model: new metamodel

[nit.git] / src / modelbuilder.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Copyright 2012 Jean Privat <jean@pryen.org>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Load nit source files and build the associated model
#
# FIXME better doc
#
# FIXME split this module into submodules
# FIXME add missing error checks
module modelbuilder

import parser
import model
import poset
import opts
import toolcontext

###

redef class ToolContext
        # Option --path
        readable var _opt_path: OptionArray = new OptionArray("Set include path for loaders (may be used more than once)", "-I", "--path")

        # Option --only-metamodel
        readable var _opt_only_metamodel: OptionBool = new OptionBool("Stop after meta-model processing", "--only-metamodel")

        # Option --only-parse
        readable var _opt_only_parse: OptionBool = new OptionBool("Only proceed to parse step of loaders", "--only-parse")

        redef init
        do
                super
                option_context.add_option(opt_path, opt_only_parse, opt_only_metamodel)
        end
end

# A model builder know how to load nit source files and build the associated model
# The important function is `parse_and_build' that does all the job.
# The others function can be used for specific tasks
class ModelBuilder
        # The model where new modules, classes and properties are added
        var model: Model

        # The toolcontext used to control the interaction with the user (getting options and displaying messages)
        var toolcontext: ToolContext

        # Instantiate a modelbuilder for a model and a toolcontext
        # Important, the options of the toolcontext must be correctly set (parse_option already called)
        init(model: Model, toolcontext: ToolContext)
        do
                self.model = model
                self.toolcontext = toolcontext

                # Setup the paths value
                paths.append(toolcontext.opt_path.value)

                var path_env = once ("NIT_PATH".to_symbol).environ
                if not path_env.is_empty then
                        paths.append(path_env.split_with(':'))
                end

                path_env = once ("NIT_DIR".to_symbol).environ
                if not path_env.is_empty then
                        var libname = "{path_env}/lib"
                        if libname.file_exists then paths.add(libname)
                end

                var libname = "{sys.program_name.dirname}/../lib"
                if libname.file_exists then paths.add(libname.simplify_path)
        end

        # Load and analyze a bunch of modules.
        # `modules' can contains filenames or module names.
        # Imported modules are automatically loaded, builds and analysed.
        # The result is the corresponding built modules.
        # Errors and warnings are printed with the toolcontext.
        #
        # FIXME: Maybe just let the client do the loop (instead of playing with Sequences)
        fun parse_and_build(modules: Sequence[String]): Array[MModule]
        do
                var time0 = get_time
                # Parse and recursively load
                self.toolcontext.info("*** PARSE ***", 1)
                var mmodules = new Array[MModule]
                for a in modules do
                        var nmodule = self.load_module(null, a)
                        if nmodule == null then continue # Skip error
                        mmodules.add(nmodule.mmodule.as(not null))
                end
                var time1 = get_time
                self.toolcontext.info("*** END PARSE: {time1-time0} ***", 2)

                self.toolcontext.check_errors

                # Build the model
                self.toolcontext.info("*** BUILD MODEL ***", 1)
                self.build_all_classes
                var time2 = get_time
                self.toolcontext.info("*** END BUILD MODEL: {time2-time1} ***", 2)

                self.toolcontext.check_errors

                return mmodules
        end

        # Return a class named `name' visible by the module `mmodule'.
        # Visibility in modules is correctly handled.
        # If no such a class exists, then null is returned.
        # If more than one class exists, then an error on `anode' is displayed and null is returned.
        # FIXME: add a way to handle class name conflict
        fun try_get_mclass_by_name(anode: ANode, mmodule: MModule, name: String): nullable MClass
        do
                var classes = model.get_mclasses_by_name(name)
                if classes == null then
                        return null
                end

                var res: nullable MClass = null
                for mclass in classes do
                        if not mmodule.in_importation <= mclass.intro_mmodule then continue
                        if not mmodule.is_visible(mclass.intro_mmodule, mclass.visibility) then continue
                        if res == null then
                                res = mclass
                        else
                                error(anode, "Ambigous class name '{name}'; conflict between {mclass.full_name} and {res.full_name}")
                                return null
                        end
                end
                return res
        end

        # Return a property named `name' on the type `mtype' visible in the module `mmodule'.
        # Visibility in modules is correctly handled.
        # Protected properties are returned (it is up to the caller to check and reject protected properties).
        # If no such a property exists, then null is returned.
        # If more than one property exists, then an error on `anode' is displayed and null is returned.
        # FIXME: add a way to handle property name conflict
        fun try_get_mproperty_by_name2(anode: ANode, mmodule: MModule, mtype: MType, name: String): nullable MProperty
        do
                var props = self.model.get_mproperties_by_name(name)
                if props == null then
                        return null
                end

                var cache = self.try_get_mproperty_by_name2_cache[mmodule, mtype, name]
                if cache != null then return cache

                var res: nullable MProperty = null
                var ress: nullable Array[MProperty] = null
                for mprop in props do
                        if not mtype.has_mproperty(mmodule, mprop) then continue
                        if not mmodule.is_visible(mprop.intro_mclassdef.mmodule, mprop.visibility) then continue
                        if res == null then
                                res = mprop
                        else
                                var restype = res.intro_mclassdef.bound_mtype
                                var mproptype = mprop.intro_mclassdef.bound_mtype
                                if restype.is_subtype(mmodule, null, mproptype) then
                                        # we keep res
                                else if mproptype.is_subtype(mmodule, null, restype) then
                                        res = mprop
                                else
                                        if ress == null then ress = new Array[MProperty]
                                        ress.add(mprop)
                                end
                        end
                end
                if ress != null then
                        var restype = res.intro_mclassdef.bound_mtype
                        for mprop in ress do
                                var mproptype = mprop.intro_mclassdef.bound_mtype
                                if not restype.is_subtype(mmodule, null, mproptype) then
                                        self.error(anode, "Ambigous property name '{name}' for {mtype}; conflict between {mprop.full_name} and {res.full_name}")
                                        return null
                                end
                        end
                end

                self.try_get_mproperty_by_name2_cache[mmodule, mtype, name] = res
                return res
        end

        private var try_get_mproperty_by_name2_cache: HashMap3[MModule, MType, String, nullable MProperty] = new HashMap3[MModule, MType, String, nullable MProperty]


