[FIR] Distinguish stub types for builder inference and for subtyping

^KT-48110 Fixed

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/FirBuilderInferenceSession.kt

@@ -67,7 +67,7 @@ class FirBuilderInferenceSession(
 
     private fun ConeKotlinType.containsStubType(): Boolean {
         return this.contains {
-            it is ConeStubType
+            it is ConeStubTypeForBuilderInference
         }
     }
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeInferenceContext.kt

@@ -262,12 +262,13 @@ interface ConeInferenceContext : TypeSystemInferenceExtensionContext, ConeTypeCo
 
     override fun createStubTypeForBuilderInference(typeVariable: TypeVariableMarker): StubTypeMarker {
         require(typeVariable is ConeTypeVariable) { "$typeVariable should subtype of ${ConeTypeVariable::class.qualifiedName}" }
-        return ConeStubType(typeVariable, ConeNullability.create(typeVariable.defaultType().isMarkedNullable()))
+        return ConeStubTypeForBuilderInference(typeVariable, ConeNullability.create(typeVariable.defaultType().isMarkedNullable()))
     }
 
-    // TODO
-    override fun createStubTypeForTypeVariablesInSubtyping(typeVariable: TypeVariableMarker) =
-        createStubTypeForBuilderInference(typeVariable)
+    override fun createStubTypeForTypeVariablesInSubtyping(typeVariable: TypeVariableMarker): StubTypeMarker{
+        require(typeVariable is ConeTypeVariable) { "$typeVariable should subtype of ${ConeTypeVariable::class.qualifiedName}" }
+        return ConeStubTypeForTypeVariableInSubtyping(typeVariable, ConeNullability.create(typeVariable.defaultType().isMarkedNullable()))
+    }
 
     override fun KotlinTypeMarker.removeAnnotations(): KotlinTypeMarker {
         require(this is ConeKotlinType)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeContext.kt

@@ -406,15 +406,15 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
     }
 
     override fun SimpleTypeMarker.isStubType(): Boolean {
-        return this is ConeStubType // TODO: distinguish stub types for builder inference and for subtyping
+        return this is ConeStubType
     }
 
     override fun SimpleTypeMarker.isStubTypeForVariableInSubtyping(): Boolean {
-        return this is ConeStubType // TODO: distinguish stub types for builder inference and for subtyping
+        return this is ConeStubTypeForTypeVariableInSubtyping
     }
 
     override fun SimpleTypeMarker.isStubTypeForBuilderInference(): Boolean {
-        return this is ConeStubType // TODO: distinguish stub types for builder inference and for subtyping
+        return this is ConeStubTypeForBuilderInference
     }
 
     override fun intersectTypes(types: List<SimpleTypeMarker>): SimpleTypeMarker {

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

@@ -156,7 +156,8 @@ fun <T : ConeKotlinType> T.withNullability(
             ConeNullability.UNKNOWN -> this // TODO: is that correct?
             ConeNullability.NOT_NULL -> this
         }
-        is ConeStubType -> ConeStubType(variable, nullability)
+        is ConeStubTypeForBuilderInference -> ConeStubTypeForBuilderInference(variable, nullability)
+        is ConeStubTypeForTypeVariableInSubtyping -> ConeStubTypeForTypeVariableInSubtyping(variable, nullability)
         is ConeDefinitelyNotNullType -> when (nullability) {
             ConeNullability.NOT_NULL -> this
             ConeNullability.NULLABLE -> original.withNullability(nullability, typeContext)