id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	difficulty
1563	"Renaming issue with ""the"""	megane		"The first argument to `##core#the` should be the validated type as
returned by `check-and-validate-type`. In the validated type all type
variables have been replaced with gensymed new names.

Here's the code for the `the` macro in its entirety:
{{{
(##sys#extend-macro-environment
 'the '()
 (##sys#er-transformer
  (lambda (x r c)
    (##sys#check-syntax 'the x '(_ _ _))
    (if (not (memq #:compiling ##sys#features))
	(caddr x)
	`(##core#the ,(chicken.compiler.scrutinizer#check-and-validate-type (cadr x) 'the)
		     #t
		     ,(caddr x))))))
}}}

Add a debug print to `check-and-validate-type` to confirm typevariables are being renamed:
{{{
(define (check-and-validate-type type loc #!optional name)
  (let-values (((t pred pure) (validate-type (strip-syntax type) name)))
   (when t (dd ""type validated ~a => ~a"" type t)) ; <- new line
    (or t 
	(error loc ""invalid type specifier"" type))))
}}}

Now try this example:

{{{
(import (chicken type))
(compiler-typecase (the (forall (a) (pair symbol a)) (pair 'sym 1))
  ((forall (a) (pair a fixnum)) 1))
}}}

This should compile without errors. One `a` should unify with `symbol`
and the other with `fixnum`.

Instead of that you get the error:

{{{
Error: at toplevel:
  (que.scm:20) no clause applies in `compiler-typecase' for expression of type `(forall (a) (pair symbol a))':
    (forall (a) (pair a fixnum))
}}}

If you check the debug output for scrutinizer you can see that both
`a`'s have actually the same name! (You can try renaming one pair of
`a`s to see it indeed compiles without errors.)

You can see `check-and-validate-type` correctly renamed the variables:
{{{
[debug|0] type validated (forall (a) (pair a fixnum)) => (forall (a18) (pair a18 fixnum))
[debug|0] type validated (forall (a) (pair symbol a)) => (forall (a20) (pair symbol a20))
}}}

But if you check the canonicalized form you see:
{{{
$ csc -debug 2 -O3 que.scm
[canonicalized]
(##core#callunit library)

(##core#callunit eval)

(##core#callunit expand)

(##core#undefined)

(##core#undefined)

(##core#undefined)

(##core#undefined)

(##core#undefined)

(let ((g1719 (##core#the (forall (a) (pair symbol a)) #t (pair 'sym '1)))) <--- no renaming here!
  (##core#typecase ""que.scm:20"" g1719 ((forall (a) (pair a fixnum)) '1)))
}}}"	defect	closed	major	5.1	expander	5.0.0	fixed	er-macro-transformer scrutinizer