[psi] KtFile: add hasImportAlias with caching

We have hotspots in UAST due to aliases, so we can reduce the time
significantly by caching `hasImportAlias` property

^KTIJ-26688

compiler/psi/src/org/jetbrains/kotlin/psi/KtCodeFragment.kt

@@ -157,6 +157,9 @@ abstract class KtCodeFragment(
         return null
     }
 
+    override val importLists: List<KtImportList>
+        get() = importsAsImportList().let(::listOfNotNull)
+
     override val importDirectives: List<KtImportDirective>
         get() = importsAsImportList()?.imports ?: emptyList()
 

compiler/psi/src/org/jetbrains/kotlin/psi/KtFile.kt

@@ -60,8 +60,20 @@ open class KtFile(viewProvider: FileViewProvider, val isCompiled: Boolean) :
     val importList: KtImportList?
         get() = importLists.firstOrNull()
 
-    private val importLists: Array<out KtImportList>
-        get() = findChildrenByTypeOrClass(KtStubElementTypes.IMPORT_LIST, KtImportList::class.java)
+    @Volatile
+    private var hasImportAlias: Boolean? = null
+
+    fun hasImportAlias(): Boolean {
+        val hasImportAlias = hasImportAlias
+        if (hasImportAlias != null) return hasImportAlias
+
+        val newValue = importLists.any(KtImportList::computeHasImportAlias)
+        this.hasImportAlias = newValue
+        return newValue
+    }
+
+    protected open val importLists: List<KtImportList>
+        get() = findChildrenByTypeOrClass(KtStubElementTypes.IMPORT_LIST, KtImportList::class.java).asList()
 
     val fileAnnotationList: KtFileAnnotationList?
         get() = findChildByTypeOrClass(KtStubElementTypes.FILE_ANNOTATION_LIST, KtFileAnnotationList::class.java)
@@ -179,15 +191,25 @@ open class KtFile(viewProvider: FileViewProvider, val isCompiled: Boolean) :
     }
 
 
-    fun findImportByAlias(name: String): KtImportDirective? =
-        importDirectives.firstOrNull { name == it.aliasName }
+    fun findImportByAlias(name: String): KtImportDirective? {
+        if (!hasImportAlias()) return null
 
-    fun findAliasByFqName(fqName: FqName): KtImportAlias? = importDirectives.firstOrNull {
-        it.alias != null && fqName == it.importedFqName
-    }?.alias
+        return importDirectives.firstOrNull { name == it.aliasName }
+    }
 
-    fun getNameForGivenImportAlias(name: Name): Name? =
-        importDirectives.find { it.importedName == name }?.importedFqName?.pathSegments()?.last()
+    fun findAliasByFqName(fqName: FqName): KtImportAlias? {
+        if (!hasImportAlias()) return null
+
+        return importDirectives.firstOrNull {
+            it.alias != null && fqName == it.importedFqName
+        }?.alias
+    }
+
+    fun getNameForGivenImportAlias(name: Name): Name? {
+        if (!hasImportAlias()) return null
+
+        return importDirectives.find { it.importedName == name }?.importedFqName?.pathSegments()?.last()
+    }
 
     @Deprecated("") // getPackageFqName should be used instead
     override fun getPackageName(): String {
@@ -217,6 +239,7 @@ open class KtFile(viewProvider: FileViewProvider, val isCompiled: Boolean) :
         isScript = null
         hasTopLevelCallables = null
         pathCached = null
+        hasImportAlias = null
     }
 
     fun isScript(): Boolean = isScript ?: stub?.isScript() ?: isScriptByTree
@@ -281,3 +304,16 @@ open class KtFile(viewProvider: FileViewProvider, val isCompiled: Boolean) :
         val FILE_DECLARATION_TYPES = TokenSet.orSet(KtTokenSets.DECLARATION_TYPES, TokenSet.create(KtStubElementTypes.SCRIPT))
     }
 }
+
+private fun KtImportList.computeHasImportAlias(): Boolean {
+    var child: PsiElement? = firstChild
+    while (child != null) {
+        if (child is KtImportDirective && child.alias != null) {
+            return true
+        }
+
+        child = child.nextSibling
+    }
+
+    return false
+}