K2: make type variable based types not class like

#KT-57921 Fixed
#KT-62420 Fixed

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/evaluate/FirCompileTimeConstantEvaluator.kt

@@ -28,7 +28,6 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirFieldSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.lazyResolveToPhase
 import org.jetbrains.kotlin.fir.types.*
-import org.jetbrains.kotlin.fir.types.impl.*
 import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.StandardClassIds
 import org.jetbrains.kotlin.psi.KtElement
@@ -312,8 +311,7 @@ internal object FirCompileTimeConstantEvaluator {
             is ConeCapturedType -> lowerType?.toConstantValueKind() ?: constructor.supertypes!!.first().toConstantValueKind()
             is ConeDefinitelyNotNullType -> original.toConstantValueKind()
             is ConeIntersectionType -> intersectedTypes.first().toConstantValueKind()
-            is ConeStubType -> null
-            is ConeIntegerLiteralType -> null
+            is ConeStubType, is ConeIntegerLiteralType, is ConeTypeVariableType -> null
         }
 
     private fun String.toConstantValueKind(): ConstantValueKind<*>? =

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ConeTypeCompatibilityChecker.kt

@@ -241,16 +241,18 @@ object ConeTypeCompatibilityChecker {
             is ConeErrorType -> emptySet() // Ignore error types
             is ConeLookupTagBasedType -> when (this) {
                 is ConeClassLikeType -> setOf(this)
-                is ConeTypeVariableType -> emptySet()
                 is ConeTypeParameterType -> emptySet()
-                else -> throw IllegalStateException("missing branch for ${javaClass.name}")
+                else -> error("missing branch for ${javaClass.name}")
             }
+            is ConeTypeVariableType -> emptySet()
             is ConeDefinitelyNotNullType -> original.collectLowerBounds()
             is ConeIntersectionType -> intersectedTypes.flatMap { it.collectLowerBounds() }.toSet()
             is ConeFlexibleType -> lowerBound.collectLowerBounds()
             is ConeCapturedType -> constructor.supertypes?.flatMap { it.collectLowerBounds() }?.toSet().orEmpty()
             is ConeIntegerConstantOperatorType -> setOf(getApproximatedType())
-            is ConeStubType, is ConeIntegerLiteralConstantType -> throw IllegalStateException("$this should not reach here")
+            is ConeStubType, is ConeIntegerLiteralConstantType -> {
+                error("$this should not reach here")
+            }
         }
     }
 

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt

@@ -832,22 +832,24 @@ fun ConeKotlinType?.collectUpperBounds(): Set<ConeClassLikeType> {
             is ConeErrorType -> return // Ignore error types
             is ConeLookupTagBasedType -> when (type) {
                 is ConeClassLikeType -> upperBounds.add(type)
-                is ConeTypeVariableType -> {
-                    val symbol = (type.lookupTag.originalTypeParameter as? ConeTypeParameterLookupTag)?.typeParameterSymbol ?: return
-                    symbol.resolvedBounds.forEach { collect(it.coneType) }
-                }
                 is ConeTypeParameterType -> {
                     val symbol = type.lookupTag.typeParameterSymbol
                     symbol.resolvedBounds.forEach { collect(it.coneType) }
                 }
-                else -> throw IllegalStateException("missing branch for ${javaClass.name}")
+                else -> error("missing branch for ${javaClass.name}")
+            }
+            is ConeTypeVariableType -> {
+                val symbol = (type.lookupTag.originalTypeParameter as? ConeTypeParameterLookupTag)?.typeParameterSymbol ?: return
+                symbol.resolvedBounds.forEach { collect(it.coneType) }
             }
             is ConeDefinitelyNotNullType -> collect(type.original)
             is ConeIntersectionType -> type.intersectedTypes.forEach(::collect)
             is ConeFlexibleType -> collect(type.upperBound)
             is ConeCapturedType -> type.constructor.supertypes?.forEach(::collect)
             is ConeIntegerConstantOperatorType -> upperBounds.add(type.getApproximatedType())
-            is ConeStubType, is ConeIntegerLiteralConstantType -> throw IllegalStateException("$type should not reach here")
+            is ConeStubType, is ConeIntegerLiteralConstantType -> {
+                error("$type should not reach here")
+            }
         }
     }
 

