typing: check correct usage of top-level methods

First, the body of top-level methods has two constraints:
 * no explicit self
 * implicit self can only call other top-level methods

Second, only self can invoke top-level methods.
Eg. no `6.print("hello")`

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/typing.nit b/src/typing.nit
index 3a8194a..5db0ada 100644 (file)
--- a/src/typing.nit
+++ b/src/typing.nit
@@ -51,6 +51,11 @@ private class TypeVisitor
 
        var selfvariable: Variable = new Variable("self")
 
+       # Is `self` use restricted?
+       # * no explicit `self`
+       # * method called on the implicit self must be top-level
+       var is_toplevel_context = false
+
        init(modelbuilder: ModelBuilder, mmodule: MModule, mpropdef: nullable MPropDef)
        do
                self.modelbuilder = modelbuilder
@@ -67,6 +72,11 @@ private class TypeVisitor
                        var selfvariable = new Variable("self")
                        self.selfvariable = selfvariable
                        selfvariable.declared_type = mclass.mclass_type
+
+                       var mprop = mpropdef.mproperty
+                       if mprop isa MMethod and mprop.is_toplevel then
+                               is_toplevel_context = true
+                       end
                end
        end
 
@@ -241,6 +251,15 @@ private class TypeVisitor
                end
 
                assert mproperty isa MMethod
+
+               if is_toplevel_context and recv_is_self and not mproperty.is_toplevel and name != "sys" and name != "exit" and name != "args" then
+                       # FIXME named methods are here as a workaround
+                       error(node, "Error: '{name}' is not a top-level method, thus need a receiver.")
+               end
+               if not recv_is_self and mproperty.is_toplevel then
+                       error(node, "Error: cannot call '{name}', a top-level method, with a receiver.")
+               end
+
                if mproperty.visibility == protected_visibility and not recv_is_self and self.mmodule.visibility_for(mproperty.intro_mclassdef.mmodule) < intrude_visibility and not modelbuilder.toolcontext.opt_ignore_visibility.value then
                        self.modelbuilder.error(node, "Error: Method '{name}' is protected and can only acceded by self.")
                        return null
@@ -1199,6 +1218,9 @@ redef class ASelfExpr
        redef var its_variable: nullable Variable
        redef fun accept_typing(v)
        do
+               if v.is_toplevel_context and not self isa AImplicitSelfExpr then
+                       v.error(self, "Error: self cannot be used in top-level method.")
+               end
                var variable = v.selfvariable
                self.its_variable = variable
                self.mtype = v.get_variable(self, variable)