support class native clause

pkg/front_end/lib/src/fasta/parser/parser.dart

Index: pkg/front_end/lib/src/fasta/parser/parser.dart
diff --git a/pkg/front_end/lib/src/fasta/parser/parser.dart b/pkg/front_end/lib/src/fasta/parser/parser.dart
index f7e2e1f90c1ca2e2ecc07d131512ef7aaa3a7661..a738931d88c46f80e4b3a88cac3d28d99dfa2cb9 100644
--- a/pkg/front_end/lib/src/fasta/parser/parser.dart
+++ b/pkg/front_end/lib/src/fasta/parser/parser.dart
@@ -857,9 +857,16 @@ class Parser {
         ++interfacesCount;
       } while (optional(',', token));
     }
+    Token nativeToken;
+    if (optional('native', token)) {
+      nativeToken = token;
+      token = parseNativeClause(token.next);
+      reportRecoverableError(
+          nativeToken, fasta.messageNativeClauseShouldBeAnnotation);
+    }
     token = parseClassBody(token);
     listener.endClassDeclaration(interfacesCount, begin, classKeyword,
-        extendsKeyword, implementsKeyword, token);
+        extendsKeyword, implementsKeyword, nativeToken, token);
     return token.next;
   }
 
@@ -2105,6 +2112,11 @@ class Parser {
     return token;
   }
 
+  Token parseNativeClause(Token token) {
+    if (!identical(token.kind, STRING_TOKEN)) return token;

[ahe, 2017/08/21 12:04:10]

We don't need to use identical on token.kind.

[danrubel, 2017/08/22 01:35:28]

Good point. Fixed.

+    return parseSingleLiteralString(token);

[ahe, 2017/08/21 12:04:10]

We should generate an event here. I'm thinking something like this:

Token parseNativeClause(Token token) {
  listener.beginNativeClause(token);
  bool hasName = false;
  if (STRING_TOKEN == token.kind) {
    hasName = true;
    token = parseLiteralString(token);
  }
  listener.endNativeClause(token, hasName);
  return token;
}

[danrubel, 2017/08/22 01:35:28]

Good point. Per discussion I've added a handleNativeClause(token, hasName)
instead. That makes the listeners a bit cleaner and clearer than my current
implementation and should make adding support for native clauses on methods and
functions a bit easier.

+  }
+
   Token skipClassBody(Token token) {
     if (!optional('{', token)) {
       return reportUnrecoverableErrorWithToken(