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

diff --git a/src/semantize/typing.nit b/src/semantize/typing.nit
index 212f43e..9676168 100644
--- a/src/semantize/typing.nit
+++ b/src/semantize/typing.nit
@@ -105,22 +105,22 @@ private class TypeVisitor
 	# If `sub` is a safe subtype of `sup` then return `sub`.
 	# If `sub` is an unsafe subtype (ie an implicit cast is required), then return `sup`.
 	#
-	# The point of the return type is to determinate the usable type on an expression:
+	# The point of the return type is to determinate the usable type on an expression when `autocast` is true:
 	# If the suptype is safe, then the return type is the one on the expression typed by `sub`.
 	# Is the subtype is unsafe, then the return type is the one of an implicit cast on `sup`.
-	fun check_subtype(node: ANode, sub, sup: MType): nullable MType
+	fun check_subtype(node: ANode, sub, sup: MType, autocast: Bool): nullable MType
 	do
 		if self.is_subtype(sub, sup) then return sub
-		if self.is_subtype(sub, self.anchor_to(sup)) then
+		if autocast and self.is_subtype(sub, self.anchor_to(sup)) then
 			# FIXME workaround to the current unsafe typing policy. To remove once fixed virtual types exists.
 			#node.debug("Unsafe typing: expected {sup}, got {sub}")
 			return sup
 		end
 		if sub.need_anchor then
 			var u = anchor_to(sub)
-			self.modelbuilder.error(node, "Type error: expected {sup}, got {sub}: {u}")
+			self.modelbuilder.error(node, "Type Error: expected `{sup}`, got `{sub}: {u}`.")
 		else
-			self.modelbuilder.error(node, "Type error: expected {sup}, got {sub}")
+			self.modelbuilder.error(node, "Type Error: expected `{sup}`, got `{sub}`.")
 		end
 		return null
 	end
@@ -150,7 +150,7 @@ private class TypeVisitor
 			end
 			return null # forward error
 		end
-		self.error(nexpr, "Type error: expected expression.")
+		self.error(nexpr, "Error: expected an expression.")
 		return null
 	end
 
@@ -166,7 +166,7 @@ private class TypeVisitor
 
 		if sup == null then return null # Forward error
 
-		var res = check_subtype(nexpr, sub, sup)
+		var res = check_subtype(nexpr, sub, sup, true)
 		if res != sub then
 			nexpr.implicit_cast_to = res
 		end
@@ -193,9 +193,9 @@ private class TypeVisitor
 		if sup == null then return null # Forward error
 
 		if sup == sub then
-			self.modelbuilder.warning(node, "useless-type-test", "Warning: Expression is already a {sup}.")
+			self.modelbuilder.warning(node, "useless-type-test", "Warning: expression is already a `{sup}`.")
 		else if self.is_subtype(sub, sup) then
-			self.modelbuilder.warning(node, "useless-type-test", "Warning: Expression is already a {sup} since it is a {sub}.")
+			self.modelbuilder.warning(node, "useless-type-test", "Warning: expression is already a `{sup}` since it is a `{sub}`.")
 		end
 		return sup
 	end
@@ -239,12 +239,16 @@ private class TypeVisitor
 
 		if not mtype2 isa MNullType then return
 
-		if mtype isa MNullType then return
-
 		# Check of useless null
 		if not check_can_be_null(anode.n_expr, mtype) then return
 
-		mtype = mtype.as_notnull
+		if mtype isa MNullType then
+			# Because of type adaptation, we cannot just stop here
+			# so return use `null` as a bottom type that will be merged easily (cf) `merge_types`
+			mtype = null
+		else
+			mtype = mtype.as_notnull
+		end
 
 		# Check for type adaptation
 		var variable = anode.n_expr.its_variable
@@ -297,15 +301,9 @@ private class TypeVisitor
 
 		#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}' call 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)
@@ -315,26 +313,35 @@ private class TypeVisitor
 		end
 
 		if mproperty == null then
-			#self.modelbuilder.error(node, "Type error: property {name} not found in {unsafe_type} (ie {recvtype})")
 			if recv_is_self then
-				self.modelbuilder.error(node, "Error: Method or variable '{name}' unknown in {recvtype}.")
+				self.modelbuilder.error(node, "Error: method or variable `{name}` unknown in `{recvtype}`.")
+			else if recvtype.need_anchor then
+				self.modelbuilder.error(node, "Error: method `{name}` does not exists in `{recvtype}: {unsafe_type}`.")
 			else
-				self.modelbuilder.error(node, "Error: Method '{name}' doesn't exists in {recvtype}.")
+				self.modelbuilder.error(node, "Error: method `{name}` does not exists in `{recvtype}`.")
 			end
 			return null
 		end
 
 		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.")
+			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.")
+			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.")
+			self.modelbuilder.error(node, "Error: method `{name}` is protected and can only accessed by `self`.")
 			return null
 		end
 
