Ensure url or options is not falsy

Fix message

Fix parameter names

Author: porsager

lib/index.js

@@ -36,8 +36,11 @@ Object.assign(Postgres, {
 
 module.exports = Postgres
 
-function Postgres(url, options) {
-  options = parseOptions(url, options)
+function Postgres(a, b) {
+  if (arguments.length && !a)
+    throw new Error(a + ' - is not a url or connection object')
+
+  const options = parseOptions(a, b)
 
   const max = Math.max(1, options.max)
       , connections = Queue()
@@ -444,10 +447,10 @@ function Postgres(url, options) {
   }
 }
 
-function parseOptions(uri, options) {
+function parseOptions(a, b) {
   const env = process.env // eslint-disable-line
-      , url = typeof uri === 'string' ? Url.parse(uri, true) : { query: {}, pathname: '' }
-      , o = (typeof uri === 'string' ? options : uri) || {}
+      , url = typeof a === 'string' ? Url.parse(a, true) : { query: {}, pathname: '' }
+      , o = (typeof a === 'string' ? b : a) || {}
       , auth = (url.auth || '').split(':')
       , host = o.hostname || o.host || url.hostname || env.PGHOST || 'localhost'
       , port = o.port || url.port || env.PGPORT || 5432