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add support for typed mid-rule actions

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Prompted on Piotr Marcińczyk's message:
http://lists.gnu.org/archive/html/bug-bison/2017-06/msg00000.html.
See also http://lists.gnu.org/archive/html/bug-bison/2018-06/msg00001.html.

Because their type is unknown to Bison, the values of midrule actions are
not treated like the others: they don't have %printer and %destructor
support.  In addition, in C++, (Bison) variants cannot work properly.

Typed midrule actions address these issues.  Instead of:

    exp: { $<ival>$ = 1; } { $<ival>$ = 2; }   { $$ = $<ival>1 + $<ival>2; }

write:

    exp: <ival>{ $$ = 1; } <ival>{ $$ = 2; }   { $$ = $1 + $2; }

* src/scan-code.h, src/scan-code.l (code_props): Add a `type` field to
record the declared type of an action.
(code_props_rule_action_init): Add a type argument.
* src/parse-gram.y: Accept an optional type tag for actions.
* src/reader.h, src/reader.c (grammar_current_rule_action_append): Add
a type argument.
(grammar_midrule_action): When a mid-rule is typed, pass its type to
the defined dummy non terminal symbol.
This commit is contained in:
Akim Demaille
2018-06-17 18:15:05 +02:00
parent 0d06a966f8
commit 7b24c424b5
6 changed files with 27 additions and 12 deletions
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16
src/reader.c
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@@ -368,7 +368,7 @@ grammar_current_rule_end (location loc)
/*-------------------------------------------------------------------.
| The previous action turns out the be a mid-rule action. Attach it |
| The previous action turns out to be a mid-rule action. Attach it |
| to the current rule, i.e., create a dummy symbol, attach it this |
| mid-rule action, and append this dummy nonterminal to the current |
| rule. |
@@ -385,6 +385,8 @@ grammar_midrule_action (void)
action. Create the MIDRULE. */
location dummy_location = current_rule->action_props.location;
symbol *dummy = dummy_symbol_get (dummy_location);
symbol_type_set(dummy,
current_rule->action_props.type, current_rule->action_props.location);
symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
/* Remember named_ref of previous action. */
@@ -399,7 +401,9 @@ grammar_midrule_action (void)
code_props_rule_action_init (&midrule->action_props,
current_rule->action_props.code,
current_rule->action_props.location,
midrule, 0,
midrule,
/* name_ref */ NULL,
/* type */ NULL,
current_rule->action_props.is_predicate);
code_props_none_init (&current_rule->action_props);
@@ -520,14 +524,15 @@ grammar_current_rule_symbol_append (symbol *sym, location loc,
void
grammar_current_rule_action_append (const char *action, location loc,
named_ref *name)
named_ref *name, uniqstr type)
{
if (current_rule->action_props.code)
grammar_midrule_action ();
/* After all symbol declarations have been parsed, packgram invokes
code_props_translate_code. */
code_props_rule_action_init (&current_rule->action_props, action, loc,
current_rule, name,
current_rule,
name, type,
/* is_predicate */ false);
}
@@ -537,7 +542,8 @@ grammar_current_rule_predicate_append (const char *pred, location loc)
if (current_rule->action_props.code)
grammar_midrule_action ();
code_props_rule_action_init (&current_rule->action_props, pred, loc,
current_rule, NULL,
current_rule,
NULL, NULL,
/* is_predicate */ true);
}