@@ -342,21 +349,21 @@ private class TypeVisitor
 		if info != null and self.mpropdef.mproperty.deprecation == null then
 			var mdoc = info.mdoc
 			if mdoc != null then
-				self.modelbuilder.warning(node, "deprecated-method", "Deprecation Warning: Method '{name}' is deprecated: {mdoc.content.first}")
+				self.modelbuilder.warning(node, "deprecated-method", "Deprecation Warning: method `{name}` is deprecated: {mdoc.content.first}")
 			else
-				self.modelbuilder.warning(node, "deprecated-method", "Deprecation Warning: Method '{name}' is deprecated.")
+				self.modelbuilder.warning(node, "deprecated-method", "Deprecation Warning: method `{name}` is deprecated.")
 			end
 		end
 
 		var propdefs = mproperty.lookup_definitions(self.mmodule, unsafe_type)
 		var mpropdef
 		if propdefs.length == 0 then
-			self.modelbuilder.error(node, "Type error: no definition found for property {name} in {unsafe_type}")
+			self.modelbuilder.error(node, "Type Error: no definition found for property `{name}` in `{unsafe_type}`.")
 			return null
 		else if propdefs.length == 1 then
 			mpropdef = propdefs.first
 		else
-			self.modelbuilder.warning(node, "property-conflict", "Warning: conflicting property definitions for property {name} in {unsafe_type}: {propdefs.join(" ")}")
+			self.modelbuilder.warning(node, "property-conflict", "Warning: conflicting property definitions for property `{name}` in `{unsafe_type}`: {propdefs.join(" ")}")
 			mpropdef = mproperty.intro
 		end
 
@@ -393,48 +400,125 @@ private class TypeVisitor
 	# Visit the expressions of args and check their conformity with the corresponding type in signature
 	# The point of this method is to handle varargs correctly
 	# Note: The signature must be correctly adapted
-	fun check_signature(node: ANode, args: Array[AExpr], name: String, msignature: MSignature): Bool
+	fun check_signature(node: ANode, args: Array[AExpr], mproperty: MProperty, msignature: MSignature): nullable SignatureMap
 	do
 		var vararg_rank = msignature.vararg_rank
 		if vararg_rank >= 0 then
 			if args.length < msignature.arity then
-				#self.modelbuilder.error(node, "Error: Incorrect number of parameters. Got {args.length}, expected at least {msignature.arity}. Signature is {msignature}")
-				self.modelbuilder.error(node, "Error: arity mismatch; prototype is '{name}{msignature}'")
-				return false
+				modelbuilder.error(node, "Error: expected at least {msignature.arity} argument(s) for `{mproperty}{msignature}`; got {args.length}. See introduction at `{mproperty.full_name}`.")
+				return null
 			end
 		else if args.length != msignature.arity then
-			self.modelbuilder.error(node, "Error: Incorrect number of parameters. Got {args.length}, expected {msignature.arity}. Signature is {msignature}")
-			return false
+			if msignature.arity == msignature.min_arity then
+				modelbuilder.error(node, "Error: expected {msignature.arity} argument(s) for `{mproperty}{msignature}`; got {args.length}. See introduction at `{mproperty.full_name}`.")
+				return null
+			end
+			if args.length > msignature.arity then
+				modelbuilder.error(node, "Error: expected at most {msignature.arity} argument(s) for `{mproperty}{msignature}`; got {args.length}. See introduction at `{mproperty.full_name}`.")
+				return null
+			end
+			if args.length < msignature.min_arity then
+				modelbuilder.error(node, "Error: expected at least {msignature.min_arity} argument(s) for `{mproperty}{msignature}`; got {args.length}. See introduction at `{mproperty.full_name}`.")
+				return null
+			end
 		end
 
 		#debug("CALL {unsafe_type}.{msignature}")
 
