clang-format: [JS] support interface as a free standing identifier.

Summary:
`interface` can be used as a fee standing identifier in JavaScript/TypeScript.
This change uses the heuristic of whether it's followed by another identifier
as an indication.

Reviewers: djasper

Subscribers: klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D19240

llvm-svn: 266789

clang/lib/Format/UnwrappedLineParser.cpp

@@ -1007,6 +1007,21 @@ void UnwrappedLineParser::parseStructuralElement() {
       if ((Style.Language == FormatStyle::LK_JavaScript ||
            Style.Language == FormatStyle::LK_Java) &&
           FormatTok->is(Keywords.kw_interface)) {
+        if (Style.Language == FormatStyle::LK_JavaScript) {
+          // In JavaScript/TypeScript, "interface" can be used as a standalone
+          // identifier, e.g. in `var interface = 1;`. If "interface" is
+          // followed by another identifier, it is very like to be an actual
+          // interface declaration.
+          unsigned StoredPosition = Tokens->getPosition();
+          FormatToken *Next = Tokens->getNextToken();
+          FormatTok = Tokens->setPosition(StoredPosition);
+          if (Next && (Next->isNot(tok::identifier) ||
+                       Next->isOneOf(Keywords.kw_instanceof, Keywords.kw_of,
+                                     Keywords.kw_in))) {
+            nextToken();
+            break;
+          }
+        }
         parseRecord();
         addUnwrappedLine();
         return;

clang/unittests/Format/FormatTestJS.cpp

@@ -136,6 +136,9 @@ TEST_F(FormatTestJS, ReservedWords) {
                "};");
   verifyFormat("var struct = 2;");
   verifyFormat("var union = 2;");
+  verifyFormat("var interface = 2;");
+  verifyFormat("interface = 2;");
+  verifyFormat("x = interface instanceof y;");
 }
 
 TEST_F(FormatTestJS, CppKeywords) {