FIR: Add separate type constructor to stub types

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt

@@ -322,7 +322,11 @@ fun ConeIntersectionType.mapTypes(func: (ConeKotlinType) -> ConeKotlinType): Con
     return ConeIntersectionType(intersectedTypes.map(func), alternativeType?.let(func))
 }
 
-sealed class ConeStubType(val variable: ConeTypeVariable, override val nullability: ConeNullability) : StubTypeMarker, ConeSimpleKotlinType() {
+data class ConeStubTypeConstructor(val variable: ConeTypeVariable, val isTypeVariableInSubtyping: Boolean) : TypeConstructorMarker
+
+sealed class ConeStubType(val constructor: ConeStubTypeConstructor, override val nullability: ConeNullability) : StubTypeMarker,
+    ConeSimpleKotlinType() {
+
     override val typeArguments: Array<out ConeTypeProjection>
         get() = emptyArray()
 
@@ -335,7 +339,7 @@ sealed class ConeStubType(val variable: ConeTypeVariable, override val nullabili
 
         other as ConeStubType
 
-        if (variable != other.variable) return false
+        if (constructor != other.constructor) return false
         if (nullability != other.nullability) return false
 
         return true
@@ -343,14 +347,16 @@ sealed class ConeStubType(val variable: ConeTypeVariable, override val nullabili
 
     override fun hashCode(): Int {
         var result = 0
-        result = 31 * result + variable.hashCode()
+        result = 31 * result + constructor.hashCode()
         result = 31 * result + nullability.hashCode()
         return result
     }
 }
 
-class ConeStubTypeForBuilderInference(variable: ConeTypeVariable, nullability: ConeNullability) : ConeStubType(variable, nullability)
-class ConeStubTypeForTypeVariableInSubtyping(variable: ConeTypeVariable, nullability: ConeNullability) : ConeStubType(variable, nullability)
+open class ConeStubTypeForBuilderInference(variable: ConeTypeVariable, nullability: ConeNullability) :
+    ConeStubType(ConeStubTypeConstructor(variable, isTypeVariableInSubtyping = false), nullability)
+class ConeStubTypeForTypeVariableInSubtyping(variable: ConeTypeVariable, nullability: ConeNullability) :
+    ConeStubType(ConeStubTypeConstructor(variable, isTypeVariableInSubtyping = true), nullability)
 
 open class ConeTypeVariable(name: String, originalTypeParameter: TypeParameterMarker? = null) : TypeVariableMarker {
     val typeConstructor = ConeTypeVariableTypeConstructor(name, originalTypeParameter)

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/TypeRenderer.kt

@@ -46,8 +46,8 @@ fun ConeKotlinType.render(): String {
                 postfix = ")"
             )
         }
-        is ConeStubTypeForBuilderInference -> "${renderAttributes()}Stub (builder inference): $variable"
-        is ConeStubType -> "${renderAttributes()}Stub (subtyping): $variable"
+        is ConeStubTypeForBuilderInference -> "${renderAttributes()}Stub (builder inference): ${constructor.variable}"
+        is ConeStubType -> "${renderAttributes()}Stub (subtyping): ${constructor.variable}"
         is ConeIntegerLiteralType -> "${renderAttributes()}ILT: $value"
     } + nullabilitySuffix
 }

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

@@ -127,7 +127,7 @@ fun ConeKotlinType.findClassRepresentation(
         is ConeTypeParameterType -> lookupTag.findClassRepresentationThatIsSubtypeOf(dispatchReceiverParameterType, session)
         is ConeTypeVariableType -> (this.lookupTag.originalTypeParameter as? ConeTypeParameterLookupTag)
             ?.findClassRepresentationThatIsSubtypeOf(dispatchReceiverParameterType, session)
-        is ConeStubType -> (this.variable.typeConstructor.originalTypeParameter as? ConeTypeParameterLookupTag)
+        is ConeStubType -> (this.constructor.variable.typeConstructor.originalTypeParameter as? ConeTypeParameterLookupTag)
             ?.findClassRepresentationThatIsSubtypeOf(dispatchReceiverParameterType, session)
         is ConeLookupTagBasedType -> null
     }

