src: fix null receiver error on useless-signature warning

[nit.git] / src / modelize / 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

intrude import modelize_class
private import annotation

redef class ToolContext
        # Run `AClassdef::build_property` on the classdefs of each module
        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
                        if nclassdef.all_defs == null then continue # skip non principal classdef
                        toolcontext.modelbuilder.build_properties(nclassdef)
                end
        end
end

redef class ModelBuilder
        # Registration of the npropdef associated to each mpropdef.
        #
        # Public clients need to use `mpropdef2node` to access stuff.
        private var mpropdef2npropdef = new HashMap[MPropDef, APropdef]

        # Retrieve the associated AST node of a mpropertydef.
        # This method is used to associate model entity with syntactic entities.
        #
        # If the property definition is not associated with a node, returns `null`.
        fun mpropdef2node(mpropdef: MPropDef): nullable ANode
        do
                var res
                res = mpropdef2npropdef.get_or_null(mpropdef)
                if res != null then
                        # Run the phases on it
                        toolcontext.run_phases_on_npropdef(res)
                        return res
                end
                if mpropdef isa MMethodDef and mpropdef.mproperty.is_root_init then
                        res = mclassdef2nclassdef.get_or_null(mpropdef.mclassdef)
                        if res != null then return res
                end
                return null
        end

        # Retrieve all the attributes nodes localy definied
        # FIXME think more about this method and how the separations separate/global and ast/model should be done.
        fun collect_attr_propdef(mclassdef: MClassDef): Array[AAttrPropdef]
        do
                var res = new Array[AAttrPropdef]
                var n = mclassdef2nclassdef.get_or_null(mclassdef)
                if n == null then return res
                for npropdef in n.n_propdefs do
                        if npropdef isa AAttrPropdef then
                                # Run the phases on it
                                toolcontext.run_phases_on_npropdef(npropdef)
                                res.add(npropdef)
                        end
                end
                return res
        end

        # 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
                if mclassdef == null then return # skip error
                if mclassdef.in_hierarchy == null then return # Skip error
                for superclassdef in mclassdef.in_hierarchy.direct_greaters do
                        if not mclassdef2nclassdef.has_key(superclassdef) then continue
                        build_properties(mclassdef2nclassdef[superclassdef])
                end

                mclassdef.build_self_type(self, nclassdef)
                for nclassdef2 in nclassdef.all_defs do
                        for npropdef in nclassdef2.n_propdefs do
                                npropdef.build_property(self, mclassdef)
                        end
                        for npropdef in nclassdef2.n_propdefs do
                                npropdef.build_signature(self)
                        end
                        for npropdef in nclassdef2.n_propdefs do
                                if not npropdef isa ATypePropdef then continue
                                # Check circularity
                                var mpropdef = npropdef.mpropdef
                                if mpropdef == null then continue
                                if mpropdef.bound == null then continue
                                if not check_virtual_types_circularity(npropdef, mpropdef.mproperty, mclassdef.bound_mtype, mclassdef.mmodule) then
                                        # Invalidate the bound
                                        mpropdef.bound = mclassdef.mmodule.model.null_type
                                end
                        end
                        for npropdef in nclassdef2.n_propdefs do
                                # Check ATypePropdef first since they may be required for the other properties
                                if not npropdef isa ATypePropdef then continue
                                npropdef.check_signature(self)
                        end

                        for npropdef in nclassdef2.n_propdefs do
                                if npropdef isa ATypePropdef then continue
                                npropdef.check_signature(self)
                        end
                end
                process_default_constructors(nclassdef)
        end

        # the root init of the Object class
        # Is usually implicitly defined
        # Then explicit or implicit definitions of root-init are attached to it
        var the_root_init_mmethod: nullable MMethod

        # 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

                # Look for the init in Object, or create it
                if mclassdef.mclass.name == "Object" and the_root_init_mmethod == null then
                        # Create the implicit root-init method
                        var mprop = new MMethod(mclassdef, "init", mclassdef.mclass.visibility)
                        mprop.is_root_init = true
                        var mpropdef = new MMethodDef(mclassdef, mprop, nclassdef.location)
                        var mparameters = new Array[MParameter]
                        var msignature = new MSignature(mparameters, null)
                        mpropdef.msignature = msignature
                        mpropdef.new_msignature = msignature
                        mprop.is_init = true
                        nclassdef.mfree_init = mpropdef
                        self.toolcontext.info("{mclassdef} gets a free empty constructor {mpropdef}{msignature}", 3)
                        the_root_init_mmethod = mprop
                        return
                end

                # Is there already a constructor defined?
                var defined_init: nullable MMethodDef = null
                for mpropdef in mclassdef.mpropdefs do
                        if not mpropdef isa MMethodDef then continue
                        if not mpropdef.mproperty.is_init then continue
                        if mpropdef.mproperty.is_root_init then
                                assert defined_init == null
                                defined_init = mpropdef
                        else if mpropdef.mproperty.name == "init" then
                                # An explicit old-style init named "init", so return
                                return
                        end
                end

                if not nclassdef isa AStdClassdef then return

                # Collect undefined attributes
                var mparameters = new Array[MParameter]
                var initializers = new Array[MProperty]
                for npropdef in nclassdef.n_propdefs do
                        if npropdef isa AMethPropdef then
                                if not npropdef.is_autoinit then continue # Skip non tagged autoinit
                                if npropdef.mpropdef == null then return # Skip broken method
                                var sig = npropdef.mpropdef.msignature
                                if sig == null then continue # Skip broken method

                                for param in sig.mparameters do
                                        var ret_type = param.mtype
                                        var mparameter = new MParameter(param.name, ret_type, false)
                                        mparameters.add(mparameter)
                                end
                                initializers.add(npropdef.mpropdef.mproperty)
                                npropdef.mpropdef.mproperty.is_autoinit = true
                        end
                        if npropdef isa AAttrPropdef then
                                var mreadpropdef = npropdef.mreadpropdef
                                if mreadpropdef == null or mreadpropdef.msignature == null then return # Skip broken attribute
                                if npropdef.noinit then continue # Skip noinit attribute
                                var atlateinit = npropdef.get_single_annotation("lateinit", self)
                                if atlateinit != null then
                                        # For lateinit attributes, call the reader to force
                                        # the lazy initialization of the attribute.
                                        initializers.add(mreadpropdef.mproperty)
                                        mreadpropdef.mproperty.is_autoinit = true
                                        continue
                                end
                                if npropdef.has_value then continue
                                var paramname = mreadpropdef.mproperty.name
                                var ret_type = mreadpropdef.msignature.return_mtype
                                if ret_type == null then return
                                var mparameter = new MParameter(paramname, ret_type, false)
                                mparameters.add(mparameter)
                                var msetter = npropdef.mwritepropdef
                                if msetter == null then
                                        # No setter, it is a readonly attribute, so just add it
                                        initializers.add(npropdef.mpropdef.mproperty)
                                        npropdef.mpropdef.mproperty.is_autoinit = true
                                else
                                        # Add the setter to the list
                                        initializers.add(msetter.mproperty)
                                        msetter.mproperty.is_autoinit = true
                                end
                        end
                end

