Re: [PATCH] use "unresolved reference" message

[Alex Rozenman]

Hi Joel, Akim, All

I would like to install the following patch. The patch adds additional
sub-messages in case of "invalid references" errors. Some issues in the
implementation:

1. I used "printf("%.*s", len, ptr); Is this stuff portable ? I suppose it's
quite old, anyway it looks tricky. Isn't strndup better ?
2. As you can see, I used the whole rule location (rule->location) for the
extra messages, that caused an ugly shift for multi-line rules (see in
test-suite). Maybe we really need to keep sub-messages aligned ?
3. In the NEWS file (symbolic/named references) . I googled:
"symbolic references" -> ~41,000
"named references" -> ~14,000 (including copies of our thread).

diff --git a/NEWS b/NEWS
index 41ab73d..f00b27b 100644
--- a/NEWS
+++ b/NEWS
@@ -53,6 +53,31 @@ Bison News

 * Changes in version 2.5 (????-??-??):

+** Symbolic References Support
+
+  Historically, Yacc and Bison have supported positional references
+  ($n, $$) to allow access to symbol values from inside of semantic
+  actions code.
+
+  Starting from this version, Bison can also accept symbolic references.
+  When no ambiguity is possible, original symbol names may be used
+  as symbolic references:
+
+    if_stmt : 'if' cond_expr 'then' then_stmt ';'
+    { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
+
+  In the more common case, explicit symbolic names may be declared:
+
+    stmt[res] : 'if' expr[cond] 'then' stmt[then] 'else' stmt[else] ';'
+    { $res = mk_if_stmt($cond, $then, $else); }
+
+  Location information is also accessible using @name syntax. When
+  accessing symbol names containing dots or dashes, explicit bracketing
+  ($[sym.1]) must be used.
+
+  These features are experimental in this version. More user feedback
+  will help to stabilize them.
+
 ** IELR(1) and Canonical LR(1) Support

   IELR(1) is a minimal LR(1) parser table generation algorithm.  That
diff --git a/src/scan-code.l b/src/scan-code.l
index b86f459..b207716 100644
--- a/src/scan-code.l
+++ b/src/scan-code.l
@@ -591,29 +591,24 @@ parse_ref (char *cp, symbol_list *rule, int
rule_length,
   switch (valid_variants)
     {
     case 0:
-      if (variant_count == 0)
-        {
-          if (explicit_bracketing || !ref_tail_fields)
-            complain_at (text_loc, _("unresolved reference: %s"),
-                         quote(text));
-          else
-            {
-              unsigned len = ref_tail_fields - text;
-              char *str = strndup (text, len);
-              text_loc.end.column = text_loc.start.column + len;
-              complain_at (text_loc, _("unresolved reference: %s"),
-                           quote (str));
-              free (str);
-            }
-        }
-      else
-        {
-          complain_at (text_loc, _("invalid reference: %s"),
-                       quote (text));
+      {
+        unsigned len = (explicit_bracketing || !ref_tail_fields) ?
+          cp_end - cp : ref_tail_fields - cp;
+        const char *message = "symbol not found in production";
+
+        complain_at (text_loc, _("invalid reference: %s"), quote (text));
+        if (midrule_rhs_index)
+          complain_at (rule->location, _("  %s before $%d: %.*s"),
+                       message, midrule_rhs_index, len, cp);
+        else
+          complain_at (rule->location, _("  %s: %.*s"),
+                       message, len, cp);
+
+        if (variant_count > 0)
           show_sub_messages (cp, explicit_bracketing, midrule_rhs_index,
                              dollar_or_at, false);
-        }
-      return INVALID_REF;
+        return INVALID_REF;
+      }
     case 1:
       {
         if (variant_count > 1)
diff --git a/tests/named-refs.at b/tests/named-refs.at
index 70741ad..9ab63e4 100644
--- a/tests/named-refs.at
+++ b/tests/named-refs.at
@@ -255,14 +255,17 @@ exp:
 ]])

