[nit.git] / src / modelize_property.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.

# Analysis and verification of property definitions to instantiate model element
module modelize_property

import modelize_class

redef class ToolContext
        var modelize_property_phase: Phase = new ModelizePropertyPhase(self, [modelize_class_phase])
end

private class ModelizePropertyPhase
        super Phase
        redef fun process_nmodule(nmodule)
        do
                for nclassdef in nmodule.n_classdefs do
                        toolcontext.modelbuilder.build_properties(nclassdef)
                end
        end
end

redef class ModelBuilder
        # 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
                nclassdef.build_properties_is_done = true
                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)
        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, "Error: 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, "Error: 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 mparameters = new Array[MParameter]
                        var msignature = new MSignature(mparameters, null)
                        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 mparameters = new Array[MParameter]
                for npropdef in nclassdef.n_propdefs do
                        if npropdef isa AAttrPropdef and npropdef.n_expr == null then
                                if npropdef.mpropdef == null then return # Skip broken attribute
                                var paramname = npropdef.mpropdef.mproperty.name.substring_from(1)
                                var ret_type = npropdef.mpropdef.static_mtype
                                if ret_type == null then return
                                var mparameter = new MParameter(paramname, ret_type, false)
                                mparameters.add(mparameter)
                        end
                end

                var mprop = new MMethod(mclassdef, "init", mclassdef.mclass.visibility)
                var mpropdef = new MMethodDef(mclassdef, mprop, nclassdef.location)
                var msignature = new MSignature(mparameters, null)
                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
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 MClassDef
        private var propdef_names = new HashSet[String]
end

redef class AClassdef
        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

        # What is the `APropdef` associated to a `MProperty`?
        # Used to check multiple definition of a property.
        var mprop2npropdef: Map[MProperty, APropdef] = new HashMap[MProperty, APropdef]
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
        # The associated main model entity
        type MPROPDEF: MPropDef

        # The associated propdef once build by a `ModelBuilder`
        var mpropdef: nullable MPROPDEF writable

        private fun build_property(modelbuilder: ModelBuilder, nclassdef: AClassdef) is abstract
        private fun build_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef) is abstract
        private fun check_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef) is abstract
        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 mvisibility == intrude_visibility then
                                modelbuilder.error(nvisibility, "Error: intrude is not a legal visibility for properties.")
                                mvisibility = public_visibility
                        end
                end
                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): Bool
        do
                if nclassdef.mprop2npropdef.has_key(mprop) then
                        modelbuilder.error(self, "Error: A property {mprop} is already defined in class {nclassdef.mclassdef.mclass}.")
                        return false
                end
                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.")
                                return false
                        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.")
                                return false
                        end
                end
                return true
        end

end

redef class ASignature
        # Is the model builder has correctly visited the signature
        var is_visited = false
        # Names of parameters from the AST
        # REQUIRE: is_visited
        var param_names = new Array[String]
        # Types of parameters from the AST
        # REQUIRE: is_visited
        var param_types = new Array[MType]
        # Rank of the vararg (of -1 if none)
        # REQUIRE: is_visited
        var vararg_rank: Int = -1
        # Return type
        var ret_type: nullable MType = null

        # Visit and fill information about a signature
        private fun visit_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef): Bool
        do
                var param_names = self.param_names
                var param_types = self.param_types
                for np in self.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 false # 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 self.vararg_rank != -1 then
                                                modelbuilder.error(np, "Error: {param_names[self.vararg_rank]} is already a vararg")
                                                return false
                                        else
                                                self.vararg_rank = param_names.length - 1
                                        end
                                end
                        end
                end
                var ntype = self.n_type
                if ntype != null then
                        self.ret_type = modelbuilder.resolve_mtype(nclassdef, ntype)
                        if self.ret_type == null then return false # Skip errir
                end

                self.is_visited = true
                return true
        end

        # Build a visited signature
        fun build_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef): nullable MSignature
        do
                if param_names.length != param_types.length then
                        # Some parameters are typed, other parameters are not typed.
                        modelbuilder.error(self.n_params[param_types.length], "Error: Untyped parameter `{param_names[param_types.length]}'.")
                        return null
                end

                var mparameters = new Array[MParameter]
                for i in [0..param_names.length[ do
                        var mparameter = new MParameter(param_names[i], param_types[i], i == vararg_rank)
                        self.n_params[i].mparameter = mparameter
                        mparameters.add(mparameter)
                end

                var msignature = new MSignature(mparameters, ret_type)
                return msignature
        end
end

redef class AParam
        # The associated mparameter if any
        var mparameter: nullable MParameter = null
end

redef class AMethPropdef
        redef type MPROPDEF: MMethodDef

        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 = "init"
                                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
                        mprop.is_new = self isa AExternInitPropdef
                        if not self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, false, mprop) then return
                else
                        if n_kwredef == null then
                                if self isa AMainMethPropdef then
                                        # no warning
                                else
                                        if not self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, true, mprop) then return
                                end
                        end
                        check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mprop)
                end
                nclassdef.mprop2npropdef[mprop] = self

