Program: 17009
Project: 17009
Buggy source:
@Override protected JstCompletion createCompletion(ObjectLiteral astNode,boolean isAfterSource){
  JstCompletion completion=null;
  CategorizedProblem problem=findProblem();
  if (problem != null) {
    int problemStart=problem.getSourceStart();
    char[] source=m_ctx.getOriginalSource();
    String prefix=new String(source,problemStart,m_ctx.getCompletionPos() - problemStart);
    String wholeError=new String(source,problemStart,problem.getSourceEnd() + 1 - problemStart);
    if (prefix.length() == 0) {
    }
    if (prefix.length() > 0 && isJavaIdentifier(prefix)) {
      completion=new JstFieldOrMethodCompletion(m_result,isStaticBlock());
      completion.setSource(createSource(problemStart,problem.getSourceEnd() + 1,m_ctx.getSourceUtil()));
      completion.setToken(prefix);
      completion.setCompositeToken(wholeError);
      m_ctx.setCreatedCompletion(true);
    }
  }
  if (!isAfterSource && completion == null) {
    if (inFieldArea(astNode)) {
      return null;
    }
    int lastFieldPos=getLastFieldPos(astNode);
    String token=getToken(lastFieldPos);
    if (token == null || token.indexOf("String_Node_Str") >= 0) {
      return null;
    }
    completion=new JstFieldOrMethodCompletion(m_result,isStaticBlock());
    if (token.trim().length() == 0) {
      completion.setCompositeToken(token.trim());
    }
 else {
      completion.setCompositeToken(token);
    }
    completion.setToken(token.trim());
    int startSource=m_ctx.getCompletionPos() - token.length();
    int endSource=startSource + token.length();
    completion.setSource(createSource(startSource,endSource,m_ctx.getSourceUtil()));
    m_ctx.setCreatedCompletion(true);
  }
  return completion;
}

Fixed version (ground truth):
@Override protected JstCompletion createCompletion(ObjectLiteral astNode,boolean isAfterSource){
  JstCompletion completion=null;
  CategorizedProblem problem=findProblem();
  if (problem != null) {
    int problemStart=problem.getSourceStart();
    char[] source=m_ctx.getOriginalSource();
    String prefix=new String(source,problemStart,m_ctx.getCompletionPos() - problemStart);
    String wholeError=new String(source,problemStart,problem.getSourceEnd() + 1 - problemStart);
    if (prefix.length() == 0) {
    }
    if (prefix.length() > 0 && isJavaIdentifier(prefix)) {
      completion=new JstFieldOrMethodCompletion(m_result,isStaticBlock());
      completion.setSource(createSource(problemStart,problem.getSourceEnd() + 1,m_ctx.getSourceUtil()));
      completion.setToken(prefix);
      completion.setCompositeToken(wholeError);
      m_ctx.setCreatedCompletion(true);
    }
  }
  if (!isAfterSource && completion == null) {
    if (inFieldArea(astNode)) {
      return null;
    }
    String token="String_Node_Str";
    int index=m_ctx.getCompletionPos() - 1;
    char c=m_ctx.getOriginalSource()[index];
    if (c != ',') {
      int lastFieldPos=getLastFieldPos(astNode);
      token=getToken(lastFieldPos);
      if (token == null || token.indexOf("String_Node_Str") >= 0) {
        return null;
      }
    }
    completion=new JstFieldOrMethodCompletion(m_result,isStaticBlock());
    if (token.trim().length() == 0) {
      completion.setCompositeToken(token.trim());
    }
 else {
      completion.setCompositeToken(token);
    }
    completion.setToken(token.trim());
    int startSource=m_ctx.getCompletionPos() - token.length();
    int endSource=startSource + token.length();
    completion.setSource(createSource(startSource,endSource,m_ctx.getSourceUtil()));
    m_ctx.setCreatedCompletion(true);
  }
  return completion;
}