Add handling for error cases in class_test regarding too few or too many TypeParameters in augments.

Also added handling for cases involving TypeParameter bounds, and fixed
several errors leading their incorrect display.

Change-Id: Ice908849daae2e115b34f50e55be1f2fca82cc96
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/448443
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: fshcheglov

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

@@ -4609,6 +4609,11 @@ abstract class InstanceFragmentImpl extends FragmentImpl
     _setters.add(fragment);
     fragment.enclosingFragment = this;
   }
+
+  void addTypeParameter(TypeParameterFragmentImpl typeParameter) {
+    _typeParameters.add(typeParameter);
+    typeParameter.enclosingFragment = this;
+  }
 }
 
 abstract class InterfaceElementImpl extends InstanceElementImpl
@@ -10127,7 +10132,8 @@ class TypeParameterFragmentImpl extends FragmentImpl
   MetadataImpl get metadata2 => metadata;
 
   @override
-  int get offset => nameOffset ?? firstTokenOffset!;
+  int get offset =>
+      nameOffset ?? firstTokenOffset ?? enclosingFragment?.offset ?? -1;
 
   void addFragment(TypeParameterFragmentImpl fragment) {
     fragment.element = element;

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

@@ -195,6 +195,26 @@ class ElementBuilder {
       lastFragment.addFragment(fragment);
 
       var lastTypeParameterFragments = lastFragment.typeParameters;
+
+      // Trim extra type parameters.
+      if (lastTypeParameterFragments.length < fragment.typeParameters.length) {
+        fragment.typeParameters.length = lastTypeParameterFragments.length;
+      }
+
+      // Synthesize missing type parameters.
+      if (lastTypeParameterFragments.length > fragment.typeParameters.length) {
+        for (
+          var i = fragment.typeParameters.length;
+          i < lastTypeParameterFragments.length;
+          i++
+        ) {
+          fragment.addTypeParameter(
+            TypeParameterFragmentImpl(name: lastTypeParameterFragments[i].name)
+              ..isSynthetic = true,
+          );
+        }
+      }
+
       for (var i = 0; i < lastTypeParameterFragments.length; i++) {
         lastTypeParameterFragments[i].addFragment(fragment.typeParameters[i]);
       }

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

@@ -569,7 +569,9 @@ class ReferenceResolver extends ThrowingAstVisitor<void> {
     if (bound != null) {
       bound.accept(this);
       var fragment = node.declaredFragment!;
-      fragment.element.bound = bound.type;
+      if (fragment.previousFragment == null) {
+        fragment.element.bound = bound.type;
+      }
       nodesToBuildType.addDeclaration(node);
     }
   }

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

@@ -396,7 +396,9 @@ class TypesBuilder {
 
   void _typeParameter(TypeParameterImpl node) {
     var fragment = node.declaredFragment!;
-    fragment.element.bound = node.bound?.type;
+    if (fragment.previousFragment == null) {
+      fragment.element.bound = node.bound?.type;
+    }
   }
 
   List<TypeParameterFragmentImpl> _typeParameters(TypeParameterListImpl? node) {