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

diff --git a/src/semantize/typing.nit b/src/semantize/typing.nit
index 15d38a2..cf8bbda 100644
--- a/src/semantize/typing.nit
+++ b/src/semantize/typing.nit
@@ -115,7 +115,12 @@ private class TypeVisitor
 			#node.debug("Unsafe typing: expected {sup}, got {sub}")
 			return sup
 		end
-		self.modelbuilder.error(node, "Type error: expected {sup}, got {sub}")
+		if sub.need_anchor then
+			var u = anchor_to(sub)
+			self.modelbuilder.error(node, "Type error: expected {sup}, got {sub}: {u}")
+		else
+			self.modelbuilder.error(node, "Type error: expected {sup}, got {sub}")
+		end
 		return null
 	end
 
@@ -194,6 +199,34 @@ private class TypeVisitor
 		return sup
 	end
 
+	# Can `mtype` be null (up to the current knowledge)?
+	fun can_be_null(mtype: MType): Bool
+	do
+		if mtype isa MNullableType or mtype isa MNullType then return true
+		if mtype isa MFormalType then
+			var x = anchor_to(mtype)
+			if x isa MNullableType or x isa MNullType then return true
+		end
+		return false
+	end
+
+	# Check that `mtype` can be null (up to the current knowledge).
+	#
+	# If not then display a `useless-null-test` warning on node and return false.
+	# Else return true.
+	fun check_can_be_null(anode: ANode, mtype: MType): Bool
+	do
+		if can_be_null(mtype) then return true
+
+		if mtype isa MFormalType then
+			var res = anchor_to(mtype)
+			modelbuilder.warning(anode, "useless-null-test", "Warning: expression is not null, since it is a `{mtype}: {res}`.")
+		else
+			modelbuilder.warning(anode, "useless-null-test", "Warning: expression is not null, since it is a `{mtype}`.")
+		end
+		return false
+	end
+
 	# Special verification on != and == for null
 	# Return true
 	fun null_test(anode: ABinopExpr)
@@ -205,24 +238,24 @@ private class TypeVisitor
 
 		if not mtype2 isa MNullType then return
 
+		if mtype isa MNullType then return
+
 		# Check of useless null
-		if not mtype isa MNullableType then
-			if not anchor_to(mtype) isa MNullableType then
-				modelbuilder.warning(anode, "useless-null-test", "Warning: expression is not null, since it is a `{mtype}`.")
-			end
-			return
-		end
+		if not check_can_be_null(anode.n_expr, mtype) then return
+
+		mtype = mtype.as_notnull
 
 		# Check for type adaptation
 		var variable = anode.n_expr.its_variable
 		if variable == null then return
 
+		# One is null (mtype2 see above) the other is not null
 		if anode isa AEqExpr then
 			anode.after_flow_context.when_true.set_var(variable, mtype2)
-			anode.after_flow_context.when_false.set_var(variable, mtype.mtype)
+			anode.after_flow_context.when_false.set_var(variable, mtype)
 		else if anode isa ANeExpr then
 			anode.after_flow_context.when_false.set_var(variable, mtype2)
-			anode.after_flow_context.when_true.set_var(variable, mtype.mtype)
+			anode.after_flow_context.when_true.set_var(variable, mtype)
 		else
 			abort
 		end
@@ -246,10 +279,7 @@ private class TypeVisitor
 
 	fun get_mclass(node: ANode, name: String): nullable MClass
 	do
-		var mclass = modelbuilder.try_get_mclass_by_name(node, mmodule, name)
-		if mclass == null then
-			self.modelbuilder.error(node, "Type Error: missing primitive class `{name}'.")
-		end
+		var mclass = modelbuilder.get_mclass_by_name(node, mmodule, name)
 		return mclass
 	end
 
@@ -268,7 +298,9 @@ private class TypeVisitor
 		if recvtype isa MNullType then
 			# `null` only accepts some methods of object.
 			if name == "==" or name == "!=" or name == "is_same_instance" then
-				unsafe_type = mmodule.object_type.as_nullable
+				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}' call on 'null'.")
 				return null
@@ -328,13 +360,14 @@ private class TypeVisitor
 		end
 
 
-		var msignature = mpropdef.new_msignature or else mpropdef.msignature.as(not null)
+		var msignature = mpropdef.new_msignature or else mpropdef.msignature
+		if msignature == null then return null # skip error
 		msignature = resolve_for(msignature, recvtype, recv_is_self).as(MSignature)
 
 		var erasure_cast = false
 		var rettype = mpropdef.msignature.return_mtype
 		if not recv_is_self and rettype != null then
-			rettype = rettype.as_notnullable
+			rettype = rettype.undecorate
 			if rettype isa MParameterType then
 				var erased_rettype = msignature.return_mtype
 				assert erased_rettype != null
@@ -450,7 +483,7 @@ private class TypeVisitor
 			var found = true
 			for t2 in col do
 				if t2 == null then continue # return null
-				if t2 isa MNullableType or t2 isa MNullType then
+				if can_be_null(t2) and not can_be_null(t1) then
 					t1 = t1.as_nullable
 				end
 				if not is_subtype(t2, t1) then found = false
@@ -569,14 +602,18 @@ redef class AMethPropdef
 		var nblock = self.n_block
 		if nblock == null then return
 
