Drop illegitimate optimisation from d5a7f2c54655.
--- a/src/Pure/Isar/expression.ML Fri Mar 02 14:28:39 2018 +0100
+++ b/src/Pure/Isar/expression.ML Fri Mar 02 15:14:59 2018 +0100
@@ -407,8 +407,7 @@
|> Variable.export_terms ctxt' ctxt
|> Element.eq_term_morphism (Proof_Context.theory_of ctxt)
|> the_default Morphism.identity;
- val ctxt'' = if null eqns then ctxt' else
- Locale.activate_declarations (loc, inst_morph $> rewrite_morph) ctxt;
+ val ctxt'' = Locale.activate_declarations (loc, inst_morph $> rewrite_morph) ctxt;
val eqnss' = eqnss @ [attrss ~~ Variable.export_terms ctxt' ctxt eqns'];
in (i + 1, insts', eqnss', ctxt'') end;