X-Git-Url: http://nitlanguage.org

diff --git a/src/metamodel/static_type.nit b/src/metamodel/static_type.nit
index 6cf53b7..25b41f8 100644
--- a/src/metamodel/static_type.nit
+++ b/src/metamodel/static_type.nit
@@ -110,6 +110,11 @@ class MMSignature
 				return false
 			end
 		end
+
+		if closures.length != s.closures.length then return false
+		for i in [0..closures.length[ do
+			if not s.closures[i] < closures[i] then return false
+		end
 		return true
 	end
 
@@ -256,6 +261,13 @@ class MMClosure
 			return self
 		end
 	end
+
+	meth <(c: MMClosure): Bool
+	do
+		if c.is_optional and not is_optional then return false
+		if not c.is_break and is_break then return false
+		return c.signature < signature
+	end
 end
 
 # Inheritance relation between two types
@@ -313,6 +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
@@ -378,11 +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