Allow and add track_caller to generators

This patch allows the usage of the `track_caller` annotation on
generators, as well as sets them conditionally if the parent also has
`track_caller` set.

Also add this annotation on the `GenFuture`'s `poll()` function.

compiler/rustc_ast_lowering/src/expr.rs

@@ -617,33 +617,47 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
             hir::ExprKind::Closure(c)
         };
-        let generator_hir_id = self.lower_node_id(closure_node_id);
-        // FIXME: only add track caller if the parent is track_caller
-        self.lower_attrs(
-            generator_hir_id,
-            &[Attribute {
-                kind: AttrKind::Normal(ptr::P(NormalAttr {
-                    item: AttrItem {
-                        path: Path::from_ident(Ident::new(sym::track_caller, span)),
-                        args: MacArgs::Empty,
-                        tokens: None,
-                    },
-                    tokens: None,
-                })),
-                id: self.tcx.sess.parse_sess.attr_id_generator.mk_attr_id(),
-                style: AttrStyle::Outer,
-                span,
-            }],
-        );
-        let generator = hir::Expr {
-            hir_id: generator_hir_id,
-            kind: generator_kind,
-            span: self.lower_span(span),
-        };
-
-        // `future::from_generator`:
+        let mut parent_has_track_caller = false;
+        for attrs in self.attrs.values() {
+            for attr in attrs.into_iter() {
+                if attr.has_name(sym::track_caller) {
+                    parent_has_track_caller = true;
+                    break;
+                }
+            }
+            if parent_has_track_caller {
+                break;
+            }
+        }
         let unstable_span =
             self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
+
+        let hir_id = if parent_has_track_caller {
+            let generator_hir_id = self.lower_node_id(closure_node_id);
+            self.lower_attrs(
+                generator_hir_id,
+                &[Attribute {
+                    kind: AttrKind::Normal(ptr::P(NormalAttr {
+                        item: AttrItem {
+                            path: Path::from_ident(Ident::new(sym::track_caller, span)),
+                            args: MacArgs::Empty,
+                            tokens: None,
+                        },
+                        tokens: None,
+                    })),
+                    id: self.tcx.sess.parse_sess.attr_id_generator.mk_attr_id(),
+                    style: AttrStyle::Outer,
+                    span: unstable_span,
+                }],
+            );
+            generator_hir_id
+        } else {
+            self.lower_node_id(closure_node_id)
+        };
+
+        let generator = hir::Expr { hir_id, kind: generator_kind, span: self.lower_span(span) };
+
+        // `future::from_generator`:
         let gen_future = self.expr_lang_item_path(
             unstable_span,
             hir::LangItem::FromGenerator,

library/core/src/future/mod.rs

@@ -82,6 +82,7 @@ where
 
     impl<T: Generator<ResumeTy, Yield = ()>> Future for GenFuture<T> {
         type Output = T::Return;
+        #[track_caller]
         fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
             // SAFETY: Safe because we're !Unpin + !Drop, and this is just a field projection.
             let gen = unsafe { Pin::map_unchecked_mut(self, |s| &mut s.0) };

src/test/ui/async-await/track-caller/panic-track-caller.rs

@@ -70,6 +70,6 @@ fn panicked_at(f: impl FnOnce() + panic::UnwindSafe) -> u32 {
 }
 
 fn main() {
-    assert_eq!(panicked_at(|| block_on(foo())), 39);
-    assert_eq!(panicked_at(|| block_on(foo_track_caller())), 52);
+    assert_eq!(panicked_at(|| block_on(foo())), 40);
+    assert_eq!(panicked_at(|| block_on(foo_track_caller())), 53);
 }