c++: make parser::symbol_name public

Reported by Martin Blais <blais@furius.ca>.
https://lists.gnu.org/r/help-bison/2020-05/msg00005.html

* data/skeletons/lalr1.cc (symbol_name): Make it public.
Add a private hidden hook to enable testing of private parts.
* tests/local.at (AT_DATA_GRAMMAR_PROLOGUE): Help Emacs find the right
language mode.
* tests/c++.at (C++ Variant-based Symbols Unit Tests): Check that we
can read symbol_name.

NEWS

@@ -6,6 +6,8 @@ GNU Bison NEWS
 
   GNU readline portability issues.
 
+  In C++, yy::parser::symbol_name is now a public member, as was intended.
+
 * Noteworthy changes in release 3.6 (2020-05-08) [stable]
 
 ** Backward incompatible changes

data/skeletons/lalr1.cc

@@ -241,6 +241,24 @@ m4_define([b4_shared_declarations],
     /// Report a syntax error.
     void error (const syntax_error& err);
 
+]b4_parse_error_bmatch(
+[custom\|detailed],
+[[    /// The user-facing name of the symbol whose (internal) number is
+    /// YYSYMBOL.  No bounds checking.
+    static const char *symbol_name (symbol_kind_type yysymbol);]],
+[simple],
+[[#if ]b4_api_PREFIX[DEBUG || ]b4_token_table_flag[
+    /// The user-facing name of the symbol whose (internal) number is
+    /// YYSYMBOL.  No bounds checking.
+    static const char *symbol_name (symbol_kind_type yysymbol);
+#endif // #if ]b4_api_PREFIX[DEBUG || ]b4_token_table_flag[
+]],
+[verbose],
+[[    /// The user-facing name of the symbol whose (internal) number is
+    /// YYSYMBOL.  No bounds checking.
+    static std::string symbol_name (symbol_kind_type yysymbol);
+]])[
+
 ]b4_token_constructor_define[
 ]b4_parse_error_bmatch([custom\|detailed\|verbose], [[
     class context
@@ -317,26 +335,14 @@ m4_define([b4_shared_declarations],
     static symbol_kind_type yytranslate_ (int t);
 
 ]b4_parse_error_bmatch(
-[custom\|detailed],
-[[    /// The user-facing name of the symbol whose (internal) number is
-    /// YYSYMBOL.  No bounds checking.
-    static const char *symbol_name (symbol_kind_type yysymbol);]],
 [simple],
 [[#if ]b4_api_PREFIX[DEBUG || ]b4_token_table_flag[
-    /// The user-facing name of the symbol whose (internal) number is
-    /// YYSYMBOL.  No bounds checking.
-    static const char *symbol_name (symbol_kind_type yysymbol);
-
     /// For a symbol, its name in clear.
     static const char* const yytname_[];
 #endif // #if ]b4_api_PREFIX[DEBUG || ]b4_token_table_flag[
 ]],
 [verbose],
-[[    /// The user-facing name of the symbol whose (internal) number is
-    /// YYSYMBOL.  No bounds checking.
-    static std::string symbol_name (symbol_kind_type yysymbol);
-
-    /// Convert the symbol name \a n to a form suitable for a diagnostic.
+[[    /// Convert the symbol name \a n to a form suitable for a diagnostic.
     static std::string yytnamerr_ (const char *yystr);
 
     /// For a symbol, its name in clear.
@@ -474,6 +480,7 @@ m4_define([b4_shared_declarations],
     };
 
 ]b4_parse_param_vars[
+]b4_percent_code_get([[yy_bison_internal_hook]])[
   };
 
 ]b4_token_ctor_if([b4_yytranslate_define([$1])[

tests/c++.at

@@ -109,11 +109,6 @@ AT_DATA_GRAMMAR([list.yy],
 %define parse.assert
 %debug
 
-%code top
-{
-  // Get access to stack_symbol_type for the tests.
-# define private public
-}
 %code provides
 {
   ]AT_YYLEX_DECLARE[
@@ -136,6 +131,14 @@ AT_DATA_GRAMMAR([list.yy],
 %code requires { #include <vector> }
 %code { int yylex (yy::parser::semantic_type* lvalp); }
 
+// A hack which relies on internal hooks to check stack_symbol_type,
+// which is private.
+%code yy_bison_internal_hook {
+  public:
+    typedef stack_symbol_type yy_stack_symbol_type;
+    typedef stack_type yy_stack_type;
+}
+
 %%
 exp: "int" { $$.push_back ($1); }
 %%
@@ -157,6 +160,8 @@ int main()
   // symbol_type: construction, accessor.
   {
     parser::symbol_type s = parser::make_INT (12);
+    assert_eq (s.kind (), parser::symbol_kind::S_INT);
+    assert_eq (parser::symbol_name (s.kind ()), "\"int\"");
     assert_eq (s.value.as<int> (), 12);
   }
 
@@ -180,12 +185,13 @@ int main()
   }
 
   // stack_symbol_type: construction, accessor.
+  typedef parser::yy_stack_symbol_type stack_symbol_type;
   {
 #if 201103L <= YY_CPLUSPLUS
-    auto ss = parser::stack_symbol_type(1, parser::make_INT(123));
+    auto ss = stack_symbol_type (1, parser::make_INT(123));
 #else
     parser::symbol_type s = parser::make_INT (123);
-    parser::stack_symbol_type ss(1, s);
+    stack_symbol_type ss(1, s);
 #endif
     assert_eq (ss.value.as<int> (), 123);
   }
@@ -194,17 +200,17 @@ int main()
   // Sufficiently many so that it will be resized.
   // Probably 3 times (starting at 200).
   {
-    parser::stack_type st;
+    parser::yy_stack_type st;
     const int mucho = 1700;
     const int int_reduction_state = 1; // Read list.output to find it.
     for (int i = 0; i < mucho; ++i)
       {
 #if 201103L <= YY_CPLUSPLUS
-        st.push(parser::stack_symbol_type{int_reduction_state,
-                                          parser::make_INT (i)});
+        st.push(stack_symbol_type{int_reduction_state,
+                                  parser::make_INT (i)});
 #else
         parser::symbol_type s = parser::make_INT (i);
-        parser::stack_symbol_type ss (int_reduction_state, s);
+        stack_symbol_type ss (int_reduction_state, s);
         st.push (ss);
 #endif
       }

tests/local.at

@@ -500,7 +500,7 @@ m4_define([AT_DATA_SOURCE_PROLOGUE],
 # The prologue that should be included in any grammar whose parser is
 # meant to be compiled.
 m4_define([AT_DATA_GRAMMAR_PROLOGUE],
-[[%code top {
+[[%code top { /* -*- ]AT_LANG[ -*- */
 ]AT_DATA_SOURCE_PROLOGUE[]dnl
 [}
 ]])