FIR: Attach candidate symbol to the ErrorNamedReference

This allows to restore the referenced candidate in cases when there are
no ambiguity

Also, change rendering of named references to be more accurate, so the
diagnostics tests pass: if reference is FirErrorNamedReference, it is
more important than if it has a not-null `candidateSymbol`

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirCallCompletionResultsWriterTransformer.kt

@@ -633,6 +633,7 @@ class FirCallCompletionResultsWriterTransformer(
         buildErrorNamedReference {
             source = this@toResolvedReference.source
             diagnostic = this@toResolvedReference.diagnostic
+            candidateSymbol = this@toResolvedReference.candidateSymbol
         }
     } else {
         buildResolvedNamedReference {

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/references/builder/FirErrorNamedReferenceBuilder.kt

@@ -23,11 +23,13 @@ import org.jetbrains.kotlin.name.Name
 @FirBuilderDsl
 class FirErrorNamedReferenceBuilder {
     var source: FirSourceElement? = null
+    var candidateSymbol: AbstractFirBasedSymbol<*>? = null
     lateinit var diagnostic: ConeDiagnostic
 
     fun build(): FirErrorNamedReference {
         return FirErrorNamedReferenceImpl(
             source,
+            candidateSymbol,
             diagnostic,
         )
     }

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/references/impl/FirErrorNamedReferenceImpl.kt

@@ -19,10 +19,10 @@ import org.jetbrains.kotlin.fir.visitors.*
 
 internal class FirErrorNamedReferenceImpl(
     override val source: FirSourceElement?,
+    override val candidateSymbol: AbstractFirBasedSymbol<*>?,
     override val diagnostic: ConeDiagnostic,
 ) : FirErrorNamedReference() {
     override val name: Name = Name.special("<${diagnostic.reason}>")
-    override val candidateSymbol: AbstractFirBasedSymbol<*>? get() = null
 
     override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {}
 

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

@@ -969,10 +969,8 @@ class FirRenderer(builder: StringBuilder, private val mode: RenderMode = RenderM
     override fun visitNamedReference(namedReference: FirNamedReference) {
         val symbol = namedReference.candidateSymbol
         when {
-            symbol != null -> {
-                print("R?C|${symbol.render()}|")
-            }
             namedReference is FirErrorNamedReference -> print("<${namedReference.diagnostic.reason}>#")
+            symbol != null -> print("R?C|${symbol.render()}|")
             else -> print("${namedReference.name}#")
         }
     }

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

@@ -423,7 +423,6 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
 
         impl(errorNamedReference) {
             default("name", "Name.special(\"<\${diagnostic.reason}>\")")
-            defaultNull("candidateSymbol", withGetter = true)
         }
 
         impl(typeProjection, "FirTypePlaceholderProjection") {