Implement type parameter linking between augmentations in non-erroneous class augmentations.

This implementation is currently for classes only, future CLs will add
it for other top-levels and methods.

It is expected that all ClassFragment(s) have the same number of type
parameters. I plan to implement recovery for incorrect cases in the
future.

Change-Id: I4708f23b74a4fef2258c33aa67e3a57d72b333c9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/448257
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: fshcheglov

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

@@ -957,7 +957,7 @@ mixin DeferredMembersReadingMixin {
 /// invoke [_ensureReadResolution].
 mixin DeferredResolutionReadingMixin {
   // TODO(scheglov): review whether we need this
-  int _lockResolutionLoading = 0;
+  static int _lockResolutionLoading = 0;
   void Function()? _readResolutionCallback;
   void Function()? _applyResolutionConstantOffsets;
 
@@ -10067,6 +10067,12 @@ class TypeParameterFragmentImpl extends FragmentImpl
   @override
   int? nameOffset;
 
+  @override
+  TypeParameterFragmentImpl? previousFragment;
+
+  @override
+  TypeParameterFragmentImpl? nextFragment;
+
   /// The element corresponding to this fragment.
   TypeParameterElementImpl? _element;
 
@@ -10120,16 +10126,14 @@ class TypeParameterFragmentImpl extends FragmentImpl
   @override
   MetadataImpl get metadata2 => metadata;
 
-  @override
-  // TODO(augmentations): Support chaining between the fragments.
-  TypeParameterFragmentImpl? get nextFragment => null;
-
   @override
   int get offset => nameOffset ?? firstTokenOffset!;
 
-  @override
-  // TODO(augmentations): Support chaining between the fragments.
-  TypeParameterFragmentImpl? get previousFragment => null;
+  void addFragment(TypeParameterFragmentImpl fragment) {
+    fragment.element = element;
+    fragment.previousFragment = this;
+    nextFragment = fragment;
+  }
 }
 
 abstract class VariableElementImpl extends ElementImpl

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

@@ -265,6 +265,19 @@ class LibraryReader {
       var fragments = _readFragmentsById<ClassFragmentImpl>();
       var element = ClassElementImpl(reference, fragments.first);
       element.linkFragments(fragments);
+
+      element.withoutLoadingResolution(() {
+        var typeParameterFragments = fragments.first.typeParameters;
+        for (var i = 0; i < typeParameterFragments.length; i++) {
+          // Side effect: set element for the fragment.
+          TypeParameterElementImpl(firstFragment: typeParameterFragments[i]);
+          fragments.reduce((previous, current) {
+            previous.typeParameters[i].addFragment(current.typeParameters[i]);
+            return current;
+          });
+        }
+      });
+
       element.readModifiers(_reader);
       element.hasNonFinalField = _reader.readBool();
 

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

@@ -193,13 +193,23 @@ class ElementBuilder {
 
     if (fragment.isAugmentation && lastFragment is ClassFragmentImpl) {
       lastFragment.addFragment(fragment);
+
+      var lastTypeParameterFragments = lastFragment.typeParameters;
+      for (var i = 0; i < lastTypeParameterFragments.length; i++) {
+        lastTypeParameterFragments[i].addFragment(fragment.typeParameters[i]);
+      }
       return;
     }
 
     var element = ClassElementImpl(
       _addTopReference('@class', fragment.name),
       fragment,
     );
+
+    for (var typeParameterFragment in fragment.typeParameters) {
+      TypeParameterElementImpl(firstFragment: typeParameterFragment);
+    }
+
     libraryElement.addClass(element);
     libraryBuilder.declare(element, element.reference);
   }

pkg/analyzer/test/src/summary/element_text.dart

@@ -1879,7 +1879,8 @@ class _Element2Writer extends _AbstractElementWriter {
 
     _sink.withIndent(() {
       _writeElementReference('element', f.element);
-      // _writeCodeRange(e);
+      _writeFragmentReference('previousFragment', f.previousFragment);
+      _writeFragmentReference('nextFragment', f.nextFragment);
 
       // var bound = e.bound;
       // if (bound != null) {