                if the_root_init_mmethod == null then return

                # Look for most-specific new-stype init definitions
                var spropdefs = the_root_init_mmethod.lookup_super_definitions(mclassdef.mmodule, mclassdef.bound_mtype)
                if spropdefs.is_empty then
                        toolcontext.error(nclassdef.location, "Error: `{mclassdef}` does not specialize `{the_root_init_mmethod.intro_mclassdef}`. Possible duplication of the root class `Object`?")
                        return
                end

                # Look at the autoinit class-annotation
                var autoinit = nclassdef.get_single_annotation("autoinit", self)
                var noautoinit = nclassdef.get_single_annotation("noautoinit", self)
                if autoinit != null then
                        # Just throws the collected initializers
                        mparameters.clear
                        initializers.clear

                        if noautoinit != null then
                                error(autoinit, "Error: `autoinit` and `noautoinit` are incompatible.")
                        end

                        if autoinit.n_args.is_empty then
                                error(autoinit, "Syntax Error: `autoinit` expects method identifiers, use `noautoinit` to clear all autoinits.")
                        end

                        # Get and check each argument
                        for narg in autoinit.n_args do
                                var id = narg.as_id
                                if id == null then
                                        error(narg, "Syntax Error: `autoinit` expects method identifiers.")
                                        return
                                end

                                # Search the property.
                                # To avoid bad surprises, try to get the setter first.
                                var p = try_get_mproperty_by_name(narg, mclassdef, id + "=")
                                if p == null then
                                        p = try_get_mproperty_by_name(narg, mclassdef, id)
                                end
                                if p == null then
                                        error(narg, "Error: unknown method `{id}`")
                                        return
                                end
                                if not p.is_autoinit then
                                        error(narg, "Error: `{p}` is not an autoinit method")
                                        return
                                end

                                # Register the initializer and the parameters
                                initializers.add(p)
                                var pd = p.intro
                                if pd isa MMethodDef then
                                        # Get the signature resolved for the current receiver
                                        var sig = pd.msignature.resolve_for(mclassdef.mclass.mclass_type, mclassdef.bound_mtype, mclassdef.mmodule, false)
                                        mparameters.add_all(sig.mparameters)
                                else
                                        # TODO attributes?
                                        abort
                                end
                        end
                else
                        # Search the longest-one and checks for conflict
                        var longest = spropdefs.first
                        if spropdefs.length > 1 then
                                # part 1. find the longest list
                                for spd in spropdefs do
                                        if spd.initializers.length > longest.initializers.length then longest = spd
                                end
                                # part 2. compare
                                # Check for conflict in the order of initializers
                                # Each initializer list must me a prefix of the longest list
                                # If `noautoinit` is set, just ignore conflicts
                                if noautoinit == null then for spd in spropdefs do
                                        var i = 0
                                        for p in spd.initializers do
                                                if p != longest.initializers[i] then
                                                        var proposal = new ArraySet[MProperty]
                                                        for spd2 in spropdefs do
                                                                proposal.add_all spd2.initializers
                                                        end
                                                        proposal.add_all initializers
                                                        self.error(nclassdef, "Error: cannot generate automatic init for class {mclassdef.mclass}. Conflict in the order in inherited initializers {spd}({spd.initializers.join(", ")}) and {longest}({longest.initializers.join(", ")}). Use `autoinit` to order initializers. eg `autoinit {proposal.join(", ")}`")
                                                        # TODO: invalidate the initializer to avoid more errors
                                                        return
                                                end
                                                i += 1
                                        end
                                end
                        end

                        if noautoinit != null then
                                # If there is local or inherited initializers, then complain.
                                if initializers.is_empty and longest.initializers.is_empty then
                                        warning(noautoinit, "useless-noautoinit", "Warning: the list of autoinit is already empty.")
                                end
                                # Just clear initializers
                                mparameters.clear
                                initializers.clear
                        else
                                # Can we just inherit?
                                if spropdefs.length == 1 and mparameters.is_empty and defined_init == null then
                                        self.toolcontext.info("{mclassdef} inherits the basic constructor {longest}", 3)
                                        mclassdef.mclass.root_init = longest
                                        return
                                end

                                # Combine the inherited list to what is collected
                                if longest.initializers.length > 0 then
                                        mparameters.prepend longest.new_msignature.mparameters
                                        initializers.prepend longest.initializers
                                end
                        end
                end

                # If we already have a basic init definition, then setup its initializers
                if defined_init != null then
                        defined_init.initializers.add_all(initializers)
                        var msignature = new MSignature(mparameters, null)
                        defined_init.new_msignature = msignature
                        self.toolcontext.info("{mclassdef} extends its basic constructor signature to {defined_init}{msignature}", 3)
                        mclassdef.mclass.root_init = defined_init
                        return
                end

                # Else create the local implicit basic init definition
                var mprop = the_root_init_mmethod.as(not null)
                var mpropdef = new MMethodDef(mclassdef, mprop, nclassdef.location)
                mpropdef.has_supercall = true
                mpropdef.initializers.add_all(initializers)
                var msignature = new MSignature(mparameters, null)
                mpropdef.new_msignature = msignature
                mpropdef.msignature = new MSignature(new Array[MParameter], null) # always an empty real signature
                nclassdef.mfree_init = mpropdef
                self.toolcontext.info("{mclassdef} gets a free constructor for attributes {mpropdef}{msignature}", 3)
                mclassdef.mclass.root_init = mpropdef
        end

        # Check the visibility of `mtype` as an element of the signature of `mpropdef`.
        fun check_visibility(node: ANode, mtype: MType, mpropdef: MPropDef)
        do
                var mmodule = mpropdef.mclassdef.mmodule
                var mproperty = mpropdef.mproperty

