Maybe surround the `else null`here and on L141 with curly braces, to be consistent? Though the Scala style guide mentions that omitting braces is okay if all the branches are single line expressions (http://docs.scala-lang.org/style/control-structures.html)
It might also be nicer to put the `if (...)` on the same line as the `constEval` declaration, to save a line/indents (applies to the block at L141 too).