FIR IDE: introduce KtFunctionalType

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/KtAnalysisSession.kt

@@ -77,8 +77,6 @@ abstract class KtAnalysisSession(final override val token: ValidityToken) : Vali
 
     fun PsiElement.getExpectedType(): KtType? = expressionTypeProvider.getExpectedType(this)
 
-    fun KtType.isBuiltInFunctionalType(): Boolean = typeProvider.isBuiltinFunctionalType(this)
-
     val builtinTypes: KtBuiltinTypes get() = typeProvider.builtinTypes
 
     fun KtClassOrObjectSymbol.buildSelfClassType(): KtType = typeProvider.buildSelfClassType(this)

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/components/KtTypeProvider.kt

@@ -5,14 +5,12 @@
 
 package org.jetbrains.kotlin.idea.frontend.api.components
 
+import org.jetbrains.kotlin.builtins.functions.FunctionClassKind
 import org.jetbrains.kotlin.idea.frontend.api.ValidityTokenOwner
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassOrObjectSymbol
 import org.jetbrains.kotlin.idea.frontend.api.types.KtType
 
 abstract class KtTypeProvider : KtAnalysisSessionComponent() {
-    //TODO get rid of it
-    abstract fun isBuiltinFunctionalType(type: KtType): Boolean
-
     abstract val builtinTypes: KtBuiltinTypes
 
     abstract fun buildSelfClassType(symbol: KtClassOrObjectSymbol): KtType

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/types/KtType.kt

@@ -33,12 +33,22 @@ sealed class KtDenotableType : KtType {
     abstract fun asString(): String
 }
 
-abstract class KtClassType : KtDenotableType(), KtTypeWithNullability {
+sealed class KtClassType : KtDenotableType(), KtTypeWithNullability {
     abstract val classId: ClassId
     abstract val classSymbol: KtClassLikeSymbol
     abstract val typeArguments: List<KtTypeArgument>
 }
 
+abstract class KtFunctionalType : KtClassType() {
+    abstract val isSuspend: Boolean
+    abstract val arity: Int
+    abstract val receiverType: KtType?
+    abstract val parameterTypes: List<KtType>
+    abstract val returnType: KtType
+}
+
+abstract class KtUsualClassType : KtClassType()
+
 abstract class KtErrorType : KtType {
     abstract val error: String
 }