Prefix 'uri!' format args to allow ignored parameters.

core/codegen/src/macros/uri.rs

@@ -128,6 +128,10 @@ pub fn uri_internal(
     // Building <$T as ::rocket::http::uri::FromUriParam<_>>::from_uri_param($e).
     for (i, &(mut ident, ref ty)) in internal.fn_args.iter().enumerate() {
         let (span, mut expr) = (exprs[i].span, exprs[i].clone());
+
+        // Format argument names cannot begin with `_`, but a function parameter
+        // might, so we prefix each parameter with the letters `fmt`.
+        ident.name = Symbol::intern(&format!("fmt{}", ident.name));
         ident.span = span;
 
         // path for call: <T as FromUriParam<_>>::from_uri_param

core/codegen/src/parser/uri_macro.rs

@@ -255,7 +255,7 @@ impl InternalUriParams {
 
     pub fn uri_fmt_string(&self) -> String {
         self.uri.node
-            .replace('<', "{")
+            .replace('<', "{fmt")
             .replace("..>", "}")
             .replace('>', "}")
     }

core/codegen/tests/typed-uris.rs

@@ -50,6 +50,9 @@ fn simple2(id: i32, name: String) -> &'static str { "" }
 #[post("/<id>/<name>")]
 fn simple2_flipped(name: String, id: i32) -> &'static str { "" }
 
+#[post("/<used>/<_unused>")]
+fn unused_param(used: i32, _unused: i32) -> &'static str { "" }
+
 #[post("/<id>")]
 fn guard_1(cookies: Cookies, id: i32) -> &'static str { "" }
 
@@ -90,6 +93,7 @@ fn check_simple_unnamed() {
     assert_uri_eq! {
         uri!(simple: 100) => "/100",
         uri!(simple: -23) => "/-23",
+        uri!(unused_param: 1, 2) => "/1/2",
     }
 
     // The "flipped" test ensures that the order of parameters depends on the
@@ -118,6 +122,7 @@ fn check_simple_named() {
     assert_uri_eq! {
         uri!(simple: id = 100) => "/100",
         uri!(simple: id = -23) => "/-23",
+        uri!(unused_param: used = 1, _unused = 2) => "/1/2",
     }
 
     assert_uri_eq! {