lib/standard/string: Fixed substring, could produce strings with a negative length

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

diff --git a/lib/standard/string.nit b/lib/standard/string.nit
index c4ae7b0..b5cfa71 100644 (file)
--- a/lib/standard/string.nit
+++ b/lib/standard/string.nit
@@ -1092,15 +1092,19 @@ class FlatString
                        from = 0
                end
 
-               var realFrom = index_from + from
+               var new_from = index_from + from
 
-               if (realFrom + count) > index_to then return new FlatString.with_infos(items, index_to - realFrom + 1, realFrom, index_to)
+               if (new_from + count) > index_to then
+                       var new_len = index_to - new_from + 1
+                       if new_len <= 0 then return empty
+                       return new FlatString.with_infos(items, new_len, new_from, index_to)
+               end
 
-               if count == 0 then return empty
+               if count <= 0 then return empty
 
-               var to = realFrom + count - 1
+               var to = new_from + count - 1
 
-               return new FlatString.with_infos(items, to - realFrom + 1, realFrom, to)
+               return new FlatString.with_infos(items, to - new_from + 1, new_from, to)
        end
 
        redef fun empty do return "".as(FlatString)