src: Update init
[nit.git] / src / modelize / modelize_property.nit
index 9465dbb..8529ed6 100644 (file)
@@ -42,6 +42,17 @@ redef class ModelBuilder
        # Public clients need to use `mpropdef2node` to access stuff.
        private var mpropdef2npropdef = new HashMap[MPropDef, APropdef]
 
+       # Associate a `npropdef` with its `mpropdef`
+       #
+       # Be careful, this method is unsafe, no checking is done when it's used.
+       # The safe way to add method it's to use the `build_property`
+       #
+       # See `mpropdef2npropdef`
+       fun unsafe_add_mpropdef2npropdef(mpropdef: MPropDef,npropdef: APropdef)
+       do
+               mpropdef2npropdef[mpropdef] = npropdef
+       end
+
        # Retrieve the associated AST node of a mpropertydef.
        # This method is used to associate model entity with syntactic entities.
        #
@@ -55,10 +66,9 @@ redef class ModelBuilder
                        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
+               # Fall back to the class node if any.
+               res = mclassdef2nclassdef.get_or_null(mpropdef.mclassdef)
+               if res != null then return res
                return null
        end
 
@@ -150,11 +160,9 @@ redef class ModelBuilder
                        var mparameters = new Array[MParameter]
                        var msignature = new MSignature(mparameters, null)
                        mpropdef.msignature = msignature
-                       mpropdef.new_msignature = msignature
                        mprop.is_init = true
                        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?
@@ -165,12 +173,14 @@ redef class ModelBuilder
                        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
+                       end
+                       if mpropdef.name == "defaultinit" then
                                return
                        end
                end
 
+               if mclassdef.default_init != null then return
+
                if not nclassdef isa AStdClassdef then return
 
                # Collect undefined attributes
@@ -183,7 +193,6 @@ redef class ModelBuilder
                                if mpropdef == null then return # Skip broken method
                                var sig = mpropdef.msignature
                                if sig == null then continue # Skip broken method
-
                                mparameters.add_all sig.mparameters
                                initializers.add(mpropdef.mproperty)
                                mpropdef.mproperty.is_autoinit = true
@@ -227,10 +236,12 @@ redef class ModelBuilder
                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
+               var spropdefs = new ArraySet[MMethodDef]
+               for x in mclassdef.in_hierarchy.direct_greaters do
+                       var y = x.mclass.intro.default_init
+                       if y == null then continue
+                       if y.is_broken or y.msignature == null then return
+                       spropdefs.add y
                end
 
                # Look at the autoinit class-annotation
@@ -284,7 +295,7 @@ redef class ModelBuilder
                                        abort
                                end
                        end
-               else
+               else if spropdefs.not_empty then
                        # Search the longest-one and checks for conflict
                        var longest = spropdefs.first
                        if spropdefs.length > 1 then
@@ -323,41 +334,26 @@ redef class ModelBuilder
                                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
+                                       mparameters.prepend longest.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)
+               # Create a specific new autoinit constructor
+               do
+                       var mprop = new MMethod(mclassdef, "defaultinit", nclassdef.location, public_visibility)
+                       mprop.is_init = true
+                       var mpropdef = new MMethodDef(mclassdef, mprop, nclassdef.location)
+                       mpropdef.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
+                       mpropdef.msignature = msignature
+                       mclassdef.default_init = mpropdef
+                       self.toolcontext.info("{mclassdef} gets a free auto constructor `{mpropdef}{msignature}`. {spropdefs}", 3)
+                       mclassdef.mclass.the_root_init_mmethod = the_root_init_mmethod
                end
-
-               # Else create the local implicit basic init definition
-               var mprop = the_root_init_mmethod
-               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
-               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`.
@@ -493,11 +489,9 @@ 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
+       # TODO: merge with `root_init` and `ModelBuilder::the_root_init_mmethod` if possible
+       var the_root_init_mmethod: nullable MMethod = null
 end
 
 redef class MClassDef
@@ -671,14 +665,13 @@ redef class ASignature
        # 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)
+                               var mtype = modelbuilder.resolve_mtype_unchecked(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)
@@ -695,7 +688,7 @@ redef class ASignature
                end
                var ntype = self.n_type
                if ntype != null then
-                       self.ret_type = modelbuilder.resolve_mtype_unchecked(mmodule, mclassdef, ntype, true)
+                       self.ret_type = modelbuilder.resolve_mtype_unchecked(mclassdef, ntype, true)
                        if self.ret_type == null then return false # Skip error
                end
 