        # Alias for try_get_mproperty_by_name2(anode, mclassdef.mmodule, mclassdef.mtype, name)
        fun try_get_mproperty_by_name(anode: ANode, mclassdef: MClassDef, name: String): nullable MProperty
        do
                return try_get_mproperty_by_name2(anode, mclassdef.mmodule, mclassdef.bound_mtype, name)
        end

        # The list of directories to search for top level modules
        # The list is initially set with :
        #   * the toolcontext --path option
        #   * the NIT_PATH environment variable
        #   * some heuristics including the NIT_DIR environment variable and the progname of the process
        # Path can be added (or removed) by the client
        var paths: Array[String] = new Array[String]

        # Get a module by its short name; if required, the module is loaded, parsed and its hierarchies computed.
        # If `mmodule' is set, then the module search starts from it up to the top level (see `paths');
        # if `mmodule' is null then the module is searched in the top level only.
        # If no module exists or there is a name conflict, then an error on `anode' is displayed and null is returned.
        # FIXME: add a way to handle module name conflict
        fun get_mmodule_by_name(anode: ANode, mmodule: nullable MModule, name: String): nullable MModule
        do
                var origmmodule = mmodule
                var modules = model.get_mmodules_by_name(name)

                var lastmodule = mmodule
                while mmodule != null do
                        var dirname = mmodule.location.file.filename.dirname

                        # Determine the owner
                        var owner: nullable MModule
                        if dirname.basename("") != mmodule.name then
                                owner = mmodule.direct_owner
                        else
                                owner = mmodule
                        end

                        # First, try the already known nested modules
                        if modules != null then
                                for candidate in modules do
                                        if candidate.direct_owner == owner then
                                                return candidate
                                        end
                                end
                        end

                        # Second, try the directory to find a file
                        var try_file = dirname + "/" + name + ".nit"
                        if try_file.file_exists then
                                var res = self.load_module(owner, try_file.simplify_path)
                                if res == null then return null # Forward error
                                return res.mmodule.as(not null)
                        end

                        # Third, try if the requested module is itself an owner
                        try_file = dirname + "/" + name + "/" + name + ".nit"
                        if try_file.file_exists then
                                var res = self.load_module(owner, try_file.simplify_path)
                                if res == null then return null # Forward error
                                return res.mmodule.as(not null)
                        end

                        lastmodule = mmodule
                        mmodule = mmodule.direct_owner
                end

                if modules != null then
                        for candidate in modules do
                                if candidate.direct_owner == null then
                                        return candidate
                                end
                        end
                end

                # Look at some known directories
                var lookpaths = self.paths

                # Look in the directory of the last module also (event if not in the path)
                if lastmodule != null then
                        var dirname = lastmodule.location.file.filename.dirname
                        if dirname.basename("") == lastmodule.name then
                                dirname = dirname.dirname
                        end
                        if not lookpaths.has(dirname) then
                                lookpaths = lookpaths.to_a
                                lookpaths.add(dirname)
                        end
                end

                var candidate: nullable String = null
                for dirname in lookpaths do
                        var try_file = (dirname + "/" + name + ".nit").simplify_path
                        if try_file.file_exists then
                                if candidate == null then
                                        candidate = try_file
                                else if candidate != try_file then
                                        error(anode, "Error: conflicting module file for {name}: {candidate} {try_file}")
                                end
                        end
                        try_file = (dirname + "/" + name + "/" + name + ".nit").simplify_path
                        if try_file.file_exists then
                                if candidate == null then
                                        candidate = try_file
                                else if candidate != try_file then
                                        error(anode, "Error: conflicting module file for {name}: {candidate} {try_file}")
                                end
                        end
                end
                if candidate == null then
                        if origmmodule != null then
                                error(anode, "Error: cannot find module {name} from {origmmodule}")
                        else
                                error(anode, "Error: cannot find module {name}")
                        end
                        return null
                end
                var res = self.load_module(mmodule, candidate)
                if res == null then return null # Forward error
                return res.mmodule.as(not null)
        end

        # Try to load a module using a path.
        # Display an error if there is a problem (IO / lexer / parser) and return null
        # Note: usually, you do not need this method, use `get_mmodule_by_name` instead.
        fun load_module(owner: nullable MModule, filename: String): nullable AModule
        do
                if not filename.file_exists then
                        self.toolcontext.error(null, "Error: file {filename} not found.")
                        return null
                end

                var x = if owner != null then owner.to_s else "."
                self.toolcontext.info("load module {filename} in {x}", 2)

                # Load the file
                var file = new IFStream.open(filename)
                var lexer = new Lexer(new SourceFile(filename, file))
                var parser = new Parser(lexer)
                var tree = parser.parse
                file.close

                # Handle lexer and parser error
                var nmodule = tree.n_base
                if nmodule == null then
                        var neof = tree.n_eof
                        assert neof isa AError
                        error(neof, neof.message)
                        return null
                end

                # Check the module name
                var mod_name = filename.basename(".nit")
                var decl = nmodule.n_moduledecl
                if decl == null then
                        #warning(nmodule, "Warning: Missing 'module' keyword") #FIXME: NOT YET FOR COMPATIBILITY
                else
                        var decl_name = decl.n_name.n_id.text
                        if decl_name != mod_name then
                                error(decl.n_name, "Error: module name missmatch; declared {decl_name} file named {mod_name}")
                        end
                end

                # Create the module
                var mmodule = new MModule(model, owner, mod_name, nmodule.location)
                nmodule.mmodule = mmodule
                nmodules.add(nmodule)
                self.mmodule2nmodule[mmodule] = nmodule

                build_module_importation(nmodule)

                return nmodule
        end

        # Analysis the module importation and fill the module_importation_hierarchy
        private fun build_module_importation(nmodule: AModule)
        do
                if nmodule.is_importation_done then return
                var mmodule = nmodule.mmodule.as(not null)
                var stdimport = true
                var imported_modules = new Array[MModule]
                for aimport in nmodule.n_imports do
                        stdimport = false
                        if not aimport isa AStdImport then
                                continue
                        end
                        var mod_name = aimport.n_name.n_id.text
                        var sup = self.get_mmodule_by_name(aimport.n_name, mmodule, mod_name)
                        if sup == null then continue # Skip error
                        imported_modules.add(sup)
                        var mvisibility = aimport.n_visibility.mvisibility
                        mmodule.set_visibility_for(sup, mvisibility)
                end
                if stdimport then
                        var mod_name = "standard"
                        var sup = self.get_mmodule_by_name(nmodule, null, mod_name)
                        if sup != null then # Skip error
                                imported_modules.add(sup)
                                mmodule.set_visibility_for(sup, public_visibility)
                        end
                end
                self.toolcontext.info("{mmodule} imports {imported_modules.join(", ")}", 3)
                mmodule.set_imported_mmodules(imported_modules)
                nmodule.is_importation_done = true
        end

