From 4d46289331395a845c5de1f6c0e0fe873c50db4f Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 3 Jul 2019 14:18:07 -0300
Subject: Local attributes can be used in list of local variables
The syntax for local attributes ('const'/'toclose') was unified with
the regular syntax for local variables, so that we can have variables
with attributes in local definitions with multiple names; for instance:
local <toclose> f, <const> err = io.open(fname)
This new syntax does not implement constant propagation, yet.
This commit also has some small improvements to the manual.
---
lparser.c | 90 +++++++++++++++++++++++++++++----------------------------------
1 file changed, 41 insertions(+), 49 deletions(-)
(limited to 'lparser.c')
diff --git a/lparser.c b/lparser.c
index 875f7d04..52486e08 100644
--- a/lparser.c
+++ b/lparser.c
@@ -1656,13 +1656,50 @@ static void localfunc (LexState *ls) {
}
-static void commonlocalstat (LexState *ls) {
- /* stat -> LOCAL NAME {',' NAME} ['=' explist] */
+static int getlocalattribute (LexState *ls) {
+ /* ATTRIB -> ['<' Name '>'] */
+ if (testnext(ls, '<')) {
+ const char *attr = getstr(str_checkname(ls));
+ checknext(ls, '>');
+ if (strcmp(attr, "const") == 0)
+ return 1; /* read-only variable */
+ else if (strcmp(attr, "toclose") == 0)
+ return 2; /* to-be-closed variable */
+ else
+ luaK_semerror(ls,
+ luaO_pushfstring(ls->L, "unknown attribute '%s'", attr));
+ }
+ return 0;
+}
+
+
+static void checktoclose (LexState *ls, int toclose) {
+ if (toclose != -1) { /* is there a to-be-closed variable? */
+ FuncState *fs = ls->fs;
+ markupval(fs, fs->nactvar + toclose + 1);
+ fs->bl->insidetbc = 1; /* in the scope of a to-be-closed variable */
+ luaK_codeABC(fs, OP_TBC, fs->nactvar + toclose, 0, 0);
+ }
+}
+
+
+static void localstat (LexState *ls) {
+ /* stat -> LOCAL ATTRIB NAME {',' ATTRIB NAME} ['=' explist] */
+ int toclose = -1; /* index of to-be-closed variable (if any) */
int nvars = 0;
int nexps;
expdesc e;
do {
- new_localvar(ls, str_checkname(ls));
+ int kind = getlocalattribute(ls);
+ Vardesc *var = new_localvar(ls, str_checkname(ls));
+ if (kind != 0) { /* is there an attribute? */
+ var->ro = 1; /* all attributes make variable read-only */
+ if (kind == 2) { /* to-be-closed? */
+ if (toclose != -1) /* one already present? */
+ luaK_semerror(ls, "multiple to-be-closed variables in local list");
+ toclose = nvars;
+ }
+ }
nvars++;
} while (testnext(ls, ','));
if (testnext(ls, '='))
@@ -1672,56 +1709,11 @@ static void commonlocalstat (LexState *ls) {
nexps = 0;
}
adjust_assign(ls, nvars, nexps, &e);
+ checktoclose(ls, toclose);
adjustlocalvars(ls, nvars);
}
-static void tocloselocalstat (LexState *ls, Vardesc *var) {
- FuncState *fs = ls->fs;
- var->ro = 1; /* to-be-closed variables are always read-only */
- markupval(fs, fs->nactvar + 1);
- fs->bl->insidetbc = 1; /* in the scope of a to-be-closed variable */
- luaK_codeABC(fs, OP_TBC, fs->nactvar, 0, 0);
-}
-
-
-static void checkattrib (LexState *ls, TString *attr, Vardesc *var) {
- if (strcmp(getstr(attr), "const") == 0)
- var->ro = 1; /* set variable as read-only */
- else if (strcmp(getstr(attr), "toclose") == 0)
- tocloselocalstat(ls, var);
- else
- luaK_semerror(ls,
- luaO_pushfstring(ls->L, "unknown attribute '%s'", getstr(attr)));
-}
-
-
-static void attriblocalstat (LexState *ls) {
- FuncState *fs = ls->fs;
- Vardesc *var;
- expdesc e;
- TString *attr = str_checkname(ls);
- testnext(ls, '>');
- var = new_localvar(ls, str_checkname(ls));
- checknext(ls, '=');
- expr(ls, &e);
- checkattrib(ls, attr, var);
- luaK_tonumeral(fs, &e, &var->val);
- luaK_exp2nextreg(fs, &e);
- adjustlocalvars(ls, 1);
-}
-
-
-static void localstat (LexState *ls) {
- /* stat -> LOCAL NAME {',' NAME} ['=' explist]
- | LOCAL *toclose NAME '=' exp */
- if (testnext(ls, '<'))
- attriblocalstat(ls);
- else
- commonlocalstat(ls);
-}
-
-
static int funcname (LexState *ls, expdesc *v) {
/* funcname -> NAME {fieldsel} [':' NAME] */
int ismethod = 0;
--
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