@@ -709,14 +702,14 @@ redef class ASignature
                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
+                               if modelbuilder.resolve_mtype(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
+                       if modelbuilder.resolve_mtype(mclassdef, ntype) == null then
                                res = false
                        end
                end
@@ -770,22 +763,27 @@ redef class AMethPropdef
        do
                var n_kwinit = n_kwinit
                var n_kwnew = n_kwnew
-               var is_init = n_kwinit != null or n_kwnew != null
+               var is_new = n_kwnew != null
+               var is_init = n_kwinit != null or is_new
                var name: String
                var amethodid = self.n_methid
                var name_node: ANode
+               var is_old_style_init = false
                if amethodid == null then
-                       if not is_init then
-                               name = "main"
-                               name_node = self
-                       else if n_kwinit != null then
+                       if n_kwinit != null then
                                name = "init"
                                name_node = n_kwinit
+                               var old_style_annot = get_single_annotation("old_style_init", modelbuilder)
+                               if  old_style_annot != null or self.n_signature.n_params.not_empty then
+                                       name = "defaultinit"
+                                       if old_style_annot != null then is_old_style_init = true
+                               end
                        else if n_kwnew != null then
                                name = "new"
                                name_node = n_kwnew
                        else
-                               abort
+                               name = "main"
+                               name_node = self
                        end
                else if amethodid isa AIdMethid then
                        name = amethodid.n_id.text
@@ -813,7 +811,7 @@ redef class AMethPropdef
 
                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 not is_init or n_kwredef != null or look_like_a_root_init 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
@@ -829,8 +827,8 @@ redef class AMethPropdef
                                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
+                       mprop.is_new = is_new
+                       if 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
                        if not self.check_redef_keyword(modelbuilder, mclassdef, n_kwredef, false, mprop) then
                                mprop.is_broken = true
@@ -858,6 +856,15 @@ redef class AMethPropdef
                mclassdef.mprop2npropdef[mprop] = self
 
                var mpropdef = new MMethodDef(mclassdef, mprop, self.location)
+               if mpropdef.name == "defaultinit" and mclassdef.is_intro then
+                       assert mclassdef.default_init == null
+                       mpropdef.is_old_style_init = is_old_style_init
+                       mclassdef.default_init = mpropdef
+                       if mpropdef.is_intro then
+                               mpropdef.initializers.add mprop
+                               mpropdef.is_calling_init = true
+                       end
+               end
 
                set_doc(mpropdef, modelbuilder)
 
@@ -874,20 +881,11 @@ redef class AMethPropdef
        do
                var mpropdef = self.mpropdef
                if mpropdef == null then return # Error thus skiped
+               var mproperty = mpropdef.mproperty
                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
 
@@ -908,7 +906,7 @@ redef class AMethPropdef
                # 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
+                       msignature = mproperty.intro.msignature
                        if msignature == null then return # Skip error
 
                        # The local signature is adapted to use the local formal types, if any.
@@ -918,14 +916,14 @@ redef class AMethPropdef
                        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}`.")
+                               modelbuilder.error(node, "Redef Error: expected {msignature.arity} parameter(s) for `{mproperty.name}{msignature}`; got {param_names.length}. See introduction at `{mproperty.full_name}`.")
                                return
                        end
-               else if mpropdef.mproperty.is_init and not mpropdef.mproperty.is_new then
+               else if mproperty.is_init and not 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)
+                               var candidate = modelbuilder.try_get_mproperty_by_name2(self, mmodule, msupertype, mproperty.name)
                                if candidate != null then
                                        if msignature == null then
                                                msignature = candidate.intro.as(MMethodDef).msignature
@@ -962,14 +960,14 @@ redef class AMethPropdef
                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
+               if ret_type == null and 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}`.")
+                       modelbuilder.error(self.n_signature.n_params.last, "Error: illegal variadic parameter `{mparameters.last}` for `{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}`.")
+                       modelbuilder.error(self.n_methid, "Error: mandatory return type for `{mproperty.name}`.")
                end
 
                msignature = new MSignature(mparameters, ret_type)
@@ -1158,8 +1156,8 @@ redef class AAttrPropdef
        # Is the node tagged optional?
        var is_optional = false
 
-       # Has the node a default value?
-       # Could be through `n_expr` or `n_block`
+       # Does the node have a default value?
+       # Could be through `n_expr`, `n_block` or `is_lazy`
        var has_value = false
 
        # The guard associated to a lazy attribute.
@@ -1207,6 +1205,12 @@ redef class AAttrPropdef
                end
                mclassdef.mprop2npropdef[mreadprop] = self
 
+               var attr_mpropdef = mpropdef
+               if attr_mpropdef != null then
+                       mreadprop.getter_for = attr_mpropdef.mproperty
+                       attr_mpropdef.mproperty.getter = mreadprop
+               end
+
                var mreadpropdef = new MMethodDef(mclassdef, mreadprop, self.location)
                self.mreadpropdef = mreadpropdef
                modelbuilder.mpropdef2npropdef[mreadpropdef] = self
@@ -1313,6 +1317,11 @@ redef class AAttrPropdef
                end
                mclassdef.mprop2npropdef[mwriteprop] = self
 
+               if attr_mpropdef != null then
+                       mwriteprop.setter_for = attr_mpropdef.mproperty
+                       attr_mpropdef.mproperty.setter = mwriteprop
+               end
+
                var mwritepropdef = new MMethodDef(mclassdef, mwriteprop, self.location)
                self.mwritepropdef = mwritepropdef
                modelbuilder.mpropdef2npropdef[mwritepropdef] = self
@@ -1348,7 +1357,7 @@ redef class AAttrPropdef
 
                var ntype = self.n_type
                if ntype != null then
-                       mtype = modelbuilder.resolve_mtype_unchecked(mmodule, mclassdef, ntype, true)
+                       mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, ntype, true)
                        if mtype == null then return
                end
 
