From 48d0866748f10e30763770e92689bdced41194e0 Mon Sep 17 00:00:00 2001
From: Jean Privat <jean@pryen.org>
Date: Thu, 11 Jun 2009 09:26:26 -0400
Subject: [PATCH] metamodel: fix and comment upcast_for

Signed-off-by: Jean Privat <jean@pryen.org>
---
 src/metamodel/genericity.nit  |    2 +-
 src/metamodel/static_type.nit |   29 ++++++++++++++++++++++++-----
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/metamodel/genericity.nit b/src/metamodel/genericity.nit
index 112212e..dfff8c3 100644
--- a/src/metamodel/genericity.nit
+++ b/src/metamodel/genericity.nit
@@ -216,7 +216,7 @@ special MMTypeFormal
 		return t
 	end
 
-	redef meth upcast_for(c) do return self
+	redef meth upcast_for(c) do return _bound.upcast_for(c)
 
  	meth bound=(t: MMType)
  	do
diff --git a/src/metamodel/static_type.nit b/src/metamodel/static_type.nit
index 0516f4f..25b41f8 100644
--- a/src/metamodel/static_type.nit
+++ b/src/metamodel/static_type.nit
@@ -325,6 +325,24 @@ abstract class MMType
 
 	# Adapt self to another local class context
 	# Useful for genericity
+	# 'c' Must be a super-class of self
+	# Example:
+	#   class A[E]
+	#   class B[F] special A[F]
+	#   class C[G] special B[String]
+	#   class D special C[Float]
+	# 'A[Int]'.upcast_for('A') -> 'A[Int]'
+	# 'A[Int]'.upcast_for('B') -> abort
+	# 'B[Int]'.upcast_for('B') -> 'B[Int]'
+	# 'B[Int]'.upcast_for('A') -> 'A[Int]'
+	# 'B[Int]'.upcast_for('C') -> abort
+	# 'C[Int]'.upcast_for('C') -> 'C[Int]'
+	# 'C[Int]'.upcast_for('B') -> 'B[String]'
+	# 'C[Int]'.upcast_for('A') -> 'A[String]'
+	# 'D'.upcast_for('D') -> 'D'
+	# 'D'.upcast_for('C') -> 'C[Float]'
+	# 'D'.upcast_for('B') -> 'C[String]'
+	# 'D'.upcast_for('A') -> 'A[String]'
 	meth upcast_for(c: MMLocalClass): MMType is abstract
 
 	# Return a type approximation if the reveiver is not self
@@ -390,11 +408,12 @@ end
 # The type of null
 class MMTypeNone
 special MMType
- 	redef readable attr _module: MMModule
- 	redef meth <(t) do return true
- 	redef meth is_supertype(t) do return false
- 	redef meth local_class do abort
- 	redef meth upcast_for(c) do return self
+	redef readable attr _module: MMModule
+	redef meth <(t) do return true
+	redef meth to_s do return "null"
+	redef meth is_supertype(t) do return false
+	redef meth local_class do abort
+	redef meth upcast_for(c) do abort
 
 	private init(m: MMModule) do _module = m
 end
-- 
1.7.9.5