[PATCH 2/7] add support for typed mid-rule actions

[Akim Demaille]

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.

fixup! add support for typed mid-rule actions
---
 THANKS           |  1 +
 src/parse-gram.y |  4 ++--
 src/reader.c     | 16 +++++++++++-----
 src/reader.h     |  2 +-
 src/scan-code.h  | 12 +++++++++---
 src/scan-code.l  |  4 +++-
 6 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/THANKS b/THANKS
index a5b29e96..74f04dd4 100644
--- a/THANKS
+++ b/THANKS
@@ -120,6 +120,7 @@ Peter Simons              address@hidden
 Petr Machata              address@hidden
 Pho                       address@hidden
 Piotr Gackiewicz          address@hidden
+Piotr Marcińczyk          address@hidden
 Quentin Hocquet           address@hidden
 Quoc Peyrot               address@hidden
 R Blake                   address@hidden
diff --git a/src/parse-gram.y b/src/parse-gram.y
index be597ae2..cf3be6d6 100644
--- a/src/parse-gram.y
+++ b/src/parse-gram.y
@@ -613,8 +613,8 @@ rhs:
                                   current_lhs_named_ref); }
 | rhs symbol named_ref.opt
     { grammar_current_rule_symbol_append ($2, @2, $3); }
-| rhs "{...}" named_ref.opt
-    { grammar_current_rule_action_append ($2, @2, $3); }
+| rhs tag.opt "{...}"[act] named_ref.opt[name]
+    { grammar_current_rule_action_append ($act, @act, $name, current_type); }
 | rhs "%?{...}"
     { grammar_current_rule_predicate_append ($2, @2); }
 | rhs "%empty"
diff --git a/src/reader.c b/src/reader.c
index 98d42f4a..198908cc 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -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);
 }
 
diff --git a/src/reader.h b/src/reader.h
index 404262ac..70128be0 100644
--- a/src/reader.h
+++ b/src/reader.h
@@ -56,7 +56,7 @@ void grammar_current_rule_symbol_append (symbol *sym, 
location loc,
                                          named_ref *nref);
 /* Attach an ACTION to the current rule.  */
 void grammar_current_rule_action_append (const char *action, location loc,
-                                         named_ref *nref);
+                                         named_ref *nref, uniqstr tag);
 /* Attach a PREDICATE to the current rule.  */
 void grammar_current_rule_predicate_append (const char *predicate, location 
loc);
 void reader (void);
diff --git a/src/scan-code.h b/src/scan-code.h
index ed70d25b..fb8b4a27 100644
--- a/src/scan-code.h
+++ b/src/scan-code.h
@@ -23,6 +23,7 @@
 
 # include "location.h"
 # include "named-ref.h"
+# include "uniqstr.h"
 
 struct symbol_list;
 
@@ -81,8 +82,11 @@ typedef struct code_props {
   /** \c NULL iff \c code_props::kind is not \c CODE_PROPS_RULE_ACTION.  */
   struct symbol_list *rule;
 
-  /* Named reference. */
+  /** Named reference. */
   named_ref *named_ref;
+
+  /** Type, for mid-rule actions.  */
+  uniqstr type;
 } code_props;
 
 /**
@@ -103,7 +107,8 @@ void code_props_none_init (code_props *self);
     /* .is_predicate = */ false,                \
     /* .is_used = */ false,                     \
     /* .rule = */ NULL,                         \
-    /* .named_ref = */ NULL                     \
+    /* .named_ref = */ NULL,                    \
+    /* .type = */ NULL,                         \
   }
 
 /** Initialized by \c CODE_PROPS_NONE_INIT with no further modification.  */
@@ -158,7 +163,8 @@ void code_props_symbol_action_init (code_props *self, char 
const *code,
  */
 void code_props_rule_action_init (code_props *self, char const *code,
                                   location code_loc, struct symbol_list *rule,
-                                  named_ref *name, bool is_predicate);
+                                  named_ref *name, uniqstr type,
+                                  bool is_predicate);
 
 /**
  * \pre
diff --git a/src/scan-code.l b/src/scan-code.l
index e79e8859..0723224d 100644
--- a/src/scan-code.l
+++ b/src/scan-code.l
@@ -825,7 +825,8 @@ code_props_symbol_action_init (code_props *self, char const 
*code,
 void
 code_props_rule_action_init (code_props *self, char const *code,
                              location code_loc, symbol_list *rule,
-                             named_ref *name, bool is_predicate)
+                             named_ref *name, uniqstr type,
+                             bool is_predicate)
 {
   code_props_none_init (self);
   self->kind = CODE_PROPS_RULE_ACTION;
@@ -833,6 +834,7 @@ code_props_rule_action_init (code_props *self, char const 
*code,
   self->location = code_loc;
   self->rule = rule;
   self->named_ref = name;
+  self->type = type;
   self->is_predicate = is_predicate;
 }
 
-- 
2.18.0