8 files changed, 125 insertions, 34 deletions

diff --git a/include/grecs/node.h b/include/grecs/node.h
index 2d879ad..752b002 100644
--- a/include/grecs/node.h
+++ b/include/grecs/node.h
@@ -32,13 +32,13 @@ typedef struct grecs_node {
         grecs_locus_t locus;
         struct grecs_node *up;
         struct grecs_node *down;
         struct grecs_node *next;
         struct grecs_node *prev;
         char *ident;
-        grecs_locus_t idloc;
+        grecs_locus_t idloc;       /* Location of the identifier */
         union {
                 grecs_value_t *value;
                 grecs_symtab_ptr_t texttab;
         } v;
 } grecs_node_t;
 
diff --git a/include/grecs/tree.h b/include/grecs/tree.h
index 2fb26dd..f13a74b 100644
--- a/include/grecs/tree.h
+++ b/include/grecs/tree.h
@@ -64,8 +64,16 @@ grecs_match_buf_t grecs_match_buf_create(int argc, char **argv,
 struct grecs_node *grecs_match_buf_first(struct grecs_match_buf *buf,
                                          struct grecs_node *tree);
 struct grecs_node *grecs_match_buf_get_node(grecs_match_buf_t buf);
 size_t grecs_match_buf_get_args(grecs_match_buf_t buf, char ***argv);
 struct grecs_node *grecs_match_buf_get_root(grecs_match_buf_t buf);
 void grecs_match_buf_set_root(grecs_match_buf_t buf, struct grecs_node *root);
+
+/* Assertions */
+int grecs_assert_value_type(const grecs_value_t *value, int type,
+                            grecs_locus_t *refloc);
+int grecs_assert_scalar_stmt(grecs_locus_t *locus,
+                             enum grecs_callback_command cmd);
+int grecs_assert_node_value_type(enum grecs_callback_command cmd,
+                                 grecs_node_t *node, int type);
 
 #endif
diff --git a/include/grecs/value.h b/include/grecs/value.h
index 8cd2800..480db9d 100644
--- a/include/grecs/value.h
+++ b/include/grecs/value.h
@@ -41,12 +41,13 @@ typedef struct grecs_value {
         (!(val) ||                                              \
          ((val)->type == GRECS_TYPE_STRING && (val)->v.string == NULL))
 
 void grecs_value_free(struct grecs_value *val);
 void grecs_value_free_content(struct grecs_value *val);
 grecs_value_t *grecs_value_ptr_from_static(grecs_value_t *input);
+const char *grecs_value_type_string(int t);
 
 int grecs_value_eq(struct grecs_value *a, struct grecs_value *b);
 int grecs_value_match(struct grecs_value *pat, struct grecs_value *b,
                       int flags);
 
 #endif
diff --git a/src/Make.am b/src/Make.am
index 227973e..9fa7688 100644
--- a/src/Make.am
+++ b/src/Make.am
@@ -43,12 +43,13 @@ if GRECS_COND_JSON
   GRECS_JSON = json-gram.y json-lex.l jsonfmt.c
   GRECS_EXTRA_JSON = json-gram.h
 endif
 
 GRECS_SRC = \
  asprintf.c\
+ assert.c\
  cidr.c\
  diag.c\
  format.c\
  grecs-gram.y\
  grecs-lex.l\
  ipstr.c\
diff --git a/src/assert.c b/src/assert.c
new file mode 100644
index 0000000..0577768
--- /dev/null
+++ b/src/assert.c
@@ -0,0 +1,58 @@
+/* grecs - Gray's Extensible Configuration System
+   Copyright (C) 2007-2019 Sergey Poznyakoff
+
+   Grecs is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 3 of the License, or (at your
+   option) any later version.
+
+   Grecs is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along
+   with Grecs. If not, see <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <errno.h>
+#include <grecs.h>
+
+int
+grecs_assert_value_type(const grecs_value_t *value, int type,
+                        grecs_locus_t *refloc)
+{
+        if (GRECS_VALUE_EMPTY_P(value)) {
+                grecs_error(refloc, 0, _("expected %s"),
+                            gettext(grecs_value_type_string(type)));
+                return 1;
+        }
+        if (value->type != type) {
+                grecs_error(&value->locus, 0, _("expected %s, but found %s"),
+                            gettext(grecs_value_type_string(type)),
+                            gettext(grecs_value_type_string(value->type)));
+                return 1;
+        }
+        return 0;
+}
+
+int
+grecs_assert_scalar_stmt(grecs_locus_t *locus, enum grecs_callback_command cmd)
+{
+        if (cmd != grecs_callback_set_value) {
+                grecs_error(locus, 0, _("unexpected block statement"));
+                return 1;
+        }
+        return 0;
+}
+
+int
+grecs_assert_node_value_type(enum grecs_callback_command cmd,
+                             grecs_node_t *node, int type)
+{
+        return grecs_assert_scalar_stmt(&node->locus, cmd)
+                && grecs_assert_value_type(node->v.value, type,
+                                           &node->locus);
+}
diff --git a/src/format.c b/src/format.c
index af87329..d7cdb0f 100644
--- a/src/format.c
+++ b/src/format.c
@@ -27,50 +27,50 @@
 
 const char *
 grecs_data_type_string(enum grecs_data_type type)
 {
         switch (type) {
         case grecs_type_void:
-                return "void";
+                return N_("void");
 
         case grecs_type_string:
-                return "string";
+                return N_("string");
 
         case grecs_type_short:
         case grecs_type_ushort:
         case grecs_type_int:
         case grecs_type_uint:
         case grecs_type_long:
         case grecs_type_ulong:
         case grecs_type_size:
                 /*FIXME case  grecs_type_off:*/
-                return "number";
+                return N_("number");
 
         case grecs_type_time:
-                return "time";
+                return N_("time");
 
         case grecs_type_bool:
-                return "boolean";
+                return N_("boolean");
 
         case grecs_type_ipv4:
-                return "IPv4";
+                return N_("IPv4");
 
         case grecs_type_cidr:
-                return "CIDR";
+                return N_("CIDR");
 
         case grecs_type_host:
-                return "hostname";
+                return N_("hostname");
 
         case grecs_type_sockaddr:
-                return "sockaddr";
+                return N_("sockaddr");
 
         case grecs_type_section:
-                return "section";
+                return N_("section");
 
         case grecs_type_null:
-                return "null";
+                return N_("null");
         }
         return "UNKNOWN?";
 }
 
 static void
 format_level(unsigned level, FILE *stream)
diff --git a/src/tree.c b/src/tree.c
index e25c6a5..27a6f21 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -59,12 +59,25 @@ void
 grecs_value_free(struct grecs_value *val)
 {
         grecs_value_free_content(val);
         grecs_free(val);
 }
 
+const char *