fix(frontends/lean): allow 'attribute <id> [priority ...]'

src/frontends/lean/decl_cmds.cpp

@@ -297,7 +297,8 @@ struct decl_attributes {
     optional<unsigned> m_priority;
     optional<unsigned> m_unfold_c_hint;
 
-    decl_attributes(bool def_only = true, bool is_abbrev = false):m_priority() {
+    decl_attributes(bool def_only = true, bool is_abbrev = false):
+        m_priority() {
         m_def_only               = def_only;
         m_is_abbrev              = is_abbrev;
         m_is_instance            = false;
@@ -350,7 +351,7 @@ struct decl_attributes {
         }
     }
 
-    void parse(parser & p) {
+    void parse(buffer<name> const & ns, parser & p) {
         while (true) {
             auto pos = p.pos();
             if (p.curr_is_token(get_instance_tk())) {
@@ -389,8 +390,18 @@ struct decl_attributes {
                 p.next();
             } else if (auto it = parse_instance_priority(p)) {
                 m_priority = *it;
-                if (!m_is_instance)
+                if (!m_is_instance) {
+                    if (ns.empty()) {
                         throw parser_error("invalid '[priority]' attribute, declaration must be marked as an '[instance]'", pos);
+                    } else {
+                        for (name const & n : ns) {
+                            if (!is_instance(p.env(), n))
+                                throw parser_error(sstream() << "invalid '[priority]' attribute, declaration '" << n
+                                                   << "' must be marked as an '[instance]'", pos);
+                        }
+                        m_is_instance = true;
+                    }
+                }
             } else if (p.curr_is_token(get_parsing_only_tk())) {
                 if (!m_is_abbrev)
                     throw parser_error("invalid '[parsing-only]' attribute, only abbreviations can be "
@@ -410,6 +421,17 @@ struct decl_attributes {
         }
     }
 
+    void parse(name const & n, parser & p) {
+        buffer<name> ns;
+        ns.push_back(n);
+        parse(ns, p);
+    }
+
+    void parse(parser & p) {
+        buffer<name> ns;
+        parse(ns, p);
+    }
+
     environment apply(environment env, io_state const & ios, name const & d, bool persistent) {
         if (m_is_instance) {
             if (m_priority) {
@@ -1113,7 +1135,7 @@ static environment attribute_cmd_core(parser & p, bool persistent) {
     }
     bool decl_only  = false;
     decl_attributes attributes(decl_only);
-    attributes.parse(p);
+    attributes.parse(ds, p);
     environment env = p.env();
     for (name const & d : ds)
         env = attributes.apply(env, p.ios(), d, persistent);

src/library/class.cpp

@@ -46,6 +46,10 @@ struct class_state {
             return LEAN_INSTANCE_DEFAULT_PRIORITY;
     }
 
+    bool is_instance(name const & i) const {
+        return m_priorities.contains(i);
+    }
+
     bool try_multiple_instances(name const & c) const {
         return m_multiple.contains(c);
     }
@@ -73,7 +77,6 @@ struct class_state {
             auto lst = filter(*it, [&](name const & i1) { return i1 != i; });
             m_instances.insert(c, insert(i, p, lst));
         }
-        if (p != LEAN_INSTANCE_DEFAULT_PRIORITY)
         m_priorities.insert(i, p);
     }
 
@@ -215,6 +218,11 @@ bool is_class(environment const & env, name const & c) {
     return s.m_instances.contains(c);
 }
 
+bool is_instance(environment const & env, name const & i) {
+    class_state const & s = class_ext::get_state(env);
+    return s.is_instance(i);
+}
+
 list<name> get_class_instances(environment const & env, name const & c) {
     class_state const & s = class_ext::get_state(env);
     return ptr_to_list(s.m_instances.find(c));

src/library/class.h

@@ -15,6 +15,8 @@ environment add_instance(environment const & env, name const & n, bool persisten
 environment add_instance(environment const & env, name const & n, unsigned priority, bool persistent);
 /** \brief Return true iff \c c was declared with \c add_class. */
 bool is_class(environment const & env, name const & c);
+/** \brief Return true iff \c i was declared with \c add_instance. */
+bool is_instance(environment const & env, name const & i);
 /** \brief Return the instances of the given class. */
 list<name> get_class_instances(environment const & env, name const & c);
 /** \brief Return the classes in the given environment. */

tests/lean/run/priority_test2.lean

@@ -26,3 +26,18 @@ foo.mk 4 4
 
 example : foo.a = 3 :=
 rfl
+
+attribute i4 [priority default+2]
+
+example : foo.a = 4 :=
+rfl
+
+attribute i1 [priority default+3]
+
+example : foo.a = 1 :=
+rfl
+
+attribute i2 [instance] [priority default+4]
+
+example : foo.a = 2 :=
+rfl