From 66f30875304e373c40e9b81aa37041d49bf7abfe Mon Sep 17 00:00:00 2001
From: =?utf8?q?Jo=C3=A3o=20T=C3=A1vora?= <joaotavora@gmail.com>
Date: Wed, 22 Sep 2021 23:53:15 +0100
Subject: [PATCH] Add #_ reader macro to escape shorthand renaming

* src/lread.c (read1): Add skip_shorthand variable.  Add a '#_'
case.  If skip_shorthand call oblookup instead of
oblookup_considering_shorthand.

* test/lisp/progmodes/elisp-mode-tests.el
(elisp-shorthand-escape): New test.

* test/lisp/progmodes/elisp-resources/simple-shorthand-test.el
(#_f-test4---): New fixture function.
---
 src/lread.c                                    | 18 +++++++++++++++---
 test/lisp/progmodes/elisp-mode-tests.el        | 10 ++++++++++
 .../elisp-resources/simple-shorthand-test.el   |  5 ++++-
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/src/lread.c b/src/lread.c
index 51a7084821e..db8c847a875 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -2972,6 +2972,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 {
   int c;
   bool uninterned_symbol = false;
+  bool skip_shorthand = false;
   bool multibyte;
   char stackbuf[stackbufsize];
   current_thread->stack_top = stackbuf;
@@ -3367,6 +3368,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
       if (c == ':')
 	{
 	  uninterned_symbol = true;
+	read_hash_prefixed_symbol:
 	  c = READCHAR;
 	  if (!(c > 040
 		&& c != NO_BREAK_SPACE
@@ -3380,6 +3382,12 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	    }
 	  goto read_symbol;
 	}
+      /* #_foo is really the symbol foo, regardless of shorthands  */
+      if (c == '_')
+	{
+	  skip_shorthand = true;
+	  goto read_hash_prefixed_symbol;
+	}
       /* ## is the empty symbol.  */
       if (c == '#')
 	return Fintern (empty_unibyte_string, Qnil);
@@ -3760,7 +3768,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	ptrdiff_t nbytes = p - read_buffer;
 	UNREAD (c);
 
-	if (!quoted && !uninterned_symbol)
+	if (!quoted && !uninterned_symbol && !skip_shorthand)
 	  {
 	    ptrdiff_t len;
 	    Lisp_Object result = string_to_number (read_buffer, 10, &len);
@@ -3795,10 +3803,14 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	      ptrdiff_t longhand_chars = 0;
 	      ptrdiff_t longhand_bytes = 0;
 
-	      Lisp_Object tem
-		= oblookup_considering_shorthand
+	      Lisp_Object tem;
+	      if (skip_shorthand)
+		tem = oblookup (obarray, read_buffer, nchars, nbytes);
+	      else {
+		tem = oblookup_considering_shorthand
 		(obarray, read_buffer, nchars, nbytes,
 		 &longhand, &longhand_chars, &longhand_bytes);
+	      }
 
 	      if (SYMBOLP (tem))
 		result = tem;
diff --git a/test/lisp/progmodes/elisp-mode-tests.el b/test/lisp/progmodes/elisp-mode-tests.el
index 9fe583d8cc3..fbf264a715f 100644
--- a/test/lisp/progmodes/elisp-mode-tests.el
+++ b/test/lisp/progmodes/elisp-mode-tests.el
@@ -1096,5 +1096,15 @@ evaluation of BODY."
                        "elisp--foo-test-complete-me"))
       (revert-buffer t t))))
 
+(ert-deftest elisp-shorthand-escape ()
+  (let ((test-file (expand-file-name "simple-shorthand-test.el"
+                                     elisp--test-resources-dir)))
+    (load test-file)
+    (should (intern-soft "f-test4---"))
+    (should-not (intern-soft "elisp--foo-test4---"))
+    (should (= 84 (funcall (intern-soft "f-test4---"))))
+    (should (unintern "f-test4---"))))
+
+
 (provide 'elisp-mode-tests)
 ;;; elisp-mode-tests.el ends here
diff --git a/test/lisp/progmodes/elisp-resources/simple-shorthand-test.el b/test/lisp/progmodes/elisp-resources/simple-shorthand-test.el
index cadcb4de89d..ec568093af2 100644
--- a/test/lisp/progmodes/elisp-resources/simple-shorthand-test.el
+++ b/test/lisp/progmodes/elisp-resources/simple-shorthand-test.el
@@ -16,10 +16,13 @@
 
 (defvar f-test-complete-me 42)
 
+(defun #_f-test4--- () 84)
+
 (when nil
   (f-test3)
   (f-test2)
-  (f-test))
+  (f-test)
+  (#_f-test4---))
 
 
 ;; Local Variables:
-- 
2.39.2