FIR: add a boolean tracking if a class ref resolves to the companion object

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/ImplementationConfigurator.kt

@@ -469,6 +469,27 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
             useTypes(expressionType)
         }
 
+        impl(resolvedQualifier) {
+            // Initialize the value to true if only the companion object is present. This makes a standalone class reference expression
+            // correctly resolve to the companion object. For example
+            // ```
+            // class A {
+            //   companion object
+            // }
+            //
+            // val companionOfA = A // This standalone class reference `A` here should resolve to the companion object.
+            // ```
+            //
+            // If this `FirResolvedQualifier` is a receiver expression of some other qualified access, the value is updated in
+            // `FirCallResolver` according to the resolution result.
+            default("resolvedToCompanionObject", "(symbol?.fir as? FirRegularClass)?.companionObject != null")
+            useTypes(regularClass)
+        }
+
+        impl(errorResolvedQualifier) {
+            defaultFalse("resolvedToCompanionObject", withGetter = true)
+        }
+
         noImpl(userTypeRef)
     }
 

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt

@@ -516,6 +516,7 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +field("classId", classIdType, nullable = true)
             +field("symbol", classLikeSymbolType, nullable = true)
             +booleanField("isNullableLHSForCallableReference", withReplace = true)
+            +booleanField("resolvedToCompanionObject", withReplace = true)
             +typeArguments.withTransform()
         }