Auto merge of #64999 - nikomatsakis:issue-60424-async-return-inference, r=cramertj

extract expected return type for async fn generators

Fixes #60424

cc @Centril, I know you've been eager to see this fixed.

r? @cramertj

35 files changed, 763 insertions, 497 deletions

diff --git a/src/librustc/hir/lowering/expr.rs b/src/librustc/hir/lowering/expr.rs
index db5b197c5d6..d5fcc0ef6ed 100644
--- a/src/librustc/hir/lowering/expr.rs
+++ b/src/librustc/hir/lowering/expr.rs
@@ -89,9 +89,14 @@ impl LoweringContext<'_> {
                 hir::MatchSource::Normal,
             ),
             ExprKind::Async(capture_clause, closure_node_id, ref block) => {
-                self.make_async_expr(capture_clause, closure_node_id, None, block.span, |this| {
-                    this.with_new_scopes(|this| this.lower_block_expr(block))
-                })
+                self.make_async_expr(
+                    capture_clause,
+                    closure_node_id,
+                    None,
+                    block.span,
+                    hir::AsyncGeneratorKind::Block,
+                    |this| this.with_new_scopes(|this| this.lower_block_expr(block)),
+                )
             }
             ExprKind::Await(ref expr) => self.lower_expr_await(e.span, expr),
             ExprKind::Closure(
@@ -457,6 +462,7 @@ impl LoweringContext<'_> {
         closure_node_id: NodeId,
         ret_ty: Option<AstP<Ty>>,
         span: Span,
+        async_gen_kind: hir::AsyncGeneratorKind,
         body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
     ) -> hir::ExprKind {
         let capture_clause = self.lower_capture_clause(capture_clause);
@@ -470,7 +476,7 @@ impl LoweringContext<'_> {
         };
         let decl = self.lower_fn_decl(&ast_decl, None, /* impl trait allowed */ false, None);
         let body_id = self.lower_fn_body(&ast_decl, |this| {
-            this.generator_kind = Some(hir::GeneratorKind::Async);
+            this.generator_kind = Some(hir::GeneratorKind::Async(async_gen_kind));
             body(this)
         });
 
@@ -522,7 +528,7 @@ impl LoweringContext<'_> {
     /// ```
     fn lower_expr_await(&mut self, await_span: Span, expr: &Expr) -> hir::ExprKind {
         match self.generator_kind {
-            Some(hir::GeneratorKind::Async) => {},
+            Some(hir::GeneratorKind::Async(_)) => {},
             Some(hir::GeneratorKind::Gen) |
             None => {
                 let mut err = struct_span_err!(
@@ -727,7 +733,7 @@ impl LoweringContext<'_> {
                     Movability::Static => hir::GeneratorMovability::Static,
                 })
             },
-            Some(hir::GeneratorKind::Async) => {
+            Some(hir::GeneratorKind::Async(_)) => {
                 bug!("non-`async` closure body turned `async` during lowering");
             },
             None => {
@@ -786,10 +792,12 @@ impl LoweringContext<'_> {
                     None
                 };
                 let async_body = this.make_async_expr(
-                    capture_clause, closure_id, async_ret_ty, body.span,
-                    |this| {
-                        this.with_new_scopes(|this| this.lower_expr(body))
-                    }
+                    capture_clause,
+                    closure_id,
+                    async_ret_ty,
+                    body.span,
+                    hir::AsyncGeneratorKind::Closure,
+                    |this| this.with_new_scopes(|this| this.lower_expr(body)),
                 );
                 this.expr(fn_decl_span, async_body, ThinVec::new())
             });
@@ -1005,7 +1013,7 @@ impl LoweringContext<'_> {
     fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind {
         match self.generator_kind {
             Some(hir::GeneratorKind::Gen) => {},
-            Some(hir::GeneratorKind::Async) => {
+            Some(hir::GeneratorKind::Async(_)) => {
                 span_err!(
                     self.sess,
                     span,
diff --git a/src/librustc/hir/lowering/item.rs b/src/librustc/hir/lowering/item.rs
index 7159db736a7..548a2fedfff 100644
--- a/src/librustc/hir/lowering/item.rs
+++ b/src/librustc/hir/lowering/item.rs
@@ -1222,7 +1222,11 @@ impl LoweringContext<'_> {
             }
 
