FIR. Refactor smart-cast representation in FIR tree

Make smart-casts non-transparent expression without delegation
to underlying FirQualifiedAccessExpression, as children delegation in
fir tree has unclear semantics
Remove two different kinds of tree nodes for smart-casts

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

@@ -8,8 +8,7 @@ package org.jetbrains.kotlin.fir.resolve
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
-import org.jetbrains.kotlin.fir.expressions.FirExpressionWithSmartcast
-import org.jetbrains.kotlin.fir.expressions.FirExpressionWithSmartcastToNothing
+import org.jetbrains.kotlin.fir.expressions.FirSmartCastExpression
 import org.jetbrains.kotlin.fir.resolve.substitution.substitutorByMap
 import org.jetbrains.kotlin.fir.scopes.FakeOverrideTypeCalculator
 import org.jetbrains.kotlin.fir.scopes.FirTypeScope
@@ -25,17 +24,16 @@ import org.jetbrains.kotlin.fir.types.impl.ConeClassLikeTypeImpl
 import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
 import org.jetbrains.kotlin.name.ClassId
 
-fun FirExpressionWithSmartcast.smartcastScope(
+fun FirSmartCastExpression.smartcastScope(
     useSiteSession: FirSession,
     scopeSession: ScopeSession
 ): FirTypeScope? {
-    val smartcastType =
-        if (this is FirExpressionWithSmartcastToNothing) smartcastTypeWithoutNullableNothing.coneType else smartcastType.coneType
+    val smartcastType = smartcastTypeWithoutNullableNothing?.coneType ?: smartcastType.coneType
     val smartcastScope = smartcastType.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)
     if (isStable) {
         return smartcastScope
     }
-    val originalScope = originalType.coneType.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)
+    val originalScope = originalExpression.typeRef.coneType.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)
         ?: return smartcastScope
 
     if (smartcastScope == null) {

compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/calls/FirReceivers.kt

@@ -5,10 +5,13 @@
 
 package org.jetbrains.kotlin.fir.resolve.calls
 
+import org.jetbrains.kotlin.KtFakeSourceElementKind
+import org.jetbrains.kotlin.fakeElement
 import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.copyWithNewSourceKind
 import org.jetbrains.kotlin.fir.diagnostics.ConeIntermediateDiagnostic
 import org.jetbrains.kotlin.fir.expressions.*
-import org.jetbrains.kotlin.fir.expressions.builder.buildExpressionWithSmartcast
+import org.jetbrains.kotlin.fir.expressions.builder.buildSmartCastExpression
 import org.jetbrains.kotlin.fir.expressions.builder.buildThisReceiverExpression
 import org.jetbrains.kotlin.fir.references.builder.buildImplicitThisReference
 import org.jetbrains.kotlin.fir.renderWithType
@@ -66,7 +69,7 @@ open class ExpressionReceiverValue(
         if (receiverExpr is FirCheckNotNullCall) {
             receiverExpr = receiverExpr.arguments.firstOrNull()
         }
-        if (receiverExpr is FirExpressionWithSmartcast) {
+        if (receiverExpr is FirSmartCastExpression) {
             return receiverExpr.smartcastScope(useSiteSession, scopeSession)
         }
         return type.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)
@@ -107,11 +110,16 @@ sealed class ImplicitReceiverValue<S : FirBasedSymbol<*>>(
         receiverExpression = if (type == originalReceiverExpression.typeRef.coneType) {
             originalReceiverExpression
         } else {
-            buildExpressionWithSmartcast {
+            buildSmartCastExpression {
                 originalExpression = originalReceiverExpression
-                smartcastType = originalReceiverExpression.typeRef.resolvedTypeFromPrototype(type)
+                this.source = originalExpression.source?.fakeElement(KtFakeSourceElementKind.SmartCastExpression)
+                smartcastType = buildResolvedTypeRef {
+                    source = originalReceiverExpression.typeRef.source?.fakeElement(KtFakeSourceElementKind.SmartCastedTypeRef)
+                    this.type = type
+                }
                 typesFromSmartCast = listOf(type)
                 smartcastStability = SmartcastStability.STABLE_VALUE
+                typeRef = smartcastType.copyWithNewSourceKind(KtFakeSourceElementKind.ImplicitTypeRef)
             }
         }
         implicitScope = type.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)