Implement augmentation tests for Extension and ExtensionType.

This CL also adds typeParameter linking between fragments in
ExtensionElement and ExtensionTypeElement.

Change-Id: If375c9f1b6a6d422be1d22067f6c8960002e1363
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/449383
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: fshcheglov

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

@@ -2524,6 +2524,10 @@ class ExtensionElementImpl extends InstanceElementImpl
       previous.addFragment(current);
       return current;
     });
+    TypeParameterFragmentImpl._linkFragments(
+      fragments,
+      getFragments: (f) => f.typeParameters,
+    );
   }
 }
 
@@ -2708,6 +2712,10 @@ class ExtensionTypeElementImpl extends InterfaceElementImpl
       previous.addFragment(current);
       return current;
     });
+    TypeParameterFragmentImpl._linkFragments(
+      fragments,
+      getFragments: (f) => f.typeParameters,
+    );
   }
 }
 

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

@@ -255,6 +255,13 @@ class ElementBuilder {
 
     if (fragment.isAugmentation && lastFragment is ExtensionFragmentImpl) {
       lastFragment.addFragment(fragment);
+
+      _linkTypeParameters(
+        lastFragments: lastFragment.typeParameters,
+        fragments: fragment.typeParameters,
+        add: fragment.addTypeParameter,
+      );
+
       return;
     }
 
@@ -276,6 +283,13 @@ class ElementBuilder {
 
     if (fragment.isAugmentation && lastFragment is ExtensionTypeFragmentImpl) {
       lastFragment.addFragment(fragment);
+
+      _linkTypeParameters(
+        lastFragments: lastFragment.typeParameters,
+        fragments: fragment.typeParameters,
+        add: fragment.addTypeParameter,
+      );
+
       return;
     }
 
@@ -1841,6 +1855,7 @@ class FragmentBuilder extends ThrowingAstVisitor<void> {
     var fieldFragment = FieldFragmentImpl(
       name: _getFragmentName(fieldNameToken),
     );
+    fieldFragment.isAugmentation = extensionFragment.isAugmentation;
     fieldFragment.isFinal = true;
     fieldFragment.metadata = _buildMetadata(representation.fieldMetadata);
 
@@ -1860,7 +1875,7 @@ class FragmentBuilder extends ThrowingAstVisitor<void> {
           ConstructorFragmentImpl(
               name: representation.constructorName?.name.lexeme ?? 'new',
             )
-            ..isAugmentation = extensionNode.augmentKeyword != null
+            ..isAugmentation = extensionFragment.isAugmentation
             ..isConst = extensionNode.constKeyword != null
             ..formalParameters = [formalParameterFragment];
       constructorFragment.typeName = extensionFragment.name;

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

@@ -222,10 +222,12 @@ class TypesBuilder {
   }
 
   void _extensionDeclaration(ExtensionDeclarationImpl node) {
-    var fragment = node.declaredFragment!;
     if (node.onClause case var onClause?) {
-      var extendedType = onClause.extendedType.typeOrThrow;
-      fragment.element.extendedType = extendedType;
+      var fragment = node.declaredFragment!;
+      if (fragment.previousFragment == null) {
+        var extendedType = onClause.extendedType.typeOrThrow;
+        fragment.element.extendedType = extendedType;
+      }
     }
   }
 
@@ -240,7 +242,7 @@ class TypesBuilder {
         .where(typeSystem.isValidExtensionTypeSuperinterface)
         .toFixedList();
     if (interfaces != null) {
-      element.interfaces = interfaces;
+      element.interfaces = [...element.interfaces, ...interfaces];
     }
   }