Improve missing argument compile-time error.

codegen/src/decorators/route.rs

@@ -41,10 +41,10 @@ fn media_type_to_expr(ecx: &ExtCtxt, ct: Option<MediaType>) -> Option<P<Expr>> {
 
 impl RouteParams {
     fn missing_declared_err<T: Display>(&self, ecx: &ExtCtxt, arg: &Spanned<T>) {
-        let fn_span = self.annotated_fn.span();
-        let msg = format!("'{}' is declared as an argument...", arg.node);
-        ecx.span_err(arg.span, &msg);
-        ecx.span_err(fn_span, "...but isn't in the function signature.");
+        let (fn_span, fn_name) = (self.annotated_fn.span(), self.annotated_fn.ident());
+        ecx.struct_span_err(arg.span, &format!("unused dynamic parameter: `{}`", arg.node))
+            .span_note(fn_span, &format!("expected argument named `{}` in `{}`", arg.node, fn_name))
+            .emit();
     }
 
     fn gen_form(&self,

codegen/tests/compile-fail/ignored_params.rs

@@ -1,16 +1,16 @@
 #![feature(plugin)]
 #![plugin(rocket_codegen)]
 
-#[get("/<name>")] //~ ERROR 'name' is declared
-fn get(other: usize) -> &'static str { "hi" } //~ ERROR isn't in the function
+#[get("/<name>")] //~ ERROR unused dynamic parameter: `name`
+fn get(other: usize) -> &'static str { "hi" } //~ NOTE expected
 
-#[get("/a?<r>")] //~ ERROR 'r' is declared
-fn get1() -> &'static str { "hi" } //~ ERROR isn't in the function
+#[get("/a?<r>")] //~ ERROR unused dynamic parameter: `r`
+fn get1() -> &'static str { "hi" } //~ NOTE expected
 
-#[post("/a", data = "<test>")] //~ ERROR 'test' is declared
-fn post() -> &'static str { "hi" } //~ ERROR isn't in the function
+#[post("/a", data = "<test>")] //~ ERROR unused dynamic parameter: `test`
+fn post() -> &'static str { "hi" } //~ NOTE expected
 
-#[get("/<_r>")] //~ ERROR '_r' is declared
-fn get2(r: usize) -> &'static str { "hi" } //~ ERROR isn't in the function
+#[get("/<_r>")] //~ ERROR unused dynamic parameter: `_r`
+fn get2(r: usize) -> &'static str { "hi" } //~ NOTE expected
 
 fn main() {  }

codegen/tests/compile-fail/phantom-declared-param.rs

@@ -1,17 +1,17 @@
 #![feature(plugin)]
 #![plugin(rocket_codegen)]
 
-#[get("/<param>")] //~ ERROR declared
-fn get() {  } //~ ERROR isn't in the function signature
+#[get("/<param>")] //~ ERROR unused dynamic parameter: `param`
+fn get() {  } //~ NOTE expected
 
-#[get("/<a>")] //~ ERROR declared
-fn get2() {  } //~ ERROR isn't in the function signature
+#[get("/<a>")] //~ ERROR unused dynamic parameter: `a`
+fn get2() {  } //~ NOTE expected
 
 #[get("/a/b/c/<a>/<b>")]
-    //~^ ERROR 'a' is declared
-    //~^^ ERROR 'b' is declared
+    //~^ ERROR unused dynamic parameter: `a`
+    //~^^ ERROR unused dynamic parameter: `b`
 fn get32() {  }
-    //~^ ERROR isn't in the function signature
-    //~^^ ERROR isn't in the function signature
+    //~^ NOTE expected
+    //~^^ NOTE expected
 
 fn main() {  }