[Guile-commits] branch master updated: Update match's no-matching-pattern code to use "throw"

[Andy Wingo]

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wingo pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
     new 087bb68  Update match's no-matching-pattern code to use "throw"
087bb68 is described below

commit 087bb683c8434643acfd210cf1ba436143918729
Author: Andy Wingo <address@hidden>
AuthorDate: Sun May 17 22:12:52 2020 +0200

    Update match's no-matching-pattern code to use "throw"
    
    * module/ice-9/match.upstream.scm (match-next): Use throw, so that CPS
      can see that there's no fallthrough.
    * module/ice-9/match.scm: Add a note about what to do in 3.1 to remove
      the old "error" definition.
---
 module/ice-9/match.scm          | 12 ++++++++----
 module/ice-9/match.upstream.scm |  2 +-
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/module/ice-9/match.scm b/module/ice-9/match.scm
index 099afb5..b9c2149 100644
--- a/module/ice-9/match.scm
+++ b/module/ice-9/match.scm
@@ -1,6 +1,6 @@
 ;;; -*- mode: scheme; coding: utf-8; -*-
 ;;;
-;;; Copyright (C) 2010, 2011, 2012 Free Software Foundation, Inc.
+;;; Copyright (C) 2010, 2011, 2012, 2020 Free Software Foundation, Inc.
 ;;;
 ;;; This library is free software; you can redistribute it and/or
 ;;; modify it under the terms of the GNU Lesser General Public
@@ -24,11 +24,15 @@
             match-let*
             match-letrec))
 
+;; Support for record matching.
+
+;; For backwards compatibility with previously-compiled files, keep the
+;; old definition of "error" around.
 (define (error _ . args)
-  ;; Error procedure for run-time "no matching pattern" errors.
   (apply throw 'match-error "match" args))
-
-;; Support for record matching.
+;; FIXME: In 3.1.x, use this new definition:
+;; (define-syntax-rule (error where msg datum)
+;;   (throw 'match-error "match" msg datum))
 
 (define-syntax slot-ref
   (syntax-rules ()
diff --git a/module/ice-9/match.upstream.scm b/module/ice-9/match.upstream.scm
index 1983c1e..b1fc371 100644
--- a/module/ice-9/match.upstream.scm
+++ b/module/ice-9/match.upstream.scm
@@ -292,7 +292,7 @@
      ;; Here we call error in non-tail context, so that the backtrace
      ;; can show the source location of the failing match form.
      (begin
-       (error 'match "no matching pattern" v)
+       (throw 'match-error "match" "no matching pattern" v)
        #f))
     ;; named failure continuation
     ((match-next v g+s (pat (=> failure) . body) . rest)