        # All the loaded modules
        var nmodules: Array[AModule] = new Array[AModule]

        # Build the classes of all modules `nmodules'.
        private fun build_all_classes
        do
                for nmodule in self.nmodules do
                        build_classes(nmodule)
                end
        end

        # Visit the AST and create the MClass objects
        private fun build_a_mclass(nmodule: AModule, nclassdef: AClassdef)
        do
                var mmodule = nmodule.mmodule.as(not null)

                var name: String
                var nkind: nullable AClasskind
                var mkind: MClassKind
                var nvisibility: nullable AVisibility
                var mvisibility: nullable MVisibility
                var arity = 0
                if nclassdef isa AStdClassdef then
                        name = nclassdef.n_id.text
                        nkind = nclassdef.n_classkind
                        mkind = nkind.mkind
                        nvisibility = nclassdef.n_visibility
                        mvisibility = nvisibility.mvisibility
                        arity = nclassdef.n_formaldefs.length
                else if nclassdef isa ATopClassdef then
                        name = "Object"
                        nkind = null
                        mkind = interface_kind
                        nvisibility = null
                        mvisibility = public_visibility
                else if nclassdef isa AMainClassdef then
                        name = "Sys"
                        nkind = null
                        mkind = concrete_kind
                        nvisibility = null
                        mvisibility = public_visibility
                else
                        abort
                end

                var mclass = try_get_mclass_by_name(nclassdef, mmodule, name)
                if mclass == null then
                        mclass = new MClass(mmodule, name, arity, mkind, mvisibility)
                        #print "new class {mclass}"
                else if nclassdef isa AStdClassdef and nclassdef.n_kwredef == null then
                        error(nclassdef, "Redef error: {name} is an imported class. Add the redef keyword to refine it.")
                        return
                else if mclass.arity != arity then
                        error(nclassdef, "Redef error: Formal parameter arity missmatch; got {arity}, expected {mclass.arity}.")
                        return
                else if nkind != null and mkind != concrete_kind and mclass.kind != mkind then
                        error(nkind, "Error: refinement changed the kind from a {mclass.kind} to a {mkind}")
                else if nvisibility != null and mvisibility != public_visibility and mclass.visibility != mvisibility then
                        error(nvisibility, "Error: refinement changed the visibility from a {mclass.visibility} to a {mvisibility}")
                end
                nclassdef.mclass = mclass
        end

        # Visit the AST and create the MClassDef objects
        private fun build_a_mclassdef(nmodule: AModule, nclassdef: AClassdef)
        do
                var mmodule = nmodule.mmodule.as(not null)
                var objectclass = try_get_mclass_by_name(nmodule, mmodule, "Object")
                var mclass = nclassdef.mclass.as(not null)
                #var mclassdef = nclassdef.mclassdef.as(not null)

                var names = new Array[String]
                var bounds = new Array[MType]
                if nclassdef isa AStdClassdef and mclass.arity > 0 then
                        # Collect formal parameter names
                        for i in [0..mclass.arity[ do
                                var nfd = nclassdef.n_formaldefs[i]
                                var ptname = nfd.n_id.text
                                if names.has(ptname) then
                                        error(nfd, "Error: A formal parameter type `{ptname}' already exists")
                                        return
                                end
                                names.add(ptname)
                        end

                        # Revolve bound for formal parameter names
                        for i in [0..mclass.arity[ do
                                var nfd = nclassdef.n_formaldefs[i]
                                var nfdt = nfd.n_type
                                if nfdt != null then
                                        var bound = resolve_mtype(nclassdef, nfdt)
                                        if bound == null then return # Forward error
                                        if bound.need_anchor then
                                                # No F-bounds!
                                                error(nfd, "Error: Formal parameter type `{names[i]}' bounded with a formal parameter type")
                                        else
                                                bounds.add(bound)
                                        end
                                else if mclass.mclassdefs.is_empty then
                                        # No bound, then implicitely bound by nullable Object
                                        bounds.add(objectclass.mclass_type.as_nullable)
                                else
                                        # Inherit the bound
                                        bounds.add(mclass.mclassdefs.first.bound_mtype.as(MGenericType).arguments[i])
                                end
                        end
                end

                var bound_mtype = mclass.get_mtype(bounds)
                var mclassdef = new MClassDef(mmodule, bound_mtype, nclassdef.location, names)
                nclassdef.mclassdef = mclassdef
                self.mclassdef2nclassdef[mclassdef] = nclassdef

                if mclassdef.is_intro then
                        self.toolcontext.info("{mclassdef} introduces new {mclass.kind} {mclass.full_name}", 3)
                else
                        self.toolcontext.info("{mclassdef} refine {mclass.kind} {mclass.full_name}", 3)
                end
        end

        # Visit the AST and set the super-types of the MClass objects (ie compute the inheritance)
        private fun build_a_mclassdef_inheritance(nmodule: AModule, nclassdef: AClassdef)
        do
                var mmodule = nmodule.mmodule.as(not null)
                var objectclass = try_get_mclass_by_name(nmodule, mmodule, "Object")
                var mclass = nclassdef.mclass.as(not null)
                var mclassdef = nclassdef.mclassdef.as(not null)

                var specobject = true
                var supertypes = new Array[MClassType]
                if nclassdef isa AStdClassdef then
                        for nsc in nclassdef.n_superclasses do
                                specobject = false
                                var ntype = nsc.n_type
                                var mtype = resolve_mtype(nclassdef, ntype)
                                if mtype == null then continue # Skip because of error
                                if not mtype isa MClassType then
                                        error(ntype, "Error: supertypes cannot be a formal type")
                                        return
                                end
                                supertypes.add mtype
                                #print "new super : {mclass} < {mtype}"
                        end
                end
                if specobject and mclass.name != "Object" and objectclass != null and mclassdef.is_intro then
                        supertypes.add objectclass.mclass_type
                end

                mclassdef.set_supertypes(supertypes)
                if not supertypes.is_empty then self.toolcontext.info("{mclassdef} new super-types: {supertypes.join(", ")}", 3)
        end

