From: Jean Privat <jean@pryen.org>
Date: Sat, 30 May 2015 00:37:22 +0000 (-0400)
Subject: Merge: Warn call on nullable receiver
X-Git-Tag: v0.7.5~4
X-Git-Url: http://nitlanguage.org?hp=-c

Merge: Warn call on nullable receiver

Followup of #1375 and #394

This introduce an advice on calls on a nullable receiver.
Since the conversion could be complex, I propose a light approach with advices (quiet warnings) instead of hard errors, so that:

1. jenkins can track them
2. nitpick (thus vim) can show them
3. mirgration can be done in an incremental and iterative way
4. issues with a strict call-on-nullable policy can be identified without breaking things
5. @Morriar can bank nitcoins in future PR

If (when?) all call on nullable can be removed, then the advice will become an error.

Pull-Request: #1414
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Romain Chanoir <chanoir.romain@courrier.uqam.ca>
---

dff7da4e0a4783718f9409ee27dc072f84e24b82
diff --combined src/model/model.nit
index 908cb60,e4b881f..4e9be82
--- a/src/model/model.nit
+++ b/src/model/model.nit
@@@ -206,9 -206,6 +206,9 @@@ redef class MModul
  	# The primitive type `Int`
  	var int_type: MClassType = self.get_primitive_class("Int").mclass_type is lazy
  
 +	# The primitive type `Byte`
 +	var byte_type: MClassType = self.get_primitive_class("Byte").mclass_type is lazy
 +
  	# The primitive type `Char`
  	var char_type: MClassType = self.get_primitive_class("Char").mclass_type is lazy
  
@@@ -2156,6 -2153,10 +2156,10 @@@ class MMetho
  	do
  		return self.is_init
  	end
+ 
+ 	# A specific method that is safe to call on null.
+ 	# Currently, only `==`, `!=` and `is_same_instance` are safe
+ 	fun is_null_safe: Bool do return name == "==" or name == "!=" or name == "is_same_instance"
  end
  
  # A global attribute
diff --combined src/semantize/typing.nit
index 3c7c9b1,10edaf1..44ed320
--- a/src/semantize/typing.nit
+++ b/src/semantize/typing.nit
@@@ -301,15 -301,9 +301,9 @@@ private class TypeVisito
  
  		#debug("recv: {recvtype} (aka {unsafe_type})")
  		if recvtype isa MNullType then
- 			# `null` only accepts some methods of object.
- 			if name == "==" or name == "!=" or name == "is_same_instance" then
- 				var objclass = get_mclass(node, "Object")
- 				if objclass == null then return null # Forward error
- 				unsafe_type = objclass.mclass_type
- 			else
- 				self.error(node, "Error: method `{name}` called on `null`.")
- 				return null
- 			end
+ 			var objclass = get_mclass(node, "Object")
+ 			if objclass == null then return null # Forward error
+ 			unsafe_type = objclass.mclass_type
  		end
  
  		var mproperty = self.try_get_mproperty_by_name2(node, unsafe_type, name)
@@@ -331,6 -325,14 +325,14 @@@
  
  		assert mproperty isa MMethod
  
+ 		# `null` only accepts some methods of object.
+ 		if recvtype isa MNullType and not mproperty.is_null_safe then
+ 			self.error(node, "Error: method `{name}` called on `null`.")
+ 			return null
+ 		else if unsafe_type isa MNullableType and not mproperty.is_null_safe then
+ 			modelbuilder.advice(node, "call-on-nullable", "Warning: method call on a nullable receiver `{recvtype}`.")
+ 		end
+ 
  		if is_toplevel_context and recv_is_self and not mproperty.is_toplevel then
  			error(node, "Error: `{name}` is not a top-level method, thus need a receiver.")
  		end
@@@ -1342,15 -1344,6 +1344,15 @@@ redef class AIntExp
  	end
  end
  
 +redef class AByteExpr
 +	redef fun accept_typing(v)
 +	do
 +		var mclass = v.get_mclass(self, "Byte")
 +		if mclass == null then return # Forward error
 +		self.mtype = mclass.mclass_type
 +	end
 +end
 +
  redef class AFloatExpr
  	redef fun accept_typing(v)
  	do