feat(frontends/lean,library/tactic/tactic_state): improve error localization

library/init/meta/tactic.lean

@@ -24,7 +24,7 @@ meta instance : has_to_format tactic_state :=
 
 inductive tactic_result (A : Type)
 | success   : A → tactic_state → tactic_result
-| exception : (unit → format) → tactic_state → tactic_result
+| exception : (unit → format) → option expr → tactic_state → tactic_result
 
 open tactic_result
 
@@ -33,8 +33,8 @@ variables {A : Type}
 variables [has_to_string A]
 
 meta definition tactic_result_to_string : tactic_result A → string
-| (success a s)   := to_string a
-| (exception .A e s) := "Exception: " ++ to_string (e ())
+| (success a s)          := to_string a
+| (exception .A t ref s) := "Exception: " ++ to_string (t ())
 
 meta instance : has_to_string (tactic_result A) :=
 ⟨tactic_result_to_string⟩
@@ -66,7 +66,7 @@ meta definition tactic_return (a : A) : tactic A :=
 meta definition tactic_orelse {A : Type} (t₁ t₂ : tactic A) : tactic A :=
 λ s, tactic_result.cases_on (t₁ s)
   success
-  (λ e₁ s', tactic_result.cases_on (t₂ s)
+  (λ e₁ ref₁ s', tactic_result.cases_on (t₂ s)
      success
      (exception A))
 end
@@ -75,7 +75,7 @@ meta instance : monad tactic :=
 ⟨@tactic_fmap, @tactic_return, @tactic_bind⟩
 
 meta definition tactic.fail {A B : Type} [has_to_format B] (msg : B) : tactic A :=
-λ s, exception A (λ u, to_fmt msg) s
+λ s, exception A (λ u, to_fmt msg) none s
 
 meta definition tactic.failed {A : Type} : tactic A :=
 tactic.fail "failed"
@@ -89,7 +89,7 @@ variables {A : Type}
 meta definition try (t : tactic A) : tactic unit :=
 λ s, tactic_result.cases_on (t s)
  (λ a, success ())
- (λ e s', success () s)
+ (λ e ref s', success () s)
 
 meta definition skip : tactic unit :=
 success ()
@@ -116,13 +116,13 @@ repeat_at_most 100000
 meta definition returnex (e : exceptional A) : tactic A :=
 λ s, match e with
 | (exceptional.success a)       := tactic_result.success a s
-| (exceptional.exception .A f) := tactic_result.exception A (λ u, f options.mk) s -- TODO(Leo): extract options from environment
+| (exceptional.exception .A f) := tactic_result.exception A (λ u, f options.mk) none s -- TODO(Leo): extract options from environment
 end
 
 meta definition returnopt (e : option A) : tactic A :=
 λ s, match e with
 | (some a) := tactic_result.success a s
-| none     := tactic_result.exception A (λ u, to_fmt "failed") s
+| none     := tactic_result.exception A (λ u, to_fmt "failed") none s
 end
 
 /- Decorate t's exceptions with msg -/

src/frontends/lean/elaborator.cpp

@@ -2133,8 +2133,15 @@ void elaborator::invoke_tactic(expr const & mvar, expr const & tactic) {
         m_env = new_s->env();
         m_ctx.set_env(m_env);
         m_ctx.set_mctx(mctx);
-    } else if (optional<pair<format, tactic_state>> ex = is_tactic_exception(S, m_opts, r)) {
-        throw_unsolved_tactic_state(ex->second, ex->first, ref);
+    } else if (optional<tactic_exception_info> ex = is_tactic_exception(S, r)) {
+        format fmt          = std::get<0>(*ex);
+        optional<expr> ref1 = std::get<1>(*ex);
+        tactic_state s1     = std::get<2>(*ex);
+        pos_info_provider * provider = get_pos_info_provider();
+        if (ref1 && provider && provider->get_pos_info(*ref1))
+            throw elaborator_exception(*ref1, fmt);
+        else
+            throw_unsolved_tactic_state(s1, fmt, ref);
     } else {
         lean_unreachable();
     }

src/library/tactic/tactic_state.cpp

@@ -223,12 +223,15 @@ optional<tactic_state> is_tactic_success(vm_obj const & o) {
     }
 }
 