        # Check the validity of the specialization heirarchy
        # FIXME Stub implementation
        private fun check_supertypes(nmodule: AModule, nclassdef: AClassdef)
        do
                var mmodule = nmodule.mmodule.as(not null)
                var objectclass = try_get_mclass_by_name(nmodule, mmodule, "Object")
                var mclass = nclassdef.mclass.as(not null)
                var mclassdef = nclassdef.mclassdef.as(not null)
        end

        # Build the classes of the module `nmodule'.
        # REQUIRE: classes of imported modules are already build. (let `build_all_classes' do the job)
        private fun build_classes(nmodule: AModule)
        do
                # Force building recursively
                if nmodule.build_classes_is_done then return
                var mmodule = nmodule.mmodule.as(not null)
                for imp in mmodule.in_importation.direct_greaters do
                        build_classes(mmodule2nmodule[imp])
                end

                # Create all classes
                for nclassdef in nmodule.n_classdefs do
                        self.build_a_mclass(nmodule, nclassdef)
                end

                # Create all classdefs
                for nclassdef in nmodule.n_classdefs do
                        self.build_a_mclassdef(nmodule, nclassdef)
                end

                # Create inheritance on all classdefs
                for nclassdef in nmodule.n_classdefs do
                        self.build_a_mclassdef_inheritance(nmodule, nclassdef)
                end

                # TODO: Check that the super-class is not intrusive

                # TODO: Check that the super-class is not already known (by transitivity)

                for nclassdef in nmodule.n_classdefs do
                        self.build_properties(nclassdef)
                end

                nmodule.build_classes_is_done = true
        end

        # Register the nmodule associated to each mmodule
        # FIXME: why not refine the MModule class with a nullable attribute?
        var mmodule2nmodule: HashMap[MModule, AModule] = new HashMap[MModule, AModule]
        # Register the nclassdef associated to each mclassdef
        # FIXME: why not refine the MClassDef class with a nullable attribute?
        var mclassdef2nclassdef: HashMap[MClassDef, AClassdef] = new HashMap[MClassDef, AClassdef]
        # Register the npropdef associated to each mpropdef
        # FIXME: why not refine the MPropDef class with a nullable attribute?
        var mpropdef2npropdef: HashMap[MPropDef, APropdef] = new HashMap[MPropDef, APropdef]

        # Build the properties of `nclassdef'.
        # REQUIRE: all superclasses are built.
        private fun build_properties(nclassdef: AClassdef)
        do
                # Force building recursively
                if nclassdef.build_properties_is_done then return
                var mclassdef = nclassdef.mclassdef.as(not null)
                if mclassdef.in_hierarchy == null then return # Skip error
                for superclassdef in mclassdef.in_hierarchy.direct_greaters do
                        build_properties(mclassdef2nclassdef[superclassdef])
                end

                for npropdef in nclassdef.n_propdefs do
                        npropdef.build_property(self, nclassdef)
                end
                for npropdef in nclassdef.n_propdefs do
                        npropdef.build_signature(self, nclassdef)
                end
                for npropdef in nclassdef.n_propdefs do
                        npropdef.check_signature(self, nclassdef)
                end
                process_default_constructors(nclassdef)
                nclassdef.build_properties_is_done = true
        end

        # Introduce or inherit default constructor
        # This is the last part of `build_properties'.
        private fun process_default_constructors(nclassdef: AClassdef)
        do
                var mclassdef = nclassdef.mclassdef.as(not null)

                # Are we a refinement
                if not mclassdef.is_intro then return

                # Is the class forbid constructors?
                if not mclassdef.mclass.kind.need_init then return

                # Is there already a constructor defined?
                for mpropdef in mclassdef.mpropdefs do
                        if not mpropdef isa MMethodDef then continue
                        if mpropdef.mproperty.is_init then return
                end

                if not nclassdef isa AStdClassdef then return

                var mmodule = nclassdef.mclassdef.mmodule
                # Do we inherit for a constructor?
                var combine = new Array[MMethod]
                var inhc: nullable MClass = null
                for st in mclassdef.supertypes do
                        var c = st.mclass
                        if not c.kind.need_init then continue
                        st = st.anchor_to(mmodule, nclassdef.mclassdef.bound_mtype)
                        var candidate = self.try_get_mproperty_by_name2(nclassdef, mmodule, st, "init").as(nullable MMethod)
                        if candidate != null and candidate.intro.msignature.arity == 0 then
                                combine.add(candidate)
                                continue
                        end
                        var inhc2 = c.inherit_init_from
                        if inhc2 == null then inhc2 = c
                        if inhc2 == inhc then continue
                        if inhc != null then
                                self.error(nclassdef, "Cannot provide a defaut constructor: conflict for {inhc} and {c}")
                        else
                                inhc = inhc2
                        end
                end
                if combine.is_empty and inhc != null then
                        # TODO: actively inherit the consturctor
                        self.toolcontext.info("{mclassdef} inherits all constructors from {inhc}", 3)
                        mclassdef.mclass.inherit_init_from = inhc
                        return
                end
                if not combine.is_empty and inhc != null then
                        self.error(nclassdef, "Cannot provide a defaut constructor: conflict for {combine.join(", ")} and {inhc}")
                        return
                end

                if not combine.is_empty then
                        nclassdef.super_inits = combine
                        var mprop = new MMethod(mclassdef, "init", mclassdef.mclass.visibility)
                        var mpropdef = new MMethodDef(mclassdef, mprop, nclassdef.location)
                        var param_names = new Array[String]
                        var param_types = new Array[MType]
                        var msignature = new MSignature(param_names, param_types, null, -1)
                        mpropdef.msignature = msignature
                        mprop.is_init = true
                        nclassdef.mfree_init = mpropdef
                        self.toolcontext.info("{mclassdef} gets a free empty constructor {mpropdef}{msignature}", 3)
                        return
                end