                # Extract visibility information of the main part of `mtype`
                # It is a case-by case
                var vis_type: nullable MVisibility = null # The own visibility of the type
                var mmodule_type: nullable MModule = null # The original module of the type
                mtype = mtype.undecorate
                if mtype isa MClassType then
                        vis_type = mtype.mclass.visibility
                        mmodule_type = mtype.mclass.intro.mmodule
                else if mtype isa MVirtualType then
                        vis_type = mtype.mproperty.visibility
                        mmodule_type = mtype.mproperty.intro_mclassdef.mmodule
                else if mtype isa MParameterType then
                        # nothing, always visible
                else if mtype isa MNullType then
                        # nothing to do.
                else
                        node.debug "Unexpected type {mtype}"
                        abort
                end

                if vis_type != null then
                        assert mmodule_type != null
                        var vis_module_type = mmodule.visibility_for(mmodule_type) # the visibility of the original module
                        if mproperty.visibility > vis_type then
                                error(node, "Error: the {mproperty.visibility} property `{mproperty}` cannot contain the {vis_type} type `{mtype}`.")
                                return
                        else if mproperty.visibility > vis_module_type then
                                error(node, "Error: the {mproperty.visibility} property `{mproperty}` cannot contain the type `{mtype}` from the {vis_module_type} module `{mmodule_type}`.")
                                return
                        end
                end

                # No error, try to go deeper in generic types
                if node isa AType then
                        for a in node.n_types do
                                var t = a.mtype
                                if t == null then continue # Error, thus skipped
                                check_visibility(a, t, mpropdef)
                        end
                else if mtype isa MGenericType then
                        for t in mtype.arguments do check_visibility(node, t, mpropdef)
                end
        end

        # Detect circularity errors for virtual types.
        fun check_virtual_types_circularity(node: ANode, mproperty: MVirtualTypeProp, recv: MType, mmodule: MModule): Bool
        do
                # Check circularity
                # Slow case: progress on each resolution until we visit all without getting a loop

                # The graph used to detect loops
                var mtype = mproperty.mvirtualtype
                var poset = new POSet[MType]

                # The work-list of types to resolve
                var todo = new List[MType]
                todo.add mtype

                while not todo.is_empty do
                        # The visited type
                        var t = todo.pop

                        if not t.need_anchor then continue

                        # Get the types derived of `t` (subtypes and bounds)
                        var nexts
                        if t isa MNullableType then
                                nexts = [t.mtype]
                        else if t isa MGenericType then
                                nexts = t.arguments
                        else if t isa MVirtualType then
                                var vt = t.mproperty
                                # Because `vt` is possibly unchecked, we have to do the bound-lookup manually
                                var defs = vt.lookup_definitions(mmodule, recv)
                                # TODO something to manage correctly bound conflicts
                                assert not defs.is_empty
                                nexts = new Array[MType]
                                for d in defs do
                                        var next = defs.first.bound
                                        if next == null then return false
                                        nexts.add next
                                end
                        else if t isa MClassType then
                                # Basic type, nothing to to
                                continue
                        else if t isa MParameterType then
                                # Parameter types cannot depend on virtual types, so nothing to do
                                continue
                        else
                                abort
                        end

                        # For each one
                        for next in nexts do
                                if poset.has_edge(next, t) then
                                        if mtype == next then
                                                error(node, "Error: circularity of virtual type definition: {next} <-> {t}.")
                                        else
                                                error(node, "Error: circularity of virtual type definition: {mtype} -> {next} <-> {t}.")
                                        end
                                        return false
                                else
                                        poset.add_edge(t, next)
                                        todo.add next
                                end
                        end
                end
                return true
        end
end

redef class MPropDef
        # Does the MPropDef contains a call to super or a call of a super-constructor?
        # Subsequent phases of the frontend (esp. typing) set it if required
        var has_supercall: Bool = false is writable
end

redef class AClassdef
        # Marker used in `ModelBuilder::build_properties`
        private var build_properties_is_done = false

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

redef class MClass
        # The base init of the class.
        # Used to get the common new_msignature and initializers
        #
        # TODO: Where to put this information is not clear because unlike other
        # informations, the initialisers are stable in a same class.
        var root_init: nullable MMethodDef = null
end

redef class MClassDef
        # 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]

        # Build the virtual type `SELF` only for introduction `MClassDef`
        fun build_self_type(modelbuilder: ModelBuilder, nclassdef: AClassdef)
        do
                if not is_intro then return

                var name = "SELF"
                var mprop = modelbuilder.try_get_mproperty_by_name(nclassdef, self, name)

                # If SELF type is declared nowherer?
                if mprop == null then return

                # SELF is not a virtual type? it is weird but we ignore it
                if not mprop isa MVirtualTypeProp then return

                # Is this the intro of SELF in the library?
                var intro = mprop.intro
                var intro_mclassdef = intro.mclassdef
                if intro_mclassdef == self then
                        var nintro = modelbuilder.mpropdef2npropdef[intro]

                        # SELF must be declared in Object, otherwise this will create conflicts
                        if intro_mclassdef.mclass.name != "Object" then
                                modelbuilder.error(nintro, "Error: the virtual type `SELF` must be declared in `Object`.")
                        end

                        # SELF must be public
                        if mprop.visibility != public_visibility then
                                modelbuilder.error(nintro, "Error: the virtual type `SELF` must be public.")
                        end

                        # SELF must not be fixed
                        if intro.is_fixed then
                                modelbuilder.error(nintro, "Error: the virtual type `SELF` cannot be fixed.")
                        end

                        return
                end

                # This class introduction inherits a SELF
                # We insert an artificial property to update it
                var mpropdef = new MVirtualTypeDef(self, mprop, self.location)
                mpropdef.bound = mclass.mclass_type
        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 is writable

        private fun build_property(modelbuilder: ModelBuilder, mclassdef: MClassDef) do end
        private fun build_signature(modelbuilder: ModelBuilder) do end
        private fun check_signature(modelbuilder: ModelBuilder) do end
        private fun new_property_visibility(modelbuilder: ModelBuilder, mclassdef: MClassDef, 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 mclassdef.mclass.visibility == private_visibility then
                        if mvisibility == protected_visibility then
                                assert nvisibility != null
                                modelbuilder.error(nvisibility, "Error: `private` is the only legal visibility for properties in a private class.")
                        else if mvisibility == private_visibility then
                                assert nvisibility != null
                                modelbuilder.advice(nvisibility, "useless-visibility", "Warning: `private` is superfluous since the only legal visibility for properties in a private class is private.")
                        end
                        mvisibility = private_visibility
                end
                return mvisibility
        end