             let async_expr = this.make_async_expr(
-                CaptureBy::Value, closure_id, None, body.span,
+                CaptureBy::Value,
+                closure_id,
+                None,
+                body.span,
+                hir::AsyncGeneratorKind::Fn,
                 |this| {
                     // Create a block from the user's function body:
                     let user_body = this.lower_block_expr(body);
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index 9b4d88a5a09..d5892794d64 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -1362,21 +1362,49 @@ impl Body {
 }
 
 /// The type of source expression that caused this generator to be created.
-// Not `IsAsync` because we want to eventually add support for `AsyncGen`
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, HashStable,
          RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum GeneratorKind {
-    /// An `async` block or function.
-    Async,
+    /// An explicit `async` block or the body of an async function.
+    Async(AsyncGeneratorKind),
+
     /// A generator literal created via a `yield` inside a closure.
     Gen,
 }
 
 impl fmt::Display for GeneratorKind {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            GeneratorKind::Async(k) => fmt::Display::fmt(k, f),
+            GeneratorKind::Gen => f.write_str("generator"),
+        }
+    }
+}
+
+/// In the case of a generator created as part of an async construct,
+/// which kind of async construct caused it to be created?
+///
+/// This helps error messages but is also used to drive coercions in
+/// type-checking (see #60424).
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, HashStable,
+         RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
+pub enum AsyncGeneratorKind {
+    /// An explicit `async` block written by the user.
+    Block,
+
+    /// An explicit `async` block written by the user.
+    Closure,
+
+    /// The `async` block generated as the body of an async function.
+    Fn,
+}
+
+impl fmt::Display for AsyncGeneratorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str(match self {
-            GeneratorKind::Async => "`async` object",
-            GeneratorKind::Gen => "generator",
+            AsyncGeneratorKind::Block => "`async` block",
+            AsyncGeneratorKind::Closure => "`async` closure body",
+            AsyncGeneratorKind::Fn => "`async fn` body",
         })
     }
 }
@@ -1758,6 +1786,7 @@ pub struct Destination {
 pub enum GeneratorMovability {
     /// May contain self-references, `!Unpin`.
     Static,
+
     /// Must not contain self-references, `Unpin`.
     Movable,
 }
diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index 35db82406ab..1f75ebbd348 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -1319,6 +1319,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         }
     }
 
+    /// Resolve any type variables found in `value` -- but only one
+    /// level.  So, if the variable `?X` is bound to some type
+    /// `Foo<?Y>`, then this would return `Foo<?Y>` (but `?Y` may
+    /// itself be bound to a type).
+    ///
+    /// Useful when you only need to inspect the outermost level of
+    /// the type and don't care about nested types (or perhaps you
+    /// will be resolving them as well, e.g. in a loop).
     pub fn shallow_resolve<T>(&self, value: T) -> T
     where
         T: TypeFoldable<'tcx>,
@@ -1579,6 +1587,9 @@ impl<'a, 'tcx> ShallowResolver<'a, 'tcx> {
         ShallowResolver { infcx }
     }
 
+    /// If `typ` is a type variable of some kind, resolve it one level
+    /// (but do not resolve types found in the result). If `typ` is
+    /// not a type variable, just return it unmodified.
     pub fn shallow_resolve(&mut self, typ: Ty<'tcx>) -> Ty<'tcx> {
         match typ.kind {
             ty::Infer(ty::TyVar(v)) => {
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index bdf8f3b1d4a..162555cd3ce 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -337,7 +337,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> ClosureSignatures<'tcx> {
         debug!("sig_of_closure_no_expectation()");
 