+		# Associate each parameter to a position in the arguments
+		var map = new SignatureMap
+
+		var setted = args.length - msignature.min_arity
+
+		# First, handle named arguments
+		for i in [0..args.length[ do
+			var e = args[i]
+			if not e isa ANamedargExpr then continue
+			var name = e.n_id.text
+			var param = msignature.mparameter_by_name(name)
+			if param == null then
+				modelbuilder.error(e.n_id, "Error: no parameter `{name}` for `{mproperty}{msignature}`.")
+				return null
+			end
+			if not param.is_default then
+				modelbuilder.error(e, "Error: parameter `{name}` is not optional for `{mproperty}{msignature}`.")
+				return null
+			end
+			var idx = msignature.mparameters.index_of(param)
+			var prev = map.map.get_or_null(idx)
+			if prev != null then
+				modelbuilder.error(e, "Error: parameter `{name}` already associated with argument #{prev} for `{mproperty}{msignature}`.")
+				return null
+			end
+			map.map[idx] = i
+			setted -= 1
+			e.mtype = self.visit_expr_subtype(e.n_expr, param.mtype)
+		end
+
+		# Second, associate remaining parameters
 		var vararg_decl = args.length - msignature.arity
+		var j = 0
 		for i in [0..msignature.arity[ do
-			var j = i
-			if i == vararg_rank then continue # skip the vararg
-			if i > vararg_rank then
-				j = i + vararg_decl
+			# Skip parameters associated by name
+			if map.map.has_key(i) then continue
+
+			var param = msignature.mparameters[i]
+			if param.is_default then
+				if setted > 0 then
+					setted -= 1
+				else
+					continue
+				end
+			end
+
+			# Search the next free argument: skip named arguments since they are already associated
+			while args[j] isa ANamedargExpr do j += 1
+			var arg = args[j]
+			map.map[i] = j
+			j += 1
+
+			if i == vararg_rank then
+				j += vararg_decl
+				continue # skip the vararg
 			end
-			var paramtype = msignature.mparameters[i].mtype
-			self.visit_expr_subtype(args[j], paramtype)
+
+			var paramtype = param.mtype
+			self.visit_expr_subtype(arg, paramtype)
 		end
+
+		# Third, check varargs
 		if vararg_rank >= 0 then
 			var paramtype = msignature.mparameters[vararg_rank].mtype
 			var first = args[vararg_rank]
-			if vararg_decl == 0 and first isa AVarargExpr then
+			if vararg_decl == 0 then
 				var mclass = get_mclass(node, "Array")
-				if mclass == null then return false # Forward error
+				if mclass == null then return null # Forward error
 				var array_mtype = mclass.get_mtype([paramtype])
-				self.visit_expr_subtype(first.n_expr, array_mtype)
-				first.mtype  = first.n_expr.mtype
+				if first isa AVarargExpr then
+					self.visit_expr_subtype(first.n_expr, array_mtype)
+					first.mtype  = first.n_expr.mtype
+				else
+					# only one vararg, maybe `...` was forgot, so be gentle!
+					var t = visit_expr(first)
+					if t == null then return null # Forward error
+					if not is_subtype(t, paramtype) and is_subtype(t, array_mtype) then
+						# Not acceptable but could be a `...`
+						error(first, "Type Error: expected `{paramtype}`, got `{t}`. Is an ellipsis `...` missing on the argument?")
+						return null
+					end
+					# Standard valid vararg, finish the job
+					map.vararg_decl = 1
+					self.visit_expr_subtype(first, paramtype)
+				end
 			else
-				for j in [vararg_rank..vararg_rank+vararg_decl] do
-					self.visit_expr_subtype(args[j], paramtype)
+				map.vararg_decl = vararg_decl + 1
+				for i in [vararg_rank..vararg_rank+vararg_decl] do
+					self.visit_expr_subtype(args[i], paramtype)
 				end
 			end
 		end
-		return true
+
+		return map
 	end
 
 	fun error(node: ANode, message: String)
@@ -444,11 +528,10 @@ private class TypeVisitor
 
 	fun get_variable(node: AExpr, variable: Variable): nullable MType
 	do
+		if not variable.is_adapted then return variable.declared_type
+
 		var flow = node.after_flow_context
-		if flow == null then
-			self.error(node, "No context!")
-			return null
-		end
+		if flow == null then return null # skip error
 
 		if flow.vars.has_key(variable) then
 			return flow.vars[variable]
@@ -505,6 +588,20 @@ private class TypeVisitor
 	end
 end
 
+# Mapping between parameters and arguments in a call.
+#
+# Parameters and arguments are not stored in the class but referenced by their position (starting from 0)
+#
+# The point of this class is to help engine and other things to map arguments in the AST to parameters of the model.
+class SignatureMap
+	# Associate a parameter to an argument
+	var map = new ArrayMap[Int, Int]
+
+	# The length of the vararg sequence
+	# 0 if no vararg or if reverse vararg (cf `AVarargExpr`)
+	var vararg_decl: Int = 0
+end
+
 # A specific method call site with its associated informations.
 class CallSite
 	# The associated node for location
@@ -537,15 +634,25 @@ class CallSite
 	# Is a implicit cast required on erasure typing policy?
 	var erasure_cast: Bool
 
+	# The mapping used on the call to associate arguments to parameters
+	# If null then no specific association is required.
+	var signaturemap: nullable SignatureMap = null
+
 	private fun check_signature(v: TypeVisitor, args: Array[AExpr]): Bool
 	do
-		return v.check_signature(self.node, args, self.mproperty.name, self.msignature)
+		var map = v.check_signature(self.node, args, self.mproperty, self.msignature)
+		signaturemap = map
+		return map == null
 	end
 end
 
 redef class Variable
 	# The declared type of the variable
 	var declared_type: nullable MType
+
+	# Was the variable type-adapted?
+	# This is used to speedup type retrieval while it remains `false`
+	private var is_adapted = false
 end
 
 redef class FlowContext
@@ -557,9 +664,11 @@ redef class FlowContext
 	# Warning2: sub-flow may have cached a unadapted variable
 	private fun set_var(v: TypeVisitor, variable: Variable, mtype: nullable MType)
 	do
+		if variable.declared_type == mtype and not variable.is_adapted then return
 		if vars.has_key(variable) and vars[variable] == mtype then return
 		self.vars[variable] = mtype
 		v.dirty = true
+		variable.is_adapted = true
 		#node.debug "set {variable} to {mtype or else "X"}"
 	end
 
