The Jargon File (version 4.4.7, 29 Dec 2003):

language lawyer
 n.

    A person, usually an experienced or senior software engineer, who is
    intimately familiar with many or most of the numerous restrictions and
    features (both useful and esoteric) applicable to one or more computer
    programming languages. A language lawyer is distinguished by the ability to
    show you the five sentences scattered through a 200-plus-page manual that
    together imply the answer to your question ?if only you had thought to look
    there?. Compare wizard, legal, legalese.


The Free On-line Dictionary of Computing (30 December 2018):

language lawyer

   A person, usually an experienced or senior software engineer,
   who is intimately familiar with many or most of the numerous
   restrictions and features (both useful and esoteric)
   applicable to one or more computer programming languages.  A
   language lawyer is distinguished by the ability to show you
   the five sentences scattered through a 200-page manual that
   together imply the answer to your question "if only you had
   thought to look there".

   Compare wizard, legal, legalese.

   [Jargon File]

   (1995-02-15)