Label the URI of Html.link

This is because it is usually convenient to be able to specify the
HTML last.

lib/html.ml

@@ -89,8 +89,8 @@ type link = {
 let html_of_link l : t =
   <:xml<<a href=$str:l.href$>$str:l.text$</a>&>>
 
-let link ?hreflang ?rel ?target ?ty ?title ?cls html l =
-  let attrs = [(("", "href"), Uri.to_string l)] in
+let link ?hreflang ?rel ?target ?ty ?title ?cls ~href html =
+  let attrs = [(("", "href"), Uri.to_string href)] in
   let attrs = match hreflang with
     | Some h -> (("", "hreflang"), h) :: attrs
     | None -> attrs in
@@ -150,8 +150,8 @@ let img ?alt ?width ?height ?ismap ?title ?cls src =
     | Some c -> (("", "class"), c) :: attrs
     | None -> attrs in
   match ismap with
-  | Some u -> link [`El((("", "img"), (("", "ismap"), "") ::attrs), [])] u
-                  ~target:`self
+  | Some u -> link ~href:u ~target:`self
+                  [`El((("", "img"), (("", "ismap"), "") ::attrs), [])]
   | None -> `El((("", "img"), attrs), [])
 
 (* color tweaks for lists *)

lib/html.mli

@@ -81,8 +81,8 @@ val link : ?hreflang: string ->
            ?ty: string ->
            ?title: string ->
            ?cls: string ->
-           t -> Uri.t -> element
-(** [link html href] generate a link from [html] to [href].
+           href:Uri.t -> t -> element
+(** [link href html] generate a link from [html] to [href].
 
     @param title specifies extra information about the element that is
                  usually as a tooltip text when the mouse moves over