IR: minor refactorings around IrType/IrCapturedType

- use identity in equals/hashCode. It was already effectively working
  like this because of `constructor === other.constructor`
- implement variance and declare it in IrSimpleType
- remove obsolete TODO
- simplify code in captureFromArguments
- use data objects

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrType.kt

@@ -91,6 +91,9 @@ abstract class IrSimpleType(kotlinType: KotlinType?) : IrTypeBase(kotlinType), S
     )
     val hasQuestionMark: Boolean
         get() = nullability == SimpleTypeNullability.MARKED_NULLABLE
+
+    override val variance: Variance
+        get() = Variance.INVARIANT
 }
 
 /**

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeSubstitutor.kt

@@ -90,7 +90,7 @@ class IrTypeSubstitutor(
     override fun isEmptySubstitution(): Boolean = substitution.isEmpty()
 }
 
-class IrCapturedTypeSubstitutor(
+internal class IrCapturedTypeSubstitutor(
     typeParameters: List<IrTypeParameterSymbol>,
     typeArguments: List<IrTypeArgument>,
     capturedTypes: List<IrCapturedType?>,

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeSystemContext.kt

@@ -239,9 +239,7 @@ interface IrTypeSystemContext : TypeSystemContext, TypeSystemCommonSuperTypesCon
      *
      * See https://kotlinlang.org/spec/type-system.html#type-capturing
      */
-
     override fun captureFromArguments(type: SimpleTypeMarker, status: CaptureStatus): SimpleTypeMarker? {
-        // TODO: is that correct?
         require(type is IrSimpleType)
 
         if (type is IrCapturedType) return null
@@ -252,43 +250,33 @@ interface IrTypeSystemContext : TypeSystemContext, TypeSystemCommonSuperTypesCon
         if (!classifier.isBound) return null
 
         val typeParameters = extractTypeParameters(classifier.owner)
-
         require(typeArguments.size == typeParameters.size)
 
         if (typeArguments.all { it is IrTypeProjection && it.variance == Variance.INVARIANT }) return type
 
-        val capturedTypes = ArrayList<IrCapturedType?>(typeArguments.size)
-
-        for (index in typeArguments.indices) {
-            val parameter = typeParameters[index]
-            val argument = typeArguments[index]
-
+        val capturedTypes = typeArguments.mapIndexed { index, argument ->
             if (argument is IrTypeProjection && argument.variance == Variance.INVARIANT) {
-                capturedTypes.add(null)
+                null
             } else {
                 val lowerType = if (argument is IrTypeProjection && argument.variance == Variance.IN_VARIANCE) {
                     argument.type
                 } else null
 
-                capturedTypes.add(IrCapturedType(status, lowerType, argument, parameter))
+                IrCapturedType(status, lowerType, argument, typeParameters[index])
             }
         }
 
-        val newArguments = ArrayList<IrTypeArgument>(typeArguments.size)
-
         val typeSubstitutor = IrCapturedTypeSubstitutor(typeParameters.memoryOptimizedMap { it.symbol }, typeArguments, capturedTypes)
 
-        for (index in typeArguments.indices) {
-            val oldArgument = typeArguments[index]
-            val parameter = typeParameters[index]
+        val newArguments = typeArguments.mapIndexed { index, oldArgument ->
             val capturedType = capturedTypes[index]
 
             if (capturedType == null) {
                 assert(oldArgument is IrTypeProjection && oldArgument.variance == Variance.INVARIANT)
-                newArguments.add(oldArgument)
+                oldArgument
             } else {
                 val capturedSuperTypes = mutableListOf<IrType>()
-                parameter.superTypes.mapTo(capturedSuperTypes) {
+                typeParameters[index].superTypes.mapTo(capturedSuperTypes) {
                     typeSubstitutor.substitute(it)
                 }
 
@@ -298,7 +286,7 @@ interface IrTypeSystemContext : TypeSystemContext, TypeSystemCommonSuperTypesCon
 
                 capturedType.constructor.initSuperTypes(capturedSuperTypes)
 
-                newArguments.add(makeTypeProjection(capturedType, Variance.INVARIANT))
+                makeTypeProjection(capturedType, Variance.INVARIANT)
             }
         }
 

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/impl/IrSimpleTypeImpl.kt

@@ -10,15 +10,11 @@ import org.jetbrains.kotlin.ir.symbols.FqNameEqualityChecker
 import org.jetbrains.kotlin.ir.symbols.IrClassifierSymbol
 import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.types.*
-import org.jetbrains.kotlin.utils.compactIfPossible
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.Variance
+import org.jetbrains.kotlin.utils.compactIfPossible
 
 abstract class IrAbstractSimpleType(kotlinType: KotlinType?) : IrSimpleType(kotlinType) {
-
-    override val variance: Variance
-        get() = Variance.INVARIANT
-
     abstract override val classifier: IrClassifierSymbol
     abstract override val nullability: SimpleTypeNullability
     abstract override val arguments: List<IrTypeArgument>

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/impl/IrTypeBase.kt

@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.ir.declarations.IrTypeParameter
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.symbols.IrClassifierSymbol
 import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.util.render
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.Variance
 import org.jetbrains.kotlin.types.model.CaptureStatus
@@ -44,11 +45,7 @@ class IrDynamicTypeImpl(
 val IrType.originalKotlinType: KotlinType?
     get() = (this as? IrTypeBase)?.kotlinType
 
