Allow automatic promotion from INT to REAL.

Fixes #2084

bin/varnishtest/tests/r02084.vtc

+varnishtest "REAL - INT types"
+
+server s1 {
+	rxreq
+	txresp
+} -start
+
+varnish v1 -vcl+backend {
+	import std;
+
+	sub vcl_deliver {
+	    set resp.http.add = 10.0 + std.integer(req.http.foo, 0);
+	    set resp.http.sub = 10.0 - std.integer(req.http.foo, 0);
+	    set resp.http.mul = 10.0 * std.integer(req.http.foo, 0);
+	    set resp.http.div = 10.0 / std.integer(req.http.foo, 0);
+	}
+
+} -start
+
+client c1 {
+	txreq -hdr "foo: 3"
+	rxresp
+	expect resp.http.add == 13.000
+	expect resp.http.sub == 7.000
+	expect resp.http.mul == 30.000
+	expect resp.http.div == 3.333
+} -run

lib/libvcc/vcc_expr.c

@@ -910,14 +910,13 @@ vcc_expr_mul(struct vcc *tl, struct expr **e, vcc_type_t fmt)
 		vcc_NextToken(tl);
 		vcc_expr4(tl, &e2, f2);
 		ERRCHK(tl);
-		if (e2->fmt->multype == NULL) {
+		if (e2->fmt != REAL && e2->fmt != INT) {
 			VSB_printf(tl->sb,
 			    "%s %.*s %s not possible.\n",
 			    f2->name, PF(tk), e2->fmt->name);
 			vcc_ErrWhere(tl, tk);
 			return;
 		}
-		assert(e2->fmt == f2);
 		if (tk->tok == '*')
 			*e = vcc_expr_edit(f3, "(\v1*\v2)", *e, e2);
 		else
@@ -1017,6 +1016,10 @@ vcc_expr_add(struct vcc *tl, struct expr **e, vcc_type_t fmt)
 		ADD_OK("-", INT,	INT,		INT);
 		ADD_OK("+", REAL,	REAL,		REAL);
 		ADD_OK("-", REAL,	REAL,		REAL);
+		ADD_OK("+", REAL,	INT,		REAL);
+		ADD_OK("-", REAL,	INT,		REAL);
+		ADD_OK("+", INT,	REAL,		REAL);
+		ADD_OK("-", INT,	REAL,		REAL);
 
 #undef ADD_OK