Re: [Sbcl-devel] Bug (non ANSI): type error not detected in safe code

[Christophe R. <cs...@ca...>]

"Paul F. Dietz" <di...@dl...> writes:

> * (LET ((X (MAKE-ARRAY 3 :INITIAL-ELEMENT 0 :ELEMENT-TYPE '(INTEGER 0 2))))
>           (DECLARE (OPTIMIZE SAFETY))
>           (SETF (AREF X 0) 3)
>           (AREF X 0))
>
> 3
>
> According to the page for TYPE:
>
> "Within the lexical scope of an array type declaration,
>   all references to array elements are assumed to satisfy
>   the expressed array element type (as opposed to the
>   upgraded array element type). A compiler can treat the
>   code within the scope of the array type declaration as
>   if each access of an array element were surrounded by
>   an appropriate THE form."

Um, yes, but you haven't declared an array type anywhere.  If you
actually insert a declaration, then you get the type error you might
be expecting, but formally your code does not contain a type error,
because the array construction explicitly means _exactly the same_ as
the construction with an element type of 
  (upgraded-array-element-type '(integer 0 2))
which includes 3.

Cheers,

Christophe