Stop signaling an error when reading "smart quotes" in symbols

Revert commits from 2018-01-28 "Fix round tripping of read->print for
symbols with strange quotes", and 2017-07-22 "Signal error for symbol
names with strange quotes (Bug#2967)".
* etc/NEWS: Remove corresponding entries.
* src/character.c (confusable_symbol_character_p):
* test/src/lread-tests.el (lread-tests--old-style-backquotes): Remove.
* src/lread.c (read1): Don't signal error on confusable character.
* src/print.c (print_object): Don't escape confusable characters.

4 files changed, 1 insertions, 37 deletions

diff --git a/src/character.c b/src/character.c
index 708eb2f7024..55ad49005a0 100644
--- a/src/character.c
+++ b/src/character.c
@@ -1056,32 +1056,6 @@ blankp (int c)
   return XFIXNUM (category) == UNICODE_CATEGORY_Zs; /* separator, space */
 }
 
-
-/* Return true for characters that would read as symbol characters,
-   but graphically may be confused with some kind of punctuation.  We
-   require an escaping backslash, when such characters begin a
-   symbol.  */
-bool
-confusable_symbol_character_p (int ch)
-{
-  switch (ch)
-    {
-    case 0x2018: /* LEFT SINGLE QUOTATION MARK */
-    case 0x2019: /* RIGHT SINGLE QUOTATION MARK */
-    case 0x201B: /* SINGLE HIGH-REVERSED-9 QUOTATION MARK */
-    case 0x201C: /* LEFT DOUBLE QUOTATION MARK */
-    case 0x201D: /* RIGHT DOUBLE QUOTATION MARK */
-    case 0x201F: /* DOUBLE HIGH-REVERSED-9 QUOTATION MARK */
-    case 0x301E: /* DOUBLE PRIME QUOTATION MARK */
-    case 0xFF02: /* FULLWIDTH QUOTATION MARK */
-    case 0xFF07: /* FULLWIDTH APOSTROPHE */
-      return true;
-
-    default:
-      return false;
-    }
-}
-
 /* hexdigit[C] is one greater than C's numeric value if C is a
    hexadecimal digit, zero otherwise.  */
 signed char const hexdigit[UCHAR_MAX + 1] =
diff --git a/src/character.h b/src/character.h
index 230fc6eab59..3642a540448 100644
--- a/src/character.h
+++ b/src/character.h
@@ -684,8 +684,6 @@ extern bool graphicp (int);
 extern bool printablep (int);
 extern bool blankp (int);
 
-extern bool confusable_symbol_character_p (int ch);
-
 /* Return a translation table of id number ID.  */
 #define GET_TRANSLATION_TABLE(id) \
   (XCDR (XVECTOR (Vtranslation_table_vector)->contents[(id)]))
diff --git a/src/lread.c b/src/lread.c
index 4ea62029727..e5a9c93c55e 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -3571,13 +3571,6 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
             if (! NILP (result) && len == nbytes)
               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_fixnum (ch)));
-          }
         {
           Lisp_Object result;
           ptrdiff_t nchars
diff --git a/src/print.c b/src/print.c
index a2c199c14ad..7105c5dbb92 100644
--- a/src/print.c
+++ b/src/print.c
@@ -2035,8 +2035,7 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
                     || c == ',' || c == '.' || c == '`'
                     || c == '[' || c == ']' || c == '?' || c <= 040
                     || c == NO_BREAK_SPACE
-                    || confusing
-                    || (i == 1 && confusable_symbol_character_p (c)))
+                    || confusing)
                   {
                     printchar ('\\', printcharfun);
                     confusing = false;