[plt-scheme] MrFlow's snips-and-arrows library

Guillaume Marceau wrote:
>I am using the snip-and-arrows library to display typing relation on
>top of the user's code. In some cases, I get the following exception:
>
>   add-one-arrow-end: untacked arrow already exists
>
>What does that means?

It means the library thinks you're trying to add an untacked arrow
where it thinks one already exists.  Your debugging output doesn't
show any duplicate arrow in the arrow lists, so that looks like a bug
in the library.

>Does it means I am using the interface
>incorrectly? The documentation mentions a seventh generation long curse
>for using the interface incorrectly. So naturally, I am a bit worried. ;)

The curse only applies if you try to register a label after calling
color-registered-labels (actually, I think one can freely intermix
registering labels and calling color-registered-labels, but the way
it's implemented it would be painfully slow).

>get arrows of [syntax: 214:89] : (([syntax: 214:89] [syntax: 152:37] orange)) 
>get arrows of [syntax: 214:89] : (([syntax: 214:89] [syntax: 152:37] orange)) 
>get arrows of [syntax: 214:89] : (([syntax: 214:89] [syntax: 152:37] orange)) 
>get arrows of [syntax: 214:48] : (([syntax: 152:10] [syntax: 214:48] green)) 
>get arrows of [syntax: 214:48] : (([syntax: 152:10] [syntax: 214:48] green)) 
>get arrows of [syntax: 214:48] : (([syntax: 152:10] [syntax: 214:48] green)) 
>get arrows of [syntax: 214:48] : (([syntax: 152:10] [syntax: 214:48] green)) 
>get arrows of [syntax: 154:33] : (([syntax: 154:33] [syntax: 141:21] orange) ([syntax: 152:37] [syntax: 154:33] orange)) 
>get arrows of [syntax: 154:33] : (([syntax: 154:33] [syntax: 141:21] orange) ([syntax: 152:37] [syntax: 154:33] orange)) 
>add-one-arrow-end: untacked arrow already exists

Can you send me some piece of code that exhibits the bug?

Philippe