Use proper span in responder codegen output.

core/codegen/src/attribute/route.rs

@@ -356,6 +356,24 @@ fn generate_internal_uri_macro(route: &Route) -> TokenStream2 {
     }
 }
 
+fn generate_respond_expr(route: &Route) -> TokenStream2 {
+    let ret_span = match route.function.sig.output {
+        syn::ReturnType::Default => route.function.sig.ident.span(),
+        syn::ReturnType::Type(_, ref ty) => ty.span().into()
+    };
+
+    define_vars_and_mods!(req);
+    define_vars_and_mods!(ret_span => handler);
+    let user_handler_fn_name = &route.function.sig.ident;
+    let parameter_names = route.inputs.iter()
+        .map(|(_, rocket_ident, _)| rocket_ident);
+
+    quote_spanned! { ret_span =>
+        let ___responder = #user_handler_fn_name(#(#parameter_names),*);
+        #handler::Outcome::from(#req, ___responder)
+    }
+}
+
 fn codegen_route(route: Route) -> Result<TokenStream> {
     // Generate the declarations for path, data, and request guard parameters.
     let mut data_stmt = None;
@@ -389,8 +407,9 @@ fn codegen_route(route: Route) -> Result<TokenStream> {
     let user_handler_fn_name = &user_handler_fn.sig.ident;
     let generated_fn_name = user_handler_fn_name.prepend(ROUTE_FN_PREFIX);
     let generated_struct_name = user_handler_fn_name.prepend(ROUTE_STRUCT_PREFIX);
-    let parameter_names = route.inputs.iter().map(|(_, rocket_ident, _)| rocket_ident);
     let generated_internal_uri_macro = generate_internal_uri_macro(&route);
+    let generated_respond_expr = generate_respond_expr(&route);
+
     let method = route.attribute.method;
     let path = route.attribute.path.origin.0.to_string();
     let rank = Optional(route.attribute.rank);
@@ -408,8 +427,7 @@ fn codegen_route(route: Route) -> Result<TokenStream> {
             #(#parameter_definitions)*
             #data_stmt
 
-            let ___responder = #user_handler_fn_name(#(#parameter_names),*);
-            #handler::Outcome::from(#req, ___responder)
+            #generated_respond_expr
         }
 
         /// Rocket code generated wrapping URI macro.

core/codegen/src/lib.rs

@@ -64,30 +64,44 @@ extern crate proc_macro;
 
 use rocket_http as http;
 
-macro_rules! define {
-    ($val:path as $v:ident) => (#[allow(non_snake_case)] let $v = quote!($val););
+macro_rules! vars_and_mods {
+    ($($name:ident => $path:path,)*) => {
+        macro_rules! define {
+            // Note: the `o` is to capture the input's span
+            $(($i:ident $name) => {
+                #[allow(non_snake_case)] let $i = quote!($path);
+            };)*
+            $(($span:expr => $i:ident $name) => {
+                #[allow(non_snake_case)] let $i = quote_spanned!($span => $path);
+            };)*
+        }
+    }
+}
+
+vars_and_mods! {
+    req => __req,
+    catcher => __catcher,
+    data => __data,
+    error => __error,
+    trail => __trail,
+    request => rocket::request,
+    response => rocket::response,
+    handler => rocket::handler,
+    log => rocket::logger,
+    Outcome => rocket::Outcome,
+    FromData => rocket::data::FromData,
+    Transform => rocket::data::Transform,
+    Query => rocket::request::Query,
+    Request => rocket::Request,
+    Response => rocket::response::Response,
+    Data => rocket::Data,
+    StaticRouteInfo => rocket::StaticRouteInfo,
+    SmallVec => rocket::http::private::SmallVec,
 }
 
 macro_rules! define_vars_and_mods {
-    (@req as $v:ident) => (define!(__req as $v));
-    (@catcher as $v:ident) => (define!(__catcher as $v));
-    (@data as $v:ident) => (define!(__data as $v));
-    (@error as $v:ident) => (define!(__error as $v));
-    (@trail as $v:ident) => (define!(__trail as $v));
-    (@request as $v:ident) => (define!(::rocket::request as $v));
-    (@response as $v:ident) => (define!(::rocket::response as $v));
-    (@handler as $v:ident) => (define!(::rocket::handler as $v));
-    (@log as $v:ident) => (define!(::rocket::logger as $v));
-    (@Outcome as $v:ident) => (define!(::rocket::Outcome as $v));
-    (@FromData as $v:ident) => (define!(::rocket::data::FromData as $v));
-    (@Transform as $v:ident) => (define!(::rocket::data::Transform as $v));
-    (@Query as $v:ident) => (define!(::rocket::request::Query as $v));
-    (@Request as $v:ident) => (define!(::rocket::Request as $v));
-    (@Response as $v:ident) => (define!(::rocket::response::Response as $v));
-    (@Data as $v:ident) => (define!(::rocket::Data as $v));
-    (@StaticRouteInfo as $v:ident) => (define!(::rocket::StaticRouteInfo as $v));
-    (@SmallVec as $v:ident) => (define!(::rocket::http::private::SmallVec as $v));
-    ($($name:ident),*) => ($(define_vars_and_mods!(@$name as $name);)*)
+    ($($name:ident),*) => ($(define!($name $name);)*);
+    ($span:expr => $($name:ident),*) => ($(define!($span => $name $name);)*)
 }
 
