+m4_define([_AT_UNUSED_VALUES_DECLARATIONS],
+[[[%token <integer> INT;
+%type <integer> a b c d e f g h i j k l;
+%destructor { destroy ($$); } INT a b c d e f g h i j k l;]]])
+
+
+# AT_CHECK_UNUSED_VALUES(DECLARATIONS_AFTER)
+# --------------------------------------------
+# Generate a grammar to test unused values,
+# compile it, run it. If DECLARATIONS_AFTER
+# is set, then the token, type, and destructor
+# declarations are generated after the rules
+# rather than before.
+
+m4_define([AT_CHECK_UNUSED_VALUES],
+[AT_DATA([input.y],
+m4_ifval($1, [
+
+
+], [_AT_UNUSED_VALUES_DECLARATIONS
+])[[%%
+start:
+ 'a' a { $]2[ } | 'b' b { $]2[ } | 'c' c { $]2[ } | 'd' d { $]2[ } | 'e' e { $]2[ }
+| 'f' f { $]2[ } | 'g' g { $]2[ } | 'h' h { $]2[ } | 'i' i { $]2[ } | 'j' j { $]2[ }
+| 'k' k { $]2[ } | 'l' l { $]2[ }
+;
+
+a: INT | INT { } INT { } INT { };
+b: INT | /* empty */;
+c: INT | INT { $]1[ } INT { } INT { };
+d: INT | INT { } INT { $]1[ } INT { };
+e: INT | INT { } INT { } INT { $]1[ };
+f: INT | INT { } INT { } INT { $]$[ = $]1[ + $]3[ + $]5[; };
+g: INT | INT { $<integer>$; } INT { $<integer>$; } INT { };
+h: INT | INT { $<integer>$; } INT { $<integer>$ = $<integer>2; } INT { };
+i: INT | INT INT { } { $]$[ = $]1[ + $]2[; };
+j: INT | INT INT { $<integer>$ = 1; } { $]$[ = $]1[ + $]2[; };
+k: INT | INT INT { $<integer>$; } { $<integer>$ = $<integer>3; } { };
+l: INT | INT { $<integer>$ = $<integer>1; } INT { $<integer>$ = $<integer>2 + $<integer>3; } INT { $<integer>$ = $<integer>4 + $<integer>5; };]]m4_ifval($1, [
+_AT_UNUSED_VALUES_DECLARATIONS])
+)
+
+AT_CHECK([bison input.y], [0], [],
+[[input.y:11.10-32: warning: unset value: $]$[
+input.y:11.10-32: warning: unused value: $]1[
+input.y:11.10-32: warning: unused value: $]3[
+input.y:11.10-32: warning: unused value: $]5[
+input.y:12.9: warning: empty rule for typed nonterminal, and no action
+input.y:13.10-35: warning: unset value: $]$[
+input.y:13.10-35: warning: unused value: $]3[
+input.y:13.10-35: warning: unused value: $]5[
+input.y:14.10-35: warning: unset value: $]$[
+input.y:14.10-35: warning: unused value: $]3[
+input.y:14.10-35: warning: unused value: $]5[
+input.y:15.10-36: warning: unset value: $]$[
+input.y:15.10-36: warning: unused value: $]3[
+input.y:15.10-36: warning: unused value: $]5[
+input.y:17.10-58: warning: unset value: $]$[
+input.y:17.10-58: warning: unused value: $]1[
+input.y:17.10-58: warning: unused value: $]2[
+input.y:17.10-58: warning: unused value: $]3[
+input.y:17.10-58: warning: unused value: $]4[
+input.y:17.10-58: warning: unused value: $]5[
+input.y:18.10-72: warning: unset value: $]$[
+input.y:18.10-72: warning: unused value: $]1[
+input.y:18.10-72: warning: unused value: $]3[
+input.y:18.10-72: warning: unused value: $]4[
+input.y:18.10-72: warning: unused value: $]5[
+input.y:20.10-55: warning: unused value: $]3[
+input.y:21.10-68: warning: unset value: $]$[
+input.y:21.10-68: warning: unused value: $]1[
+input.y:21.10-68: warning: unused value: $]2[
+input.y:21.10-68: warning: unused value: $]4[
+]])])
+
+
+## --------------- ##
+## Unused values. ##
+## --------------- ##
+
+AT_SETUP([Unused values])
+AT_CHECK_UNUSED_VALUES
+AT_CLEANUP
+
+
+## ------------------------------------------ ##
+## Unused values before symbol declarations. ##
+## ------------------------------------------ ##
+
+AT_SETUP([Unused values before symbol declarations])
+AT_CHECK_UNUSED_VALUES([1])
+AT_CLEANUP
+
+
+## --------------------------------------------- ##
+## Default %printer and %destructor redeclared. ##
+## --------------------------------------------- ##
+
+AT_SETUP([Default %printer and %destructor redeclared])
+
+AT_DATA([[input.y]],
+[[%destructor { destroy ($$); } %symbol-default %symbol-default
+%printer { destroy ($$); } %symbol-default %symbol-default
+
+%destructor { destroy ($$); } %symbol-default
+%printer { destroy ($$); } %symbol-default