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fix(library/class_instance_resolution): make sure that terms synthesized by type class resolution have override the ones synthesized by solving unification constraints.

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Leonardo de Moura 2015-10-18 18:38:41 -07:00
parent b71a68c606
commit 2edccf007b
1 changed files with 9 additions and 8 deletions
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17
src/library/class_instance_resolution.cpp
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@ -978,7 +978,15 @@ struct cienv {
return false; return false;
} }
r = Fun(locals, r); r = Fun(locals, r);
assign(mvar, r); if (is_assigned(mvar)) {
// Remark: if the metavariable is already assigned, we should check whether
// the previous assignment (obtained by solving unification constraints) and the
// synthesized one are definitionally equal. We don't do that for performance reasons.
// Moreover, the is_def_eq defined here is not complete (e.g., it only unfolds reducible constants).
update_assignment(mvar, r);
} else {
assign(mvar, r);
}
// copy new_inst_mvars to stack // copy new_inst_mvars to stack
unsigned i = new_inst_mvars.size(); unsigned i = new_inst_mvars.size();
while (i > 0) { while (i > 0) {
@ -1088,13 +1096,6 @@ struct cienv {
lean_assert(!is_done()); lean_assert(!is_done());
unsigned depth = head(m_state.m_stack).first; unsigned depth = head(m_state.m_stack).first;
expr mvar = head(m_state.m_stack).second; expr mvar = head(m_state.m_stack).second;
if (is_assigned(mvar)) {
// Remark: if the metavariable is already assigned, another alternative is to
// execute type class resolution and ensure the synthesized answer is equal to the
// one assigned by solving unification constraints.
m_state.m_stack = tail(m_state.m_stack);
return true; // metavariable was assigned by solving unification constraints
}
if (!mk_choice_point(mvar)) if (!mk_choice_point(mvar))
return false; return false;
m_state.m_stack = tail(m_state.m_stack); m_state.m_stack = tail(m_state.m_stack);