                # Collect undefined attributes
                var param_names = new Array[String]
                var param_types = new Array[MType]
                for npropdef in nclassdef.n_propdefs do
                        if npropdef isa AAttrPropdef and npropdef.n_expr == null then
                                param_names.add(npropdef.mpropdef.mproperty.name.substring_from(1))
                                var ret_type = npropdef.mpropdef.static_mtype
                                if ret_type == null then return
                                param_types.add(ret_type)
                        end
                end

                var mprop = new MMethod(mclassdef, "init", mclassdef.mclass.visibility)
                var mpropdef = new MMethodDef(mclassdef, mprop, nclassdef.location)
                var msignature = new MSignature(param_names, param_types, null, -1)
                mpropdef.msignature = msignature
                mprop.is_init = true
                nclassdef.mfree_init = mpropdef
                self.toolcontext.info("{mclassdef} gets a free constructor for attributes {mpropdef}{msignature}", 3)
        end

        # Return the static type associated to the node `ntype'.
        # `classdef' is the context where the call is made (used to understand formal types)
        # The mmodule used as context is `nclassdef.mmodule'
        # In case of problem, an error is displayed on `ntype' and null is returned.
        # FIXME: the name "resolve_mtype" is awful
        fun resolve_mtype(nclassdef: AClassdef, ntype: AType): nullable MType
        do
                var name = ntype.n_id.text
                var mclassdef = nclassdef.mclassdef
                var mmodule = nclassdef.parent.as(AModule).mmodule.as(not null)
                var res: MType

                # Check virtual type
                if mclassdef != null then
                        var prop = try_get_mproperty_by_name(ntype, mclassdef, name).as(nullable MVirtualTypeProp)
                        if prop != null then
                                if not ntype.n_types.is_empty then
                                        error(ntype, "Type error: formal type {name} cannot have formal parameters.")
                                end
                                res = prop.mvirtualtype
                                if ntype.n_kwnullable != null then res = res.as_nullable
                                return res
                        end
                end

                # Check parameter type
                if mclassdef != null and mclassdef.parameter_names.has(name) then
                        if not ntype.n_types.is_empty then
                                error(ntype, "Type error: formal type {name} cannot have formal parameters.")
                        end
                        for i in [0..mclassdef.parameter_names.length[ do
                                if mclassdef.parameter_names[i] == name then
                                        res = mclassdef.mclass.mclass_type.as(MGenericType).arguments[i]
                                        if ntype.n_kwnullable != null then res = res.as_nullable
                                        return res
                                end
                        end
                        abort
                end

                # Check class
                var mclass = try_get_mclass_by_name(ntype, mmodule, name)
                if mclass != null then
                        var arity = ntype.n_types.length
                        if arity != mclass.arity then
                                if arity == 0 then
                                        error(ntype, "Type error: '{name}' is a generic class.")
                                else if mclass.arity == 0 then
                                        error(ntype, "Type error: '{name}' is not a generic class.")
                                else
                                        error(ntype, "Type error: '{name}' has {mclass.arity} parameters ({arity} are provided).")
                                end
                                return null
                        end
                        if arity == 0 then
                                res = mclass.mclass_type
                                if ntype.n_kwnullable != null then res = res.as_nullable
                                return res
                        else
                                var mtypes = new Array[MType]
                                for nt in ntype.n_types do
                                        var mt = resolve_mtype(nclassdef, nt)
                                        if mt == null then return null # Forward error
                                        mtypes.add(mt)
                                end
                                res = mclass.get_mtype(mtypes)
                                if ntype.n_kwnullable != null then res = res.as_nullable
                                return res
                        end
                end

                # If everything fail, then give up :(
                error(ntype, "Type error: class {name} not found in module {mmodule}.")
                return null
        end

        # Helper function to display an error on a node.
        # Alias for `self.toolcontext.error(n.hot_location, text)'
        fun error(n: ANode, text: String)
        do
                self.toolcontext.error(n.hot_location, text)
        end

        # Helper function to display a warning on a node.
        # Alias for: `self.toolcontext.warning(n.hot_location, text)'
        fun warning(n: ANode, text: String)
        do
                self.toolcontext.warning(n.hot_location, text)
        end
end

redef class AModule
        # The associated MModule once build by a `ModelBuilder'
        var mmodule: nullable MModule
        # Flag that indicate if the importation is already completed
        var is_importation_done: Bool = false
        # Flag that indicate if the class and prop building is already completed
        var build_classes_is_done: Bool = false
end

redef class MClass
        # The class whose self inherit all the constructors.
        # FIXME: this is needed to implement the crazy constructor mixin thing of the of old compiler. We need to think what to do with since this cannot stay in the modelbuilder
        var inherit_init_from: nullable MClass = null
end

redef class AClassdef
        # The associated MClass once build by a `ModelBuilder'
        var mclass: nullable MClass
        # The associated MClassDef once build by a `ModelBuilder'
        var mclassdef: nullable MClassDef
        var build_properties_is_done: Bool = false
        # The list of super-constructor to call at the start of the free constructor
        # FIXME: this is needed to implement the crazy constructor thing of the of old compiler. We need to think what to do with since this cannot stay in the modelbuilder
        var super_inits: nullable Collection[MMethod] = null

        # The free init (implicitely constructed by the class if required)
        var mfree_init: nullable MMethodDef = null
end

redef class AClasskind
        # The class kind associated with the AST node class
        private fun mkind: MClassKind is abstract
end
redef class AConcreteClasskind
        redef fun mkind do return concrete_kind
end
redef class AAbstractClasskind
        redef fun mkind do return abstract_kind
end
redef class AInterfaceClasskind
        redef fun mkind do return interface_kind
end
redef class AEnumClasskind
        redef fun mkind do return enum_kind
end
redef class AExternClasskind
        redef fun mkind do return extern_kind
end

redef class AVisibility
        # The visibility level associated with the AST node class
        private fun mvisibility: MVisibility is abstract
end
redef class AIntrudeVisibility
        redef fun mvisibility do return intrude_visibility
end
redef class APublicVisibility
        redef fun mvisibility do return public_visibility
end
redef class AProtectedVisibility
        redef fun mvisibility do return protected_visibility
end
redef class APrivateVisibility
        redef fun mvisibility do return private_visibility
end


