FIR: introduce helpers to get resolved reference / symbol

compiler/fir/tree/src/org/jetbrains/kotlin/fir/Utils.kt

@@ -14,6 +14,9 @@ import org.jetbrains.kotlin.fakeElement
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.expressions.FirBlock
 import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.references.FirReference
+import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
+import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
 import org.jetbrains.kotlin.fir.types.FirDynamicTypeRef
 import org.jetbrains.kotlin.fir.types.FirErrorTypeRef
 import org.jetbrains.kotlin.fir.types.FirImplicitTypeRef
@@ -69,3 +72,6 @@ val FirFile.packageFqName: FqName
 val FirElement.psi: PsiElement? get() = (source as? KtPsiSourceElement)?.psi
 val FirElement.realPsi: PsiElement? get() = (source as? KtRealPsiSourceElement)?.psi
 
+val FirReference.resolved: FirResolvedNamedReference? get() = this as? FirResolvedNamedReference
+val FirReference.resolvedSymbol: FirBasedSymbol<*>? get() = resolved?.resolvedSymbol
+

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/utils/FirDeclarationUtil.kt

@@ -7,7 +7,7 @@ package org.jetbrains.kotlin.fir.declarations.utils
 
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccess
-import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
+import org.jetbrains.kotlin.fir.resolvedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.ConeClassLikeType
 import org.jetbrains.kotlin.fir.types.coneTypeSafe
@@ -39,8 +39,7 @@ val FirClass.delegateFields: List<FirField>
 
 val FirQualifiedAccess.referredPropertySymbol: FirPropertySymbol?
     get() {
-        val reference = calleeReference as? FirResolvedNamedReference ?: return null
-        return reference.resolvedSymbol as? FirPropertySymbol
+        return calleeReference.resolvedSymbol as? FirPropertySymbol
     }
 
 inline val FirDeclaration.isJava: Boolean

compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/FirExpressionUtil.kt

@@ -16,6 +16,8 @@ import org.jetbrains.kotlin.fir.expressions.impl.FirResolvedArgumentList
 import org.jetbrains.kotlin.fir.expressions.impl.FirSingleExpressionBlock
 import org.jetbrains.kotlin.fir.references.FirReference
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
+import org.jetbrains.kotlin.fir.resolved
+import org.jetbrains.kotlin.fir.resolvedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.types.ConeClassLikeType
 import org.jetbrains.kotlin.fir.types.FirResolvedTypeRef
@@ -56,7 +58,7 @@ inline val FirCall.argumentMapping: LinkedHashMap<FirExpression, FirValueParamet
     }
 
 fun FirExpression.toResolvedCallableReference(): FirResolvedNamedReference? {
-    return toReference() as? FirResolvedNamedReference
+    return toReference()?.resolved
 }
 
 fun FirExpression.toReference(): FirReference? {
@@ -69,7 +71,7 @@ fun FirExpression.toResolvedCallableSymbol(): FirCallableSymbol<*>? {
 }
 
 fun FirReference.toResolvedCallableSymbol(): FirCallableSymbol<*>? {
-    return (this as? FirResolvedNamedReference)?.resolvedSymbol as? FirCallableSymbol<*>
+    return this.resolvedSymbol as? FirCallableSymbol<*>
 }
 
 fun buildErrorLoop(source: KtSourceElement?, diagnostic: ConeDiagnostic): FirErrorLoop {

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirFunctionSymbol.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.FirDelegatedConstructorCall
 import org.jetbrains.kotlin.fir.references.FirControlFlowGraphReference
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
+import org.jetbrains.kotlin.fir.resolvedSymbol
 import org.jetbrains.kotlin.fir.symbols.ensureResolved
 import org.jetbrains.kotlin.name.*
 
@@ -63,7 +64,7 @@ class FirConstructorSymbol(
     val resolvedDelegatedConstructor: FirConstructorSymbol?
         get() {
             val delegatedConstructorCall = resolvedDelegatedConstructorCall ?: return null
-            return (delegatedConstructorCall.calleeReference as? FirResolvedNamedReference)?.resolvedSymbol as? FirConstructorSymbol
+            return delegatedConstructorCall.calleeReference.resolvedSymbol as? FirConstructorSymbol
         }
 
     val resolvedDelegatedConstructorCall: FirDelegatedConstructorCall?