From c73dcd6958ed73daff240ca46cc8b0f774a28e22 Mon Sep 17 00:00:00 2001
From: Akim Demaille <akim.demaille@gmail.com>
Date: Sat, 23 Jan 2021 10:14:19 +0100
Subject: [PATCH] skeletons: introduce "slot"s for symbols

Extracted from d9cf99b6a5cb0345e91dfb90fe6d6473024ea97a, in the master
branch.

* data/skeletons/bison.m4 (b4_symbol_slot): New, with safer semantics
than type and type_tag.
---
 data/README.md          |  8 +++++++-
 data/skeletons/bison.m4 | 14 ++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/data/README.md b/data/README.md
index 50fbe525..59b220b0 100644
--- a/data/README.md
+++ b/data/README.md
@@ -142,11 +142,17 @@ The macro `b4_symbol(NUM, FIELD)` gives access to the following FIELDS:
   When api.value.type=union, the generated name for the union member.
   yytype_INT etc. for symbols that has_id, otherwise yytype_1 etc.
 
-- `type`
+- `type`: string
   If it has a semantic value, its type tag, or, if variant are used,
   its type.
   In the case of api.value.type=union, type is the real type (e.g. int).
 
+- `slot`: string
+  If it has a semantic value, the name of the union member (i.e., bounces to
+  either `type_tag` or `type`).  It would be better to fix our mess and
+  always use `type` for the true type of the member, and `type_tag` for the
+  name of the union member.
+
 - `has_printer`: 0, 1
 - `printer`: string
 - `printer_file`: string
diff --git a/data/skeletons/bison.m4 b/data/skeletons/bison.m4
index 12155123..156b0689 100644
--- a/data/skeletons/bison.m4
+++ b/data/skeletons/bison.m4
@@ -465,6 +465,19 @@ m4_case([$1],
 # but are S_YYEMPTY and symbol_kind::S_YYEMPTY in C++.
 m4_copy([b4_symbol_kind_base], [b4_symbol_kind])
 
+
+# b4_symbol_slot(NUM)
+# -------------------
+# The name of union member that contains the value of these symbols.
+# Currently, we are messy, this should actually be type_tag, but type_tag
+# has several meanings.
+m4_define([b4_symbol_slot],
+[m4_case(b4_percent_define_get([[api.value.type]]),
+         [union],   [b4_symbol([$1], [type_tag])],
+         [variant], [b4_symbol([$1], [type_tag])],
+         [b4_symbol([$1], [type])])])
+
+
 # b4_symbol(NUM, FIELD)
 # ---------------------
 # Fetch FIELD of symbol #NUM (or "orig NUM").  Fail if undefined.
@@ -475,6 +488,7 @@ m4_define([b4_symbol],
          [id],        [b4_symbol_token_kind([$1])],
          [kind_base], [b4_symbol_kind_base([$1])],
          [kind],      [b4_symbol_kind([$1])],
+         [slot],      [b4_symbol_slot([$1])],
          [_b4_symbol($@)])])