syntax: do_lvalue_typing do not do the final type check

Clients can now deals with the fact that in
  x += 1
that is equivalent to
  x_new = x_old + 1
the static type of x_old is different from the one accepted by x_new.

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/syntax/typing.nit b/src/syntax/typing.nit
index 721c76b..4300a8f 100644 (file)
--- a/src/syntax/typing.nit
+++ b/src/syntax/typing.nit
@@ -550,24 +550,26 @@ redef class AVarAssignExpr
 end
 
 redef class AReassignFormExpr
-       # Compute and check method used through the reassigment operator 
-       private meth do_lvalue_typing(v: TypingVisitor, type_lvalue: MMType)
+       # Compute and check method used through the reassigment operator
+       # On success return the static type of the result of the reassigment operator
+       # Else display an error and return null
+       private meth do_rvalue_typing(v: TypingVisitor, type_lvalue: MMType): MMType
        do
                if type_lvalue == null then
-                       return
+                       return null
                end
                var name = n_assign_op.method_name
                var lc = type_lvalue.local_class
                if not lc.has_global_property_by_name(name) then
                        v.error(self, "Error: Method '{name}' doesn't exists in {type_lvalue}.")
-                       return
+                       return null
                end
                var prop = lc.select_method(name)
                prop.global.check_visibility(v, self, v.module, false)
                var psig = prop.signature_for(type_lvalue)
                _assign_method = prop
-               if not v.check_conform_expr(n_value, psig[0].not_for_self) then return
-               if not v.check_conform(self, psig.return_type.not_for_self, n_value.stype) then return
+               if not v.check_conform_expr(n_value, psig[0].not_for_self) then return null
+               return psig.return_type.not_for_self
        end
 
        # Method used through the reassigment operator (once computed)
@@ -580,7 +582,9 @@ redef class AVarReassignExpr
                v.variable_ctx.check_is_set(self, variable)
                v.variable_ctx.mark_is_set(variable)
                var t = v.variable_ctx.stype(variable)
-               do_lvalue_typing(v, t)
+               var t2 = do_rvalue_typing(v, t)
+               if t2 == null then return
+               v.check_conform(self, t2, n_value.stype)
                _is_typed = true
        end
 end
@@ -918,7 +922,9 @@ redef class AAttrReassignExpr
        do
                do_typing(v)
                if prop == null then return
-               do_lvalue_typing(v, attr_type)
+               var t = do_rvalue_typing(v, attr_type)
+               if t == null then return
+               v.check_conform(self, t, n_value.stype)
                _is_typed = true
        end
 end
@@ -1199,7 +1205,9 @@ special AReassignFormExpr
                var t = prop.signature_for(n_expr.stype).return_type
                if not n_expr.is_self then t = t.not_for_self
 
-               do_lvalue_typing(v, t)
+               var t2 = do_rvalue_typing(v, t)
+               if t2 == null then return
+               v.check_conform(self, t2, n_value.stype)
 
                _read_prop = prop
                var old_args = arguments