-        let bound_sig = self.supplied_sig_of_closure(expr_def_id, decl);
+        let bound_sig = self.supplied_sig_of_closure(expr_def_id, decl, body);
 
         self.closure_sigs(expr_def_id, body, bound_sig)
     }
@@ -490,7 +490,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         //
         // (See comment on `sig_of_closure_with_expectation` for the
         // meaning of these letters.)
-        let supplied_sig = self.supplied_sig_of_closure(expr_def_id, decl);
+        let supplied_sig = self.supplied_sig_of_closure(expr_def_id, decl, body);
 
         debug!(
             "check_supplied_sig_against_expectation: supplied_sig={:?}",
@@ -591,14 +591,31 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         expr_def_id: DefId,
         decl: &hir::FnDecl,
+        body: &hir::Body,
     ) -> ty::PolyFnSig<'tcx> {
         let astconv: &dyn AstConv<'_> = self;
 
+        debug!(
+            "supplied_sig_of_closure(decl={:?}, body.generator_kind={:?})",
+            decl,
+            body.generator_kind,
+        );
+
         // First, convert the types that the user supplied (if any).
         let supplied_arguments = decl.inputs.iter().map(|a| astconv.ast_ty_to_ty(a));
         let supplied_return = match decl.output {
             hir::Return(ref output) => astconv.ast_ty_to_ty(&output),
-            hir::DefaultReturn(_) => astconv.ty_infer(None, decl.output.span()),
+            hir::DefaultReturn(_) => match body.generator_kind {
+                // In the case of the async block that we create for a function body,
+                // we expect the return type of the block to match that of the enclosing
+                // function.
+                Some(hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Fn)) => {
+                    debug!("supplied_sig_of_closure: closure is async fn body");
+                    self.deduce_future_output_from_obligations(expr_def_id)
+                }
+
+                _ => astconv.ty_infer(None, decl.output.span()),
+            }
         };
 
         let result = ty::Binder::bind(self.tcx.mk_fn_sig(
@@ -620,6 +637,117 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         result
     }
 
