Among doing other things, Phab:D201
(bc2289e13d9586be087bd8136943dc35a0130c88) tried to improve the error
messages thrown by the parser. For example a missing else clause now
prints "parse error in if statement: else clause empty" instead of
"parse error (possibly incorrect indentation or mismatched brackets)".
Some error messages got much worse however (see tests), and the result
seems to be a net negative. Although not entirely satisfactory, this
commits therefore reverts those parser changes.