+AT_LALR1_CC_IF(
+ [AT_CHECK([bison -o input.cc input.y])
+ AT_COMPILE_CXX([input])],
+ [AT_CHECK([bison -o input.c input.y])
+ AT_COMPILE([input])])
+
+
+# Check the location of "empty"
+# -----------------------------
+# I.e., epsilon-reductions, as in "(x)" which ends by reducing
+# an empty "line" nterm.
+# FIXME: This location is not satisfying. Depend on the lookahead?
+AT_PARSER_CHECK([./input '(x)'], 0,
+[[sending: '(' (0@0-9)
+sending: 'x' (1@10-19)
+thing (1@10-19): 'x' (1@10-19)
+sending: ')' (2@20-29)
+line (0@0-29): '(' (0@0-9) thing (1@10-19) ')' (2@20-29)
+sending: EOF (3@30-39)
+input (0@29-29): /* Nothing */
+input (2@0-29): line (0@0-29) input (0@29-29)
+Freeing nterm input (2@0-29)
+Successful parse.
+]])
+
+
+# Check locations in error recovery
+# ---------------------------------
+# '(y)' is an error, but can be recovered from. But what's the location
+# of the error itself ('y'), and of the resulting reduction ('(error)').
+AT_PARSER_CHECK([./input '(y)'], 0,
+[[sending: '(' (0@0-9)
+sending: 'y' (1@10-19)
+10-19: syntax error, unexpected 'y', expecting 'x'
+Freeing token 'y' (1@10-19)
+sending: ')' (2@20-29)
+line (-1@0-29): '(' (0@0-9) error (@10-19) ')' (2@20-29)
+sending: EOF (3@30-39)
+input (0@29-29): /* Nothing */
+input (2@0-29): line (-1@0-29) input (0@29-29)
+Freeing nterm input (2@0-29)
+Successful parse.
+]])
+
+
+# Syntax errors caught by the parser
+# ----------------------------------
+# Exercise the discarding of stack top and input until `error'
+# can be reduced.
+#
+# '(', 'x', 'x', 'x', 'x', 'x', ')',
+#
+# Load the stack and provoke an error that cannot be caught by the
+# grammar, to check that the stack is cleared. And make sure the
+# lookahead is freed.
+#
+# '(', 'x', ')',
+# '(', 'x', ')',
+# 'y'
+AT_PARSER_CHECK([./input '(xxxxx)(x)(x)y'], 1,
+[[sending: '(' (0@0-9)
+sending: 'x' (1@10-19)
+thing (1@10-19): 'x' (1@10-19)
+sending: 'x' (2@20-29)
+thing (2@20-29): 'x' (2@20-29)
+sending: 'x' (3@30-39)
+30-39: syntax error, unexpected 'x', expecting ')'
+Freeing nterm thing (2@20-29)
+Freeing nterm thing (1@10-19)
+Freeing token 'x' (3@30-39)
+sending: 'x' (4@40-49)
+Freeing token 'x' (4@40-49)
+sending: 'x' (5@50-59)
+Freeing token 'x' (5@50-59)
+sending: ')' (6@60-69)
+line (-1@0-69): '(' (0@0-9) error (@10-59) ')' (6@60-69)
+sending: '(' (7@70-79)
+sending: 'x' (8@80-89)
+thing (8@80-89): 'x' (8@80-89)
+sending: ')' (9@90-99)
+line (7@70-99): '(' (7@70-79) thing (8@80-89) ')' (9@90-99)
+sending: '(' (10@100-109)
+sending: 'x' (11@110-119)
+thing (11@110-119): 'x' (11@110-119)
+sending: ')' (12@120-129)
+line (10@100-129): '(' (10@100-109) thing (11@110-119) ')' (12@120-129)
+sending: 'y' (13@130-139)
+input (0@129-129): /* Nothing */
+input (2@100-129): line (10@100-129) input (0@129-129)
+input (2@70-129): line (7@70-99) input (2@100-129)
+input (2@0-129): line (-1@0-69) input (2@70-129)
+130-139: syntax error, unexpected 'y', expecting $end
+Freeing nterm input (2@0-129)
+Freeing token 'y' (13@130-139)