@@ -641,7 +750,7 @@ redef class AMethPropdef
 
 		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).")
+			v.error(self, "Error: reached end of function; expected `return` with a value.")
 		end
 	end
 end
@@ -651,15 +760,15 @@ redef class AAttrPropdef
 	do
 		if not has_value then return
 
-		var mpropdef = self.mpropdef
-		if mpropdef == null then return # skip error
+		var mpropdef = self.mreadpropdef
+		if mpropdef == null or mpropdef.msignature == null then return # skip error
 
 		var v = new TypeVisitor(modelbuilder, mpropdef.mclassdef.mmodule, mpropdef)
 		self.selfvariable = v.selfvariable
 
 		var nexpr = self.n_expr
 		if nexpr != null then
-			var mtype = self.mpropdef.static_mtype
+			var mtype = self.mtype
 			v.visit_expr_subtype(nexpr, mtype)
 		end
 		var nblock = self.n_block
@@ -667,7 +776,7 @@ redef class AAttrPropdef
 			v.visit_stmt(nblock)
 			if not nblock.after_flow_context.is_unreachable then
 				# We reach the end of the init without having a return, it is bad
-				v.error(self, "Control error: Reached end of block (a 'return' with a value was expected).")
+				v.error(self, "Error: reached end of block; expected `return`.")
 			end
 		end
 	end
@@ -813,18 +922,11 @@ redef class AReassignFormExpr
 	# Return the static type of the value to store.
 	private fun resolve_reassignment(v: TypeVisitor, readtype, writetype: MType): nullable MType
 	do
-		var reassign_name: String
-		if self.n_assign_op isa APlusAssignOp then
-			reassign_name = "+"
-		else if self.n_assign_op isa AMinusAssignOp then
-			reassign_name = "-"
-		else
-			abort
-		end
+		var reassign_name = self.n_assign_op.operator
 
 		self.read_type = readtype
 
-		var callsite = v.get_method(self, readtype, reassign_name, false)
+		var callsite = v.get_method(self.n_assign_op, readtype, reassign_name, false)
 		if callsite == null then return null # Skip error
 		self.reassign_callsite = callsite
 
@@ -835,7 +937,7 @@ redef class AReassignFormExpr
 		var value_type = v.visit_expr_subtype(self.n_value, msignature.mparameters.first.mtype)
 		if value_type == null then return null # Skip error
 
-		v.check_subtype(self, rettype, writetype)
+		v.check_subtype(self, rettype, writetype, false)
 		return rettype
 	end
 end
@@ -903,10 +1005,10 @@ redef class AReturnExpr
 				v.visit_expr_subtype(nexpr, ret_type)
 			else
 				v.visit_expr(nexpr)
-				v.error(self, "Error: Return with value in a procedure.")
+				v.error(nexpr, "Error: `return` with value in a procedure.")
 			end
 		else if ret_type != null then
-			v.error(self, "Error: Return without value in a function.")
+			v.error(self, "Error: `return` without value in a function.")
 		end
 		self.is_typed = true
 	end
@@ -949,7 +1051,7 @@ redef class AIfexprExpr
 
 		var t = v.merge_types(self, [t1, t2])
 		if t == null then
-			v.error(self, "Type Error: ambiguous type {t1} vs {t2}")
+			v.error(self, "Type Error: ambiguous type `{t1}` vs `{t2}`.")
 		end
 		self.mtype = t
 	end
@@ -998,7 +1100,7 @@ redef class AForExpr
 	private fun do_type_iterator(v: TypeVisitor, mtype: MType)
 	do
 		if mtype isa MNullType then
-			v.error(self, "Type error: 'for' cannot iterate over 'null'")
+			v.error(self, "Type Error: `for` cannot iterate over `null`.")
 			return
 		end
 
@@ -1009,7 +1111,7 @@ redef class AForExpr
 		# check iterator method
 		var itdef = v.get_method(self, mtype, "iterator", n_expr isa ASelfExpr)
 		if itdef == null then
-			v.error(self, "Type Error: 'for' expects a type providing 'iterator' method, got '{mtype}'.")
+			v.error(self, "Type Error: `for` expects a type providing an `iterator` method, got `{mtype}`.")
 			return
 		end
 		self.method_iterator = itdef
@@ -1017,7 +1119,7 @@ redef class AForExpr
 		# check that iterator return something
 		var ittype = itdef.msignature.return_mtype
 		if ittype == null then
-			v.error(self, "Type Error: 'for' expects method 'iterator' to return an 'Iterator' or 'MapIterator' type'.")
+			v.error(self, "Type Error: `for` expects the method `iterator` to return an `Iterator` or `MapIterator` type.")
 			return
 		end
 
