FIR: introduce package directive

The package directive is needed for KtElement -> FirElement mapping in IDE.
There should be some FirElement which will be result of mapping of elements
inside KtPackageDirective.

idea/idea-frontend-fir/idea-fir-low-level-api/src/org/jetbrains/kotlin/idea/fir/low/level/api/diagnostics/FileStructureElementDiagnosticRetriever.kt

@@ -112,6 +112,7 @@ internal object FileDiagnosticRetriever : FileStructureElementDiagnosticRetrieve
             withSuppressedDiagnostics(file) {
                 visitWithDeclaration(file) {
                     file.annotations.forEach { it.accept(this, data) }
+                    file.packageDirective.accept(this, data)
                     file.imports.forEach { it.accept(this, data) }
                     // do not visit declarations here
                 }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/references/FirReferenceResolveHelper.kt

@@ -6,9 +6,7 @@
 package org.jetbrains.kotlin.idea.references
 
 import com.intellij.psi.tree.TokenSet
-import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
-import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.ROOT_PREFIX_FOR_IDE_RESOLUTION_MODE
+import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.builder.buildImport
 import org.jetbrains.kotlin.fir.declarations.synthetic.FirSyntheticProperty
@@ -17,7 +15,6 @@ import org.jetbrains.kotlin.fir.declarations.utils.isCompanion
 import org.jetbrains.kotlin.fir.declarations.utils.isLocal
 import org.jetbrains.kotlin.fir.declarations.utils.isStatic
 import org.jetbrains.kotlin.fir.expressions.*
-import org.jetbrains.kotlin.fir.psi
 import org.jetbrains.kotlin.fir.references.*
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.calls.FirSyntheticPropertySymbol
@@ -46,7 +43,6 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.collectDescendantsOfType
-import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelector
 import org.jetbrains.kotlin.psi.psiUtil.unwrapNullability
 import org.jetbrains.kotlin.utils.addIfNotNull
@@ -184,7 +180,8 @@ internal object FirReferenceResolveHelper {
                 getSymbolsForResolvedQualifier(fir, expression, session, symbolBuilder)
             is FirAnnotationCall -> getSymbolsForAnnotationCall(fir, session, symbolBuilder)
             is FirResolvedImport -> getSymbolsByResolvedImport(expression, symbolBuilder, fir, session)
-            is FirFile -> getSymbolsByFirFile(expression, symbolBuilder, fir)
+            is FirPackageDirective -> getSymbolsForPackageDirective(expression, symbolBuilder)
+            is FirFile -> getSymbolsByFirFile(symbolBuilder, fir)
             is FirArrayOfCall -> {
                 // We can't yet find PsiElement for arrayOf, intArrayOf, etc.
                 emptyList()
@@ -199,6 +196,14 @@ internal object FirReferenceResolveHelper {
         }
     }
 
+    private fun getSymbolsForPackageDirective(
+        expression: KtSimpleNameExpression,
+        symbolBuilder: KtSymbolByFirBuilder
+    ): List<KtFirPackageSymbol> {
+        return listOfNotNull(getPackageSymbolFor(expression, symbolBuilder, forQualifiedType = false))
+    }
+
+
     private fun getSymbolByResolvedNameReference(
         fir: FirResolvedNamedReference,
         session: FirSession,
@@ -319,14 +324,9 @@ internal object FirReferenceResolveHelper {
     }
 
     private fun getSymbolsByFirFile(
-        expression: KtSimpleNameExpression,
         symbolBuilder: KtSymbolByFirBuilder,
         fir: FirFile
     ): List<KtSymbol> {
-        if (expression.getNonStrictParentOfType<KtPackageDirective>() != null) {
-            // Special: package reference in the middle of package directive
-            return listOfNotNull(getPackageSymbolFor(expression, symbolBuilder, forQualifiedType = false))
-        }
         return listOf(symbolBuilder.buildSymbol(fir))
     }