Fix SSE example, clean-up SSE related code.

Also updates UI tests for latest nightly.

core/codegen/tests/ui-fail/from_form_type_errors.stderr

@@ -3,9 +3,13 @@ error[E0277]: the trait bound `Unknown: FromFormValue<'_>` is not satisfied
   |
 7 |     field: Unknown,
   |     ^^^^^^^^^^^^^^ the trait `FromFormValue<'_>` is not implemented for `Unknown`
+  |
+  = note: required by `from_form_value`
 
 error[E0277]: the trait bound `Foo<usize>: FromFormValue<'_>` is not satisfied
   --> $DIR/from_form_type_errors.rs:15:5
    |
 15 |     field: Foo<usize>,
    |     ^^^^^^^^^^^^^^^^^ the trait `FromFormValue<'_>` is not implemented for `Foo<usize>`
+   |
+   = note: required by `from_form_value`

core/codegen/tests/ui-fail/route-type-errors.stderr

@@ -3,24 +3,32 @@ error[E0277]: the trait bound `Q: FromParam<'_>` is not satisfied
   |
 8 | fn f0(foo: Q) {} //~ ERROR FromParam
   |       ^^^^^^ the trait `FromParam<'_>` is not implemented for `Q`
+  |
+  = note: required by `from_param`
 
 error[E0277]: the trait bound `Q: FromSegments<'_>` is not satisfied
   --> $DIR/route-type-errors.rs:11:7
    |
 11 | fn f1(foo: Q) {} //~ ERROR FromSegments
    |       ^^^^^^ the trait `FromSegments<'_>` is not implemented for `Q`
+   |
+   = note: required by `from_segments`
 
 error[E0277]: the trait bound `Q: FromFormValue<'_>` is not satisfied
   --> $DIR/route-type-errors.rs:14:7
    |
 14 | fn f2(foo: Q) {} //~ ERROR FromFormValue
    |       ^^^^^^ the trait `FromFormValue<'_>` is not implemented for `Q`
+   |
+   = note: required by `from_form_value`
 
 error[E0277]: the trait bound `Q: FromQuery<'_>` is not satisfied
   --> $DIR/route-type-errors.rs:17:7
    |
 17 | fn f3(foo: Q) {} //~ ERROR FromQuery
    |       ^^^^^^ the trait `FromQuery<'_>` is not implemented for `Q`
+   |
+   = note: required by `from_query`
 
 error[E0277]: the trait bound `Q: FromDataSimple` is not satisfied
   --> $DIR/route-type-errors.rs:20:7
@@ -35,27 +43,37 @@ error[E0277]: the trait bound `Q: FromRequest<'_, '_>` is not satisfied
    |
 23 | fn f5(a: Q, foo: Q) {}
    |       ^^^^ the trait `FromRequest<'_, '_>` is not implemented for `Q`
+   |
+   = note: required by `from_request`
 
 error[E0277]: the trait bound `Q: FromParam<'_>` is not satisfied
   --> $DIR/route-type-errors.rs:23:13
    |
 23 | fn f5(a: Q, foo: Q) {}
    |             ^^^^^^ the trait `FromParam<'_>` is not implemented for `Q`
+   |
+   = note: required by `from_param`
 
 error[E0277]: the trait bound `Q: FromRequest<'_, '_>` is not satisfied
   --> $DIR/route-type-errors.rs:28:7
    |
 28 | fn f6(a: Q, foo: Q, good: usize, bar: Q) {}
    |       ^^^^ the trait `FromRequest<'_, '_>` is not implemented for `Q`
+   |
+   = note: required by `from_request`
 
 error[E0277]: the trait bound `Q: FromParam<'_>` is not satisfied
   --> $DIR/route-type-errors.rs:28:13
    |
 28 | fn f6(a: Q, foo: Q, good: usize, bar: Q) {}
    |             ^^^^^^ the trait `FromParam<'_>` is not implemented for `Q`
+   |
+   = note: required by `from_param`
 
 error[E0277]: the trait bound `Q: FromParam<'_>` is not satisfied
   --> $DIR/route-type-errors.rs:28:34
    |
 28 | fn f6(a: Q, foo: Q, good: usize, bar: Q) {}
    |                                  ^^^^^^ the trait `FromParam<'_>` is not implemented for `Q`
+   |
+   = note: required by `from_param`

core/codegen/tests/ui-fail/typed-uri-bad-type.stderr

@@ -39,6 +39,8 @@ error[E0277]: the trait bound `S: FromUriParam<rocket::http::uri::Path, _>` is n
    |
 59 |     uri!(not_uri_display: 10, S);
    |                               ^ the trait `FromUriParam<rocket::http::uri::Path, _>` is not implemented for `S`
+   |
+   = note: required by `from_uri_param`
 
 error[E0277]: the trait bound `i32: FromUriParam<rocket::http::uri::Path, Option<{integer}>>` is not satisfied
   --> $DIR/typed-uri-bad-type.rs:65:26
@@ -51,6 +53,7 @@ error[E0277]: the trait bound `i32: FromUriParam<rocket::http::uri::Path, Option
              <i32 as FromUriParam<P, &'x mut i32>>
              <i32 as FromUriParam<P, i32>>
    = note: required because of the requirements on the impl of `FromUriParam<rocket::http::uri::Path, Option<{integer}>>` for `Option<i32>`
+   = note: required by `from_uri_param`
 
 error[E0277]: the trait bound `std::string::String: FromUriParam<rocket::http::uri::Path, std::result::Result<_, _>>` is not satisfied
   --> $DIR/typed-uri-bad-type.rs:65:43
@@ -65,6 +68,7 @@ error[E0277]: the trait bound `std::string::String: FromUriParam<rocket::http::u
              <std::string::String as FromUriParam<P, &'x mut std::string::String>>
            and 2 others
    = note: required because of the requirements on the impl of `FromUriParam<rocket::http::uri::Path, std::result::Result<_, _>>` for `std::result::Result<std::string::String, &RawStr>`
+   = note: required by `from_uri_param`
 
 error[E0277]: the trait bound `isize: FromUriParam<rocket::http::uri::Query, &str>` is not satisfied
   --> $DIR/typed-uri-bad-type.rs:69:20
@@ -95,12 +99,16 @@ error[E0277]: the trait bound `S: FromUriParam<rocket::http::uri::Query, _>` is
    |
 75 |     uri!(other_q: 100, S);
    |                        ^ the trait `FromUriParam<rocket::http::uri::Query, _>` is not implemented for `S`
+   |
+   = note: required by `from_uri_param`
 
 error[E0277]: the trait bound `S: FromUriParam<rocket::http::uri::Query, _>` is not satisfied
   --> $DIR/typed-uri-bad-type.rs:78:26
    |
 78 |     uri!(other_q: rest = S, id = 100);
    |                          ^ the trait `FromUriParam<rocket::http::uri::Query, _>` is not implemented for `S`
+   |
+   = note: required by `from_uri_param`
 
 error[E0277]: the trait bound `S: Ignorable<rocket::http::uri::Query>` is not satisfied
    --> $DIR/typed-uri-bad-type.rs:42:29
@@ -139,3 +147,5 @@ error[E0277]: the trait bound `S: FromUriParam<rocket::http::uri::Query, _>` is
    |
 83 |     uri!(other_q: rest = S, id = _);
    |                          ^ the trait `FromUriParam<rocket::http::uri::Query, _>` is not implemented for `S`
+   |
+   = note: required by `from_uri_param`