#

redef class Prod
        # Join the text of all tokens
        # Used to get the 'real name' of method definitions.
        fun collect_text: String
        do
                var v = new TextCollectorVisitor
                v.enter_visit(self)
                assert v.text != ""
                return v.text
        end
end

private class TextCollectorVisitor
        super Visitor
        var text: String = ""
        redef fun visit(n)
        do
                if n isa Token then text += n.text
                n.visit_all(self)
        end
end

redef class APropdef
        private fun build_property(modelbuilder: ModelBuilder, nclassdef: AClassdef)
        do
        end
        private fun build_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef)
        do
        end
        private fun check_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef)
        do
        end
        private fun new_property_visibility(modelbuilder: ModelBuilder, nclassdef: AClassdef, nvisibility: nullable AVisibility): MVisibility
        do
                var mvisibility = public_visibility
                if nvisibility != null then mvisibility = nvisibility.mvisibility
                if nclassdef.mclassdef.mclass.visibility == private_visibility then
                        if mvisibility == protected_visibility then
                                assert nvisibility != null
                                modelbuilder.error(nvisibility, "Error: The only legal visibility for properties in a private class is private.")
                        else if mvisibility == private_visibility then
                                assert nvisibility != null
                                # Not yet
                                # modelbuilder.warning(nvisibility, "Warning: private is unrequired since the only legal visibility for properties in a private class is private.")
                        end
                        mvisibility = private_visibility
                end
                return mvisibility
        end

        private fun check_redef_property_visibility(modelbuilder: ModelBuilder, nclassdef: AClassdef, nvisibility: nullable AVisibility, mprop: MProperty)
        do
                if nvisibility == null then return
                var mvisibility = nvisibility.mvisibility
                if mvisibility != mprop.visibility and mvisibility != public_visibility then
                                modelbuilder.error(nvisibility, "Error: redefinition changed the visibility from a {mprop.visibility} to a {mvisibility}")
                end
        end

        private fun check_redef_keyword(modelbuilder: ModelBuilder, nclassdef: AClassdef, kwredef: nullable Token, need_redef: Bool, mprop: MProperty)
        do
                if kwredef == null then
                        if need_redef then
                                modelbuilder.error(self, "Redef error: {nclassdef.mclassdef.mclass}::{mprop.name} is an inherited property. To redefine it, add the redef keyword.")
                        end
                else
                        if not need_redef then
                                modelbuilder.error(self, "Error: No property {nclassdef.mclassdef.mclass}::{mprop.name} is inherited. Remove the redef keyword to define a new property.")
                        end
                end
        end
end

redef class AMethPropdef
        # The associated MMethodDef once build by a `ModelBuilder'
        var mpropdef: nullable MMethodDef

        # The associated super init if any
        var super_init: nullable MMethod
        redef fun build_property(modelbuilder, nclassdef)
        do
                var is_init = self isa AInitPropdef
                var mclassdef = nclassdef.mclassdef.as(not null)
                var name: String
                var amethodid = self.n_methid
                var name_node: ANode
                if amethodid == null then
                        if self isa AMainMethPropdef then
                                name = "main"
                                name_node = self
                        else if self isa AConcreteInitPropdef then
                                name = "init"
                                name_node = self.n_kwinit
                        else if self isa AExternInitPropdef then
                                name = "new"
                                name_node = self.n_kwnew
                        else
                                abort
                        end
                else if amethodid isa AIdMethid then
                        name = amethodid.n_id.text
                        name_node = amethodid
                else
                        # operator, bracket or assign
                        name = amethodid.collect_text
                        name_node = amethodid

                        if name == "-" and self.n_signature.n_params.length == 0 then
                                name = "unary -"
                        end
                end

                var mprop: nullable MMethod = null
                if not is_init or n_kwredef != null then mprop = modelbuilder.try_get_mproperty_by_name(name_node, mclassdef, name).as(nullable MMethod)
                if mprop == null then
                        var mvisibility = new_property_visibility(modelbuilder, nclassdef, self.n_visibility)
                        mprop = new MMethod(mclassdef, name, mvisibility)
                        mprop.is_init = is_init
                        self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, false, mprop)
                else
                        if n_kwredef == null then
                                if self isa AMainMethPropdef then
                                        # no warning
                                else
                                        self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, true, mprop)
                                end
                        end
                        check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mprop)
                end

                var mpropdef = new MMethodDef(mclassdef, mprop, self.location)

                self.mpropdef = mpropdef
                modelbuilder.mpropdef2npropdef[mpropdef] = self
                if mpropdef.is_intro then
                        modelbuilder.toolcontext.info("{mpropdef} introduces new method {mprop.full_name}", 3)
                else
                        modelbuilder.toolcontext.info("{mpropdef} redefines method {mprop.full_name}", 3)
                end
        end

        redef fun build_signature(modelbuilder, nclassdef)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skiped
                var mmodule = mpropdef.mclassdef.mmodule
                var nsig = self.n_signature

                # Retrieve info from the signature AST
                var param_names = new Array[String] # Names of parameters from the AST
                var param_types = new Array[MType] # Types of parameters from the AST
                var vararg_rank = -1
                var ret_type: nullable MType = null # Return type from the AST
                if nsig != null then
                        for np in nsig.n_params do
                                param_names.add(np.n_id.text)
                                var ntype = np.n_type
                                if ntype != null then
                                        var mtype = modelbuilder.resolve_mtype(nclassdef, ntype)
                                        if mtype == null then return # Skip error
                                        for i in [0..param_names.length-param_types.length[ do
                                                param_types.add(mtype)
                                        end
                                        if np.n_dotdotdot != null then
                                                if vararg_rank != -1 then
                                                        modelbuilder.error(np, "Error: {param_names[vararg_rank]} is already a vararg")
                                                else
                                                        vararg_rank = param_names.length - 1
                                                end
                                        end
                                end
                        end
                        var ntype = nsig.n_type
                        if ntype != null then
                                ret_type = modelbuilder.resolve_mtype(nclassdef, ntype)
                                if ret_type == null then return # Skip errir
                        end
                end

                # Look for some signature to inherit
                # FIXME: do not inherit from the intro, but from the most specific
                var msignature: nullable MSignature = null
                if not mpropdef.is_intro then
                        msignature = mpropdef.mproperty.intro.msignature
                        if msignature == null then return # Skip error
                else if mpropdef.mproperty.is_init then
                        # FIXME UGLY: inherit signature from a super-constructor
                        for msupertype in nclassdef.mclassdef.supertypes do
                                msupertype = msupertype.anchor_to(mmodule, nclassdef.mclassdef.bound_mtype)
                                var candidate = modelbuilder.try_get_mproperty_by_name2(self, mmodule, msupertype, mpropdef.mproperty.name)
                                if candidate != null then
                                        if msignature == null then
                                                msignature = candidate.intro.as(MMethodDef).msignature
                                        end
                                end
                        end
                end

