Index out of bounds stream error when compiling with C-c C-c on non-exhaustive match

[macrologist]

(defpackage  #:ugg
     (:use #:coalton #:coalton-prelude))

(in-package #:ugg)

(named-readtables:in-readtable coalton:coalton)


(coalton-toplevel

  (define hmm
    (match (lisp Integer () (cl:random 3))
      (0 "hey")
      (2 "oh"))))

If you C-c C-c on the coalton-toplevel form, an index out of bounds for stream error is signalled

Index 110 out of bounds for stream #<CHAR-POSITION-STREAM {7008D3F3E3}>
[Condition of type COMMON-LISP:SIMPLE-ERROR]

This points to a possible bug in the reporting of warnings about match non-exhaustiveness.

If you C-c C-k this compiles fine.

[jbouwman]

SWANK-COMPILE-STRING receives the 122 char string, and writes it to a temp file for compilation. If the coalton readtable isn't active, when the coalton-toplevel macro is expanded, the coalton readtable is bound, and the macro's body is printed, and provided as a string input stream, to a recursive invocation of cl:read.

The contents of that stream are:

(COALTON-TOPLEVEL
  (DEFINE HMM
    (MATCH (LISP INTEGER
               COMMON-LISP:NIL
             (COMMON-LISP:RANDOM 3))
      (0 "hey")
      (2 "oh"))))

So text positions in the two versions of the input no longer correspond.

[macrologist]

Ahh so the fact that I've only been seeing it with match is a red herring.

[jbouwman]

I'll rewind main a bit to see how behavior has changed and add my findings here.

And moreover add your example to the test suite.

[jbouwman]

Ahh so the fact that I've only been seeing it with match is a red herring.

I also feel bound to mention that 'match' is a close homonym for an important type of herring https://en.wiktionary.org/wiki/Matjes

[jbouwman]

I'll rewind main a bit to see how behavior has changed and add my findings here.

For reference as of 34bc744 the non-exhaustive match is reported after C-c C-c as

; caught COMMON-LISP:STYLE-WARNING:
;   warn: Non-exhaustive match
;     --> /private/var/tmp/slimeMuww0B:4:4
;      |
;    4 |        (match (lisp Integer () (cl:random 3))
;      |  ______^
;      | | _____-
;    5 | ||       (0 "hey")
;    6 | ||       (2 "oh"))))
;      | ||_______________- Missing case _
;      | |________________^ non-exhaustive match
;   

; processing (COMMON-LISP:PROGN (COMMON-LISP:EVAL-WHEN # ...) ...)
; 
; compilation unit finished
;   caught 1 STYLE-WARNING condition