feat(frontends/lean,library/blast/forward/pattern): check whether patterns can be inferred at declaration time

src/frontends/lean/builtin_cmds.cpp

@@ -234,14 +234,12 @@ static void print_metaclasses(parser const & p) {
 
 static void print_patterns(parser & p, name const & n) {
     if (is_forward_lemma(p.env(), n)) {
-        blast::scope_debug scope(p.env(), p.ios());
         // we regenerate the patterns to make sure they reflect the current set of reducible constants
         try {
-            auto lemma = blast::mk_hi_lemma(n, LEAN_FORWARD_LEMMA_DEFAULT_PRIORITY);
+            if (auto mps = mk_multipatterns(p.env(), p.ios(), n)) {
-            if (lemma.m_multi_patterns) {
                 io_state_stream out = p.regular_stream();
                 out << "(multi-)patterns:\n";
-                for (multi_pattern const & mp : lemma.m_multi_patterns) {
+                for (multi_pattern const & mp : mps) {
                     out << "{";
                     bool first = true;
                     for (expr const & p : mp) {

src/frontends/lean/decl_attributes.cpp

@@ -241,6 +241,7 @@ environment decl_attributes::apply(environment env, io_state const & ios, name c
             env = add_backward_rule(env, d, LEAN_BACKWARD_DEFAULT_PRIORITY, m_persistent);
     }
     if (forward) {
+        mk_multipatterns(env, ios, d); // try to create patterns
         if (m_priority)
             env = add_forward_lemma(env, d, *m_priority, m_persistent);
         else

src/library/blast/forward/pattern.cpp

@@ -130,7 +130,7 @@ expr mk_pattern_hint(expr const & e) {
     if (has_pattern_hints(e))
         throw exception("invalid pattern hint, nested patterns hints are not allowed");
     if (!is_app(e))
-        throw_generic_exception("invalid pattern hint, pattern must be applications", e);
+        throw_generic_exception("invalid pattern hint, pattern hints must be applications", e);
     return mk_annotation(*g_pattern_hint, e);
 }
 
@@ -630,6 +630,13 @@ hi_lemma mk_hi_lemma(name const & c, unsigned priority) {
 }
 }
 
+list<multi_pattern> mk_multipatterns(environment const & env, io_state const & ios, name const & c) {
+    blast::scope_debug scope(env, ios);
+    // we regenerate the patterns to make sure they reflect the current set of reducible constants
+    auto lemma = blast::mk_hi_lemma(c, LEAN_FORWARD_LEMMA_DEFAULT_PRIORITY);
+    return lemma.m_multi_patterns;
+}
+
 void initialize_pattern() {
     g_name              = new name("no_pattern");
     g_key               = new std::string("NOPAT");

src/library/blast/forward/pattern.h

@@ -48,6 +48,9 @@ struct hi_lemma_cmp {
     int operator()(hi_lemma const & l1, hi_lemma const & l2) const { return expr_quick_cmp()(l1.m_prop, l2.m_prop); }
 };
 
+/** \brief Try to compute multipatterns for declaration \c c using the current environment configuration. */
+list<multi_pattern> mk_multipatterns(environment const & env, io_state const & ios, name const & c);
+
 namespace blast {
 /** \brief Create a (local) heuristic instantiation lemma for \c H.
     The maximum number of steps is extracted from the blast config object. */

tests/lean/bad_pattern.lean

@@ -16,3 +16,6 @@ reveal tst₀ tst₁ tst₃
 print tst₀
 print tst₁
 print tst₃
+
+definition tst₄ [forward] : ∀ x : nat, (: id x :) = x :=
+λ x, rfl

tests/lean/bad_pattern.lean.expected.out

@@ -1,4 +1,4 @@
-bad_pattern.lean:9:33: error: invalid pattern hint, pattern must be applications
+bad_pattern.lean:9:33: error: invalid pattern hint, pattern hints must be applications
 theorem tst₀ [forward] : ∀ (x : ℕ), P x :=
 sorry
 (multi-)patterns:
@@ -11,3 +11,4 @@ theorem tst₃ [forward] : ∀ (x : ℕ), P (:id x:) :=
 sorry
 (multi-)patterns:
 {P ?M_1}
+bad_pattern.lean:20:0: error: pattern inference failed for [forward] annotation, (solution: provide pattern hints using the notation '(: t :)' )