@@ -1032,7 +1134,7 @@ redef class AForExpr
 			var coltype = ittype.supertype_to(v.mmodule, v.anchor, colit_cla)
 			var variables =  self.variables
 			if variables.length != 1 then
-				v.error(self, "Type Error: 'for' expects only one variable when using 'Iterator'.")
+				v.error(self, "Type Error: `for` expects only one variable when using `Iterator`.")
 			else
 				variables.first.declared_type = coltype.arguments.first
 			end
@@ -1044,7 +1146,7 @@ redef class AForExpr
 			var coltype = ittype.supertype_to(v.mmodule, v.anchor, mapit_cla)
 			var variables = self.variables
 			if variables.length != 2 then
-				v.error(self, "Type Error: 'for' expects two variables when using 'MapIterator'.")
+				v.error(self, "Type Error: `for` expects two variables when using `MapIterator`.")
 			else
 				variables[0].declared_type = coltype.arguments[0]
 				variables[1].declared_type = coltype.arguments[1]
@@ -1053,7 +1155,7 @@ redef class AForExpr
 		end
 
 		if not is_col and not is_map then
-			v.error(self, "Type Error: 'for' expects method 'iterator' to return an 'Iterator' or 'MapIterator' type'.")
+			v.error(self, "Type Error: `for` expects the method `iterator` to return an `Iterator` or `MapIterator` type.")
 			return
 		end
 
@@ -1066,21 +1168,21 @@ redef class AForExpr
 		# get methods is_ok, next, item
 		var ikdef = v.get_method(self, ittype, "is_ok", false)
 		if ikdef == null then
-			v.error(self, "Type Error: 'for' expects a method 'is_ok' in 'Iterator' type {ittype}.")
+			v.error(self, "Type Error: `for` expects a method `is_ok` in type `{ittype}`.")
 			return
 		end
 		self.method_is_ok = ikdef
 
 		var itemdef = v.get_method(self, ittype, "item", false)
 		if itemdef == null then
-			v.error(self, "Type Error: 'for' expects a method 'item' in 'Iterator' type {ittype}.")
+			v.error(self, "Type Error: `for` expects a method `item` in type `{ittype}`.")
 			return
 		end
 		self.method_item = itemdef
 
 		var nextdef = v.get_method(self, ittype, "next", false)
 		if nextdef == null then
-			v.error(self, "Type Error: 'for' expects a method 'next' in 'Iterator' type {ittype}.")
+			v.error(self, "Type Error: `for` expects a method `next` in type {ittype}.")
 			return
 		end
 		self.method_next = nextdef
@@ -1090,7 +1192,7 @@ redef class AForExpr
 		if is_map then
 			var keydef = v.get_method(self, ittype, "key", false)
 			if keydef == null then
-				v.error(self, "Type Error: 'for' expects a method 'key' in 'Iterator' type {ittype}.")
+				v.error(self, "Type Error: `for` expects a method `key` in type `{ittype}`.")
 				return
 			end
 			self.method_key = keydef
@@ -1200,7 +1302,7 @@ redef class AOrElseExpr
 		end
 
 		if t1 isa MNullType then
-			v.error(n_expr, "Type error: or else on null")
+			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
@@ -1242,6 +1344,15 @@ redef class AIntExpr
 	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
@@ -1327,13 +1438,15 @@ redef class AArrayExpr
 			end
 			set_comprehension(e)
 			if mtype != null then
-				if v.check_subtype(e, t, mtype) == null then return # Skip error
+				if v.check_subtype(e, t, mtype, false) == null then return # Forward error
 				if t == mtype then useless = true
 			else
 				mtypes.add(t)
 			end
 		end
 		if mtype == null then
+			# Ensure monotony for type adaptation on loops
+			if self.element_mtype != null then mtypes.add self.element_mtype
 			mtype = v.merge_types(self, mtypes)
 		end
 		if mtype == null or mtype isa MNullType then
@@ -1377,7 +1490,7 @@ redef class ARangeExpr
 		else if v.is_subtype(t2, t1) then
 			mtype = mclass.get_mtype([t1])
 		else
-			v.error(self, "Type Error: Cannot create range: {t1} vs {t2}")
+			v.error(self, "Type Error: cannot create range: `{t1}` vs `{t2}`.")
 			return
 		end
 
@@ -1439,7 +1552,7 @@ redef class AAsNotnullExpr
 		if mtype == null then return # Forward error
 
 		if mtype isa MNullType then
-			v.error(self, "Type error: as(not null) on null")
+			v.error(self, "Type Error: `as(not null)` on `null`.")
 			return
 		end
 
