veb: add method.location too, to the invalid return type error, to ease diagnosing problems while prototyping

Author: spytheman

vlib/veb/veb.v

@@ -56,7 +56,7 @@ fn generate_routes[A, X](app &A) !map[string]Route {
 		} $else {
 			// If we have route attributes, but the wrong return type, return an error
 			if has_route_attributes(method.attrs) {
-				return error('method `${method.name}` has route attributes but invalid return type. Handler methods must return `veb.Result`, not `!veb.Result` or other types')
+				return error('method `${method.name}` at `${method.location}` has route attributes but invalid return type. Handler methods must return `veb.Result`, not `!veb.Result` or other types')
 			}
 		}
 	}