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feat(library/tactic/rewrite_tactic): improve rewrite tactic error messages

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closes #471
This commit is contained in:
Leonardo de Moura 2015-03-12 20:28:56 -07:00
parent 14aeac180a
commit cda19f5aa6
3 changed files with 180 additions and 12 deletions
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178
src/library/tactic/rewrite_tactic.cpp
View file

@ -11,6 +11,7 @@ Author: Leonardo de Moura
#include "util/rb_map.h"
#include "util/sexpr/option_declarations.h"
#include "kernel/instantiate.h"
#include "kernel/error_msgs.h"
#include "kernel/abstract.h"
#include "kernel/replace_fn.h"
#include "kernel/for_each_fn.h"
@ -41,10 +42,14 @@ Author: Leonardo de Moura
#define LEAN_DEFAULT_REWRITER_SYNTACTIC false
#endif
#ifndef LEAN_DEFAULT_REWRITER_TRACE
#define LEAN_DEFAULT_REWRITER_TRACE true
#endif
namespace lean {
static name * g_rewriter_max_iterations = nullptr;
static name * g_rewriter_syntactic = nullptr;
static name * g_rewriter_trace = nullptr;
unsigned get_rewriter_max_iterations(options const & opts) {
return opts.get_unsigned(*g_rewriter_max_iterations, LEAN_DEFAULT_REWRITER_MAX_ITERATIONS);
@ -54,6 +59,10 @@ bool get_rewriter_syntactic(options const & opts) {
return opts.get_bool(*g_rewriter_syntactic, LEAN_DEFAULT_REWRITER_SYNTACTIC);
}
bool get_rewriter_trace(options const & opts) {
return opts.get_bool(*g_rewriter_trace, LEAN_DEFAULT_REWRITER_TRACE);
}
class unfold_info {
list<name> m_names;
location m_location;
@ -448,6 +457,7 @@ class rewrite_fn {
substitution m_subst;
expr m_expr_loc; // auxiliary expression used for error localization
bool m_use_trace;
unsigned m_max_iter;
buffer<optional<level>> m_lsubst; // auxiliary buffer for pattern matching
@ -825,6 +835,135 @@ class rewrite_fn {
some_expr(type), m_expr_loc.get_tag(), cfg, nullptr);
}
// target, new_target, H : represents the rewrite (H : target = new_target) for hypothesis
// and (H : new_target = target) for goals
typedef optional<std::tuple<expr, expr, expr>> find_result;
struct failure {
enum kind { Unification, Exception, HasMetavars };
expr m_elab_lemma;
expr m_subterm;
kind m_kind;
failure(expr const & elab_lemma, expr const & subterm, kind k):
m_elab_lemma(elab_lemma), m_subterm(subterm), m_kind(k) {}
format pp(formatter const & fmt) const {
format r;
switch (m_kind) {
case Unification:
r = compose(line(), format("-fail to unify equation source"));
r += pp_indent_expr(fmt, m_elab_lemma);
r += compose(line(), format("with subterm"));
r += pp_indent_expr(fmt, m_subterm);
return r;
case Exception:
r = compose(line(), format("-an exception occurred when unifying the subterm"));
r += pp_indent_expr(fmt, m_subterm);
return r;
case HasMetavars:
r = compose(line(), format("-lemma still contains meta-variables"));
r += pp_indent_expr(fmt, m_elab_lemma);
r += compose(line(), format("after the equation source has been unified with subterm"));
r += pp_indent_expr(fmt, m_subterm);
return r;
}
lean_unreachable();
}
};
// Store information for a goal or hypothesis being rewritten
struct target_trace {
bool m_is_hypothesis;
expr m_target; // term being rewritten
list<failure> m_failures; // sub-terms that matched but failed to unify
optional<expr> m_matched; // sub-term that matched and unified
target_trace(expr const & t, bool is_hyp): m_is_hypothesis(is_hyp), m_target(t) {}
format pp(formatter const & fmt) const {
if (m_matched)
return format();
if (!m_failures) {
if (m_is_hypothesis)
return line() + format("no subterm in the hypothesis '") + fmt(m_target) + format("' matched the pattern");
else
return line() + format("no subterm in the goal matched the pattern");
}
format r;
if (m_is_hypothesis)
r = line() + format("matching failures in the hypothesis '") + fmt(m_target) + format("'");
else
r = line() + format("matching failures in the goal");
buffer<failure> b;
unsigned indent = get_pp_indent(fmt.get_options());
to_buffer(m_failures, b);
unsigned i = b.size();
while (i > 0) {
--i;
r += nest(indent, b[i].pp(fmt));
}
return r;
}
};
struct trace {
expr m_lemma; // lemma being used for rewriting
expr m_pattern; // extracted or given pattern
buffer<target_trace> m_targets; // trace for each element we tried to rewrite using m_lemma
format pp(formatter const & fmt) const {
format r("rewrite step failed using pattern");
r += pp_indent_expr(fmt, m_pattern);
for (target_trace const & t : m_targets) {
r += t.pp(fmt);
}
return r;
}
};
bool m_trace_initialized;
trace m_trace; // temporary object used to store execution trace for a rewrite step
void clear_trace() {
m_trace_initialized = false;
}
void init_trace(expr const & lemma, expr const & pattern) {
if (m_use_trace) {
m_trace_initialized = true;
m_trace.m_lemma = lemma;
m_trace.m_pattern = pattern;
m_trace.m_targets.clear();
}
}
void add_target(expr const & t, bool is_hyp) {
if (m_use_trace)
m_trace.m_targets.push_back(target_trace(t, is_hyp));
}
target_trace & latest_target() {