-object IrStarProjectionImpl : IrStarProjection {
-    override fun equals(other: Any?): Boolean = this === other
-
-    override fun hashCode(): Int = System.identityHashCode(this)
-}
+data object IrStarProjectionImpl : IrStarProjection
 
 /**
  * An instance which should be used when creating an IR element whose type cannot be determined at the moment of creation.
@@ -60,15 +57,11 @@ object IrStarProjectionImpl : IrStarProjection {
  * however this could lead to a situation where we forget to set return type sometimes. This would result in crashes at unexpected moments,
  * especially in Kotlin/JS where function return types are not present in the resulting binary files.
  */
-object IrUninitializedType : IrType() {
+data object IrUninitializedType : IrType() {
     override val annotations: List<IrConstructorCall> = emptyList()
-
-    override fun equals(other: Any?): Boolean = this === other
-
-    override fun hashCode(): Int = System.identityHashCode(this)
 }
 
-class ReturnTypeIsNotInitializedException(function: IrFunction) : IllegalStateException(
+internal class ReturnTypeIsNotInitializedException(function: IrFunction) : IllegalStateException(
     "Return type is not initialized for function '${function.name}'"
 )
 
@@ -80,19 +73,12 @@ class IrCapturedType(
     projection: IrTypeArgument,
     typeParameter: IrTypeParameter
 ) : IrSimpleType(null), CapturedTypeMarker {
-
-    override val variance: Variance
-        get() = TODO("Not yet implemented")
-
-    class Constructor(val argument: IrTypeArgument, val typeParameter: IrTypeParameter) :
-        CapturedTypeConstructorMarker {
-
-        private var _superTypes: List<IrType> = emptyList()
-
-        val superTypes: List<IrType> get() = _superTypes
+    class Constructor(val argument: IrTypeArgument, val typeParameter: IrTypeParameter) : CapturedTypeConstructorMarker {
+        var superTypes: List<IrType> = emptyList()
+            private set
 
         fun initSuperTypes(superTypes: List<IrType>) {
-            _superTypes = superTypes
+            this.superTypes = superTypes
         }
     }
 
@@ -100,18 +86,13 @@ class IrCapturedType(
 
     override val classifier: IrClassifierSymbol get() = error("Captured Type does not have a classifier")
     override val arguments: List<IrTypeArgument> get() = emptyList()
-    override val abbreviation: IrTypeAbbreviation? get () = null
+    override val abbreviation: IrTypeAbbreviation? get() = null
     override val nullability: SimpleTypeNullability get() = SimpleTypeNullability.DEFINITELY_NOT_NULL
     override val annotations: List<IrConstructorCall> get() = emptyList()
 
-    override fun equals(other: Any?): Boolean {
-        return other is IrCapturedType
-                && captureStatus == other.captureStatus
-                && lowerType == other.lowerType
-                && constructor === other.constructor
-    }
+    override fun equals(other: Any?): Boolean = this === other
 
-    override fun hashCode(): Int {
-        return (captureStatus.hashCode() * 31 + (lowerType?.hashCode() ?: 0)) * 31 + constructor.hashCode()
-    }
+    override fun hashCode(): Int = System.identityHashCode(this)
+
+    override fun toString(): String = "IrCapturedType(${constructor.argument.render()}"
 }

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/linkage/partial/PartiallyLinkedMarkerType.kt

@@ -8,8 +8,11 @@ package org.jetbrains.kotlin.backend.common.linkage.partial
 import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.linkage.partial.ExploredClassifier
-import org.jetbrains.kotlin.ir.types.*
-import org.jetbrains.kotlin.types.Variance
+import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
+import org.jetbrains.kotlin.ir.types.IrSimpleType
+import org.jetbrains.kotlin.ir.types.IrTypeAbbreviation
+import org.jetbrains.kotlin.ir.types.IrTypeArgument
+import org.jetbrains.kotlin.ir.types.SimpleTypeNullability
 
 /**
  * Replacement for IR types that reference unusable classifier symbols.
@@ -17,15 +20,14 @@ import org.jetbrains.kotlin.types.Variance
  */
 internal class PartiallyLinkedMarkerType(
     builtIns: IrBuiltIns,
-    val unusableClassifier: ExploredClassifier.Unusable
+    val unusableClassifier: ExploredClassifier.Unusable,
 ) : IrSimpleType(null) {
-    override val annotations get() = emptyList<IrConstructorCall>()
-    override val classifier = builtIns.anyClass
-    override val nullability get() = SimpleTypeNullability.MARKED_NULLABLE
-    override val arguments get() = emptyList<IrTypeArgument>()
+    override val annotations: List<IrConstructorCall> get() = emptyList()
+    override val classifier: IrClassSymbol = builtIns.anyClass
+    override val nullability: SimpleTypeNullability get() = SimpleTypeNullability.MARKED_NULLABLE
+    override val arguments: List<IrTypeArgument> get() = emptyList()
     override val abbreviation: IrTypeAbbreviation? get() = null
-    override val variance get() = Variance.INVARIANT
 
-    override fun equals(other: Any?) = (other as? PartiallyLinkedMarkerType)?.unusableClassifier == unusableClassifier
-    override fun hashCode() = unusableClassifier.hashCode()
+    override fun equals(other: Any?): Boolean = (other as? PartiallyLinkedMarkerType)?.unusableClassifier == unusableClassifier
+    override fun hashCode(): Int = unusableClassifier.hashCode()
 }