+    /// Invoked when we are translating the generator that results
+    /// from desugaring an `async fn`. Returns the "sugared" return
+    /// type of the `async fn` -- that is, the return type that the
+    /// user specified. The "desugared" return type is a `impl
+    /// Future<Output = T>`, so we do this by searching through the
+    /// obligations to extract the `T`.
+    fn deduce_future_output_from_obligations(
+        &self,
+        expr_def_id: DefId,
+    ) -> Ty<'tcx> {
+        debug!("deduce_future_output_from_obligations(expr_def_id={:?})", expr_def_id);
+
+        let ret_coercion =
+            self.ret_coercion
+            .as_ref()
+            .unwrap_or_else(|| span_bug!(
+                self.tcx.def_span(expr_def_id),
+                "async fn generator outside of a fn"
+            ));
+
+        // In practice, the return type of the surrounding function is
+        // always a (not yet resolved) inference variable, because it
+        // is the hidden type for an `impl Trait` that we are going to
+        // be inferring.
+        let ret_ty = ret_coercion.borrow().expected_ty();
+        let ret_ty = self.inh.infcx.shallow_resolve(ret_ty);
+        let ret_vid = match ret_ty.kind {
+            ty::Infer(ty::TyVar(ret_vid)) => ret_vid,
+            _ => {
+                span_bug!(
+                    self.tcx.def_span(expr_def_id),
+                    "async fn generator return type not an inference variable"
+                )
+            }
+        };
+
+        // Search for a pending obligation like
+        //
+        // `<R as Future>::Output = T`
+        //
+        // where R is the return type we are expecting. This type `T`
+        // will be our output.
+        let output_ty = self.obligations_for_self_ty(ret_vid)
+            .find_map(|(_, obligation)| {
+                if let ty::Predicate::Projection(ref proj_predicate) = obligation.predicate {
+                    self.deduce_future_output_from_projection(
+                        obligation.cause.span,
+                        proj_predicate
+                    )
+                } else {
+                    None
+                }
+            })
+            .unwrap();
+
+        debug!("deduce_future_output_from_obligations: output_ty={:?}", output_ty);
+        output_ty
+    }
+
+    /// Given a projection like
+    ///
+    /// `<X as Future>::Output = T`
+    ///
+    /// where `X` is some type that has no late-bound regions, returns
+    /// `Some(T)`. If the projection is for some other trait, returns
+    /// `None`.
+    fn deduce_future_output_from_projection(
+        &self,
+        cause_span: Span,
+        predicate: &ty::PolyProjectionPredicate<'tcx>,
+    ) -> Option<Ty<'tcx>> {
+        debug!("deduce_future_output_from_projection(predicate={:?})", predicate);
+
+        // We do not expect any bound regions in our predicate, so
+        // skip past the bound vars.
+        let predicate = match predicate.no_bound_vars() {
+            Some(p) => p,
+            None => {
+                debug!("deduce_future_output_from_projection: has late-bound regions");
+                return None;
+            }
+        };
+
+        // Check that this is a projection from the `Future` trait.
+        let trait_ref = predicate.projection_ty.trait_ref(self.tcx);
+        let future_trait = self.tcx.lang_items().future_trait().unwrap();
+        if trait_ref.def_id != future_trait {
+            debug!("deduce_future_output_from_projection: not a future");
+            return None;
+        }
+
+        // The `Future` trait has only one associted item, `Output`,
+        // so check that this is what we see.
+        let output_assoc_item = self.tcx.associated_items(future_trait).nth(0).unwrap().def_id;
+        if output_assoc_item != predicate.projection_ty.item_def_id {
+            span_bug!(
+                cause_span,
+                "projecting associated item `{:?}` from future, which is not Output `{:?}`",
+                predicate.projection_ty.item_def_id,
+                output_assoc_item,
+            );
+        }
+
+        // Extract the type from the projection. Note that there can
+        // be no bound variables in this type because the "self type"
+        // does not have any regions in it.
+        let output_ty = self.resolve_vars_if_possible(&predicate.ty);
+        debug!("deduce_future_output_from_projection: output_ty={:?}", output_ty);
+        Some(output_ty)
+    }
+
     /// Converts the types that the user supplied, in case that doing
     /// so should yield an error, but returns back a signature where
     /// all parameters are of type `TyErr`.
diff --git a/src/librustc_typeck/check/generator_interior.rs b/src/librustc_typeck/check/generator_interior.rs
index 940537a5f48..619768e018c 100644
--- a/src/librustc_typeck/check/generator_interior.rs
+++ b/src/librustc_typeck/check/generator_interior.rs
@@ -55,7 +55,7 @@ impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> {
             expr_and_pat_count: 0,
             source: match self.kind { // Guess based on the kind of the current generator.
                 hir::GeneratorKind::Gen => hir::YieldSource::Yield,
-                hir::GeneratorKind::Async => hir::YieldSource::Await,
+                hir::GeneratorKind::Async(_) => hir::YieldSource::Await,
             },
         }));
 
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 3ab474d16b8..880998ab72e 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -562,7 +562,19 @@ pub struct FnCtxt<'a, 'tcx> {
     // if type checking is run in parallel.
     err_count_on_creation: usize,
 
+    /// If `Some`, this stores coercion information for returned
+    /// expressions. If `None`, this is in a context where return is
+    /// inappropriate, such as a const expression.
+    ///
+    /// This is a `RefCell<DynamicCoerceMany>`, which means that we
+    /// can track all the return expressions and then use them to
+    /// compute a useful coercion from the set, similar to a match
+    /// expression or other branching context. You can use methods
+    /// like `expected_ty` to access the declared return type (if
+    /// any).
     ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
+
+    /// First span of a return site that we find. Used in error messages.
     ret_coercion_span: RefCell<Option<Span>>,
 