        private fun set_doc(mpropdef: MPropDef, modelbuilder: ModelBuilder)
        do
                var ndoc = self.n_doc
                if ndoc != null then
                        var mdoc = ndoc.to_mdoc
                        mpropdef.mdoc = mdoc
                        mdoc.original_mentity = mpropdef
                else if mpropdef.is_intro and mpropdef.mproperty.visibility >= protected_visibility then
                        modelbuilder.advice(self, "missing-doc", "Documentation warning: Undocumented property `{mpropdef.mproperty}`")
                end

                var at_deprecated = get_single_annotation("deprecated", modelbuilder)
                if at_deprecated != null then
                        if not mpropdef.is_intro then
                                modelbuilder.error(self, "Error: method redefinition cannot be deprecated.")
                        else
                                var info = new MDeprecationInfo
                                ndoc = at_deprecated.n_doc
                                if ndoc != null then info.mdoc = ndoc.to_mdoc
                                mpropdef.mproperty.deprecation = info
                        end
                end
        end

        private fun check_redef_property_visibility(modelbuilder: ModelBuilder, 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 `{mprop.visibility}` to `{mvisibility}`.")
                end
        end

        private fun check_redef_keyword(modelbuilder: ModelBuilder, mclassdef: MClassDef, kwredef: nullable Token, need_redef: Bool, mprop: MProperty): Bool
        do
                if mclassdef.mprop2npropdef.has_key(mprop) then
                        modelbuilder.error(self, "Error: a property `{mprop}` is already defined in class `{mclassdef.mclass}` at line {mclassdef.mprop2npropdef[mprop].location.line_start}.")
                        return false
                end
                if mprop isa MMethod and mprop.is_root_init then return true
                if kwredef == null then
                        if need_redef then
                                modelbuilder.error(self, "Redef Error: `{mclassdef.mclass}::{mprop.name}` is an inherited property. To redefine it, add the `redef` keyword.")
                                return false
                        end

                        # Check for full-name conflicts in the package.
                        # A public property should have a unique qualified name `package::class::prop`.
                        if mprop.intro_mclassdef.mmodule.mgroup != null and mprop.visibility >= protected_visibility then
                                var others = modelbuilder.model.get_mproperties_by_name(mprop.name)
                                if others != null then for other in others do
                                        if other != mprop and other.intro_mclassdef.mmodule.mgroup != null and other.intro_mclassdef.mmodule.mgroup.mpackage == mprop.intro_mclassdef.mmodule.mgroup.mpackage and other.intro_mclassdef.mclass.name == mprop.intro_mclassdef.mclass.name and other.visibility >= protected_visibility then
                                                modelbuilder.advice(self, "full-name-conflict", "Warning: A property named `{other.full_name}` is already defined in module `{other.intro_mclassdef.mmodule}` for the class `{other.intro_mclassdef.mclass.name}`.")
                                                break
                                        end
                                end
                        end
                else
                        if not need_redef then
                                modelbuilder.error(self, "Error: no property `{mclassdef.mclass}::{mprop.name}` is inherited. Remove the `redef` keyword to define a new property.")
                                return false
                        end
                end
                return true
        end

        # Checks for useless type in redef signatures.
        private fun check_repeated_types(modelbuilder: ModelBuilder) do 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, mclassdef: MClassDef): Bool
        do
                var mmodule = mclassdef.mmodule
                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_unchecked(mmodule, mclassdef, ntype, true)
                                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_unchecked(mmodule, mclassdef, ntype, true)
                        if self.ret_type == null then return false # Skip error
                end

                self.is_visited = true
                return true
        end

        private fun check_signature(modelbuilder: ModelBuilder, mclassdef: MClassDef): Bool
        do
                var res = true
                for np in self.n_params do
                        var ntype = np.n_type
                        if ntype != null then
                                if modelbuilder.resolve_mtype(mclassdef.mmodule, mclassdef, ntype) == null then
                                        res = false
                                end
                        end
                end
                var ntype = self.n_type
                if ntype != null then
                        if modelbuilder.resolve_mtype(mclassdef.mmodule, mclassdef, ntype) == null then
                                res = false
                        end
                end
                return res
        end
end

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

redef class AMethPropdef
        redef type MPROPDEF: MMethodDef

        # Is the method annotated `autoinit`?
        var is_autoinit = false

        # Can self be used as a root init?
        private fun look_like_a_root_init(modelbuilder: ModelBuilder, mclassdef: MClassDef): Bool
        do
                # Need the `init` keyword
                if n_kwinit == null then return false
                # Need to by anonymous
                if self.n_methid != null then return false
                # No annotation on itself
                if get_single_annotation("old_style_init", modelbuilder) != null then return false
                # Nor on its module
                var amod = self.parent.parent.as(AModule)
                var amoddecl = amod.n_moduledecl
                if amoddecl != null then
                        var old = amoddecl.get_single_annotation("old_style_init", modelbuilder)
                        if old != null then return false
                end
                # No parameters
                if self.n_signature.n_params.length > 0 then
                        modelbuilder.advice(self, "old-init", "Warning: init with signature in {mclassdef}")
                        return false
                end
                # Cannot be private or something
                if not self.n_visibility isa APublicVisibility then
                        modelbuilder.advice(self, "old-init", "Warning: non-public init in {mclassdef}")
                        return false
                end

                return true
        end

        redef fun build_property(modelbuilder, mclassdef)
        do
                var n_kwinit = n_kwinit
                var n_kwnew = n_kwnew
                var is_init = n_kwinit != null or n_kwnew != null
                var name: String
                var amethodid = self.n_methid
                var name_node: ANode
                if amethodid == null then
                        if not is_init then
                                name = "main"
                                name_node = self
                        else if n_kwinit != null then
                                name = "init"
                                name_node = n_kwinit
                        else if n_kwnew != null then
                                name = "new"
                                name_node = 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

