clang-format: [JS] fix uninitialized memory.

[mprobst]

Summary

SortJavaScriptImports attempts to set its currently parsed token to an
invalid token when it reaches the end of the line. However in doing so,
it used a FormatToken, which contains a Token Tok. Token does not
have a constructor, so its fields start out as uninitialized memory.

Token::startToken() initializes all fields. Calling it in
JavaScriptImportSorter's constructor thus fixes the problem.

clang/lib/Format/SortJavaScriptImports.cpp

 
 // JavaScriptImportSorter sorts JavaScript ES6 imports and exports. It is
 // implemented as a TokenAnalyzer because ES6 imports have substantial syntactic
 // structure, making it messy to sort them using regular expressions.
 class JavaScriptImportSorter : public TokenAnalyzer {
 public:
   JavaScriptImportSorter(const Environment &Env, const FormatStyle &Style)
       : TokenAnalyzer(Env, Style),
-        FileContents(Env.getSourceManager().getBufferData(Env.getFileID())) {}
+        FileContents(Env.getSourceManager().getBufferData(Env.getFileID())) {
+    // FormatToken.Tok starts out in an uninitialized state.
+    invalidToken.Tok.startToken();
+  }
 
   std::pair<tooling::Replacements, unsigned>
   analyze(TokenAnnotator &Annotator,
           SmallVectorImpl<AnnotatedLine *> &AnnotatedLines,
           FormatTokenLexer &Tokens) override {
     tooling::Replacements Result;
     AffectedRangeMgr.computeAffectedLines(AnnotatedLines);
 
private:
   }
 
   void nextToken() {
     Current = Current->Next;
     skipComments();
     if (!Current || Current == LineEnd->Next) {
       // Set the current token to an invalid token, so that further parsing on
       // this line fails.
-      invalidToken.Tok.setKind(tok::unknown);
       Current = &invalidToken;
     }
   }
 
   StringRef getSourceText(SourceRange Range) {
     return getSourceText(Range.getBegin(), Range.getEnd());
   }