@@ -1368,71 +1377,12 @@ redef class AAttrPropdef
                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 AAsCastExpr 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: nullable MClass
-                                       if nexpr.is_ascii then
-                                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Byte")
-                                       else if nexpr.is_code_point then
-                                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
-                                       else
-                                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Char")
-                                       end
-                                       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: nullable MClass
-                                       if nexpr.is_bytestring then
-                                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bytes")
-                                       else if nexpr.is_re then
-                                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Regex")
-                                       else if nexpr.is_string then
-                                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
-                                       else
-                                               abort
-                                       end
-                                       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
-
+                               mtype = infer_static_type(modelbuilder, nexpr, mclassdef, mmodule, mreadpropdef)
                                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)
+                               var xmtype = modelbuilder.resolve_mtype_unchecked(mclassdef, nexpr.n_type, true)
                                if xmtype == mtype then
                                        modelbuilder.advice(ntype, "useless-type", "Warning: useless type definition")
                                end
@@ -1475,6 +1425,102 @@ redef class AAttrPropdef
                check_repeated_types(modelbuilder)
        end
 
+       # Detect the static type from the value assigned to the attribute `self`
+       #
+       # Return the static type if it can be safely inferred.
+       private fun infer_static_type(modelbuilder: ModelBuilder, nexpr: AExpr,
+               mclassdef: MClassDef, mmodule: MModule, mreadpropdef: MPropDef): nullable MType
+       do
+               var mtype = null
+               if nexpr isa ANewExpr then
+                       mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, nexpr.n_type, true)
+               else if nexpr isa AAsCastExpr then
+                       mtype = modelbuilder.resolve_mtype_unchecked(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: nullable MClass
+                       if nexpr.is_code_point then
+                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
+                       else
+                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Char")
+                       end
+                       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: nullable MClass
+                       if nexpr.is_bytestring then
+                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bytes")
+                       else if nexpr.is_re then
+                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Regex")
+                       else if nexpr.is_string then
+                               cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
+                       else
+                               abort
+                       end
+                       if cla != null then mtype = cla.mclass_type
+               else if nexpr isa AArrayExpr and nexpr.n_type == null and nexpr.n_exprs.not_empty then
+                       # Non-empty arrays without an explicit type
+
+                       var item_mtypes = new Set[MType]
+                       var fails = false
+                       for node in nexpr.n_exprs do
+                               var item_mtype = infer_static_type(modelbuilder, node, mclassdef, mmodule, mreadpropdef)
+                               if item_mtype == null then
+                                       fails = true
+                               else
+                                       item_mtypes.add item_mtype
+                               end
+                       end
+
+                       if fails then return null # Failed to infer some types
+
+                       if item_mtypes.length > 1 then
+                               modelbuilder.error(self, "Type Error: ambiguous array type {item_mtypes.join(" ")}")
+                       end
+
+                       mtype = mmodule.array_type(item_mtypes.first)
+               else if nexpr isa AUminusExpr and (nexpr.n_expr isa AIntegerExpr or nexpr.n_expr isa AFloatExpr) then
+                       # The Int and Float unary - is defined in `kernel`, so this may
+                       # result in an invalid behavior when using a custom kernel.
+                       # A workaround is to declare the attribute static type.
+                       # This is still very useful, especially to novice programmers.
+                       mtype = infer_static_type(modelbuilder, nexpr.n_expr, mclassdef, mmodule, mreadpropdef)
+               else if nexpr isa AOnceExpr then
+                       mtype = infer_static_type(modelbuilder, nexpr.n_expr, mclassdef, mmodule, mreadpropdef)
+               else
+                       modelbuilder.error(self, "Error: untyped attribute `{mreadpropdef}`. Implicit typing allowed only for literals and new.")
+               end
+               return mtype
+       end
+
        redef fun check_signature(modelbuilder)
        do
                var mpropdef = self.mpropdef
@@ -1488,11 +1534,11 @@ redef class AAttrPropdef
 
                # Check types
                if ntype != null then
-                       if modelbuilder.resolve_mtype(mmodule, mclassdef, ntype) == null then return
+                       if modelbuilder.resolve_mtype(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
+                       if modelbuilder.resolve_mtype(mclassdef, nexpr.n_type) == null then return
                end
 
                # Lookup for signature in the precursor
@@ -1645,11 +1691,10 @@ redef class ATypePropdef
                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)
+               mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, ntype, true)
                if mtype == null then return
 
                mpropdef.bound = mtype
@@ -1671,7 +1716,7 @@ redef class ATypePropdef
                var anchor = mclassdef.bound_mtype
 
                var ntype = self.n_type
-               if modelbuilder.resolve_mtype(mmodule, mclassdef, ntype) == null then
+               if modelbuilder.resolve_mtype(mclassdef, ntype) == null then
                        mpropdef.bound = null
                        return
                end