Add KotlinBuiltIns#isBuiltIn, use it instead of other utilities

js/js.frontend/src/org/jetbrains/kotlin/js/descriptorUtils/descriptorUtils.kt

@@ -17,23 +17,16 @@
 package org.jetbrains.kotlin.js.descriptorUtils
 
 import com.intellij.openapi.util.text.StringUtil
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
-import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorUtils
-import org.jetbrains.kotlin.resolve.descriptorUtil.builtIns
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.utils.addToStdlib.check
 
 val KotlinType.nameIfStandardType: Name?
-    get() {
-        return constructor.declarationDescriptor
-                ?.check { descriptor ->
-                    descriptor.builtIns.isBuiltInPackageFragment(descriptor.containingDeclaration as? PackageFragmentDescriptor)
-                }
-                ?.name
-    }
+    get() = constructor.declarationDescriptor?.check(KotlinBuiltIns::isBuiltIn)?.name
 
 fun KotlinType.getJetTypeFqName(printTypeArguments: Boolean): String {
     val declaration = requireNotNull(constructor.declarationDescriptor)
@@ -47,8 +40,9 @@ fun KotlinType.getJetTypeFqName(printTypeArguments: Boolean): String {
     if (printTypeArguments && !typeArguments.isEmpty()) {
         val joinedTypeArguments = StringUtil.join(typeArguments, { projection -> projection.type.getJetTypeFqName(false) }, ", ")
 
-        typeArgumentsAsString = "<" + joinedTypeArguments + ">"
-    } else {
+        typeArgumentsAsString = "<$joinedTypeArguments>"
+    }
+    else {
         typeArgumentsAsString = ""
     }