branch: scratch/mheerdegen-preview
commit 5057b57db4e79eed6c4674132b9bd55163745eba
Author: Michael Heerdegen <[email protected]>
Commit: Michael Heerdegen <[email protected]>
WIP [el-search] Discourage using symbols as LPATS in `append' and `l'
---
packages/el-search/el-search-x.el | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/packages/el-search/el-search-x.el
b/packages/el-search/el-search-x.el
index 03b3acf..30190c1 100644
--- a/packages/el-search/el-search-x.el
+++ b/packages/el-search/el-search-x.el
@@ -88,6 +88,14 @@ nil."
list2 (cons (car last-list1) list2)))))
match))
+(defun el-search-append--error-for-symbols (patterns &optional allowed-symbols)
+ (when-let ((symbol (cl-some (lambda (p) (and (symbolp p)
+ (not (keywordp p))
+ (not (memq p (append (list nil
t '_) allowed-symbols)))
+ p))
+ patterns)))
+ (user-error "Forbidden symbol binding: `%S'" symbol)))
+
(el-search-defpattern append (&rest patterns)
"Matches any list factorable into lists matched by PATTERNS in order.
@@ -97,16 +105,18 @@ equal to the concatenation of L1..Ln. Ln is allowed to be
no
list.
When different ways of matching are possible, it is unspecified
-which one is chosen.
+which one is chosen. There is no backtracking, and trying to
+create symbol bindings in an `append' pattern form is forbidden.
Example: the pattern
- (append '(1 2 3) x (app car-safe 7))
+ (append '(1 2 3) _ (app car-safe 7))
-matches the list (1 2 3 4 5 6 7 8 9), binding `x' to (4 5 6)."
+matches the list (1 2 3 4 5 6 7 8 9)."
(cond
((null patterns) '(pred null))
((equal patterns '(_)) '(pred listp))
+ ((el-search-append--error-for-symbols patterns))
(t
(pcase-let ((`(,pattern . ,more-patterns) patterns))
(cond
@@ -163,11 +173,9 @@ __ Matches any number (including zero) of list
elements.
$ Matches zero elements, but only at the end of a list.
Only allowed as the last of the LPATS.
PAT Anything else is interpreted as a standard pattern and
- matches one list element matched by it. Note: If
- matching PAT binds any symbols, occurrences in any
- following patterns are not turned into equivalence tests;
- the scope of symbol bindings is limited to the PAT
- itself.
+ matches one list element matched by it. Note: Since this
+ pattern type doesn't implement backtracking, binding
+ symbols in a PAT is discouraged.
Example: To match defuns that contain \"hl\" in the defined name
and have at least one mandatory, but also optional arguments, you
@@ -187,6 +195,7 @@ could use this pattern:
(_ (funcall (el-search-heuristic-matcher
(el-search--transform-nontrivial-lpat lpat))
file-name-or-buffer atoms-thunk))))
lpats)))))
+ (unless el-search-lazy-l (el-search-append--error-for-symbols lpats (list
'__ '_ '_? '^ '$)))
(let ((match-start nil) (match-end nil))
(when (eq (car-safe lpats) '^)
(setq match-start t)
