feat(library): add module for tracking noncomputable definitions

src/library/CMakeLists.txt

@@ -15,6 +15,6 @@ add_library(library deep_copy.cpp expr_lt.cpp io_state.cpp occurs.cpp
   unfold_macros.cpp app_builder.cpp projection.cpp abbreviation.cpp
   relation_manager.cpp export.cpp user_recursors.cpp
   class_instance_synth.cpp idx_metavar.cpp composition_manager.cpp
-  tc_multigraph.cpp)
+  tc_multigraph.cpp noncomputable.cpp)
 
 target_link_libraries(library ${LEAN_LIBS})

src/library/init_module.cpp

@@ -40,6 +40,7 @@ Author: Leonardo de Moura
 #include "library/user_recursors.h"
 #include "library/class_instance_synth.h"
 #include "library/composition_manager.h"
+#include "library/noncomputable.h"
 
 namespace lean {
 void initialize_library_module() {
@@ -79,9 +80,11 @@ void initialize_library_module() {
     initialize_user_recursors();
     initialize_class_instance_elaborator();
     initialize_composition_manager();
+    initialize_noncomputable();
 }
 
 void finalize_library_module() {
+    finalize_noncomputable();
     finalize_composition_manager();
     finalize_class_instance_elaborator();
     finalize_user_recursors();

src/library/noncomputable.cpp

@@ -0,0 +1,103 @@
+/*
+Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#include <utility>
+#include <string>
+#include "util/sstream.h"
+#include "kernel/for_each_fn.h"
+#include "kernel/type_checker.h"
+#include "library/module.h"
+#include "library/util.h"
+#include "library/fingerprint.h"
+
+namespace lean {
+struct noncomputable_ext : public environment_extension {
+    name_set m_noncomputable;
+    noncomputable_ext() {}
+};
+
+struct noncomputable_ext_reg {
+    unsigned m_ext_id;
+    noncomputable_ext_reg() {
+        m_ext_id = environment::register_extension(std::make_shared<noncomputable_ext>());
+    }
+};
+
+static noncomputable_ext_reg * g_ext = nullptr;
+static noncomputable_ext const & get_extension(environment const & env) {
+    return static_cast<noncomputable_ext const &>(env.get_extension(g_ext->m_ext_id));
+}
+static environment update(environment const & env, noncomputable_ext const & ext) {
+    return env.update(g_ext->m_ext_id, std::make_shared<noncomputable_ext>(ext));
+}
+
+static name * g_noncomputable = nullptr;
+static std::string * g_key    = nullptr;
+
+static void noncomputable_reader(deserializer & d, shared_environment & senv,
+                                 std::function<void(asynch_update_fn const &)> &,
+                                 std::function<void(delayed_update_fn const &)> &) {
+    name n;
+    d >> n;
+    senv.update([=](environment const & env) -> environment {
+            noncomputable_ext ext = get_extension(env);
+            ext.m_noncomputable.insert(n);
+            return update(env, ext);
+        });
+}
+
+static bool is_noncomputable(type_checker & tc, noncomputable_ext const & ext, name const & n) {
+    if (ext.m_noncomputable.contains(n))
+        return true;
+    declaration const & d = tc.env().get(n);
+    return d.is_axiom() && !tc.is_prop(d.get_type()).first;
+}
+
+bool is_noncomputable(environment const & env, name const & n) {
+    type_checker tc(env);
+    auto ext = get_extension(env);
+    return is_noncomputable(tc, ext, n);
+}
+
+environment mark_noncomputable(environment const & env, name const & n) {
+    auto ext = get_extension(env);
+    ext.m_noncomputable.insert(n);
+    environment new_env = update(env, ext);
+    return module::add(new_env, *g_key, [=](environment const &, serializer & s) { s << n; });
+}
+
+void validate_computable_definition(environment const & env, name const & n) {
+    if (!is_standard(env))
+        return; // do nothing if it is not a standard kernel
+    type_checker tc(env);
+    declaration const & d = env.get(n);
+    if (!d.is_definition())
+        return;
+    if (tc.is_prop(d.get_type()).first)
+        return; // definition is a proposition, then do nothing
+    expr const & v = d.get_value();
+    auto ext = get_extension(env);
+    for_each(v, [&](expr const & e, unsigned) {
+            if (is_constant(e) && is_noncomputable(tc, ext, const_name(e))) {
+                throw exception(sstream() << "definition '" << n << "' is noncomputable, it depends on '" << const_name(e) << "'");
+            }
+            return true;
+        });
+}
+
+void initialize_noncomputable() {
+    g_ext           = new noncomputable_ext_reg();
+    g_noncomputable = new name("noncomputable");
+    g_key           = new std::string("ncomp");
+    register_module_object_reader(*g_key, noncomputable_reader);
+}
+
+void finalize_noncomputable() {
+    delete g_key;
+    delete g_noncomputable;
+    delete g_ext;
+}
+}

src/library/noncomputable.h

@@ -0,0 +1,19 @@
+/*
+Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#pragma once
+#include "kernel/environment.h"
+
+namespace lean {
+/** \brief Return true if \c n is noncomputable */
+bool is_noncomputable(environment const & env, name const & n);
+/** \brief Mark \c n as noncomputable */
+environment mark_noncomputable(environment const & env, name const & n);
+/** \brief Throw an exception if \c n depends on a noncomputable definition */
+void validate_computable_definition(environment const & env, name const & n);
+void initialize_noncomputable();
+void finalize_noncomputable();
+}