dartfmt and lints

lib/src/element_type.dart

@@ -101,7 +101,7 @@ class UndefinedElementType extends ElementType {
 
   @override
   String get name {
-    if (type.isVoid) return 'void';
+    if (type is VoidType) return 'void';
     if (type.isDynamic) return 'dynamic';
     assert(const {'Never'}.contains(typeElement!.name),
         'Unrecognized type for UndefinedElementType: ${type.toString()}');
@@ -436,7 +436,7 @@ class GenericTypeAliasElementType extends TypeParameterElementType {
 extension on DartType {
   /// The dartdoc nullability suffix for this type in [library].
   String nullabilitySuffixWithin(Library library) {
-    if (!isVoid && !isBottom) {
+    if (this is! VoidType && !isBottom) {
       /// If a legacy type appears inside the public interface of a Null
       /// safety library, we pretend it is nullable for the purpose of
       /// documentation (since star-types are not supposed to be public).

lib/src/model/extension.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:dartdoc/src/element_type.dart';
 import 'package:dartdoc/src/model/comment_referable.dart';
 import 'package:dartdoc/src/model/extension_target.dart';
@@ -23,7 +24,7 @@ class Extension extends Container implements EnclosedElement {
   /// Detect if this extension applies to every object.
   bool get alwaysApplies =>
       extendedType.instantiatedType.isDynamic ||
-      extendedType.instantiatedType.isVoid ||
+      extendedType.instantiatedType is VoidType ||
       extendedType.instantiatedType.isDartCoreObject;
 
   bool couldApplyTo<T extends ExtensionTarget>(T c) =>
@@ -32,7 +33,7 @@ class Extension extends Container implements EnclosedElement {
   /// Whether this extension could apply to [type].
   bool _couldApplyTo(DefinedElementType type) {
     if (extendedType.instantiatedType.isDynamic ||
-        extendedType.instantiatedType.isVoid) {
+        extendedType.instantiatedType is VoidType) {
       return true;
     }
     var typeInstantiated = type.instantiatedType;

lib/src/model/mixin.dart

@@ -67,6 +67,7 @@ class Mixin extends InheritingContainer with TypeImplementing {
   bool get isInterface => false;
 
   @override
+
   /// Mixins are not mixin classes by definition.
   bool get isMixinClass => false;