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

@@ -131,7 +131,7 @@ interface ConeInferenceContext : TypeSystemInferenceExtensionContext, ConeTypeCo
 
     override fun StubTypeMarker.getOriginalTypeVariable(): TypeVariableTypeConstructorMarker {
         require(this is ConeStubType)
-        return this.variable.typeConstructor
+        return this.constructor.variable.typeConstructor
     }
 
     override fun KotlinTypeMarker.typeDepth() = when (this) {

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

@@ -144,7 +144,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
             is ConeCapturedType -> constructor
             is ConeTypeVariableType -> lookupTag
             is ConeIntersectionType -> this
-            is ConeStubType -> variable.typeConstructor
+            is ConeStubType -> constructor
             is ConeDefinitelyNotNullType -> original.typeConstructor()
             is ConeIntegerLiteralType -> this
             else -> error("?: $this")
@@ -244,6 +244,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
                 }
             }
             is ConeIntegerLiteralType -> 0
+            is ConeStubTypeConstructor -> 0
             else -> unknownConstructorError()
         }
     }
@@ -271,6 +272,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
     override fun TypeConstructorMarker.supertypes(): Collection<ConeKotlinType> {
         if (this is ErrorTypeConstructor) return emptyList()
         return when (this) {
+            is ConeStubTypeConstructor -> emptyList()
             is ConeTypeVariableTypeConstructor -> emptyList()
             is ConeTypeParameterLookupTag -> symbol.fir.bounds.map { it.coneType }
             is ConeClassLikeLookupTag -> {
@@ -342,6 +344,7 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
             is ConeClassLikeLookupTag,
             is ConeTypeParameterLookupTag -> true
 
+            is ConeStubTypeConstructor,
             is ConeCapturedTypeConstructor,
             is ErrorTypeConstructor,
             is ConeTypeVariableTypeConstructor,

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

@@ -165,8 +165,8 @@ fun <T : ConeKotlinType> T.withNullability(
             ConeNullability.UNKNOWN -> this // TODO: is that correct?
             ConeNullability.NOT_NULL -> this
         }
-        is ConeStubTypeForBuilderInference -> ConeStubTypeForBuilderInference(variable, nullability)
-        is ConeStubTypeForTypeVariableInSubtyping -> ConeStubTypeForTypeVariableInSubtyping(variable, nullability)
+        is ConeStubTypeForBuilderInference -> ConeStubTypeForBuilderInference(constructor.variable, nullability)
+        is ConeStubTypeForTypeVariableInSubtyping -> ConeStubTypeForTypeVariableInSubtyping(constructor.variable, nullability)
         is ConeDefinitelyNotNullType -> when (nullability) {
             ConeNullability.NOT_NULL -> this
             ConeNullability.NULLABLE -> original.withNullability(nullability, typeContext)

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

@@ -169,7 +169,7 @@ class FirBuilderInferenceSession(
 
         val bindings = mutableMapOf<TypeConstructorMarker, ConeKotlinType>()
         for ((variable, nonFixedType) in stubsForPostponedVariables) {
-            bindings[nonFixedType.variable.typeConstructor] = variable.defaultType
+            bindings[nonFixedType.constructor] = variable.defaultType
         }
 
         return ctx.typeSubstitutorByTypeConstructor(bindings)

compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/ConeKotlinTypeComparator.kt

@@ -145,7 +145,7 @@ object ConeKotlinTypeComparator : Comparator<ConeKotlinType> {
                 require(b is ConeStubType) {
                     "priority is inconsistent: ${a.render()} v.s. ${b.render()}"
                 }
-                val nameDiff = a.variable.typeConstructor.name.compareTo(b.variable.typeConstructor.name)
+                val nameDiff = a.constructor.variable.typeConstructor.name.compareTo(b.constructor.variable.typeConstructor.name)
                 if (nameDiff != 0) {
                     return nameDiff
                 }

compiler/tests-compiler-utils/tests/org/jetbrains/kotlin/fir/RenderingForDebugInfo.kt

@@ -39,7 +39,7 @@ fun ConeKotlinType.renderForDebugInfo(): String {
                 separator = " & ",
             ) { it.renderForDebugInfo() }
         }
-        is ConeStubType -> "Stub: $variable"
+        is ConeStubType -> "Stub: ${constructor.variable}"
         is ConeIntegerLiteralType -> "ILT: $value"
     } + nullabilitySuffix
 }