                # Inherit the signature
                if msignature != null and param_names.length != param_types.length and param_names.length == msignature.arity and param_types.length == 0 then
                        # Parameters are untyped, thus inherit them
                        param_types = msignature.parameter_mtypes
                        vararg_rank = msignature.vararg_rank
                end
                if msignature != null and ret_type == null then
                        ret_type = msignature.return_mtype
                end

                if param_names.length != param_types.length then
                        # Some parameters are typed, other parameters are not typed.
                        modelbuilder.warning(nsig.n_params[param_types.length], "Error: Untyped parameter `{param_names[param_types.length]}'.")
                        return
                end

                msignature = new MSignature(param_names, param_types, ret_type, vararg_rank)
                mpropdef.msignature = msignature
        end

        redef fun check_signature(modelbuilder, nclassdef)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skiped
                var mmodule = mpropdef.mclassdef.mmodule
                var nsig = self.n_signature
                var mysignature = self.mpropdef.msignature
                if mysignature == null then return # Error thus skiped

                # Lookup for signature in the precursor
                # FIXME all precursors should be considered
                if not mpropdef.is_intro then
                        var msignature = mpropdef.mproperty.intro.msignature
                        if msignature == null then return

                        if mysignature.arity != msignature.arity then
                                var node: ANode
                                if nsig != null then node = nsig else node = self
                                modelbuilder.error(node, "Redef Error: {mysignature.arity} parameters found, {msignature.arity} expected. Signature is {mpropdef}{msignature}")
                                return
                        end
                        var precursor_ret_type = msignature.return_mtype
                        var ret_type = mysignature.return_mtype
                        if ret_type != null and precursor_ret_type == null then
                                modelbuilder.error(nsig.n_type.as(not null), "Redef Error: {mpropdef.mproperty} is a procedure, not a function.")
                                return
                        end

                        if mysignature.arity > 0 then
                                # Check parameters types
                                for i in [0..mysignature.arity[ do
                                        var myt = mysignature.parameter_mtypes[i]
                                        var prt = msignature.parameter_mtypes[i]
                                        if not myt.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, prt) and
                                                        not prt.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, myt) then
                                                modelbuilder.error(nsig.n_params[i], "Redef Error: Wrong type for parameter `{mysignature.parameter_names[i]}'. found {myt}, expected {prt}.")
                                        end
                                end
                        end
                        if precursor_ret_type != null then
                                if ret_type == null then
                                        # Inherit the return type
                                        ret_type = precursor_ret_type
                                else if not ret_type.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, precursor_ret_type) then
                                        modelbuilder.error(nsig.n_type.as(not null), "Redef Error: Wrong return type. found {ret_type}, expected {precursor_ret_type}.")
                                end
                        end
                end
        end
end

redef class AAttrPropdef
        # The associated MAttributeDef once build by a `ModelBuilder'
        var mpropdef: nullable MAttributeDef
        # The associated getter (read accessor) if any
        var mreadpropdef: nullable MMethodDef
        # The associated setter (write accessor) if any
        var mwritepropdef: nullable MMethodDef
        redef fun build_property(modelbuilder, nclassdef)
        do
                var mclassdef = nclassdef.mclassdef.as(not null)
                var mclass = mclassdef.mclass

                var name: String
                if self.n_id != null then
                        name = self.n_id.text
                else
                        name = self.n_id2.text
                end

                if mclass.kind == interface_kind or mclassdef.mclass.kind == enum_kind then
                        modelbuilder.error(self, "Error: Attempt to define attribute {name} in the interface {mclass}.")
                else if mclass.kind == enum_kind then
                        modelbuilder.error(self, "Error: Attempt to define attribute {name} in the enum class {mclass}.")
                end

                var nid = self.n_id
                if nid != null then
                        # Old attribute style
                        var mprop = modelbuilder.try_get_mproperty_by_name(nid, mclassdef, name)
                        if mprop == null then
                                var mvisibility = new_property_visibility(modelbuilder, nclassdef, self.n_visibility)
                                mprop = new MAttribute(mclassdef, name, mvisibility)
                                self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, false, mprop)
                        else
                                assert mprop isa MAttribute
                                check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mprop)
                                self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, true, mprop)
                        end
                        var mpropdef = new MAttributeDef(mclassdef, mprop, self.location)
                        self.mpropdef = mpropdef
                        modelbuilder.mpropdef2npropdef[mpropdef] = self

                        var nreadable = self.n_readable
                        if nreadable != null then
                                var readname = name.substring_from(1)
                                var mreadprop = modelbuilder.try_get_mproperty_by_name(nid, mclassdef, readname).as(nullable MMethod)
                                if mreadprop == null then
                                        var mvisibility = new_property_visibility(modelbuilder, nclassdef, nreadable.n_visibility)
                                        mreadprop = new MMethod(mclassdef, readname, mvisibility)
                                        self.check_redef_keyword(modelbuilder, nclassdef, nreadable.n_kwredef, false, mreadprop)
                                else
                                        self.check_redef_keyword(modelbuilder, nclassdef, nreadable.n_kwredef, true, mreadprop)
                                        check_redef_property_visibility(modelbuilder, nclassdef, nreadable.n_visibility, mreadprop)
                                end
                                var mreadpropdef = new MMethodDef(mclassdef, mreadprop, self.location)
                                self.mreadpropdef = mreadpropdef
                                modelbuilder.mpropdef2npropdef[mreadpropdef] = self
                        end

                        var nwritable = self.n_writable
                        if nwritable != null then
                                var writename = name.substring_from(1) + "="
                                var mwriteprop = modelbuilder.try_get_mproperty_by_name(nid, mclassdef, writename).as(nullable MMethod)
                                if mwriteprop == null then
                                        var mvisibility = new_property_visibility(modelbuilder, nclassdef, nwritable.n_visibility)
                                        mwriteprop = new MMethod(mclassdef, writename, mvisibility)
                                        self.check_redef_keyword(modelbuilder, nclassdef, nwritable.n_kwredef, false, mwriteprop)
                                else
                                        self.check_redef_keyword(modelbuilder, nclassdef, nwritable.n_kwredef, true, mwriteprop)
                                        check_redef_property_visibility(modelbuilder, nclassdef, nwritable.n_visibility, mwriteprop)
                                end
                                var mwritepropdef = new MMethodDef(mclassdef, mwriteprop, self.location)
                                self.mwritepropdef = mwritepropdef
                                modelbuilder.mpropdef2npropdef[mwritepropdef] = self
                        end
                else
                        # New attribute style
                        var nid2 = self.n_id2.as(not null)
                        var mprop = new MAttribute(mclassdef, "@" + name, none_visibility)
                        var mpropdef = new MAttributeDef(mclassdef, mprop, self.location)
                        self.mpropdef = mpropdef
                        modelbuilder.mpropdef2npropdef[mpropdef] = self