@@ -1470,7 +1583,7 @@ redef class ASelfExpr
 	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.")
+			v.error(self, "Error: `self` cannot be used in top-level method.")
 		end
 		var variable = v.selfvariable
 		self.its_variable = variable
@@ -1498,20 +1611,21 @@ redef class ASendExpr
 		var nrecv = self.n_expr
 		var recvtype = v.visit_expr(nrecv)
 		var name = self.property_name
+		var node = self.property_node
 
 		if recvtype == null then return # Forward error
 
 		var callsite = null
 		var unsafe_type = v.anchor_to(recvtype)
-		var mproperty = v.try_get_mproperty_by_name2(self, unsafe_type, name)
+		var mproperty = v.try_get_mproperty_by_name2(node, unsafe_type, name)
 		if mproperty == null and nrecv isa AImplicitSelfExpr then
 			# Special fall-back search in `sys` when noting found in the implicit receiver.
-			var sysclass = v.try_get_mclass(self, "Sys")
+			var sysclass = v.try_get_mclass(node, "Sys")
 			if sysclass != null then
 				var systype = sysclass.mclass_type
-				mproperty = v.try_get_mproperty_by_name2(self, systype, name)
+				mproperty = v.try_get_mproperty_by_name2(node, systype, name)
 				if mproperty != null then
-					callsite = v.get_method(self, systype, name, false)
+					callsite = v.get_method(node, systype, name, false)
 					if callsite == null then return # Forward error
 					# Update information, we are looking at `sys` now, not `self`
 					nrecv.is_sys = true
@@ -1523,7 +1637,7 @@ redef class ASendExpr
 		end
 		if callsite == null then
 			# If still nothing, just exit
-			callsite = v.get_method(self, recvtype, name, nrecv isa ASelfExpr)
+			callsite = v.get_method(node, recvtype, name, nrecv isa ASelfExpr)
 			if callsite == null then return
 		end
 
@@ -1537,10 +1651,10 @@ redef class ASendExpr
 		if callsite.mproperty.is_init then
 			var vmpropdef = v.mpropdef
 			if not (vmpropdef isa MMethodDef and vmpropdef.mproperty.is_init) then
-				v.error(self, "Can call a init only in another init")
+				v.error(node, "Error: an `init` can only be called from another `init`.")
 			end
 			if vmpropdef isa MMethodDef and vmpropdef.mproperty.is_root_init and not callsite.mproperty.is_root_init then
-				v.error(self, "Error: {vmpropdef} cannot call a factory {callsite.mproperty}")
+				v.error(node, "Error: `{vmpropdef}` cannot call a factory `{callsite.mproperty}`.")
 			end
 		end
 
@@ -1556,6 +1670,11 @@ redef class ASendExpr
 	# Each subclass simply provide the correct name.
 	private fun property_name: String is abstract
 
+	# The node identifying the name (id, operator, etc) for messages.
+	#
+	# Is `self` by default
+	private fun property_node: ANode do return self
+
 	# An array of all arguments (excluding self)
 	fun raw_arguments: Array[AExpr] do return compute_raw_arguments
 
@@ -1564,9 +1683,10 @@ end
 
 redef class ABinopExpr
 	redef fun compute_raw_arguments do return [n_expr2]
+	redef fun property_name do return operator
+	redef fun property_node do return n_op
 end
 redef class AEqExpr
-	redef fun property_name do return "=="
 	redef fun accept_typing(v)
 	do
 		super
@@ -1574,66 +1694,28 @@ redef class AEqExpr
 	end
 end
 redef class ANeExpr
-	redef fun property_name do return "!="
 	redef fun accept_typing(v)
 	do
 		super
 		v.null_test(self)
 	end
 end
-redef class ALtExpr
-	redef fun property_name do return "<"
-end
-redef class ALeExpr
-	redef fun property_name do return "<="
-end
-redef class ALlExpr
-	redef fun property_name do return "<<"
-end
-redef class AGtExpr
-	redef fun property_name do return ">"
-end
-redef class AGeExpr
-	redef fun property_name do return ">="
-end
-redef class AGgExpr
-	redef fun property_name do return ">>"
-end
-redef class APlusExpr
-	redef fun property_name do return "+"
-end
-redef class AMinusExpr
-	redef fun property_name do return "-"
-end
-redef class AStarshipExpr
-	redef fun property_name do return "<=>"
-end
-redef class AStarExpr
-	redef fun property_name do return "*"
-end
-redef class AStarstarExpr
-	redef fun property_name do return "**"
-end
-redef class ASlashExpr
-	redef fun property_name do return "/"
-end
-redef class APercentExpr
-	redef fun property_name do return "%"
-end
 
-redef class AUminusExpr
-	redef fun property_name do return "unary -"
+redef class AUnaryopExpr
+	redef fun property_name do return "unary {operator}"
 	redef fun compute_raw_arguments do return new Array[AExpr]
 end
 
 
 redef class ACallExpr
 	redef fun property_name do return n_id.text
+	redef fun property_node do return n_id
 	redef fun compute_raw_arguments do return n_args.to_a
 end
 
 redef class ACallAssignExpr
 	redef fun property_name do return n_id.text + "="
+	redef fun property_node do return n_id
 	redef fun compute_raw_arguments
 	do
 		var res = n_args.to_a
@@ -1665,11 +1747,12 @@ redef class ASendReassignFormExpr
 	do
 		var recvtype = v.visit_expr(self.n_expr)
 		var name = self.property_name
+		var node = self.property_node
 
 		if recvtype == null then return # Forward error
 
 		var for_self = self.n_expr isa ASelfExpr
-		var callsite = v.get_method(self, recvtype, name, for_self)
+		var callsite = v.get_method(node, recvtype, name, for_self)
 
 		if callsite == null then return
 		self.callsite = callsite
@@ -1680,11 +1763,11 @@ redef class ASendReassignFormExpr
 
 		var readtype = callsite.msignature.return_mtype
 		if readtype == null then
-			v.error(self, "Error: {name} is not a function")
+			v.error(node, "Error: `{name}` is not a function.")
 			return
 		end
 
