Introduce a "reserved" symboltype and wrangle an error message or two.

bin/varnishtest/tests/m00001.vtc

@@ -66,7 +66,7 @@ varnish v1 -cliok "vcl.discard vcl2"
 varnish v1 -cliok "vcl.list"
 varnish v1 -cliok "debug.vmod"
 
-varnish v1 -errvcl {Symbol type (vmod) can not be used in expression.} {
+varnish v1 -errvcl {Symbol 'std' type (vmod) can not be used in expression.} {
 	import std;
 
 	sub vcl_recv {

bin/varnishtest/tests/v00020.vtc

@@ -20,7 +20,7 @@ varnish v1 -errvcl {Found: '0' at} { 0; }
 # VCLs tokenstream.
 # XXX: A better error message would be desirable
 
-varnish v1 -errvcl {Symbol not found} " sub vcl_recv { { } { "
+varnish v1 -errvcl {Symbol cannot be used here} " sub vcl_recv { { } { "
 
 varnish v1 -errvcl {Comparison of different types: INT '!=' STRING} {
 	sub vcl_recv {
@@ -31,7 +31,7 @@ varnish v1 -errvcl {Comparison of different types: INT '!=' STRING} {
 	}
 }
 
-varnish v1 -errvcl {Symbol type (sub) can not be used in expression.} {
+varnish v1 -errvcl {Symbol 'vcl_recv' type (sub) can not be used in expression.} {
 	sub vcl_recv {
 		set req.http.foo = vcl_recv;
 	}
@@ -307,6 +307,11 @@ varnish v1 -errvcl {'||' must be preceeded by BOOL, found REAL.} {
 	sub vcl_recv { if (std.random(0,1) || 0) { } }
 }
 
+varnish v1 -errvcl {Symbol 'acl' has wrong type (reserved):} {
+	import std;
+	sub vcl_recv { call acl; }
+}
+
 server s1 {
 	rxreq
 	txresp -hdr "bar: X"

include/tbl/symbol_kind.h

@@ -30,6 +30,7 @@
 /*lint -save -e525 -e539 */
 
 VCC_KIND(NONE,		none)
+VCC_KIND(RESERVED,	reserved)
 VCC_KIND(ACL,		acl)
 VCC_KIND(ACTION,	action)
 VCC_KIND(BACKEND,	backend)

lib/libvcc/vcc_action.c

@@ -46,11 +46,12 @@ vcc_act_call(struct vcc *tl, struct token *t, struct symbol *sym)
 	(void)t;
 	ExpectErr(tl, ID);
 	sym = VCC_SymbolGet(tl, SYM_SUB, SYMTAB_CREATE, XREF_REF);
-	AN(sym);
-	vcc_AddCall(tl, sym);
-	VCC_GlobalSymbol(sym, SUB, "VGC_function");
-	Fb(tl, 1, "%s(ctx);\n", sym->rname);
-	SkipToken(tl, ';');
+	if (sym != NULL) {
+		vcc_AddCall(tl, sym);
+		VCC_GlobalSymbol(sym, SUB, "VGC_function");
+		Fb(tl, 1, "%s(ctx);\n", sym->rname);
+		SkipToken(tl, ';');
+	}
 }
 
 /*--------------------------------------------------------------------*/

lib/libvcc/vcc_expr.c

@@ -713,9 +713,9 @@ vcc_expr4(struct vcc *tl, struct expr **e, vcc_type_t fmt)
 			return;
 		}
 		VSB_printf(tl->sb,
-		    "Symbol type (%s) can not be used in expression.\n",
-		    sym->kind->name);
-		vcc_ErrWhere(tl, tl->t);
+		    "Symbol '%.*s' type (%s) can not be used in expression.\n",
+		    PF(t), sym->kind->name);
+		vcc_ErrWhere(tl, t);
 		if (sym->def_b != NULL) {
 			VSB_printf(tl->sb, "That symbol was defined here:\n");
 			vcc_ErrWhere(tl, sym->def_b);

lib/libvcc/vcc_parse.c

@@ -434,5 +434,5 @@ vcc_Parse_Init(struct vcc *tl)
 	struct toplev *tp;
 
 	for (tp = toplev; tp->name != NULL; tp++)
-		AN(VCC_MkSym(tl, tp->name, SYM_NONE, tp->vcllo, tp->vclhi));
+		AN(VCC_MkSym(tl, tp->name, SYM_RESERVED, tp->vcllo, tp->vclhi));
 }