 #[macro_use]

core/codegen/tests/ui-fail/responder-types.rs

@@ -1,6 +1,8 @@
 // normalize-stderr-test: "<(.*) as (.*)>" -> "$1 as $$TRAIT"
 // normalize-stderr-test: "and \d+ others" -> "and $$N others"
 
+#![feature(proc_macro_hygiene)]
+
 #[macro_use] extern crate rocket;
 
 #[derive(Responder)]
@@ -32,4 +34,8 @@ struct Thing4 {
     //~^ ERROR Header
 }
 
+#[get("/")]
+fn foo() -> usize { 0 }
+//~^ ERROR Responder
+
 fn main() {  }

core/codegen/tests/ui-fail/responder-types.stderr

@@ -1,15 +1,15 @@
 error[E0277]: the trait bound `u8: rocket::response::Responder<'_>` is not satisfied
- --> $DIR/responder-types.rs:8:5
+  --> $DIR/responder-types.rs:10:5
    |
-8 |     thing: u8,
+10 |     thing: u8,
    |     ^^^^^^^^^ the trait `rocket::response::Responder<'_>` is not implemented for `u8`
    |
    = note: required by `rocket::response::Responder::respond_to`
 
 error[E0277]: the trait bound `rocket::http::Header<'_>: std::convert::From<u8>` is not satisfied
-  --> $DIR/responder-types.rs:15:5
+  --> $DIR/responder-types.rs:17:5
    |
-15 |     other: u8,
+17 |     other: u8,
    |     ^^^^^^^^^ the trait `std::convert::From<u8>` is not implemented for `rocket::http::Header<'_>`
    |
    = help: the following implementations were found:
@@ -21,17 +21,17 @@ error[E0277]: the trait bound `rocket::http::Header<'_>: std::convert::From<u8>`
    = note: required because of the requirements on the impl of `std::convert::Into<rocket::http::Header<'_>>` for `u8`
 
 error[E0277]: the trait bound `u8: rocket::response::Responder<'_>` is not satisfied
-  --> $DIR/responder-types.rs:21:5
+  --> $DIR/responder-types.rs:23:5
    |
-21 |     thing: u8,
+23 |     thing: u8,
    |     ^^^^^^^^^ the trait `rocket::response::Responder<'_>` is not implemented for `u8`
    |
    = note: required by `rocket::response::Responder::respond_to`
 
 error[E0277]: the trait bound `rocket::http::Header<'_>: std::convert::From<u8>` is not satisfied
-  --> $DIR/responder-types.rs:23:5
+  --> $DIR/responder-types.rs:25:5
    |
-23 |     other: u8,
+25 |     other: u8,
    |     ^^^^^^^^^ the trait `std::convert::From<u8>` is not implemented for `rocket::http::Header<'_>`
    |
    = help: the following implementations were found:
@@ -43,9 +43,9 @@ error[E0277]: the trait bound `rocket::http::Header<'_>: std::convert::From<u8>`
    = note: required because of the requirements on the impl of `std::convert::Into<rocket::http::Header<'_>>` for `u8`
 
 error[E0277]: the trait bound `rocket::http::Header<'_>: std::convert::From<std::string::String>` is not satisfied
-  --> $DIR/responder-types.rs:31:5
+  --> $DIR/responder-types.rs:33:5
    |
-31 |     then: String,
+33 |     then: String,
    |     ^^^^^^^^^^^^ the trait `std::convert::From<std::string::String>` is not implemented for `rocket::http::Header<'_>`
    |
    = help: the following implementations were found:
@@ -56,6 +56,14 @@ error[E0277]: the trait bound `rocket::http::Header<'_>: std::convert::From<std:
            and $N others
    = note: required because of the requirements on the impl of `std::convert::Into<rocket::http::Header<'_>>` for `std::string::String`
 
-error: aborting due to 5 previous errors
+error[E0277]: the trait bound `usize: rocket::response::Responder<'_>` is not satisfied
+  --> $DIR/responder-types.rs:38:13
+   |
+38 | fn foo() -> usize { 0 }
+   |             ^^^^^ the trait `rocket::response::Responder<'_>` is not implemented for `usize`
+   |
+   = note: required by `rocket::handler::<impl rocket::Outcome<rocket::Response<'r>, rocket::http::Status, rocket::Data>>::from`
+
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0277`.