Rename all XyzElementImpl into XyzFragmentImpl.

Change-Id: I65b55925fbdccc0c22dc1f8243db4152ccae0ee2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/434742
Reviewed-by: Paul Berry <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: fshcheglov

pkg/analyzer/lib/src/dart/constant/evaluation.dart

@@ -90,7 +90,7 @@ class ConstantEvaluationEngine {
 
     var library = constant.library2 as LibraryElementImpl;
     if (constant is FormalParameterFragmentImpl) {
-      if (constant is ConstVariableElement) {
+      if (constant is ConstVariableFragment) {
         var defaultValue = constant.constantInitializer;
         if (defaultValue != null) {
           var diagnosticListener = RecordingDiagnosticListener();

pkg/analyzer/lib/src/dart/constant/utilities.dart

@@ -198,8 +198,8 @@ class ConstantFinder extends RecursiveAstVisitor<void> {
                 !element.isStatic)) {
       constantsToCompute.add(element);
       // Fill error nodes.
-      if (element is ConstVariableElement) {
-        var constElement = element as ConstVariableElement;
+      if (element is ConstVariableFragment) {
+        var constElement = element as ConstVariableFragment;
         configuration.addErrorNode(
           fromElement: constElement.constantInitializer,
           fromAst: node.initializer,