                        var arity = self.n_signature.n_params.length
                        if name == "+" and arity == 0 then
                                name = "unary +"
                        else if name == "-" and arity == 0 then
                                name = "unary -"
                        else if name == "~" and arity == 0 then
                                name = "unary ~"
                        else
                                if amethodid.is_binary and arity != 1 then
                                        modelbuilder.error(self.n_signature, "Syntax Error: binary operator `{name}` requires exactly one parameter; got {arity}.")
                                else if amethodid.min_arity > arity then
                                        modelbuilder.error(self.n_signature, "Syntax Error: `{name}` requires at least {amethodid.min_arity} parameter(s); got {arity}.")
                                end
                        end
                end

                var look_like_a_root_init = look_like_a_root_init(modelbuilder, mclassdef)
                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 and look_like_a_root_init then
                        mprop = modelbuilder.the_root_init_mmethod
                        var nb = n_block
                        if nb isa ABlockExpr and nb.n_expr.is_empty and n_doc == null then
                                modelbuilder.advice(self, "useless-init", "Warning: useless empty init in {mclassdef}")
                        end
                end
                if mprop == null then
                        var mvisibility = new_property_visibility(modelbuilder, mclassdef, self.n_visibility)
                        mprop = new MMethod(mclassdef, name, mvisibility)
                        if look_like_a_root_init and modelbuilder.the_root_init_mmethod == null then
                                modelbuilder.the_root_init_mmethod = mprop
                                mprop.is_root_init = true
                        end
                        mprop.is_init = is_init
                        mprop.is_new = n_kwnew != null
                        if mprop.is_new then mclassdef.mclass.has_new_factory = true
                        if name == "sys" then mprop.is_toplevel = true # special case for sys allowed in `new` factories
                        self.check_redef_keyword(modelbuilder, mclassdef, n_kwredef, false, mprop)
                else
                        if not self.check_redef_keyword(modelbuilder, mclassdef, n_kwredef, not self isa AMainMethPropdef, mprop) then return
                        check_redef_property_visibility(modelbuilder, self.n_visibility, mprop)
                end

                # Check name conflicts in the local class for constructors.
                if is_init then
                        for p, n in mclassdef.mprop2npropdef do
                                if p != mprop and p isa MMethod and p.name == name then
                                        check_redef_keyword(modelbuilder, mclassdef, n_kwredef, false, p)
                                        break
                                end
                        end
                end

                mclassdef.mprop2npropdef[mprop] = self

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

                set_doc(mpropdef, modelbuilder)

                self.mpropdef = mpropdef
                modelbuilder.mpropdef2npropdef[mpropdef] = self
                if mpropdef.is_intro then
                        modelbuilder.toolcontext.info("{mpropdef} introduces new method {mprop.full_name}", 4)
                else
                        modelbuilder.toolcontext.info("{mpropdef} redefines method {mprop.full_name}", 4)
                end
        end

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

                if mpropdef.mproperty.is_root_init and not mclassdef.is_intro then
                        var root_init = mclassdef.mclass.root_init
                        if root_init != null then
                                # Inherit the initializers by refinement
                                mpropdef.new_msignature = root_init.new_msignature
                                assert mpropdef.initializers.is_empty
                                mpropdef.initializers.add_all root_init.initializers
                        end
                end

                var accept_special_last_parameter = self.n_methid == null or self.n_methid.accept_special_last_parameter
                var return_is_mandatory = self.n_methid != null and self.n_methid.return_is_mandatory

                # 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, mclassdef) 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

                        # The local signature is adapted to use the local formal types, if any.
                        msignature = msignature.resolve_for(mclassdef.mclass.mclass_type, mclassdef.bound_mtype, mmodule, false)

                        # 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: expected {msignature.arity} parameter(s) for `{mpropdef.mproperty.name}{msignature}`; got {param_names.length}. See introduction at `{mpropdef.mproperty.full_name}`.")
                                return
                        end
                else if mpropdef.mproperty.is_init and not mpropdef.mproperty.is_new then
                        # FIXME UGLY: inherit signature from a super-constructor
                        for msupertype in mclassdef.supertypes do
                                msupertype = msupertype.anchor_to(mmodule, 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

                # In `new`-factories, the return type is by default the classtype.
                if ret_type == null and mpropdef.mproperty.is_new then ret_type = mclassdef.mclass.mclass_type

                # Special checks for operator methods
                if not accept_special_last_parameter and mparameters.not_empty and mparameters.last.is_vararg then
                        modelbuilder.error(self.n_signature.n_params.last, "Error: illegal variadic parameter `{mparameters.last}` for `{mpropdef.mproperty.name}`.")
                end
                if ret_type == null and return_is_mandatory then
                        modelbuilder.error(self.n_methid, "Error: mandatory return type for `{mpropdef.mproperty.name}`.")
                end

                msignature = new MSignature(mparameters, ret_type)
                mpropdef.msignature = msignature
                mpropdef.is_abstract = self.get_single_annotation("abstract", modelbuilder) != null
                mpropdef.is_intern = self.get_single_annotation("intern", modelbuilder) != null
                mpropdef.is_extern = self.n_extern_code_block != null or self.get_single_annotation("extern", modelbuilder) != null

                # Check annotations
                var at = self.get_single_annotation("lazy", modelbuilder)
                if at != null then modelbuilder.error(at, "Syntax Error: `lazy` must be used on attributes.")

                var atautoinit = self.get_single_annotation("autoinit", modelbuilder)
                if atautoinit != null then
                        if not mpropdef.is_intro then
                                modelbuilder.error(atautoinit, "Error: `autoinit` cannot be set on redefinitions.")
                        else if not mclassdef.is_intro then
                                modelbuilder.error(atautoinit, "Error: `autoinit` cannot be used in class refinements.")
                        else
                                self.is_autoinit = true
                        end
                end
        end

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

                # Check
                if nsig != null then
                        if not nsig.check_signature(modelbuilder, mclassdef) then
                                self.mpropdef.msignature = null # invalidate
                                return # Forward error
                        end
                end

                # 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.")
                                self.mpropdef.msignature = null
                                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
                                        var node = nsig.n_params[i]
                                        if not modelbuilder.check_sametype(node, mmodule, mclassdef.bound_mtype, myt, prt) then
                                                modelbuilder.error(node, "Redef Error: expected `{prt}` for parameter `{mysignature.mparameters[i].name}'; got `{myt}`.")
                                                self.mpropdef.msignature = null
                                        end
                                end
                        end
                        if precursor_ret_type != null then
                                var node: nullable ANode = null
                                if nsig != null then node = nsig.n_type
                                if node == null then node = self
                                if ret_type == null then
                                        # Inherit the return type
                                        ret_type = precursor_ret_type
                                else if not modelbuilder.check_subtype(node, mmodule, mclassdef.bound_mtype, ret_type, precursor_ret_type) then
                                        modelbuilder.error(node, "Redef Error: expected `{precursor_ret_type}` for return type; got `{ret_type}`.")
                                        self.mpropdef.msignature = null
                                end
                        end
                end

                if mysignature.arity > 0 then
                        # Check parameters visibility
                        for i in [0..mysignature.arity[ do
                                var nt = nsig.n_params[i].n_type
                                if nt != null then modelbuilder.check_visibility(nt, nt.mtype.as(not null), mpropdef)
                        end
                        var nt = nsig.n_type
                        if nt != null then modelbuilder.check_visibility(nt, nt.mtype.as(not null), mpropdef)
                end
                check_repeated_types(modelbuilder)
        end

