This bug report is not about ASAN Use After Free issue. This bug is
about missed calling of the method LEX::cleanup_lex_after_parse_error
that should happen on parse error.

Aforementioned method calls sphead::restore_thd_mem_root to clean up
resources acquired on processing a stored routine. Particularly,
the method sp_head::restore_tht_mem_root is called to restore
an original mem root and reset LEX::sphead into nullptr.

The method LEX::cleanup_lex_after_parse_error is invoked by the macros
MYSQL_YYABORT. Unfortunately, some rules of grammar for handling
user variables in SQL use YYABORT instead of MYSQL_YYABORT to handle
parser errors. As a consequence, in case a statement with setting of
a user variable is called inside a stored routine, it results in
assert failure in sp_head destructor.

To fix the issue the macros YYABORT should be replaced by MYSQL_YYABORT
in those grammar rules that handle assignment of user variables.