size - toIndex} trailing arguments were found in $this type" }
+
+        return PossiblyInnerType(classDescriptor, argumentsSubList, null)
+    }
+
+    return PossiblyInnerType(
+            classDescriptor, argumentsSubList,
+            buildPossiblyInnerType(classDescriptor.containingDeclaration as? ClassDescriptor, toIndex))
+}

core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt

@@ -246,15 +246,6 @@ internal class DescriptorRendererImpl(
         }.toString()
     }
 
-    private fun renderTypeArgumentsForTypeConstructor(
-            type: KotlinType,
-            typeConstructor: TypeConstructor
-    ): String {
-        return type.arguments.zip(type.constructor.parameters).filter {
-            (it.second.original.containingDeclaration as? ClassifierDescriptor)?.typeConstructor == typeConstructor
-        }.map { it.first }.let { renderTypeArguments(it) }
-    }
-
     private fun renderDefaultType(type: KotlinType): String {
         val sb = StringBuilder()
 
@@ -278,27 +269,31 @@ internal class DescriptorRendererImpl(
             type: KotlinType,
             typeConstructor: TypeConstructor = type.constructor
     ): String =
-        StringBuilder().apply {
+        buildString {
-            val classDescriptor = typeConstructor.declarationDescriptor as? ClassDescriptor
 
-            if (classDescriptor is MissingDependencyErrorClass) {
+            val possiblyInnerType = type.buildPossiblyInnerType()
+            if (possiblyInnerType == null) {
                 append(renderTypeConstructor(typeConstructor))
                 append(renderTypeArguments(type.arguments))
-                return@apply
+                return@buildString
             }
 
-            if (classDescriptor != null && classDescriptor.isInner) {
+            append(renderPossiblyInnerType(possiblyInnerType))
-                append(renderTypeConstructorAndArguments(type, (classDescriptor.containingDeclaration as ClassDescriptor).typeConstructor))
-                append('.')
-                append(renderName(classDescriptor.name))
-            }
-            else {
-                append(renderTypeConstructor(typeConstructor))
-            }
-
-            append(renderTypeArgumentsForTypeConstructor(type, typeConstructor))
         }.toString()
 
+    private fun renderPossiblyInnerType(possiblyInnerType: PossiblyInnerType): String =
+        buildString {
+            possiblyInnerType.outerType?.let {
+                append(renderPossiblyInnerType(it))
+                append('.')
+                append(renderName(possiblyInnerType.classDescriptor.name))
+            } ?: append(renderTypeConstructor(possiblyInnerType.classDescriptor.typeConstructor))
+
+            append(renderTypeArguments(possiblyInnerType.arguments))
+        }
+
+
+
     override fun renderTypeConstructor(typeConstructor: TypeConstructor): String {
         val cd = typeConstructor.getDeclarationDescriptor()
         return when (cd) {