 AT_BISON_CHECK([-o test.c test.y], 1, [],
-[[test.y:50.51-60: unresolved reference: `$<ival>lo9'
+[[test.y:50.51-60: invalid reference: `$<ival>lo9'
+test.y:50.3-68:   symbol not found in production: lo9
 test.y:51.51-60: warning: misleading reference: `$<ival>exp'
 test.y:42.1-3: warning:   refers to: $exp at $$
 test.y:51.7: warning:   possibly meant: $x, hiding $exp at $1
 test.y:51.41: warning:   possibly meant: $r, hiding $exp at $4
 test.y:52.51-52: $l of `exp' has no declared type
-test.y:55.46-49: unresolved reference: `$r12'
-test.y:56.29-33: unresolved reference: `$expo'
+test.y:55.46-49: invalid reference: `$r12'
+test.y:55.3-53:   symbol not found in production: r12
+test.y:56.29-33: invalid reference: `$expo'
+test.y:56.3-46:   symbol not found in production: expo
 ]])
 AT_CLEANUP

@@ -353,33 +356,44 @@ factor:     '(' expr ')'  { $$ = $2; }
     ;
 ]])
 AT_BISON_CHECK([-o test.c test.y], 1, [],
-[[test.y:24.36-41: unresolved reference: `$cond1'
+[[test.y:24.36-41: invalid reference: `$cond1'
+test.y:23.11-24.62:   symbol not found in production: cond1
 test.y:26.43-53: invalid reference: `$stmt.field'
+test.y:25.11-26.60:   symbol not found in production: stmt
 test.y:25.35-38:   possibly meant: $then.field, hiding $stmt.field at $4
 test.y:28.43-52: invalid reference: `$stmt.list'
+test.y:27.11-28.59:   symbol not found in production: stmt
 test.y:27.30-38:   possibly meant: $[stmt.list] at $4
 test.y:30.43-46: ambiguous reference: `$xyz'
 test.y:29.35-37:   refers to: $xyz at $4
 test.y:29.50-52:   refers to: $xyz at $6
 test.y:32.43-52: invalid reference: `$stmt.list'
+test.y:31.11-32.63:   symbol not found in production: stmt
 test.y:31.40-43:   possibly meant: $then, hiding $[stmt.list] at $4
 test.y:31.61-64:   possibly meant: $else, hiding $[stmt.list] at $6
 test.y:34.43-58: invalid reference: `$stmt.list.field'
+test.y:33.11-34.69:   symbol not found in production: stmt
 test.y:33.40-43:   possibly meant: $then.field, hiding $[stmt.list].field
at $4
 test.y:33.61-64:   possibly meant: $else.field, hiding $[stmt.list].field
at $6
 test.y:36.43-54: invalid reference: `$[stmt.list]'
+test.y:35.11-36.71:   symbol not found in production: stmt.list
 test.y:35.40-43:   possibly meant: $then, hiding $[stmt.list] at $4
 test.y:35.61-64:   possibly meant: $else, hiding $[stmt.list] at $6
 test.y:38.43-49: invalid reference: `$then.1'
+test.y:37.11-38.60:   symbol not found in production: then
 test.y:37.40-45:   possibly meant: $[then.1] at $4
 test.y:40.43-55: invalid reference: `$then.1.field'
+test.y:39.11-40.66:   symbol not found in production: then
 test.y:39.40-45:   possibly meant: $[then.1].field at $4
 test.y:42.44-50: invalid reference: `$stmt.x'
+test.y:41.12-42.57:   symbol not found in production: stmt
 test.y:41.36-41:   possibly meant: $[stmt.x].x, hiding $stmt.x at $4
 test.y:41.36-41:   possibly meant: $[stmt.x] at $4
 test.y:44.13-22: invalid reference: `$if-stmt-a'
+test.y:43.12-44.59:   symbol not found in production: if