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

                if mclassdef.propdef_names.has(mprop.name) then
                        var loc: nullable Location = null
                        for i in mclassdef.mpropdefs do
                                if i.mproperty.name == mprop.name then
                                        loc = i.location
                                        break
                                end
                        end
                        if loc == null then abort
                        modelbuilder.error(self, "Error: a property {mprop} is already defined in class {mclassdef.mclass} at {loc}")
                end

                mclassdef.propdef_names.add(mpropdef.mproperty.name)

                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
                        if not nsig.visit_signature(modelbuilder, nclassdef) then return
                        param_names = nsig.param_names
                        param_types = nsig.param_types
                        vararg_rank = nsig.vararg_rank
                        ret_type = nsig.ret_type
                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

                        # Check inherited signature arity
                        if param_names.length != msignature.arity then
                                var node: ANode
                                if nsig != null then node = nsig else node = self
                                modelbuilder.error(node, "Redef error: {mpropdef} redefines {mpropdef.mproperty.intro} with {param_names.length} parameter(s), {msignature.arity} expected. Signature is {mpropdef}{msignature}")
                                return
                        end
                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 = new Array[MType]
                        for mparameter in msignature.mparameters do
                                param_types.add(mparameter.mtype)
                        end
                        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.error(nsig.n_params[param_types.length], "Error: Untyped parameter `{param_names[param_types.length]}'.")
                        return
                end

                var mparameters = new Array[MParameter]
                for i in [0..param_names.length[ do
                        var mparameter = new MParameter(param_names[i], param_types[i], i == vararg_rank)
                        if nsig != null then nsig.n_params[i].mparameter = mparameter
                        mparameters.add(mparameter)
                end

                msignature = new MSignature(mparameters, ret_type)
                mpropdef.msignature = msignature
                mpropdef.is_abstract = self isa ADeferredMethPropdef
        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

                        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.mparameters[i].mtype
                                        var prt = msignature.mparameters[i].mtype
                                        if not myt.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, prt) or
                                                        not prt.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, myt) then
                                                modelbuilder.error(nsig.n_params[i], "Redef Error: Wrong type for parameter `{mysignature.mparameters[i].name}'. found {myt}, expected {prt} as in {mpropdef.mproperty.intro}.")
                                        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} as in {mpropdef.mproperty.intro}.")
                                end
                        end
                end
        end
end

redef class AAttrPropdef
        redef type MPROPDEF: MAttributeDef

        # The associated getter (read accessor) if any
        var mreadpropdef: nullable MMethodDef writable
        # The associated setter (write accessor) if any
        var mwritepropdef: nullable MMethodDef writable
        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}.")
                else if mclass.kind == extern_kind then
                        modelbuilder.error(self, "Error: Attempt to define attribute {name} in the extern 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)
                                if not self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, false, mprop) then return
                        else
                                assert mprop isa MAttribute
                                check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mprop)
                                if not self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, true, mprop) then return
                        end
                        nclassdef.mprop2npropdef[mprop] = self

                        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)
                                        if not self.check_redef_keyword(modelbuilder, nclassdef, nreadable.n_kwredef, false, mreadprop) then return
                                else
                                        if not self.check_redef_keyword(modelbuilder, nclassdef, nreadable.n_kwredef, true, mreadprop) then return
                                        check_redef_property_visibility(modelbuilder, nclassdef, nreadable.n_visibility, mreadprop)
                                end
                                nclassdef.mprop2npropdef[mreadprop] = self

                                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)
                                        if not self.check_redef_keyword(modelbuilder, nclassdef, nwritable.n_kwredef, false, mwriteprop) then return
                                else
                                        if not self.check_redef_keyword(modelbuilder, nclassdef, nwritable.n_kwredef, true, mwriteprop) then return
                                        check_redef_property_visibility(modelbuilder, nclassdef, nwritable.n_visibility, mwriteprop)
                                end
                                nclassdef.mprop2npropdef[mwriteprop] = self