        # For parameters, type is always useless in a redef.
        # For return type, type is useless if not covariant with introduction.
        redef fun check_repeated_types(modelbuilder) do
                if mpropdef.is_intro or n_signature == null then return
                # check params
                for param in n_signature.n_params do
                        if param.n_type != null then
                                modelbuilder.advice(param.n_type, "useless-signature", "Warning: useless type repetition on parameter `{param.n_id.text}` for redefined method `{mpropdef.name}`")
                        end
                end
                # get intro
                var intro = mpropdef.mproperty.intro
                var n_intro = modelbuilder.mpropdef2npropdef.get_or_null(intro)
                if n_intro == null or not n_intro isa AMethPropdef then return
                # check return type
                var ret_type = n_signature.ret_type
                if ret_type != null and ret_type == n_intro.n_signature.ret_type then
                        modelbuilder.advice(n_signature.n_type, "useless-signature", "Warning: useless return type repetition for redefined method `{mpropdef.name}`")
                end
        end
end

redef class AMethid
        # Is a return required?
        #
        # * True for operators and brackets.
        # * False for id and assignment.
        fun return_is_mandatory: Bool do return true

        # Can the last parameter be special like a vararg?
        #
        # * False for operators: the last one is in fact the only one.
        # * False for assignments: it is the right part of the assignment.
        # * True for ids and brackets.
        fun accept_special_last_parameter: Bool do return false

        # The minimum required number of parameters.
        #
        # * 1 for binary operators
        # * 1 for brackets
        # * 1 for assignments
        # * 2 for bracket assignments
        # * 0 for ids
        fun min_arity: Int do return 1

        # Is the `self` a binary operator?
        fun is_binary: Bool do return true
end

redef class AIdMethid
        redef fun return_is_mandatory do return false
        redef fun accept_special_last_parameter do return true
        redef fun min_arity do return 0
        redef fun is_binary do return false
end

redef class ABraMethid
        redef fun accept_special_last_parameter do return true
        redef fun is_binary do return false
end

redef class ABraassignMethid
        redef fun return_is_mandatory do return false
        redef fun min_arity do return 2
        redef fun is_binary do return false
end

redef class AAssignMethid
        redef fun return_is_mandatory do return false
        redef fun is_binary do return false
end

redef class AAttrPropdef
        redef type MPROPDEF: MAttributeDef

        # The static type of the property (declared, inferred or inherited)
        # This attribute is also used to check if the property was analyzed and is valid.
        var mtype: nullable MType

        # Is the node tagged `noinit`?
        var noinit = false

        # Is the node tagged lazy?
        var is_lazy = false

        # Has the node a default value?
        # Could be through `n_expr` or `n_block`
        var has_value = false

        # The guard associated to a lazy attribute.
        # Because some engines does not have a working `isset`,
        # this additional attribute is used to guard the lazy initialization.
        # TODO: to remove once isset is correctly implemented
        var mlazypropdef: nullable MAttributeDef

        # The associated getter (read accessor) if any
        var mreadpropdef: nullable MMethodDef is writable
        # The associated setter (write accessor) if any
        var mwritepropdef: nullable MMethodDef is writable

        redef fun build_property(modelbuilder, mclassdef)
        do
                var mclass = mclassdef.mclass
                var nid2 = n_id2
                var name = nid2.text

                var atabstract = self.get_single_annotation("abstract", modelbuilder)
                if atabstract == null then
                        if not mclass.kind.need_init then
                                modelbuilder.error(self, "Error: attempt to define attribute `{name}` in the {mclass.kind} `{mclass}`.")
                        end

                        var mprop = new MAttribute(mclassdef, "_" + name, private_visibility)
                        var mpropdef = new MAttributeDef(mclassdef, mprop, self.location)
                        self.mpropdef = mpropdef
                        modelbuilder.mpropdef2npropdef[mpropdef] = self
                end

                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, mclassdef, self.n_visibility)
                        mreadprop = new MMethod(mclassdef, readname, mvisibility)
                        if not self.check_redef_keyword(modelbuilder, mclassdef, n_kwredef, false, mreadprop) then return
                else
                        if not self.check_redef_keyword(modelbuilder, mclassdef, n_kwredef, true, mreadprop) then return
                        check_redef_property_visibility(modelbuilder, self.n_visibility, mreadprop)
                end
                mclassdef.mprop2npropdef[mreadprop] = self

                var mreadpropdef = new MMethodDef(mclassdef, mreadprop, self.location)
                self.mreadpropdef = mreadpropdef
                modelbuilder.mpropdef2npropdef[mreadpropdef] = self
                set_doc(mreadpropdef, modelbuilder)
                if mpropdef != null then mpropdef.mdoc = mreadpropdef.mdoc
                if atabstract != null then mreadpropdef.is_abstract = true

                has_value = n_expr != null or n_block != null

                if atabstract != null and has_value then
                        modelbuilder.error(atabstract, "Error: `abstract` attributes cannot have an initial value.")
                        return
                end

                var atnoinit = self.get_single_annotation("noinit", modelbuilder)
                if atnoinit == null then atnoinit = self.get_single_annotation("noautoinit", modelbuilder)
                if atnoinit != null then
                        noinit = true
                        if has_value then
                                modelbuilder.error(atnoinit, "Error: `noautoinit` attributes cannot have an initial value.")
                                return
                        end
                        if atabstract != null then
                                modelbuilder.warning(atnoinit, "useless-noautoinit", "Warning: superfluous `noautoinit` on abstract attribute.")
                        end
                end

                var atlazy = self.get_single_annotation("lazy", modelbuilder)
                var atlateinit = self.get_single_annotation("lateinit", modelbuilder)
                if atlazy != null or atlateinit != null then
                        if atlazy != null and atlateinit != null then
                                modelbuilder.error(atlazy, "Error: `lazy` incompatible with `lateinit`.")
                                return
                        end
                        if not has_value then
                                if atlazy != null then
                                        modelbuilder.error(atlazy, "Error: `lazy` attributes need a value.")
                                else if atlateinit != null then
                                        modelbuilder.error(atlateinit, "Error: `lateinit` attributes need a value.")
                                end
                                has_value = true
                                return
                        end
                        is_lazy = true
                        var mlazyprop = new MAttribute(mclassdef, "lazy _" + name, none_visibility)
                        var mlazypropdef = new MAttributeDef(mclassdef, mlazyprop, self.location)
                        self.mlazypropdef = mlazypropdef
                end

