Create DeclaredSimpleIdentifier when parse a declaration with Fasta.

pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart

Index: pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
index 857220999f4a2342aa7fd6cc437b38556504afc3..55b4fc8c25fc067cd00873dd4ef4deb75c49c27c 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
@@ -182,7 +182,8 @@ class AstBuilder extends ScopeListener {
       return;
     }
 
-    SimpleIdentifier identifier = ast.simpleIdentifier(analyzerToken);
+    SimpleIdentifier identifier = ast.simpleIdentifier(analyzerToken,
+        isDeclaration: context.inDeclaration);
     if (context.inLibraryOrPartOfDeclaration) {
       if (!context.isContinuation) {
         push([identifier]);
@@ -1313,7 +1314,7 @@ class AstBuilder extends ScopeListener {
           toAnalyzerToken(modifiers?.externalKeyword),
           toAnalyzerToken(modifiers?.finalConstOrVarKeyword),
           null, // TODO(paulberry): factoryKeyword
-          returnType,
+          ast.simpleIdentifier(returnType.token),
           period,
           name,
           parameters,