CoCoA » CoCoA-5

Add an optional warning which points out (apparently) incorrect arity.
The warning needs to be optional since it may produce "false positives"
(though the hope is that happens only rarely). The intended purposes
are to help package authors detect (arity) bugs without having to devise
test cases with 100% coverage, and to help people updating C4 code to C5
(where some functions have changed arity).

1. if a fn-proc definition has been seen then (during parsing) we issue
   a warning if a call has incorrect arity -- this may produce needless
   warnings if the fn-proc is about to be redefined with different arity.
2. if no definition has been seen then we issue warnings only if two calls
   have different arity -- this may produce needless warnings if the fn-proc
   is later defined to accept any number of args.

Here are some examples:

The following should produce a warning:

Define f(x)  If x > 0 Then Return g(x); Else Return g(x,x); EndIf; EndDefine;

The following should produce no warning:

Define g(...) Return 0; EndDefine;
Define f(x)  If x > 0 Then Return g(x); Else Return g(x,x); EndIf; EndDefine;

The following should produce a warning (in the defn of f):

Define g(x) Return x+1; EndDefine;
Define f(x) Return g(x,x); EndDefine;
Define g(x,y) Return x+y; EndDefine;

The following is a bit trickier; I think it should produce a warning:

Define f(g,x)
  If x > 0 Then Return g(x);
  Else Return g(x,x);
  EndIf;
EndDefine;