                                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)
                                if not self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, false, mreadprop) then return
                        else
                                if not self.check_redef_keyword(modelbuilder, nclassdef, n_kwredef, true, mreadprop) then return
                                check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mreadprop)
                        end
                        nclassdef.mprop2npropdef[mreadprop] = self

                        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)
                                if not self.check_redef_keyword(modelbuilder, nclassdef, nwkwredef, false, mwriteprop) then return
                        else
                                if not self.check_redef_keyword(modelbuilder, nclassdef, nwkwredef, true, mwriteprop) then return
                                if nwritable != null then
                                        check_redef_property_visibility(modelbuilder, nclassdef, nwritable.n_visibility, mwriteprop)
                                end
                        end
                        nclassdef.mprop2npropdef[mwriteprop] = self

                        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

                var nexpr = self.n_expr
                if mtype == null then
                        if nexpr != null then
                                if nexpr isa ANewExpr then
                                        mtype = modelbuilder.resolve_mtype(nclassdef, nexpr.n_type)
                                else if nexpr isa AIntExpr then
                                        var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
                                        if cla != null then mtype = cla.mclass_type
                                else if nexpr isa AFloatExpr then
                                        var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Float")
                                        if cla != null then mtype = cla.mclass_type
                                else if nexpr isa ACharExpr then
                                        var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Char")
                                        if cla != null then mtype = cla.mclass_type
                                else if nexpr isa ABoolExpr then
                                        var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bool")
                                        if cla != null then mtype = cla.mclass_type
                                else if nexpr isa ASuperstringExpr then
                                        var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
                                        if cla != null then mtype = cla.mclass_type
                                else if nexpr isa AStringFormExpr then
                                        var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
                                        if cla != null then mtype = cla.mclass_type
                                else
                                        modelbuilder.error(self, "Error: Untyped attribute {mpropdef}. Implicit typing allowed only for literals and new.")
                                end

                        else
                                modelbuilder.error(self, "Error: Untyped attribute {mpropdef}")
                        end
                else
                        assert ntype != null
                        if nexpr isa ANewExpr then
                                var xmtype = modelbuilder.resolve_mtype(nclassdef, nexpr.n_type)
                                if xmtype == mtype and modelbuilder.toolcontext.opt_warn.value >= 2 then
                                        modelbuilder.warning(ntype, "Warning: useless type definition")
                                end
                        end
                end

                if mtype == null then return

                mpropdef.static_mtype = mtype

                var mreadpropdef = self.mreadpropdef
                if mreadpropdef != null then
                        var msignature = new MSignature(new Array[MParameter], mtype)
                        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 mparameter = new MParameter(name, mtype, false)
                        var msignature = new MSignature([mparameter], null)
                        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

                # Check getter and setter
                var meth = self.mreadpropdef
                if meth != null then self.check_method_signature(modelbuilder, nclassdef, meth)
                meth = self.mwritepropdef
                if meth != null then self.check_method_signature(modelbuilder, nclassdef, meth)
        end

        private fun check_method_signature(modelbuilder: ModelBuilder, nclassdef: AClassdef, mpropdef: MMethodDef)
        do
                var mmodule = mpropdef.mclassdef.mmodule
                var nsig = self.n_type
                var mysignature = 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
                                var node: ANode
                                if nsig != null then node = nsig else node = self
                                modelbuilder.error(node, "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.mparameters[i].mtype
                                        var prt = msignature.mparameters[i].mtype
                                        if not myt.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, prt) and
                                                        not prt.is_subtype(mmodule, nclassdef.mclassdef.bound_mtype, myt) then
                                                var node: ANode
                                                if nsig != null then node = nsig else node = self
                                                modelbuilder.error(node, "Redef Error: Wrong type for parameter `{mysignature.mparameters[i].name}'. 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
                                        var node: ANode
                                        if nsig != null then node = nsig else node = self
                                        modelbuilder.error(node, "Redef Error: Wrong return type. found {ret_type}, expected {precursor_ret_type}.")
                                end
                        end
                end
        end
end

redef class ATypePropdef
        redef type MPROPDEF: 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)
                        for c in name do if c >= 'a' and c<= 'z' then
                                modelbuilder.warning(n_id, "Warning: lowercase in the virtual type {name}")
                                break
                        end
                        if not self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, false, mprop) then return
                else
                        if not self.check_redef_keyword(modelbuilder, nclassdef, self.n_kwredef, true, mprop) then return
                        assert mprop isa MVirtualTypeProp
                        check_redef_property_visibility(modelbuilder, nclassdef, self.n_visibility, mprop)
                end
                nclassdef.mprop2npropdef[mprop] = self

                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