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

@@ -5,7 +5,6 @@
 
 package org.jetbrains.kotlin.fir.types
 
-import org.jetbrains.kotlin.fir.symbols.ConeClassifierLookupTag
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.types.model.*
 
@@ -13,10 +12,9 @@ import org.jetbrains.kotlin.types.model.*
 
 class ConeTypeVariableType(
     override val nullability: ConeNullability,
-    override val lookupTag: ConeTypeVariableTypeConstructor,
+    val lookupTag: ConeTypeVariableTypeConstructor,
     override val attributes: ConeAttributes = ConeAttributes.Empty,
-    // TODO: Make ConeSimpleKotlinType. KT-62420
-) : ConeLookupTagBasedType() {
+) : ConeSimpleKotlinType() {
     override val typeArguments: Array<out ConeTypeProjection> get() = EMPTY_ARRAY
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
@@ -39,9 +37,8 @@ class ConeTypeVariableType(
 class ConeTypeVariableTypeConstructor(
     val debugName: String,
     val originalTypeParameter: TypeParameterMarker?
-    // TODO: Remove ConeClassifierLookupTag supertype. KT-62420
-) : ConeClassifierLookupTag(), TypeVariableTypeConstructorMarker {
-    override val name: Name get() = Name.identifier(debugName)
+) : TypeVariableTypeConstructorMarker {
+    val name: Name get() = Name.identifier(debugName)
 
     var isContainedInInvariantOrContravariantPositions: Boolean = false
         private set

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt

@@ -237,8 +237,7 @@ class Fir2IrTypeConverter(
                 val approximated = approximateForIrOrNull()!!
                 approximated.toIrType(typeOrigin)
             }
-            is ConeStubType -> createErrorType()
-            is ConeIntegerLiteralType -> createErrorType()
+            is ConeStubType, is ConeIntegerLiteralType, is ConeTypeVariableType -> createErrorType()
         }
     }
 

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

@@ -40,8 +40,7 @@ fun ConeClassifierLookupTag.toSymbol(useSiteSession: FirSession): FirClassifierS
     when (this) {
         is ConeClassLikeLookupTag -> toSymbol(useSiteSession)
         is ConeClassifierLookupTagWithFixedSymbol -> this.symbol
-        // TODO: replace null with error(), see KT-57921
-        else -> null
+        else -> error("missing branch for ${javaClass.name}")
     }
 
 /**

compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt

@@ -85,7 +85,7 @@ abstract class AbstractConeSubstitutor(protected val typeContext: ConeTypeContex
     private fun ConeKotlinType.substituteRecursive(): ConeKotlinType? {
         return when (this) {
             is ConeClassLikeType -> this.substituteArguments()
-            is ConeLookupTagBasedType -> return null
+            is ConeLookupTagBasedType, is ConeTypeVariableType -> return null
             is ConeFlexibleType -> this.substituteBounds()?.let {
                 // TODO: may be (?) it's worth adding regular type comparison via AbstractTypeChecker
                 // However, the simplified check here should be enough for typical flexible types
@@ -156,7 +156,7 @@ abstract class AbstractConeSubstitutor(protected val typeContext: ConeTypeContex
         return null
     }
 
-    private fun ConeClassLikeType.substituteArguments(): ConeKotlinType? {
+    private fun ConeSimpleKotlinType.substituteArguments(): ConeKotlinType? {
         val newArguments by lazy { arrayOfNulls<ConeTypeProjection>(typeArguments.size) }
         var initialized = false
 
@@ -325,7 +325,7 @@ internal class ConeTypeSubstitutorByTypeConstructor(
     private val approximateIntegerLiterals: Boolean
 ) : AbstractConeSubstitutor(typeContext), TypeSubstitutorMarker {
     override fun substituteType(type: ConeKotlinType): ConeKotlinType? {
-        if (type !is ConeLookupTagBasedType && type !is ConeStubType) return null
+        if (type !is ConeLookupTagBasedType && type !is ConeStubType && type !is ConeTypeVariableType) return null
         val new = map[type.typeConstructor(typeContext)] ?: return null
         val approximatedIntegerLiteralType = if (approximateIntegerLiterals) new.approximateIntegerLiteralType() else new
         return approximatedIntegerLiteralType.updateNullabilityIfNeeded(type)?.withCombinedAttributesFrom(type)