Give a nice error when uri! macro is empty.

codegen/src/macros/uri.rs

@@ -25,14 +25,14 @@ pub fn uri(
 ) -> Box<MacResult + 'static> {
     // Generate the path to the internal macro.
     let mut parser = ecx.new_parser_from_tts(args);
-    let (_, mut macro_path) = try_parse!(sp, UriParams::parse_prelude(&mut parser));
-    prefix_path(URI_INFO_MACRO_PREFIX, &mut macro_path);
+    let (_, mut path) = try_parse!(sp, UriParams::parse_prelude(ecx, &mut parser));
+    prefix_path(URI_INFO_MACRO_PREFIX, &mut path);
 
     // It's incredibly important we use `sp` as the Span for the generated code
     // so that errors from the `internal` call show up on the user's code.
     let expr = parser.mk_mac_expr(sp,
         ast::Mac_ {
-            path: macro_path,
+            path: path,
             tts: args.to_vec().into_iter().collect::<TokenStream>().into(),
         },
         ::syntax::util::ThinVec::new(),

codegen/src/parser/uri_macro.rs

@@ -65,8 +65,14 @@ impl Arg {
 impl UriParams {
     // Parses the mount point, if any, and route identifier.
     pub fn parse_prelude<'a>(
+        ecx: &'a ExtCtxt,
         parser: &mut Parser<'a>
     ) -> PResult<'a, (Option<Spanned<InternedString>>, Path)> {
+        if parser.token == Token::Eof {
+            return Err(ecx.struct_span_err(ecx.call_site(),
+                "call to `uri!` cannot be empty"));
+        }
+
         // Parse the mount point and suffixing ',', if any.
         let mount_point = match parser.parse_optional_str() {
             Some((symbol, _, _)) => {
@@ -91,9 +97,12 @@ impl UriParams {
         }
     }
 
-    pub fn parse<'a>( ecx: &'a ExtCtxt, parser: &mut Parser<'a>,) -> PResult<'a, UriParams> {
+    pub fn parse<'a>(
+        ecx: &'a ExtCtxt,
+        parser: &mut Parser<'a>
+    ) -> PResult<'a, UriParams> {
         // Parse the mount point and suffixing ',', if any.
-        let (mount_point, route_path) = Self::parse_prelude(parser)?;
+        let (mount_point, route_path) = Self::parse_prelude(ecx, parser)?;
 
         // If there are no arguments, finish early.
         if !parser.eat(&Token::Colon) {