At the moment code completion matches possible completions only on the first characters (see attached image). This is not that great because a lot of possible completions are not shown. It would be far better if the complete identifier is searched for substrings that match the already typed identifier. This would mean that for the following code example containsIdentInUpper and containsidentInLower would be shown too.

class CodeCompletionTest {
  def ident = 0
  def containsIdentInUpper = 0
  def containsidentInLower = 0

  val res = ident
}

To achieve best user experience it is necessary to implement some other features before this one. There is #1001695 which would highlight the matched part of the identifier in a special way. Furthermore as described by #1001696 it is necessary for this feature to overwrite existing identifiers correctly and not only append the missing part of an identifier to the editor.