                var atreadonly = self.get_single_annotation("readonly", modelbuilder)
                if atreadonly != null then
                        if not has_value then
                                modelbuilder.error(atreadonly, "Error: `readonly` attributes need a value.")
                        end
                        # No setter, so just leave
                        return
                end

                if not mclassdef.is_intro and not has_value and not noinit then
                        modelbuilder.advice(self, "attr-in-refinement", "Warning: attributes in refinement need a value or `noautoinit`.")
                end

                var writename = name + "="
                var atwritable = self.get_single_annotation("writable", modelbuilder)
                if atwritable != null then
                        if not atwritable.n_args.is_empty then
                                writename = atwritable.arg_as_id(modelbuilder) or else writename
                        end
                end
                var mwriteprop = modelbuilder.try_get_mproperty_by_name(nid2, mclassdef, writename).as(nullable MMethod)
                var nwkwredef: nullable Token = null
                if atwritable != null then nwkwredef = atwritable.n_kwredef
                if mwriteprop == null then
                        var mvisibility
                        if atwritable != null then
                                mvisibility = new_property_visibility(modelbuilder, mclassdef, atwritable.n_visibility)
                        else
                                mvisibility = mreadprop.visibility
                                # By default, use protected visibility at most
                                if mvisibility > protected_visibility then mvisibility = protected_visibility
                        end
                        mwriteprop = new MMethod(mclassdef, writename, mvisibility)
                        if not self.check_redef_keyword(modelbuilder, mclassdef, nwkwredef, false, mwriteprop) then return
                        mwriteprop.deprecation = mreadprop.deprecation
                else
                        if not self.check_redef_keyword(modelbuilder, mclassdef, nwkwredef or else n_kwredef, true, mwriteprop) then return
                        if atwritable != null then
                                check_redef_property_visibility(modelbuilder, atwritable.n_visibility, mwriteprop)
                        end
                end
                mclassdef.mprop2npropdef[mwriteprop] = self

                var mwritepropdef = new MMethodDef(mclassdef, mwriteprop, self.location)
                self.mwritepropdef = mwritepropdef
                modelbuilder.mpropdef2npropdef[mwritepropdef] = self
                mwritepropdef.mdoc = mreadpropdef.mdoc
                if atabstract != null then mwritepropdef.is_abstract = true

                var atautoinit = self.get_single_annotation("autoinit", modelbuilder)
                if atautoinit != null then
                        if has_value then
                                modelbuilder.error(atautoinit, "Error: `autoinit` attributes cannot have an initial value.")
                        else if not mwritepropdef.is_intro then
                                modelbuilder.error(atautoinit, "Error: `autoinit` attributes cannot be set on redefinitions.")
                        else if not mclassdef.is_intro then
                                modelbuilder.error(atautoinit, "Error: `autoinit` attributes cannot be used in class refinements.")
                        else if atabstract == null then
                                modelbuilder.warning(atautoinit, "useless-autoinit", "Warning: superfluous `autoinit` on attribute.")
                        end
                else if atabstract != null then
                        # By default, abstract attribute are not autoinit
                        noinit = true
                end
        end

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


                var ntype = self.n_type
                if ntype != null then
                        mtype = modelbuilder.resolve_mtype_unchecked(mmodule, mclassdef, ntype, true)
                        if mtype == null then return
                end

                var inherited_type: nullable MType = null
                # Inherit the type from the getter (usually an abstract getter)
                if not mreadpropdef.is_intro then
                        var msignature = mreadpropdef.mproperty.intro.msignature
                        if msignature == null then return # Error, thus skipped
                        inherited_type = msignature.return_mtype
                        if inherited_type != null then
                                # The inherited type is adapted to use the local formal types, if any.
                                inherited_type = inherited_type.resolve_for(mclassdef.mclass.mclass_type, mclassdef.bound_mtype, mmodule, false)
                                if mtype == null then mtype = inherited_type
                        end
                end

                var nexpr = self.n_expr
                if mtype == null then
                        if nexpr != null then
                                if nexpr isa ANewExpr then
                                        mtype = modelbuilder.resolve_mtype_unchecked(mmodule, mclassdef, nexpr.n_type, true)
                                else if nexpr isa AIntegerExpr then
                                        var cla: nullable MClass = null
                                        if nexpr.value isa Int then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
                                        else if nexpr.value isa Byte then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Byte")
                                        else if nexpr.value isa Int8 then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int8")
                                        else if nexpr.value isa Int16 then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int16")
                                        else if nexpr.value isa UInt16 then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "UInt16")
                                        else if nexpr.value isa Int32 then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int32")
                                        else if nexpr.value isa UInt32 then
                                                cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "UInt32")
                                        else
                                                # Should not happen, and should be updated as new types are added
                                                abort
                                        end
                                        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 `{mreadpropdef}`. Implicit typing allowed only for literals and new.")
                                end

                                if mtype == null then return
                        end
                else if ntype != null and inherited_type == mtype then
                        if nexpr isa ANewExpr then
                                var xmtype = modelbuilder.resolve_mtype_unchecked(mmodule, mclassdef, nexpr.n_type, true)
                                if xmtype == mtype then
                                        modelbuilder.advice(ntype, "useless-type", "Warning: useless type definition")
                                end
                        end
                end

                if mtype == null then
                        modelbuilder.error(self, "Error: untyped attribute `{mreadpropdef}`.")
                        return
                end

                self.mtype = mtype

                if mpropdef != null then
                        mpropdef.static_mtype = mtype
                end

                do
                        var msignature = new MSignature(new Array[MParameter], mtype)
                        mreadpropdef.msignature = msignature
                end

                var mwritepropdef = self.mwritepropdef
                if mwritepropdef != null then
                        var name: String
                        name = n_id2.text
                        var mparameter = new MParameter(name, mtype, false)
                        var msignature = new MSignature([mparameter], null)
                        mwritepropdef.msignature = msignature
                end

                var mlazypropdef = self.mlazypropdef
                if mlazypropdef != null then
                        mlazypropdef.static_mtype = modelbuilder.model.get_mclasses_by_name("Bool").first.mclass_type
                end
                check_repeated_types(modelbuilder)
        end

        redef fun check_signature(modelbuilder)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skipped
                var ntype = self.n_type
                var mtype = self.mtype
                if mtype == null then return # Error thus skipped

                var mclassdef = mpropdef.mclassdef
                var mmodule = mclassdef.mmodule