 test.y:43.1-9:   possibly meant: $[if-stmt-a] at $$
 test.y:46.46-54: invalid reference: `$then-a.f'
+test.y:45.12-46.65:   symbol not found in production: then
 test.y:45.41-46:   possibly meant: $[then-a].f at $4
 ]])
 AT_CLEANUP
@@ -513,21 +527,37 @@ sym_a : 'a';
 sym_b : 'b';
 ]])
 AT_BISON_CHECK([-o test.c test.y], 1, [],
-[[test.y:13.8-11: unresolved reference: `$sym'
-test.y:16.8-15: unresolved reference: `$<aa>sym'
-test.y:19.8-19: unresolved reference: `$[sym.field]'
-test.y:22.8-23: unresolved reference: `$<aa>[sym.field]'
-test.y:25.8-11: unresolved reference: `$sym'
-test.y:28.8-15: unresolved reference: `$<aa>sym'
-test.y:31.8-13: unresolved reference: `$[sym]'
-test.y:33.8-17: unresolved reference: `$<aa>[sym]'
-test.y:37.8-11: unresolved reference: `$sym'
-test.y:40.8-15: unresolved reference: `$<aa>sym'
-test.y:43.8-19: unresolved reference: `$[sym-field]'
-test.y:46.8-23: unresolved reference: `$<aa>[sym-field]'
-test.y:49.8-11: unresolved reference: `$sym'
-test.y:52.8-15: unresolved reference: `$<aa>sym'
-test.y:55.8-13: unresolved reference: `$[sym]'
-test.y:57.8-17: unresolved reference: `$<aa>[sym]'
+[[test.y:13.8-17: invalid reference: `$sym.field'
+test.y:12.1-13.21:   symbol not found in production: sym
+test.y:16.8-21: invalid reference: `$<aa>sym.field'
+test.y:15.1-16.25:   symbol not found in production: sym
+test.y:19.8-19: invalid reference: `$[sym.field]'
+test.y:18.1-19.23:   symbol not found in production: sym.field
+test.y:22.8-23: invalid reference: `$<aa>[sym.field]'
+test.y:21.1-22.27:   symbol not found in production: sym.field
+test.y:25.8-11: invalid reference: `$sym'
+test.y:24.1-25.15:   symbol not found in production: sym
+test.y:28.8-15: invalid reference: `$<aa>sym'
+test.y:27.1-28.19:   symbol not found in production: sym
+test.y:31.8-13: invalid reference: `$[sym]'
+test.y:30.1-33.21:   symbol not found in production before $3: sym
+test.y:33.8-17: invalid reference: `$<aa>[sym]'
+test.y:30.1-33.21:   symbol not found in production: sym
+test.y:37.8-17: invalid reference: `$sym-field'
+test.y:36.1-37.21:   symbol not found in production: sym
+test.y:40.8-21: invalid reference: `$<aa>sym-field'
+test.y:39.1-40.25:   symbol not found in production: sym
+test.y:43.8-19: invalid reference: `$[sym-field]'
+test.y:42.1-43.23:   symbol not found in production: sym-field
+test.y:46.8-23: invalid reference: `$<aa>[sym-field]'
+test.y:45.1-46.27:   symbol not found in production: sym-field
+test.y:49.8-11: invalid reference: `$sym'
+test.y:48.1-49.15:   symbol not found in production: sym
+test.y:52.8-15: invalid reference: `$<aa>sym'
+test.y:51.1-52.19:   symbol not found in production: sym
+test.y:55.8-13: invalid reference: `$[sym]'
+test.y:54.1-57.21:   symbol not found in production before $3: sym
+test.y:57.8-17: invalid reference: `$<aa>[sym]'
+test.y:54.1-57.21:   symbol not found in production: sym
 ]])
 AT_CLEANUP


-- 
Best regards,
Alex Rozenman (address@hidden).