Redefintion of variables in same scope is allowed in annotations

ID0002125: This issue was created automatically from Mantis Issue 2125. Further discussion may take place here.

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Id	Project	Category	View	Due Date	Updated
ID0002125	Frama-C	Kernel > ACSL implementation	public	2015-06-01	2015-06-02

Reporter	gaggarwal	Assigned To	virgile	Resolution	open
Priority	normal	Severity	minor	Reproducibility	always
Platform	-	OS	-	OS Version	-
Product Version	Frama-C Neon-20140301	Target Version	-	Fixed in Version	-

Description :

Consider an example:

/*@
   predicate is_valid(int* n, int n) =
           (0 <= n) ;
*/

Frama-C doesn't throw any exception for the above predicate, even though variable "n" is defined twice in the same scope and it uses n as of Type int and allows comparison 0 <= n.

If I change the above predicate to following:

/*@
   predicate is_valid_int_range(int n, int* n) =
           (0 <= n) ;
*/

Frama-c complains "[kernel] user error: comparison of incompatible types: ℤ and int * in annotation" for comparison 0 <= n in above example, which means that it treats n of type int*.

Similarly, redefinition of variable in same scope is allowed in quantifier expressions like:

    loop invariant \forall int k, char k; 0 <= k && k< i ==> a[k] == b[k];

In C language it is not allowed to redefine variable in same scope. Is this an intentional behavior? And if so that is the purpose behind it? I don't see this matter is discussed in ACSL document.