                # Check types
                if ntype != null then
                        if modelbuilder.resolve_mtype(mmodule, mclassdef, ntype) == null then return
                end
                var nexpr = n_expr
                if nexpr isa ANewExpr then
                        if modelbuilder.resolve_mtype(mmodule, mclassdef, nexpr.n_type) == null then return
                end

                # 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: expected `{precursor_type}` type as a bound; got `{mtype}`.")
                                return
                        end
                end

                # Check getter and setter
                var meth = self.mreadpropdef
                if meth != null then
                        self.check_method_signature(modelbuilder, meth)
                        var node: nullable ANode = ntype
                        if node == null then node = self
                        modelbuilder.check_visibility(node, mtype, meth)
                end
                meth = self.mwritepropdef
                if meth != null then
                        self.check_method_signature(modelbuilder, meth)
                        var node: nullable ANode = ntype
                        if node == null then node = self
                        modelbuilder.check_visibility(node, mtype, meth)
                end
        end

        private fun check_method_signature(modelbuilder: ModelBuilder, mpropdef: MMethodDef)
        do
                var mclassdef = mpropdef.mclassdef
                var mmodule = 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: expected {msignature.arity} parameter(s) for `{mpropdef.mproperty.name}{msignature}`; got {mysignature.arity}. See introduction at `{mpropdef.mproperty.full_name}`.")
                                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
                                        var node: ANode
                                        if nsig != null then node = nsig else node = self
                                        if not modelbuilder.check_sametype(node, mmodule, mclassdef.bound_mtype, myt, prt) then
                                                modelbuilder.error(node, "Redef Error: expected `{prt}` type for parameter `{mysignature.mparameters[i].name}'; got `{myt}`.")
                                        end
                                end
                        end
                        if precursor_ret_type != null then
                                var node: ANode
                                if nsig != null then node = nsig else node = self
                                if ret_type == null then
                                        # Inherit the return type
                                        ret_type = precursor_ret_type
                                else if not modelbuilder.check_subtype(node, mmodule, mclassdef.bound_mtype, ret_type, precursor_ret_type) then
                                        modelbuilder.error(node, "Redef Error: expected `{precursor_ret_type}` return type; got `{ret_type}`.")
                                end
                        end
                end
        end

        # Type is useless if the attribute type is the same thant the intro.
        redef fun check_repeated_types(modelbuilder) do
                if mreadpropdef.is_intro or n_type == null then return
                # get intro
                var intro = mreadpropdef.mproperty.intro
                var n_intro = modelbuilder.mpropdef2npropdef.get_or_null(intro)
                if n_intro == null then return
                # get intro type
                var ntype = null
                if n_intro isa AMethPropdef then
                        ntype = n_intro.n_signature.ret_type
                else if n_intro isa AAttrPropdef and n_intro.n_type != null then
                        ntype = n_intro.n_type.mtype
                end
                # check
                if ntype == null or ntype != n_type.mtype or mpropdef == null then return
                modelbuilder.advice(n_type, "useless-signature", "Warning: useless type repetition on redefined attribute `{mpropdef.name}`")
        end
end

redef class ATypePropdef
        redef type MPROPDEF: MVirtualTypeDef

        redef fun build_property(modelbuilder, mclassdef)
        do
                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, mclassdef, self.n_visibility)
                        mprop = new MVirtualTypeProp(mclassdef, name, mvisibility)
                        for c in name.chars do if c >= 'a' and c<= 'z' then
                                modelbuilder.warning(n_id, "bad-type-name", "Warning: lowercase in the virtual type `{name}`.")
                                break
                        end
                        if not self.check_redef_keyword(modelbuilder, mclassdef, self.n_kwredef, false, mprop) then return
                else
                        if not self.check_redef_keyword(modelbuilder, mclassdef, self.n_kwredef, true, mprop) then return
                        assert mprop isa MVirtualTypeProp
                        check_redef_property_visibility(modelbuilder, self.n_visibility, mprop)
                end
                mclassdef.mprop2npropdef[mprop] = self

                var mpropdef = new MVirtualTypeDef(mclassdef, mprop, self.location)
                self.mpropdef = mpropdef
                modelbuilder.mpropdef2npropdef[mpropdef] = self
                if mpropdef.is_intro then
                        modelbuilder.toolcontext.info("{mpropdef} introduces new type {mprop.full_name}", 4)
                else
                        modelbuilder.toolcontext.info("{mpropdef} redefines type {mprop.full_name}", 4)
                end
                set_doc(mpropdef, modelbuilder)

                var atfixed = get_single_annotation("fixed", modelbuilder)
                if atfixed != null then
                        mpropdef.is_fixed = true
                end
        end

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

                var ntype = self.n_type
                mtype = modelbuilder.resolve_mtype_unchecked(mmodule, mclassdef, ntype, true)
                if mtype == null then return

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

        redef fun check_signature(modelbuilder)
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skipped

                var bound = mpropdef.bound
                if bound == null then return # Error thus skipped

                modelbuilder.check_visibility(n_type, bound, mpropdef)

                var mclassdef = mpropdef.mclassdef
                var mmodule = mclassdef.mmodule
                var anchor = mclassdef.bound_mtype

                var ntype = self.n_type
                if modelbuilder.resolve_mtype(mmodule, mclassdef, ntype) == null then
                        mpropdef.bound = null
                        return
                end

                # Check redefinitions
                for p in mpropdef.mproperty.lookup_super_definitions(mmodule, anchor) do
                        var supbound = p.bound
                        if supbound == null then break # broken super bound, skip error
                        if p.is_fixed then
                                modelbuilder.error(self, "Redef Error: virtual type `{mpropdef.mproperty}` is fixed in super-class `{p.mclassdef.mclass}`.")
                                break
                        end
                        if p.mclassdef.mclass == mclassdef.mclass then
                                # Still a warning to pass existing bad code
                                modelbuilder.warning(n_type, "refine-type", "Redef Error: a virtual type cannot be refined.")
                                break
                        end
                        if not modelbuilder.check_subtype(n_type, mmodule, anchor, bound, supbound) then
                                modelbuilder.error(n_type, "Redef Error: expected `{supbound}` bound type; got `{bound}`.")
                                break
                        end
                end
        end
end