                        var readname = name
                        var mreadprop = modelbuilder.try_get_mproperty_by_name(nid2, mclassdef, readname).as(nullable MMethod)
                        if mreadprop == null then
                                var mvisibility = new_property_visibility(modelbuilder, nclassdef, self.n_visibility)
                                mreadprop = new MMethod(mclassdef, readname, mvisibility)
                                self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, false, mreadprop)
                        else
                                self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, true, mreadprop)
                                check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mreadprop)
                        end
                        var mreadpropdef = new MMethodDef(mclassdef, mreadprop, self.location)
                        self.mreadpropdef = mreadpropdef
                        modelbuilder.mpropdef2npropdef[mreadpropdef] = self

                        var writename = name + "="
                        var nwritable = self.n_writable
                        var mwriteprop = modelbuilder.try_get_mproperty_by_name(nid2, mclassdef, writename).as(nullable MMethod)
                        var nwkwredef: nullable Token = null
                        if nwritable != null then nwkwredef = nwritable.n_kwredef
                        if mwriteprop == null then
                                var mvisibility
                                if nwritable != null then
                                        mvisibility = new_property_visibility(modelbuilder, nclassdef, nwritable.n_visibility)
                                else
                                        mvisibility = private_visibility
                                end
                                mwriteprop = new MMethod(mclassdef, writename, mvisibility)
                                self.check_redef_keyword(modelbuilder, nclassdef, nwkwredef, false, mwriteprop)
                        else
                                self.check_redef_keyword(modelbuilder, nclassdef, nwkwredef, true, mwriteprop)
                                if nwritable != null then
                                        check_redef_property_visibility(modelbuilder, nclassdef, nwritable.n_visibility, mwriteprop)
                                end
                        end
                        var mwritepropdef = new MMethodDef(mclassdef, mwriteprop, self.location)
                        self.mwritepropdef = mwritepropdef
                        modelbuilder.mpropdef2npropdef[mwritepropdef] = self
                end
        end

        redef fun build_signature(modelbuilder, nclassdef)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skiped
                var mmodule = mpropdef.mclassdef.mmodule
                var mtype: nullable MType = null

                var ntype = self.n_type
                if ntype != null then
                        mtype = modelbuilder.resolve_mtype(nclassdef, ntype)
                        if mtype == null then return
                end

                if mtype == null then
                        modelbuilder.warning(self, "Error: Untyped attribute {mpropdef}")
                        return
                end

                mpropdef.static_mtype = mtype

                var mreadpropdef = self.mreadpropdef
                if mreadpropdef != null then
                        var msignature = new MSignature(new Array[String], new Array[MType], mtype, -1)
                        mreadpropdef.msignature = msignature
                end

                var msritepropdef = self.mwritepropdef
                if mwritepropdef != null then
                        var name: String
                        if n_id != null then
                                name = n_id.text.substring_from(1)
                        else
                                name = n_id2.text
                        end
                        var msignature = new MSignature([name], [mtype], null, -1)
                        mwritepropdef.msignature = msignature
                end
        end

        redef fun check_signature(modelbuilder, nclassdef)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skiped
                var mmodule = mpropdef.mclassdef.mmodule
                var ntype = self.n_type
                var mtype = self.mpropdef.static_mtype
                if mtype == null then return # Error thus skiped

                # Lookup for signature in the precursor
                # FIXME all precursors should be considered
                if not mpropdef.is_intro then
                        var precursor_type = mpropdef.mproperty.intro.static_mtype
                        if precursor_type == null then return

                        if mtype != precursor_type then
                                modelbuilder.error(ntype.as(not null), "Redef Error: Wrong static type. found {mtype}, expected {precursor_type}.")
                                return
                        end
                end

                # FIXME: Check getter ans setter
        end
end

redef class ATypePropdef
        # The associated MVirtualTypeDef once build by a `ModelBuilder'
        var mpropdef: nullable MVirtualTypeDef
        redef fun build_property(modelbuilder, nclassdef)
        do
                var mclassdef = nclassdef.mclassdef.as(not null)
                var name = self.n_id.text
                var mprop = modelbuilder.try_get_mproperty_by_name(self.n_id, mclassdef, name)
                if mprop == null then
                        var mvisibility = new_property_visibility(modelbuilder, nclassdef, self.n_visibility)
                        mprop = new MVirtualTypeProp(mclassdef, name, mvisibility)
                        self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, false, mprop)
                else
                        self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, true, mprop)
                        assert mprop isa MVirtualTypeProp
                        check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mprop)
                end
                var mpropdef = new MVirtualTypeDef(mclassdef, mprop, self.location)
                self.mpropdef = mpropdef
        end

        redef fun build_signature(modelbuilder, nclassdef)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skiped
                var mmodule = mpropdef.mclassdef.mmodule
                var mtype: nullable MType = null

                var ntype = self.n_type
                mtype = modelbuilder.resolve_mtype(nclassdef, ntype)
                if mtype == null then return

                mpropdef.bound = mtype
                # print "{mpropdef}: {mtype}"
        end

        redef fun check_signature(modelbuilder, nclassdef)
        do
                var bound = self.mpropdef.bound

                # Fast case: the bound is not a formal type
                if not bound isa MVirtualType then return

                var mmodule = nclassdef.mclassdef.mmodule
                var anchor = nclassdef.mclassdef.bound_mtype

                # Slow case: progress on each resolution until: (i) we loop, or (ii) we found a non formal type
                var seen = [self.mpropdef.mproperty.mvirtualtype]
                loop
                        if seen.has(bound) then
                                seen.add(bound)
                                modelbuilder.error(self, "Error: circularity of virtual type definition: {seen.join(" -> ")}")
                                return
                        end
                        seen.add(bound)
                        var next = bound.lookup_bound(mmodule, anchor)
                        if not next isa MVirtualType then return
                        bound = next
                end
        end
end