lean_assert(m_use_trace);
lean_assert(!m_trace.m_targets.empty());
return m_trace.m_targets.back();
}
void add_target_failure(expr const & elab_term, expr const & subterm, failure::kind k) {
if (m_use_trace) {
target_trace & tt = latest_target();
lean_assert(!tt.m_matched);
tt.m_failures = cons(failure(elab_term, subterm, k), tt.m_failures);
}
}
void add_target_match(expr const & m) {
if (m_use_trace) {
target_trace & tt = latest_target();
lean_assert(!tt.m_matched);
tt.m_matched = m;
}
}
// rule, new_t
typedef optional<pair<expr, expr>> unify_result;
@ -859,8 +998,10 @@ class rewrite_fn {
src = app_arg(rule_type);
else
src = app_arg(app_fn(rule_type));
if (!m_tc->is_def_eq(t, src, justification(), cs_seq))
if (!m_tc->is_def_eq(t, src, justification(), cs_seq)) {
add_target_failure(src, t, failure::Unification);
return unify_result();
}
cs_seq.linearize(cs);
unifier_config cfg;
cfg.m_kind = unifier_kind::Liberal;
@ -870,11 +1011,14 @@ class rewrite_fn {
substitution new_subst = p->first.first;
rule = new_subst.instantiate_all(rule);
rule_type = new_subst.instantiate_all(rule_type);
if (has_expr_metavar_strict(rule) || has_expr_metavar_strict(rule_type))
if (has_expr_metavar_strict(rule) || has_expr_metavar_strict(rule_type)) {
add_target_failure(rule, t, failure::HasMetavars);
return unify_result(); // rule was not completely instantiated.
}
m_subst = new_subst;
expr lhs = app_arg(app_fn(rule_type));
expr rhs = app_arg(rule_type);
add_target_match(t);
if (is_goal) {
if (symm) {
return unify_result(rule, lhs);
@ -890,14 +1034,14 @@ class rewrite_fn {
return unify_result(rule, rhs);
}
}
}
} catch (exception&) {}
} else {
add_target_failure(src, t, failure::Unification);
return unify_result();
}
} catch (exception&) {}
add_target_failure(orig_elem, t, failure::Exception);
return unify_result();
}
// target, new_target, H : represents the rewrite (H : target = new_target) for hypothesis
// and (H : new_target = target) for goals
typedef optional<std::tuple<expr, expr, expr>> find_result;
// Search for \c pattern in \c e. If \c t is a match, then try to unify the type of the rule
// in the rewrite step \c orig_elem with \c t.
@ -930,6 +1074,7 @@ class rewrite_fn {
}
bool process_rewrite_hypothesis(expr const & hyp, expr const & orig_elem, expr const & pattern, occurrence const & occ) {
add_target(hyp, true);
expr Pa = mlocal_type(hyp);
bool is_goal = false;
if (auto it = find_target(Pa, pattern, orig_elem, is_goal)) {
@ -978,6 +1123,7 @@ class rewrite_fn {
bool process_rewrite_goal(expr const & orig_elem, expr const & pattern, occurrence const & occ) {
expr Pa = m_g.get_type();
add_target(Pa, false);
bool is_goal = true;
if (auto it = find_target(Pa, pattern, orig_elem, is_goal)) {
expr a, Heq, b;
@ -1043,6 +1189,7 @@ class rewrite_fn {
bool process_rewrite_step(expr const & elem, expr const & orig_elem) {
lean_assert(is_rewrite_step(elem));
expr pattern = get_pattern(elem);
init_trace(orig_elem, pattern);
// regular(m_env, m_ios) << "pattern: " << pattern << "\n";
rewrite_info const & info = get_rewrite_info(elem);
unsigned i, num;
@ -1086,6 +1233,7 @@ class rewrite_fn {
// Process the given rewrite element/step. This method destructively update
// m_g, m_subst, m_ngen. It returns true if it succeeded and false otherwise.
bool process_step(expr const & elem) {
clear_trace();
if (is_rewrite_unfold_step(elem)) {
return process_unfold_step(elem);
} else if (is_rewrite_fold_step(elem)) {
@ -1161,6 +1309,7 @@ public:
update_goal(head(gs));
m_subst = m_ps.get_subst();
m_max_iter = get_rewriter_max_iterations(ios.get_options());
m_use_trace = get_rewriter_trace(ios.get_options());
}
proof_state_seq operator()(buffer<expr> const & elems) {
@ -1169,8 +1318,18 @@ public:
if (!process_step(elem)) {
if (m_ps.report_failure()) {
proof_state curr_ps(m_ps, cons(m_g, tail(m_ps.get_goals())), m_subst, m_ngen);
if (!m_use_trace || !m_trace_initialized) {
throw tactic_exception("rewrite step failed", some_expr(elem), curr_ps,
[](formatter const &) { return format("invalid 'rewrite' tactic, rewrite step failed"); });
} else {
trace saved_trace = m_trace;
throw tactic_exception("rewrite step failed", some_expr(elem), curr_ps,
[=](formatter const & fmt) {
format r = format("invalid 'rewrite' tactic, ");
r += saved_trace.pp(fmt);
return r;
});
}
}
return proof_state_seq();
}
@ -1204,6 +1363,9 @@ void initialize_rewrite_tactic() {
g_rewriter_syntactic = new name{"rewriter", "syntactic"};
register_bool_option(*g_rewriter_syntactic, LEAN_DEFAULT_REWRITER_SYNTACTIC,
"(rewriter tactic) if true tactic will not unfold any constant when performing pattern matching");
g_rewriter_trace = new name{"rewriter", "trace"};
register_bool_option(*g_rewriter_trace, LEAN_DEFAULT_REWRITER_TRACE,
"(rewriter tactic) if true tactic will generate a trace for rewrite step failures");
name rewrite_tac_name{"tactic", "rewrite_tac"};
g_rewrite_tac = new expr(Const(rewrite_tac_name));
g_rewrite_reduce_name = new name("rewrite_reduce");