-		var mpropdef = self.mpropdef.as(not null)
+		var mpropdef = self.mpropdef
+		if mpropdef == null then return # skip error
+
 		var v = new TypeVisitor(modelbuilder, mpropdef.mclassdef.mmodule, mpropdef)
 		self.selfvariable = v.selfvariable
 
 		var mmethoddef = self.mpropdef.as(not null)
-		for i in [0..mmethoddef.msignature.arity[ do
-			var mtype = mmethoddef.msignature.mparameters[i].mtype
-			if mmethoddef.msignature.vararg_rank == i then
+		var msignature = mmethoddef.msignature
+		if msignature == null then return # skip error
+		for i in [0..msignature.arity[ do
+			var mtype = msignature.mparameters[i].mtype
+			if msignature.vararg_rank == i then
 				var arrayclass = v.get_mclass(self.n_signature.n_params[i], "Array")
 				if arrayclass == null then return # Skip error
 				mtype = arrayclass.get_mtype([mtype])
@@ -587,7 +624,7 @@ redef class AMethPropdef
 		end
 		v.visit_stmt(nblock)
 
-		if not nblock.after_flow_context.is_unreachable and mmethoddef.msignature.return_mtype != null then
+		if not nblock.after_flow_context.is_unreachable and msignature.return_mtype != null then
 			# We reach the end of the function without having a return, it is bad
 			v.error(self, "Control error: Reached end of function (a 'return' with a value was expected).")
 		end
@@ -599,7 +636,9 @@ redef class AAttrPropdef
 	do
 		if not has_value then return
 
-		var mpropdef = self.mpropdef.as(not null)
+		var mpropdef = self.mpropdef
+		if mpropdef == null then return # skip error
+
 		var v = new TypeVisitor(modelbuilder, mpropdef.mclassdef.mmodule, mpropdef)
 		self.selfvariable = v.selfvariable
 
@@ -698,7 +737,9 @@ redef class AVardeclExpr
 
 		var decltype = mtype
 		if mtype == null or mtype isa MNullType then
-			decltype = v.get_mclass(self, "Object").mclass_type.as_nullable
+			var objclass = v.get_mclass(self, "Object")
+			if objclass == null then return # skip error
+			decltype = objclass.mclass_type.as_nullable
 			if mtype == null then mtype = decltype
 		end
 
@@ -1003,7 +1044,7 @@ redef class AForExpr
 		# anchor formal and virtual types
 		if mtype.need_anchor then mtype = v.anchor_to(mtype)
 
-		mtype = mtype.as_notnullable
+		mtype = mtype.undecorate
 		self.coltype = mtype.as(MClassType)
 
 		# get methods is_ok, next, item
@@ -1140,12 +1181,18 @@ redef class AOrElseExpr
 			return # Skip error
 		end
 
-		t1 = t1.as_notnullable
+		if t1 isa MNullType then
+			v.error(n_expr, "Type error: or else on null")
+		else if v.check_can_be_null(n_expr, t1) then
+			t1 = t1.as_notnull
+		end
 
 		var t = v.merge_types(self, [t1, t2])
 		if t == null then
-			t = v.mmodule.object_type
-			if t2 isa MNullableType then
+			var c = v.get_mclass(self, "Object")
+			if c == null then return # forward error
+			t = c.mclass_type
+			if v.can_be_null(t2) then
 				t = t.as_nullable
 			end
 			#v.error(self, "Type Error: ambiguous type {t1} vs {t2}")
@@ -1210,8 +1257,11 @@ redef class ASuperstringExpr
 		var mclass = v.get_mclass(self, "String")
 		if mclass == null then return # Forward error
 		self.mtype = mclass.mclass_type
+		var objclass = v.get_mclass(self, "Object")
+		if objclass == null then return # Forward error
+		var objtype = objclass.mclass_type
 		for nexpr in self.n_exprs do
-			v.visit_expr_subtype(nexpr, v.mmodule.object_type)
+			v.visit_expr_subtype(nexpr, objtype)
 		end
 	end
 end
@@ -1374,22 +1424,12 @@ redef class AAsNotnullExpr
 			v.error(self, "Type error: as(not null) on null")
 			return
 		end
-		if mtype isa MNullableType then
-			self.mtype = mtype.mtype
-			return
-		end
-		self.mtype = mtype
 
-		if mtype isa MClassType then
-			v.modelbuilder.warning(self, "useless-type-test", "Warning: expression is already not null, since it is a `{mtype}`.")
-			return
-		end
-		assert mtype.need_anchor
-		var u = v.anchor_to(mtype)
-		if not u isa MNullableType then
-			v.modelbuilder.warning(self, "useless-type-test", "Warning: expression is already not null, since it is a `{mtype}: {u}`.")
-			return
+		if v.check_can_be_null(n_expr, mtype) then
+			mtype = mtype.as_notnull
 		end
+
+		self.mtype = mtype
 	end
 end
 
@@ -1836,7 +1876,8 @@ redef class AAttrFormExpr
 		var mpropdefs = mproperty.lookup_definitions(v.mmodule, unsafe_type)
 		assert mpropdefs.length == 1
 		var mpropdef = mpropdefs.first
-		var attr_type = mpropdef.static_mtype.as(not null)
+		var attr_type = mpropdef.static_mtype
+		if attr_type == null then return # skip error
 		attr_type = v.resolve_for(attr_type, recvtype, self.n_expr isa ASelfExpr)
 		self.attr_type = attr_type
 	end