Inheritance of constructors.

A class without constructors can inherit those of its superclasses.
These classes are called "Mixin" since their subclasses do not have to care about their initialisation.

The inherited constructors are all that belong to the most specific non-mixin superclass.

diff --git a/src/metamodel/inheritance.nit b/src/metamodel/inheritance.nit
index 15ac695..50924cd 100644 (file)
--- a/src/metamodel/inheritance.nit
+++ b/src/metamodel/inheritance.nit
@@ -130,19 +130,26 @@ redef class MMLocalClass
                                        continue
                                end
 
-                               var gname = glob.intro.name
-                               var conf_set: Array[MMGlobalProperty]
-                               if names.has_key(gname) then
-                                       conf_set = names[gname]
-                               else
-                                       conf_set = new Array[MMGlobalProperty]
-                                       names[gname] = conf_set
-                               end
-                               conf_set.add(glob)
+                               make_visible_an_inherited_global_property(glob)
                        end
                end
        end
 
+       # Make the name of a global property meaningful in the class
+       meth make_visible_an_inherited_global_property(glob: MMGlobalProperty)
+       do
+               var names = _properties_by_name
+               var gname = glob.intro.name
+               var conf_set: Array[MMGlobalProperty]
+               if names.has_key(gname) then
+                       conf_set = names[gname]
+               else
+                       conf_set = new Array[MMGlobalProperty]
+                       names[gname] = conf_set
+               end
+               conf_set.add(glob)
+       end
+
        # Add super stype of this current local class
        meth add_direct_parent(p: MMAncestor)
        do

diff --git a/src/syntax/mmbuilder.nit b/src/syntax/mmbuilder.nit
index 8d52ce3..129b50f 100644 (file)
--- a/src/syntax/mmbuilder.nit
+++ b/src/syntax/mmbuilder.nit
@@ -93,7 +93,10 @@ redef class MMSrcModule
 
                        # Global property introduction and redefinition 
                        c.accept_class_visitor(mmbv2)
-                       if c isa MMSrcLocalClass then
+
+                       # Default and inherited constructor if needed
+                       if c isa MMSrcLocalClass and c.global.intro == c and not c.global.is_universal and not c.global.is_interface then
+                               c.process_default_constructors(mmbv2)
                        end
 
                        # Note that inherited unredefined property are processed on demand latter
@@ -149,6 +152,65 @@ redef class MMSrcLocalClass
                        p.accept_property_visitor(v)
                end
        end
+
+       # A mixin class can be build the same way that one of its superclasses
+       readable attr _is_mixin: Bool = false
+
+       # Introduce or inherit default constructors
+       private meth process_default_constructors(v: PropertyBuilderVisitor)
+       do
+               # Is there already a constructor ?
+               for gp in global_properties do
+                       if gp.is_init then
+                               # Return if explicit constructor in the class
+                               if gp.intro.local_class == self then return
+                       end
+               end
+
+               # Collect visible constructors in super stateful classes
+               var super_constructors = new ArraySet[MMGlobalProperty]
+               for sc in che.direct_greaters do
+                       if sc.global.is_universal or sc.global.is_interface then continue
+                       for gp in sc.global_properties do
+                               if not gp.is_init then continue
+                               super_constructors.add(gp)
+                       end
+               end
+
+               if not super_constructors.is_empty then
+                       # Select most specific classes introducing inheritable constructors
+                       # Mixin classes are skipped
+                       var supers = new Array[MMLocalClass]
+                       for gp in super_constructors do
+                               var sc = gp.local_class
+                               if supers.has(sc) then continue
+                               assert sc isa MMSrcLocalClass
+                               if not sc.is_mixin then
+                                       supers.add(sc)
+                               end
+                       end
+                       supers = che.order.select_smallests(supers)
+
+                       # A mixin class can only have 0 or 1 most specific non-mixin superclass
+                       var superclass: MMLocalClass = null # This most specific non-mixin superclass (if any)
+
+                       if supers.length > 1 then
+                               v.error(nodes.first, "Error: Explicit constructor required in {self} since multiple inheritance of constructor is forbiden. Conflicting classes are {supers.join(", ")}. Costructors are {super_constructors.join(", ")}.")
+                               return
+                       else if supers.length == 1 then
+                               superclass = supers.first
+                       end
+
+                       for gp in super_constructors do
+                               # Inherit constructors : the one of the non-mixin super class or all from the all mixin super-classes
+                               if superclass == null or gp.local_class == superclass then
+                                       make_visible_an_inherited_global_property(gp)
+                               end
+                       end
+                       _is_mixin = true
+               end
+       end
+
        # Add a source property
        # Register it to the class and attach it to global property
        private meth add_src_local_property(v: PropertyBuilderVisitor, prop: MMLocalProperty)