[NI] Refactoring: rename NonFixedType -> StubType

core/descriptors/src/org/jetbrains/kotlin/types/StubType.kt

@@ -9,7 +9,7 @@ import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 
 // This type is used as a stub for postponed type variables, which are important for coroutine inference
-class NonFixedType(
+class StubType(
     private val originalTypeVariable: TypeConstructor,
     override val isMarkedNullable: Boolean,
     override val constructor: TypeConstructor =
@@ -32,7 +32,7 @@ class NonFixedType(
         return if (newNullability == isMarkedNullable)
             this
         else
-            NonFixedType(originalTypeVariable, newNullability, constructor, memberScope)
+            StubType(originalTypeVariable, newNullability, constructor, memberScope)
     }
 
     override fun toString(): String {

core/descriptors/src/org/jetbrains/kotlin/types/checker/NewKotlinTypeChecker.kt

@@ -186,7 +186,7 @@ object NewKotlinTypeChecker : KotlinTypeChecker {
             return StrictEqualityTypeChecker.strictEqualTypes(subType.makeNullableAsSpecified(false), superType.makeNullableAsSpecified(false))
         }
 
-        if (subType is NonFixedType || superType is NonFixedType) return true
+        if (subType is StubType || superType is StubType) return true
 
         if (superType is NewCapturedType && superType.lowerType != null) {
             when (getLowerCapturedTypePolicy(subType, superType)) {