added 'system.shallow'

compiler/msgs.nim

@@ -411,7 +411,9 @@ var
 
 proc newFileInfo(fullPath, projPath: string): TFileInfo =
   result.fullPath = fullPath
+  shallow(result.fullPath)
   result.projPath = projPath
+  shallow(result.projPath)
 
 proc fileInfoIdx*(filename: string): int32 =
   var
@@ -420,6 +422,7 @@ proc fileInfoIdx*(filename: string): int32 =
 
   try:
     canon = canonicalizePath(filename)
+    shallow(canon)
   except:
     canon = filename
     # The compiler uses "filenames" such as `command line` or `stdin`