8
tests/lean/quasireducible.lean.expected.out
View file

@ -1,4 +1,6 @@
quasireducible.lean:11:11: error:invalid 'rewrite' tactic, rewrite step failed
quasireducible.lean:11:11: error:invalid 'rewrite' tactic, rewrite step failed using pattern
f a
no subterm in the goal matched the pattern
proof state:
a : nat,
H : f a = a
@ -10,7 +12,9 @@ H : f a = a
quasireducible.lean:11:3: error: failed to add declaration '14.1' to environment, value has metavariables
λ (a : nat) (H : f a = a),
?M_1
quasireducible.lean:16:11: error:invalid 'rewrite' tactic, rewrite step failed
quasireducible.lean:16:11: error:invalid 'rewrite' tactic, rewrite step failed using pattern
f a
no subterm in the goal matched the pattern
proof state:
a : nat,
H : f a = a

4
tests/lean/rewrite_fail.lean.expected.out
View file

@ -1,4 +1,6 @@
rewrite_fail.lean:5:15: error:invalid 'rewrite' tactic, rewrite step failed
rewrite_fail.lean:5:15: error:invalid 'rewrite' tactic, rewrite step failed using pattern
a
no subterm in the goal matched the pattern
proof state:
a b : ℕ,
Ha : a = 0,