feat(library/coercion): improve get_user_coercions API

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/library/coercion.cpp

@@ -391,7 +391,7 @@ optional<expr> get_coercion_to_fun(environment const & env, expr const & C) {
     return get_coercion(env, C, coercion_class::mk_fun());
 }
 
-bool get_user_coercions(environment const & env, expr const & C, buffer<std::pair<expr, name>> & result) {
+bool get_user_coercions(environment const & env, expr const & C, buffer<std::tuple<name, expr, expr>> & result) {
     buffer<expr> args;
     expr const & C_fn = get_app_rev_args(C, args);
     if (!is_constant(C_fn))
@@ -407,7 +407,10 @@ bool get_user_coercions(environment const & env, expr const & C, buffer<std::pai
             length(info.m_level_params) == length(const_levels(C_fn))) {
             expr f = instantiate_params(info.m_fun, info.m_level_params, const_levels(C_fn));
             expr c = apply_beta(f, args.size(), args.data());
-            result.emplace_back(c, info.m_to.get_name());
+            expr t = instantiate_params(info.m_fun_type, info.m_level_params, const_levels(C_fn));
+            for (unsigned i = 0; i < args.size(); i++) t = binding_body(t);
+            t = instantiate(t, args.size(), args.data());
+            result.emplace_back(info.m_to.get_name(), c, t);
             r = true;
         }
     }
@@ -472,16 +475,18 @@ static int get_coercion(lua_State * L) { return push_optional_expr(L, get_coerci
 static int get_coercion_to_sort(lua_State * L) { return push_optional_expr(L, get_coercion_to_sort(to_environment(L, 1), to_expr(L, 2))); }
 static int get_coercion_to_fun(lua_State * L) { return push_optional_expr(L, get_coercion_to_fun(to_environment(L, 1), to_expr(L, 2))); }
 static int get_user_coercions(lua_State * L) {
-    buffer<std::pair<expr, name>> r;
+    buffer<std::tuple<name, expr, expr>> r;
     get_user_coercions(to_environment(L, 1), to_expr(L, 2), r);
     lua_newtable(L);
     int i = 1;
     for (auto p : r) {
         lua_newtable(L);
-        push_expr(L, p.first);
+        push_name(L, std::get<0>(p));
         lua_rawseti(L, -2, 1);
-        push_name(L, p.second);
+        push_expr(L, std::get<1>(p));
         lua_rawseti(L, -2, 2);
+        push_expr(L, std::get<2>(p));
+        lua_rawseti(L, -2, 3);
         lua_rawseti(L, -2, i);
         i = i + 1;
     }

src/library/coercion.h

@@ -53,12 +53,12 @@ optional<expr> get_coercion_to_sort(environment const & env, expr const & C);
 optional<expr> get_coercion_to_fun(environment const & env, expr const & C);
 /**
    \brief Return all user coercions C >-> D for the type C of the form (C_name.{l1 ... lk} t_1 ... t_n)
-   The result is a pair (coercion, user-class D), and is stored in the result buffer \c result.
+   The result is a pair (user-class D, coercion, coercion type), and is stored in the result buffer \c result.
    The Boolean result is true if at least one pair is added to \c result.
 
    \remark The most recent coercions occur first.
 */
-bool get_user_coercions(environment const & env, expr const & C, buffer<std::pair<expr, name>> & result);
+bool get_user_coercions(environment const & env, expr const & C, buffer<std::tuple<name, expr, expr>> & result);
 
 void for_each_coercion_user(environment const & env,
                             std::function<void(name const &, name const &, expr const &, level_param_names const &, unsigned)> const & f);

tests/lua/coe1.lua

@@ -67,3 +67,16 @@ env2 = add_coercion(env2, "lst2nat")
 print("---------")
 for_each_coercion_user(env2, function(C, D, f) print(tostring(C) .. " >-> " .. tostring(D)) end)
 for_each_coercion_user(env2, function(C, D, f) print(tostring(C) .. " >-> " .. tostring(D) .. " : " .. tostring(f)) end)
+
+assert(has_coercions_from(env2, lst_nat))
+assert(not has_coercions_from(env2, Const("foo")))
+assert(not has_coercions_from(env2, Const("lst", {1})))
+assert(has_coercions_from(env2, Const("vec", {1})(nat, one)))
+assert(not has_coercions_from(env2, Const("vec", {1})(nat)))
+assert(not has_coercions_from(env2, Const("vec")(nat, one)))
+
+print("Coercions (vec nat one): ")
+cs = get_user_coercions(env2, Const("vec", {1})(nat, one))
+for i = 1, #cs do
+   print(tostring(cs[i][1]) .. " : " .. tostring(cs[i][3]) .. " : " .. tostring(cs[i][2]))
+end