From 8c96cf694bea41704433f991a7604ae5160ad641 Mon Sep 17 00:00:00 2001
From: Jean Privat <jean@pryen.org>
Date: Tue, 10 Jun 2014 22:00:17 -0400
Subject: [PATCH] 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>
---
 src/typing.nit |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/typing.nit b/src/typing.nit
index 3a8194a..5db0ada 100644
--- 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)
-- 
1.7.9.5