-		var wcallsite = v.get_method(self, recvtype, name + "=", self.n_expr isa ASelfExpr)
+		var wcallsite = v.get_method(node, recvtype, name + "=", self.n_expr isa ASelfExpr)
 		if wcallsite == null then return
 		self.write_callsite = wcallsite
 
@@ -1701,6 +1784,7 @@ end
 
 redef class ACallReassignExpr
 	redef fun property_name do return n_id.text
+	redef fun property_node do return n_id
 	redef fun compute_raw_arguments do return n_args.to_a
 end
 
@@ -1711,6 +1795,7 @@ end
 
 redef class AInitExpr
 	redef fun property_name do return "init"
+	redef fun property_node do return n_kwinit
 	redef fun compute_raw_arguments do return n_args.to_a
 end
 
@@ -1737,7 +1822,7 @@ redef class ASuperExpr
 		assert recvtype != null
 		var mproperty = v.mpropdef.mproperty
 		if not mproperty isa MMethod then
-			v.error(self, "Error: super only usable in a method")
+			v.error(self, "Error: `super` only usable in a `method`.")
 			return
 		end
 		var superprops = mproperty.lookup_super_definitions(v.mmodule, anchor)
@@ -1746,7 +1831,7 @@ redef class ASuperExpr
 				process_superinit(v)
 				return
 			end
-			v.error(self, "Error: No super method to call for {mproperty}.")
+			v.error(self, "Error: no super method to call for `{mproperty}`.")
 			return
 		end
 		# FIXME: covariance of return type in linear extension?
@@ -1756,7 +1841,7 @@ redef class ASuperExpr
 		msignature = v.resolve_for(msignature, recvtype, true).as(MSignature)
 		var args = self.n_args.to_a
 		if args.length > 0 then
-			v.check_signature(self, args, mproperty.name, msignature)
+			signaturemap = v.check_signature(self, args, mproperty, msignature)
 		end
 		self.mtype = msignature.return_mtype
 		self.is_typed = true
@@ -1764,6 +1849,10 @@ redef class ASuperExpr
 		mpropdef = v.mpropdef.as(MMethodDef)
 	end
 
+	# The mapping used on the call to associate arguments to parameters.
+	# If null then no specific association is required.
+	var signaturemap: nullable SignatureMap
+
 	private fun process_superinit(v: TypeVisitor)
 	do
 		var anchor = v.anchor
@@ -1786,7 +1875,7 @@ redef class ASuperExpr
 				continue
 			end
 			if superprop != null and superprop.mproperty != candidate and not superprop.mproperty.is_root_init then
-				v.error(self, "Error: conflicting super constructor to call for {mproperty}: {candidate.full_name}, {superprop.mproperty.full_name}")
+				v.error(self, "Error: conflicting super constructor to call for `{mproperty}`: `{candidate.full_name}`, `{superprop.mproperty.full_name}`")
 				return
 			end
 			var candidatedefs = candidate.lookup_definitions(v.mmodule, anchor)
@@ -1795,13 +1884,13 @@ redef class ASuperExpr
 				candidatedefs.add(superprop)
 			end
 			if candidatedefs.length > 1 then
-				v.error(self, "Error: conflicting property definitions for property {mproperty} in {recvtype}: {candidatedefs.join(", ")}")
+				v.error(self, "Error: conflicting property definitions for property `{mproperty}` in `{recvtype}`: {candidatedefs.join(", ")}")
 				return
 			end
 			superprop = candidatedefs.first
 		end
 		if superprop == null then
-			v.error(self, "Error: No super method to call for {mproperty}.")
+			v.error(self, "Error: no super method to call for `{mproperty}`.")
 			return
 		end
 
