Delete type alias augmentation tests because typedef can no longer be augmented.

Change-Id: I6dd41018d5fd51681668baafe9fcf7aeab8dea07
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/450965
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: fshcheglov

pkg/analyzer/api.txt

@@ -4168,8 +4168,8 @@ package:analyzer/dart/element/element.dart:
     new (constructor: TypeAliasFragment Function())
     element (getter: TypeAliasElement)
     enclosingFragment (getter: LibraryFragment?)
-    nextFragment (getter: TypeAliasFragment?)
-    previousFragment (getter: TypeAliasFragment?)
+    nextFragment (getter: Null)
+    previousFragment (getter: Null)
   TypeDefiningElement (class extends Object implements Element, Annotatable):
     new (constructor: TypeDefiningElement Function())
     firstFragment (getter: TypeDefiningFragment)

pkg/analyzer/lib/dart/element/element.dart

@@ -3943,10 +3943,10 @@ abstract class TypeAliasFragment
   LibraryFragment? get enclosingFragment;
 
   @override
-  TypeAliasFragment? get nextFragment;
+  Null get nextFragment;
 
   @override
-  TypeAliasFragment? get previousFragment;
+  Null get previousFragment;
 }
 
 /// An element that defines a type.

pkg/analyzer/lib/src/dart/element/element.dart

@@ -10697,10 +10697,10 @@ class TypeAliasFragmentImpl extends FragmentImpl
   List<TypeParameterFragmentImpl> _typeParameters = const [];
 
   @override
-  TypeAliasFragmentImpl? previousFragment;
+  Null previousFragment;
 
   @override
-  TypeAliasFragmentImpl? nextFragment;
+  Null nextFragment;
 
   /// Is `true` if the element has direct or indirect reference to itself
   /// from anywhere except a class element or type parameter bounds.
@@ -10775,12 +10775,6 @@ class TypeAliasFragmentImpl extends FragmentImpl
   @Deprecated('Use typeParameters instead')
   @override
   List<TypeParameterFragmentImpl> get typeParameters2 => typeParameters;
-
-  void addFragment(TypeAliasFragmentImpl fragment) {
-    fragment.element = element;
-    fragment.previousFragment = this;
-    nextFragment = fragment;
-  }
 }
 
 class TypeParameterElementImpl extends ElementImpl

pkg/analyzer/lib/src/summary2/element_builder.dart

@@ -162,7 +162,7 @@ class ElementBuilder {
               fragment,
             );
           case TypeAliasFragmentImpl():
-            _handleTypeAliasFragment(libraryFragment, lastFragment, fragment);
+            _handleTypeAliasFragment(libraryFragment, fragment);
           default:
             throw UnimplementedError('${fragment.runtimeType}');
         }
@@ -804,21 +804,16 @@ class ElementBuilder {
 
   void _handleTypeAliasFragment(
     LibraryFragmentImpl libraryFragment,
-    FragmentImpl? lastFragment,
     TypeAliasFragmentImpl fragment,
   ) {
     libraryFragment.addTypeAlias(fragment);
 
-    if (lastFragment is TypeAliasFragmentImpl && fragment.isAugmentation) {
-      lastFragment.addFragment(fragment);
-    } else {
-      var element = TypeAliasElementImpl(
-        _addTopReference('@typeAlias', fragment.name),
-        fragment,
-      );
-      libraryElement.typeAliases.add(element);
-      libraryBuilder.declare(element, element.reference);
-    }
+    var element = TypeAliasElementImpl(
+      _addTopReference('@typeAlias', fragment.name),
+      fragment,
+    );
+    libraryElement.typeAliases.add(element);
+    libraryBuilder.declare(element, element.reference);
   }
 
   List<FormalParameterFragmentImpl> _linkFormalParameters({