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* src/lread.c: Remove old-style backquotes support

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(new_backquote_flag): Delete variable.
(load_error_old_style_backquotes): Delete function.
(force_new_style_backquotes): Delete variable.
(read_internal_start): Don't obey it any more.
This commit is contained in:
Stefan Monnier 2020-02-14 11:18:00 -05:00
parent d737e497a8
commit 2e81e5733d
2 changed files with 15 additions and 89 deletions
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2
etc/NEWS
View file

@ -173,6 +173,8 @@ by mistake and were not useful to Lisp code.
* Lisp Changes in Emacs 28.1
** Remove final remaining traces of old-style backquotes
** The module header 'emacs-module.h' now contains type aliases
'emacs_function' and 'emacs_finalizer' for module functions and
finalizers, respectively.

102
src/lread.c
View file

@ -152,12 +152,6 @@ static ptrdiff_t prev_saved_doc_string_length;
/* This is the file position that string came from. */
static file_offset prev_saved_doc_string_position;
/* True means inside a new-style backquote with no surrounding
parentheses. Fread initializes this to the value of
`force_new_style_backquotes', so we need not specbind it or worry
about what happens to it when there is an error. */
static bool new_backquote_flag;
/* A list of file names for files being loaded in Fload. Used to
check for recursive loads. */
@ -1035,18 +1029,6 @@ load_error_handler (Lisp_Object data)
return Qnil;
}
static AVOID
load_error_old_style_backquotes (void)
{
if (NILP (Vload_file_name))
xsignal1 (Qerror, build_string ("Old-style backquotes detected!"));
else
{
AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
xsignal1 (Qerror, CALLN (Fformat_message, format, Vload_file_name));
}
}
static void
load_warn_unescaped_character_literals (Lisp_Object file)
{
@ -2283,7 +2265,6 @@ read_internal_start (Lisp_Object stream, Lisp_Object start, Lisp_Object end)
Lisp_Object retval;
readchar_count = 0;
new_backquote_flag = force_new_style_backquotes;
/* We can get called from readevalloop which may have set these
already. */
if (! HASH_TABLE_P (read_objects_map)
@ -3271,70 +3252,24 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
return list2 (Qquote, read0 (readcharfun));
case '`':
{
int next_char = READCHAR;
UNREAD (next_char);
/* Transition from old-style to new-style:
If we see "(`" it used to mean old-style, which usually works
fine because ` should almost never appear in such a position
for new-style. But occasionally we need "(`" to mean new
style, so we try to distinguish the two by the fact that we
can either write "( `foo" or "(` foo", where the first
intends to use new-style whereas the second intends to use
old-style. For Emacs-25, we should completely remove this
first_in_list exception (old-style can still be obtained via
"(\`" anyway). */
if (!new_backquote_flag && first_in_list && next_char == ' ')
load_error_old_style_backquotes ();
else
{
Lisp_Object value;
bool saved_new_backquote_flag = new_backquote_flag;
return list2 (Qbackquote, read0 (readcharfun));
new_backquote_flag = 1;
value = read0 (readcharfun);
new_backquote_flag = saved_new_backquote_flag;
return list2 (Qbackquote, value);
}
}
case ',':
{
int next_char = READCHAR;
UNREAD (next_char);
/* Transition from old-style to new-style:
It used to be impossible to have a new-style , other than within
a new-style `. This is sufficient when ` and , are used in the
normal way, but ` and , can also appear in args to macros that
will not interpret them in the usual way, in which case , may be
used without any ` anywhere near.
So we now use the same heuristic as for backquote: old-style
unquotes are only recognized when first on a list, and when
followed by a space.
Because it's more difficult to peek 2 chars ahead, a new-style
,@ can still not be used outside of a `, unless it's in the middle
of a list. */
if (new_backquote_flag
|| !first_in_list
|| (next_char != ' ' && next_char != '@'))
{
Lisp_Object comma_type = Qnil;
Lisp_Object value;
int ch = READCHAR;
Lisp_Object comma_type = Qnil;
Lisp_Object value;
int ch = READCHAR;
if (ch == '@')
comma_type = Qcomma_at;
else
{
if (ch >= 0) UNREAD (ch);
comma_type = Qcomma;
}
value = read0 (readcharfun);
return list2 (comma_type, value);
}
if (ch == '@')
comma_type = Qcomma_at;
else
load_error_old_style_backquotes ();
{
if (ch >= 0) UNREAD (ch);
comma_type = Qcomma;
}
value = read0 (readcharfun);
return list2 (comma_type, value);
}
case '?':
{
@ -5065,17 +5000,6 @@ Note that if you customize this, obviously it will not affect files
that are loaded before your customizations are read! */);
load_prefer_newer = 0;
DEFVAR_BOOL ("force-new-style-backquotes", force_new_style_backquotes,
doc: /* Non-nil means to always use the current syntax for backquotes.
If nil, `load' and `read' raise errors when encountering some
old-style variants of backquote and comma. If non-nil, these
constructs are always interpreted as described in the Info node
`(elisp)Backquote', even if that interpretation is incompatible with
previous versions of Emacs. Setting this variable to non-nil makes
Emacs compatible with the behavior planned for Emacs 28. In Emacs 28,
this variable will become obsolete. */);
force_new_style_backquotes = false;
/* Vsource_directory was initialized in init_lread. */
DEFSYM (Qcurrent_load_list, "current-load-list");