[PATCH 00/13] Better error messages

[Akim Demaille]

This series of patches builds on top of the previous one
(https://lists.gnu.org/r/bison-patches/2020-01/msg00044.html).  It
brings the following features with parse.error=custom or detailed
(which I prefer to my previous proposal, 'rich').

Comments and feedback would be most useful.  It is again also
available on Savannah, and here:
https://github.com/akimd/bison/pull/22.

1.  Faithfulness

The token strings are no longer doubly-quoted, and no longer depend on
the current locale.  So for instance

%token MAXWELL "∇⃗×𝐸⃗ = -∂𝐵⃗/∂t"

gives with an UTF-8 able locale

static const char *const yytname[] =
{
  "$end", "error", "$undefined", "\"∇⃗×𝐸⃗ = -∂𝐵⃗/∂t\"",
  "$accept", "e", YY_NULLPTR
};

With the C locale, you get

static const char *const yytname[] =
{
  "$end", "error", "$undefined",
  
"\"\\342\\210\\207\\342\\203\\227\\303\\227\\360\\235\\220\\270\\342\\203\\227 
= -\\342\\210\\202\\360\\235\\220\\265\\342\\203\\227/\\342\\210\\202t\"",
  "$accept", "e", YY_NULLPTR
};

With custom/detailed, you always get

  static const char *const yy_sname[] =
  {
  "$end", "error", "$undefined", "∇⃗×𝐸⃗ = -∂𝐵⃗/∂t",
  "$accept", "e", YY_NULLPTR
  };


2.  Internationalization

Token aliases can be (selectively) translated.  For instance in the
gramnar file

%token NUMBER _("number")

in which case the yysymbol_name function returns _("number") instead
of "number".  It is the user responsibility to define a _ function
(and N_).

 data/skeletons/bison.m4 |  13 +-
 data/skeletons/c.m4     |   2 +-
 data/skeletons/glr.c    | 126 ++++----
 data/skeletons/yacc.c   |  55 +++-
 src/output.c            |  89 +++++-
 src/parse-gram.c        | 657 +++++++++++++++++++---------------------
 src/parse-gram.h        | 131 ++++----
 src/parse-gram.y        |  28 +-
 src/scan-gram.l         |  25 +-
 src/symtab.c            |   3 +-
 src/symtab.h            |   7 +-
 tests/calc.at           |  77 +++--
 tests/local.at          |   5 +-
 tests/regression.at     |  24 +-
 14 files changed, 691 insertions(+), 551 deletions(-)

-- 
2.24.1