Extend import resolution for library-to-source analysis

Use composite importing scope for references when resolution anchors are enabled.
Composite scope provides additional descriptors from scope of resolution anchor module.
Overriding old importing scope with a new one is not possible as it breaks library
dependencies on other libraries, which are inaccessible in anchor scope (scope for sources).

KT-24309 In Progress

compiler/frontend/src/org/jetbrains/kotlin/resolve/QualifiedExpressionResolver.kt

@@ -20,6 +20,7 @@ import com.intellij.psi.impl.source.DummyHolder
 import com.intellij.util.SmartList
 import org.jetbrains.kotlin.config.AnalysisFlags
 import org.jetbrains.kotlin.config.LanguageVersionSettings
+import org.jetbrains.kotlin.config.isLibraryToSourceAnalysisEnabled
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.incremental.KotlinLookupLocation
@@ -35,6 +36,7 @@ import org.jetbrains.kotlin.resolve.calls.CallExpressionElement
 import org.jetbrains.kotlin.resolve.calls.checkers.UnderscoreUsageChecker
 import org.jetbrains.kotlin.resolve.calls.unrollToLeftMostQualifiedExpression
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
+import org.jetbrains.kotlin.resolve.scopes.CompositePrioritizedImportingScope
 import org.jetbrains.kotlin.resolve.scopes.ImportingScope
 import org.jetbrains.kotlin.resolve.scopes.LexicalScope
 import org.jetbrains.kotlin.resolve.scopes.receivers.*
@@ -221,6 +223,31 @@ class QualifiedExpressionResolver(val languageVersionSettings: LanguageVersionSe
         trace: BindingTrace,
         excludedImportNames: Collection<FqName>,
         packageFragmentForVisibilityCheck: PackageFragmentDescriptor?
+    ): ImportingScope? {
+        fun processReferenceInContextOf(moduleDescriptor: ModuleDescriptor): ImportingScope? =
+            doProcessImportReference(
+                importDirective,
+                moduleDescriptor,
+                trace,
+                excludedImportNames,
+                packageFragmentForVisibilityCheck
+            )
+
+        val primaryImportingScope = processReferenceInContextOf(moduleDescriptor)
+        if (!languageVersionSettings.isLibraryToSourceAnalysisEnabled) return primaryImportingScope
+
+        val resolutionAnchor = moduleDescriptor.getResolutionAnchorIfAny() ?: return primaryImportingScope
+        val secondaryImportingScope = processReferenceInContextOf(resolutionAnchor) ?: return primaryImportingScope
+        if (primaryImportingScope == null) return secondaryImportingScope
+        return CompositePrioritizedImportingScope(primaryImportingScope, secondaryImportingScope)
+    }
+
+    private fun doProcessImportReference(
+        importDirective: KtImportInfo,
+        moduleDescriptor: ModuleDescriptor,
+        trace: BindingTrace,
+        excludedImportNames: Collection<FqName>,
+        packageFragmentForVisibilityCheck: PackageFragmentDescriptor?
     ): ImportingScope? { // null if some error happened
         ProgressIndicatorAndCompilationCanceledStatus.checkCanceled()