@@ -1817,7 +1906,7 @@ redef class ASuperExpr
 		else
 			# Check there is at least enough parameters
 			if mpropdef.msignature.arity < msignature.arity then
-				v.error(self, "Error: Not enough implicit arguments to pass. Got {mpropdef.msignature.arity}, expected at least {msignature.arity}. Signature is {msignature}")
+				v.error(self, "Error: not enough implicit arguments to pass. Got `{mpropdef.msignature.arity}`, expected at least `{msignature.arity}`. Signature is `{msignature}`.")
 				return
 			end
 			# Check that each needed parameter is conform
@@ -1825,7 +1914,7 @@ redef class ASuperExpr
 			for sp in msignature.mparameters do
 				var p = mpropdef.msignature.mparameters[i]
 				if not v.is_subtype(p.mtype, sp.mtype) then
-					v.error(self, "Type error: expected argument #{i} of type {sp.mtype}, got implicit argument {p.name} of type {p.mtype}. Signature is {msignature}")
+					v.error(self, "Type Error: expected argument #{i} of type `{sp.mtype}`, got implicit argument `{p.name}` of type `{p.mtype}`. Signature is {msignature}")
 					return
 				end
 				i += 1
@@ -1852,30 +1941,50 @@ redef class ANewExpr
 
 		if not recvtype isa MClassType then
 			if recvtype isa MNullableType then
-				v.error(self, "Type error: cannot instantiate the nullable type {recvtype}.")
+				v.error(self, "Type Error: cannot instantiate the nullable type `{recvtype}`.")
+				return
+			else if recvtype isa MFormalType then
+				v.error(self, "Type Error: cannot instantiate the formal type `{recvtype}`.")
 				return
 			else
-				v.error(self, "Type error: cannot instantiate the formal type {recvtype}.")
+				v.error(self, "Type Error: cannot instantiate the type `{recvtype}`.")
 				return
 			end
 		end
 
 		self.recvtype = recvtype
+		var kind = recvtype.mclass.kind
 
 		var name: String
 		var nid = self.n_id
+		var node: ANode
 		if nid != null then
 			name = nid.text
+			node = nid
 		else
 			name = "new"
+			node = self.n_kwnew
+		end
+		if name == "intern" then
+			if kind != concrete_kind then
+				v.error(self, "Type Error: cannot instantiate {kind} {recvtype}.")
+				return
+			end
+			if n_args.n_exprs.not_empty then
+				v.error(n_args, "Type Error: the intern constructor expects no arguments.")
+				return
+			end
+			# Our job is done
+			self.mtype = recvtype
+			return
 		end
-		var callsite = v.get_method(self, recvtype, name, false)
+
+		var callsite = v.get_method(node, recvtype, name, false)
 		if callsite == null then return
 
 		if not callsite.mproperty.is_new then
-			var kind = recvtype.mclass.kind
 			if kind != concrete_kind then
-				v.error(self, "Type Error: Cannot instantiate {kind} {recvtype}.")
+				v.error(self, "Type Error: cannot instantiate {kind} `{recvtype}`.")
 				return
 			end
 			self.mtype = recvtype
@@ -1887,7 +1996,7 @@ redef class ANewExpr
 		self.callsite = callsite
 
 		if not callsite.mproperty.is_init_for(recvtype.mclass) then
-			v.error(self, "Error: {name} is not a constructor.")
+			v.error(self, "Error: `{name}` is not a constructor.")
 			return
 		end
 
@@ -1899,27 +2008,28 @@ end
 ####
 
 redef class AAttrFormExpr
-	# The attribute acceded.
+	# The attribute accessed.
 	var mproperty: nullable MAttribute
 
 	# The static type of the attribute.
 	var attr_type: nullable MType
 
-	# Resolve the attribute acceded.
+	# Resolve the attribute accessed.
 	private fun resolve_property(v: TypeVisitor)
 	do
 		var recvtype = v.visit_expr(self.n_expr)
 		if recvtype == null then return # Skip error
-		var name = self.n_id.text
+		var node = self.n_id
+		var name = node.text
 		if recvtype isa MNullType then
-			v.error(self, "Error: Attribute '{name}' access on 'null'.")
+			v.error(node, "Error: attribute `{name}` access on `null`.")
 			return
 		end
 
 		var unsafe_type = v.anchor_to(recvtype)
-		var mproperty = v.try_get_mproperty_by_name2(self, unsafe_type, name)
+		var mproperty = v.try_get_mproperty_by_name2(node, unsafe_type, name)
 		if mproperty == null then
-			v.modelbuilder.error(self, "Error: Attribute {name} doesn't exists in {recvtype}.")
+			v.modelbuilder.error(node, "Error: attribute `{name}` does not exist in `{recvtype}`.")
 			return
 		end
 		assert mproperty isa MAttribute
@@ -1978,7 +2088,7 @@ redef class AIssetAttrExpr
 		var recvtype = self.n_expr.mtype.as(not null)
 		var bound = v.resolve_for(mtype, recvtype, false)
 		if bound isa MNullableType then
-			v.error(self, "Error: isset on a nullable attribute.")
+			v.error(n_id, "Type Error: `isset` on a nullable attribute.")
 		end
 		self.mtype = v.type_bool(self)
 	end
@@ -1990,7 +2100,7 @@ redef class AVarargExpr
 		# This kind of pseudo-expression can be only processed trough a signature
 		# See `check_signature`
 		# Other cases are a syntax error.
-		v.error(self, "Syntax error: unexpected `...`")
+		v.error(self, "Syntax Error: unexpected `...`.")
 	end
 end