[FIR] Fix qualifier handling by FirQualifierNameResolver

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt

@@ -150,7 +150,9 @@ class FirCallResolver(
 
         @Suppress("NAME_SHADOWING")
         val qualifiedAccess = qualifiedAccess.transformExplicitReceiver(transformer, ResolutionMode.ContextIndependent)
-        qualifiedResolver.replacedQualifier(qualifiedAccess)?.let { return it }
+        qualifiedResolver.replacedQualifier(qualifiedAccess)?.let { resolvedQualifierPart ->
+            return resolvedQualifierPart
+        }
 
         val info = CallInfo(
             CallKind.VariableAccess,
@@ -182,10 +184,17 @@ class FirCallResolver(
             result.currentApplicability
         )
 
-        if (qualifiedAccess.explicitReceiver == null &&
-            (reducedCandidates.size <= 1 && result.currentApplicability < CandidateApplicability.SYNTHETIC_RESOLVED)
-        ) {
-            qualifiedResolver.tryResolveAsQualifier(qualifiedAccess.source)?.let { return it }
+        if (qualifiedAccess.explicitReceiver == null) {
+            if (result.currentApplicability < CandidateApplicability.SYNTHETIC_RESOLVED
+            ) {
+                // We should run QualifierResolver if no successful candidates are available
+                // Otherwise expression (even ambiguous) beat qualifier
+                qualifiedResolver.tryResolveAsQualifier(qualifiedAccess.source)?.let { resolvedQualifier ->
+                    return resolvedQualifier
+                }
+            } else {
+                qualifiedResolver.reset()
+            }
         }
 
         val referencedSymbol = when (nameReference) {
@@ -194,10 +203,6 @@ class FirCallResolver(
             else -> null
         }
 
-        if (qualifiedAccess.explicitReceiver == null) {
-            qualifiedResolver.reset()
-        }
-
         when {
             referencedSymbol is FirClassLikeSymbol<*> -> {
                 val classId = referencedSymbol.classId

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirQualifiedNameResolver.kt

@@ -25,6 +25,7 @@ class FirQualifiedNameResolver(components: BodyResolveComponents) : BodyResolveC
 
     fun reset() {
         qualifierStack.clear()
+        qualifierPartsToDrop = 0
     }
 
     fun initProcessingQualifiedAccess(qualifiedAccess: FirQualifiedAccess, callee: FirSimpleNamedReference) {
@@ -44,6 +45,9 @@ class FirQualifiedNameResolver(components: BodyResolveComponents) : BodyResolveC
         }
 
     fun tryResolveAsQualifier(source: FirSourceElement?): FirResolvedQualifier? {
+        if (qualifierStack.isEmpty()) {
+            return null
+        }
         val symbolProvider = session.firSymbolProvider
         var qualifierParts = qualifierStack.asReversed().map { it.asString() }
         var resolved: PackageOrClass?