Ensure consistency between requiresAuth and authenticate.

web/vibe/web/auth.d

@@ -245,6 +245,8 @@ package template AuthInfo(C, CA = C)
 			static if (is(typeof(ATTS[idx])) && isInstanceOf!(RequiresAuthAttribute, typeof(ATTS[idx]))) {
 				static if (is(typeof(C.init.authenticate(HTTPServerRequest.init, HTTPServerResponse.init)))) {
 					alias impl = typeof(C.init.authenticate(HTTPServerRequest.init, HTTPServerResponse.init));
+					static assert(is(ATTS[idx].AuthInfo == void) || is(ATTS[idx].AuthInfo == impl),
+						"Type mismatch between the @requiresAuth annotation and the authenticate() method.");
 				} else static if (is(C == interface)) {
 					alias impl = ATTS[idx].AuthInfo;
 					static assert(!is(impl == void), "Interface "~C.stringof~" either needs to supply an authenticate method or must supply the authentication information via @requiresAuth!T.");