Improve code based on feedback.

This patch improves the readability of some of the code by using
if-let-chains. Also, make use of the `add_feature_diagnostics` function.

Author: bryangarza

compiler/rustc_ast_lowering/src/expr.rs

@@ -662,29 +662,27 @@ impl<'hir> LoweringContext<'_, 'hir> {
             span,
             self.allow_gen_future.clone(),
         );
-        if self.tcx.features().closure_track_caller {
-            let track_caller = self
-                .attrs
-                .get(&outer_hir_id.local_id)
-                .map_or(false, |attrs| attrs.into_iter().any(|attr| attr.has_name(sym::track_caller)));
-            if track_caller {
-                self.lower_attrs(
-                    hir_id,
-                    &[Attribute {
-                        kind: AttrKind::Normal(ptr::P(NormalAttr {
-                            item: AttrItem {
-                                path: Path::from_ident(Ident::new(sym::track_caller, span)),
-                                args: AttrArgs::Empty,
-                                tokens: None,
-                            },
+
+        if self.tcx.features().closure_track_caller
+            && let Some(attrs) = self.attrs.get(&outer_hir_id.local_id)
+            && attrs.into_iter().any(|attr| attr.has_name(sym::track_caller))
+        {
+            self.lower_attrs(
+                hir_id,
+                &[Attribute {
+                    kind: AttrKind::Normal(ptr::P(NormalAttr {
+                        item: AttrItem {
+                            path: Path::from_ident(Ident::new(sym::track_caller, span)),
+                            args: AttrArgs::Empty,
                             tokens: None,
-                        })),
-                        id: self.tcx.sess.parse_sess.attr_id_generator.mk_attr_id(),
-                        style: AttrStyle::Outer,
-                        span: unstable_span,
-                    }],
-                    );
-            }
+                        },
+                        tokens: None,
+                    })),
+                    id: self.tcx.sess.parse_sess.attr_id_generator.mk_attr_id(),
+                    style: AttrStyle::Outer,
+                    span: unstable_span,
+                }],
+            );
         }
 
         let generator = hir::Expr { hir_id, kind: generator_kind, span: self.lower_span(span) };

compiler/rustc_error_messages/locales/en-US/lint.ftl

@@ -351,7 +351,7 @@ lint_builtin_mutable_transmutes =
 lint_builtin_unstable_features = unstable feature
 
 lint_ungated_async_fn_track_caller = `#[track_caller]` on async functions is a no-op
-     .suggestion = enable this unstable feature
+     .label = this function will not propagate the caller location
 
 lint_builtin_unreachable_pub = unreachable `pub` {$what}
     .suggestion = consider restricting its visibility

compiler/rustc_lint/src/builtin.rs

@@ -1416,33 +1416,27 @@ impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
         span: Span,
         hir_id: HirId,
     ) {
-        if fn_kind.asyncness() == IsAsync::Async && !cx.tcx.features().closure_track_caller {
+        if fn_kind.asyncness() == IsAsync::Async
+            && !cx.tcx.features().closure_track_caller
+            && let attrs = cx.tcx.hir().attrs(hir_id)
             // Now, check if the function has the `#[track_caller]` attribute
-            let attrs = cx.tcx.hir().attrs(hir_id);
-            let maybe_track_caller = attrs.iter().find(|attr| attr.has_name(sym::track_caller));
-            if let Some(attr) = maybe_track_caller {
+            && let Some(attr) = attrs.iter().find(|attr| attr.has_name(sym::track_caller))
+            {
                 cx.struct_span_lint(
                     UNGATED_ASYNC_FN_TRACK_CALLER,
                     attr.span,
                     fluent::lint_ungated_async_fn_track_caller,
                     |lint| {
-                        lint.span_label(
-                            span,
-                            "this function will not propagate the caller location",
+                        lint.span_label(span, fluent::label);
+                        rustc_session::parse::add_feature_diagnostics(
+                            lint,
+                            &cx.tcx.sess.parse_sess,
+                            sym::closure_track_caller,
                         );
-                        if cx.tcx.sess.is_nightly_build() {
-                            lint.span_suggestion(
-                                attr.span,
-                                fluent::suggestion,
-                                "closure_track_caller",
-                                Applicability::MachineApplicable,
-                            );
-                        }
                         lint
                     },
                 );
             }
-        }
     }
 }
 

src/test/ui/async-await/track-caller/issue-104588-no-op-track-caller.rs

@@ -2,23 +2,28 @@ warning: `#[track_caller]` on async functions is a no-op
   --> $DIR/panic-track-caller.rs:50:1
    |
 LL |   #[track_caller]
-   |   ^^^^^^^^^^^^^^^ help: enable this unstable feature: `closure_track_caller`
+   |   ^^^^^^^^^^^^^^^
 LL | / async fn bar_track_caller() {
 LL | |     panic!()
 LL | | }
    | |_- this function will not propagate the caller location
    |
+   = note: see issue #87417 <https://github.com/rust-lang/rust/issues/87417> for more information
+   = help: add `#![feature(closure_track_caller)]` to the crate attributes to enable
    = note: `#[warn(ungated_async_fn_track_caller)]` on by default
 
 warning: `#[track_caller]` on async functions is a no-op
   --> $DIR/panic-track-caller.rs:62:5
    |
 LL |       #[track_caller]
-   |       ^^^^^^^^^^^^^^^ help: enable this unstable feature: `closure_track_caller`
+   |       ^^^^^^^^^^^^^^^
 LL | /     async fn bar_assoc() {
 LL | |         panic!();
 LL | |     }
    | |_____- this function will not propagate the caller location
+   |
+   = note: see issue #87417 <https://github.com/rust-lang/rust/issues/87417> for more information
+   = help: add `#![feature(closure_track_caller)]` to the crate attributes to enable
 
 warning: 2 warnings emitted