parser: move checks inside the called functions

[Akim Demaille]

commit 7803c3ccd2b92680484d647059306c9b9dc36f7b
Author: Akim Demaille <address@hidden>
Date:   Fri Nov 30 06:11:00 2018 +0100

    parser: move checks inside the called functions
    
    Revamping the handling of the symbols is the grammar is much more
    delicate than I anticipated.  Let's first move things around for
    clarity.
    
    * src/symtab.c (symbol_make_alias): Don't accept to alias
    non-terminals.
    (symbol_user_token_number_set): Don't accept user token numbers
    for non-terminals.
    Don't do anything in case of redefinition, instead of trying to
    update.  The flow is eaier to follow this way.

diff --git a/src/parse-gram.y b/src/parse-gram.y
index bfb0f351..e9aee7dd 100644
--- a/src/parse-gram.y
+++ b/src/parse-gram.y
@@ -466,8 +466,8 @@ symbol.prec:
 | symbol INT
     {
       $$ = $1;
-      symbol_user_token_number_set ($1, $2, @2);
       symbol_class_set ($1, token_sym, @1, false);
+      symbol_user_token_number_set ($1, $2, @2);
     }
 ;
 
@@ -507,23 +507,9 @@ symbol_def:
       symbol_class_set ($id, current_class, @id, true);
       symbol_type_set ($id, current_type, @id);
       if (0 <= $num)
-        {
-          if (current_class != token_sym)
-            gram_error (&@num,
-                        _("non-terminals cannot be given an explicit number"));
-          else
-            symbol_user_token_number_set ($id, $num, @num);
-        }
+        symbol_user_token_number_set ($id, $num, @num);
       if ($alias)
-        {
-          if (current_class != token_sym)
-            gram_error (&@alias,
-                        _("non-terminals cannot be given a string alias"));
-          else
-            symbol_make_alias ($id, $alias, @alias);
-        }
-      if (current_class != token_sym && (0 <= $num || $alias))
-        YYERROR;
+        symbol_make_alias ($id, $alias, @alias);
     }
 ;
 
diff --git a/src/symtab.c b/src/symtab.c
index 9a062aaf..5a9c7ac6 100644
--- a/src/symtab.c
+++ b/src/symtab.c
@@ -463,21 +463,26 @@ void
 symbol_user_token_number_set (symbol *sym, int user_token_number, location loc)
 {
   int *user_token_numberp = &sym->content->user_token_number;
-  if (*user_token_numberp != USER_NUMBER_UNDEFINED
-      && *user_token_numberp != user_token_number)
+  if (sym->content->class != token_sym)
+    complain (&loc, complaint,
+              _("non-terminals cannot be given an explicit number"));
+  else if (*user_token_numberp != USER_NUMBER_UNDEFINED
+           && *user_token_numberp != user_token_number)
     complain (&loc, complaint, _("redefining user token number of %s"),
               sym->tag);
-
-  *user_token_numberp = user_token_number;
-  /* User defined $end token? */
-  if (user_token_number == 0)
+  else
     {
-      endtoken = sym->content->symbol;
-      /* It is always mapped to 0, so it was already counted in
-         NTOKENS.  */
-      if (endtoken->content->number != NUMBER_UNDEFINED)
-        --ntokens;
-      endtoken->content->number = 0;
+      *user_token_numberp = user_token_number;
+      /* User defined $end token? */
+      if (user_token_number == 0)
+        {
+          endtoken = sym->content->symbol;
+          /* It is always mapped to 0, so it was already counted in
+             NTOKENS.  */
+          if (endtoken->content->number != NUMBER_UNDEFINED)
+            --ntokens;
+          endtoken->content->number = 0;
+        }
     }
 }
 
@@ -594,7 +599,10 @@ symbol_merge_properties (symbol *sym, symbol *str)
 void
 symbol_make_alias (symbol *sym, symbol *str, location loc)
 {
-  if (str->alias)
+  if (sym->content->class != token_sym)
+    complain (&loc, complaint,
+              _("non-terminals cannot be given a string alias"));
+  else if (str->alias)
     complain (&loc, Wother,
               _("symbol %s used more than once as a literal string"), 
str->tag);
   else if (sym->alias)
diff --git a/src/symtab.h b/src/symtab.h
index 71ade8a7..23806b5f 100644
--- a/src/symtab.h
+++ b/src/symtab.h
@@ -137,6 +137,10 @@ struct sym_content
   location prec_location;
   int prec;
   assoc assoc;
+
+  /** The user specified token number.
+
+      E.g., %token FOO 42.*/
   int user_token_number;
 
   symbol_class class;
@@ -212,7 +216,10 @@ code_props *symbol_code_props_get (symbol *sym, 
code_props_type kind);
     Do nothing if invoked with \c undef_assoc as \c assoc.  */
 void symbol_precedence_set (symbol *sym, int prec, assoc a, location loc);
 
-/** Set the \c class associated with \c sym.  */
+/** Set the \c class associated with \c sym.
+
+    Whether \c declaring means whether this class definition comes
+    from %nterm or %token.  */
 void symbol_class_set (symbol *sym, symbol_class class, location loc,
                        bool declaring);