From c9d1e761cea56e94d9ad3d783c8ed7fcf448b082 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <address@hidden>
Date: Sun, 4 Feb 2018 16:20:32 -0500
Subject: [PATCH v1] [sketch] Catch strange quotes on error time

* src/keyboard.c (Fcommand_error_default_function): Check for RIGHT
SINGLE QUOTATION MARK and give a more detailed message.  TODO: check
for other confusables.
* src/lread.c (read1): Don't signal error on strange quotes.
* src/eval.c (Fsetq): Pass full arglist in error data.  TODO: the same
for all the other Qwrong_number_of_arguments cases.
---
 src/eval.c     |  3 ++-
 src/keyboard.c | 20 ++++++++++++++++++++
 src/lread.c    |  7 -------
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/src/eval.c b/src/eval.c
index 7db4dbcf18..db61c0421f 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -507,7 +507,8 @@ DEFUN ("setq", Fsetq, Ssetq, 0, UNEVALLED, 0,
       Lisp_Object sym = XCAR (tail), lex_binding;
       tail = XCDR (tail);
       if (!CONSP (tail))
-	xsignal2 (Qwrong_number_of_arguments, Qsetq, make_number (nargs + 1));
+        xsignal3 (Qwrong_number_of_arguments, Qsetq,
+                  make_number (nargs + 1), args);
       Lisp_Object arg = XCAR (tail);
       tail = XCDR (tail);
       val = eval_sub (arg);
diff --git a/src/keyboard.c b/src/keyboard.c
index 4324991da4..24c5f66934 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -1047,6 +1047,26 @@ DEFUN ("command-error-default-function", Fcommand_error_default_function,
       bitch_at_user ();
 
       print_error_message (data, Qt, SSDATA (context), signal);
+
+      Lisp_Object errname = Fcar (data);
+      /* TODO: Add arglist to Qwrong_number_of_arguments errors, and
+         check those too.  */
+      if (EQ (errname, Qvoid_variable))
+        {
+          Lisp_Object void_symname = Fsymbol_name (Fnth (make_number (1), data));
+          if (SCHARS (void_symname) > 0 &&
+              /* TODO: check all confusables.  */
+              EQ (Faref (void_symname, make_number (0)), make_number (0x2019)))
+            {
+              Lisp_Object msg = CALLN
+                (Fformat_message,
+                 build_string ("\nSymbol has with `%c' (%s) at character 0,"
+                               " did you mean `%c' (%s)"),
+                 make_number (0x2019), build_string ("RIGHT SINGLE QUOTATION MARK"),
+                 make_number ('\''), build_string ("APOSTROPHE"));
+              Fprinc (msg, Qt);
+            }
+        }
     }
   return Qnil;
 }
diff --git a/src/lread.c b/src/lread.c
index 3b0a17c90b..ee08902f81 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -3470,13 +3470,6 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	    if (! NILP (result))
 	      return unbind_to (count, result);
 	  }
-        if (!quoted && multibyte)
-          {
-            int ch = STRING_CHAR ((unsigned char *) read_buffer);
-            if (confusable_symbol_character_p (ch))
-              xsignal2 (Qinvalid_read_syntax, build_string ("strange quote"),
-                        CALLN (Fstring, make_number (ch)));
-          }
 	{
 	  Lisp_Object result;
 	  ptrdiff_t nbytes = p - read_buffer;
-- 
2.11.0