-optional<pair<format, tactic_state>> is_tactic_exception(vm_state & S, options const & opts, vm_obj const & ex) {
+optional<tactic_exception_info> is_tactic_exception(vm_state & S, vm_obj const & ex) {
     if (is_constructor(ex) && cidx(ex) == 1) {
-        vm_obj fmt = S.invoke(cfield(ex, 0), to_obj(opts));
-        return optional<pair<format, tactic_state>>(mk_pair(to_format(fmt), to_tactic_state(cfield(ex, 1))));
+        vm_obj fmt = S.invoke(cfield(ex, 0), mk_vm_unit());
+        optional<expr> ref;
+        if (!is_none(cfield(ex, 1)))
+            ref = to_expr(get_some_value(cfield(ex, 1)));
+        return optional<tactic_exception_info>(to_format(fmt), ref, to_tactic_state(cfield(ex, 2)));
     } else {
-        return optional<pair<format, tactic_state>>();
+        return optional<tactic_exception_info>();
     }
 }
 
@@ -241,13 +244,23 @@ vm_obj mk_tactic_success(tactic_state const & s) {
 }
 
 vm_obj mk_tactic_exception(vm_obj const & fn, tactic_state const & s) {
-    return mk_vm_constructor(1, fn, to_obj(s));
+    return mk_vm_constructor(1, fn, mk_vm_none(), to_obj(s));
+}
+
+vm_obj mk_tactic_exception(vm_obj const & fn, vm_obj const & ref, tactic_state const & s) {
+    return mk_vm_constructor(1, fn, ref, to_obj(s));
 }
 
 vm_obj mk_tactic_exception(throwable const & ex, tactic_state const & s) {
     vm_obj _ex = to_obj(ex);
     vm_obj fn  = mk_vm_closure(get_throwable_to_format_fun_idx(), 1, &_ex);
-    return mk_tactic_exception(fn, s);
+    optional<expr> ref;
+    if (auto kex = dynamic_cast<ext_exception const *>(&ex))
+        ref = kex->get_main_expr();
+    else if (auto fex = dynamic_cast<formatted_exception const *>(&ex))
+        ref = fex->get_main_expr();
+    vm_obj _ref = ref ? mk_vm_some(to_obj(*ref)) : mk_vm_none();
+    return mk_tactic_exception(fn, _ref, s);
 }
 
 vm_obj mk_tactic_exception(format const & fmt, tactic_state const & s) {

src/library/tactic/tactic_state.h

@@ -108,9 +108,11 @@ format pp_indented_expr(tactic_state const & s, expr const & e);
 /* If r is (base_tactic_result.success a s), then return s */
 optional<tactic_state> is_tactic_success(vm_obj const & r);
 
-/* If ex is (base_tactic_result.exception fn), then return (fn opts).
-   The vm_state S is used to execute (fn opts). */
-optional<pair<format, tactic_state>> is_tactic_exception(vm_state & S, options const & opts, vm_obj const & ex);
+typedef std::tuple<format, optional<expr>, tactic_state> tactic_exception_info;
+
+/* If ex is (base_tactic_result.exception fn), then return (fn ()).
+   The vm_state S is used to execute (fn ()). */
+optional<tactic_exception_info> is_tactic_exception(vm_state & S, vm_obj const & ex);
 
 type_context mk_type_context_for(tactic_state const & s, transparency_mode m = transparency_mode::Semireducible);
 type_context mk_type_context_for(tactic_state const & s, local_context const & lctx, transparency_mode m = transparency_mode::Semireducible);

tests/lean/auto_quote_error.lean

@@ -0,0 +1,6 @@
+example (a b c : nat) : a = b → b = c → c = a :=
+begin
+  intro h1,
+  intro h2,
+  exact eq.symm (eq.trans h1 _),
+end

tests/lean/auto_quote_error.lean.expected.out

@@ -0,0 +1,6 @@
+auto_quote_error.lean:5:29: error: don't know how to synthesize placeholder
+state:
+a b c : ℕ,
+h1 : a = b,
+h2 : b = c
+⊢ b = c