     yield_ty: Option<Ty<'tcx>>,
@@ -4534,7 +4546,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let item_id = self.tcx().hir().get_parent_node(self.body_id);
         if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
             let body = self.tcx().hir().body(body_id);
-            if let Some(hir::GeneratorKind::Async) = body.generator_kind {
+            if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
                 let sp = expr.span;
                 // Check for `Future` implementations by constructing a predicate to
                 // prove: `<T as Future>::Output == U`
diff --git a/src/test/ui/async-await/async-block-control-flow-static-semantics.rs b/src/test/ui/async-await/async-block-control-flow-static-semantics.rs
index 753a4e49155..971d4476334 100644
--- a/src/test/ui/async-await/async-block-control-flow-static-semantics.rs
+++ b/src/test/ui/async-await/async-block-control-flow-static-semantics.rs
@@ -20,7 +20,7 @@ fn return_targets_async_block_not_fn() -> u8 {
 }
 
 async fn return_targets_async_block_not_async_fn() -> u8 {
-    //~^ ERROR type mismatch resolving
+    //~^ ERROR mismatched types
     let block = async {
         return 0u8;
     };
diff --git a/src/test/ui/async-await/async-block-control-flow-static-semantics.stderr b/src/test/ui/async-await/async-block-control-flow-static-semantics.stderr
index c36caa5586f..a9b0e7ae779 100644
--- a/src/test/ui/async-await/async-block-control-flow-static-semantics.stderr
+++ b/src/test/ui/async-await/async-block-control-flow-static-semantics.stderr
@@ -39,6 +39,22 @@ LL |     let _: &dyn Future<Output = ()> = &block;
               found type `()`
    = note: required for the cast to the object type `dyn std::future::Future<Output = ()>`
 
+error[E0308]: mismatched types
+  --> $DIR/async-block-control-flow-static-semantics.rs:22:58
+   |
+LL |   async fn return_targets_async_block_not_async_fn() -> u8 {
+   |  __________________________________________________________^
+LL | |
+LL | |     let block = async {
+LL | |         return 0u8;
+...  |
+LL | |
+LL | | }
+   | |_^ expected u8, found ()
+   |
+   = note: expected type `u8`
+              found type `()`
+
 error[E0271]: type mismatch resolving `<impl std::future::Future as std::future::Future>::Output == ()`
   --> $DIR/async-block-control-flow-static-semantics.rs:27:39
    |
@@ -49,16 +65,6 @@ LL |     let _: &dyn Future<Output = ()> = &block;
               found type `()`
    = note: required for the cast to the object type `dyn std::future::Future<Output = ()>`
 
-error[E0271]: type mismatch resolving `<impl std::future::Future as std::future::Future>::Output == u8`
-  --> $DIR/async-block-control-flow-static-semantics.rs:22:55
-   |
-LL | async fn return_targets_async_block_not_async_fn() -> u8 {
-   |                                                       ^^ expected (), found u8
-   |
-   = note: expected type `()`
-              found type `u8`
-   = note: the return type of a function must have a statically known size
-
 error[E0308]: mismatched types
   --> $DIR/async-block-control-flow-static-semantics.rs:48:44
    |
diff --git a/src/test/ui/async-await/async-error-span.rs b/src/test/ui/async-await/async-error-span.rs
index dec3ac0f685..28132c9789c 100644
--- a/src/test/ui/async-await/async-error-span.rs
+++ b/src/test/ui/async-await/async-error-span.rs
@@ -9,7 +9,7 @@ fn get_future() -> impl Future<Output = ()> {
 }
 
 async fn foo() {
-    let a; //~ ERROR type inside `async` object must be known in this context
+    let a; //~ ERROR type inside `async fn` body must be known in this context
     get_future().await;
 }
 
diff --git a/src/test/ui/async-await/async-error-span.stderr b/src/test/ui/async-await/async-error-span.stderr
index 47441f5e4ef..b551b99587d 100644
--- a/src/test/ui/async-await/async-error-span.stderr
+++ b/src/test/ui/async-await/async-error-span.stderr
@@ -1,10 +1,10 @@
-error[E0698]: type inside `async` object must be known in this context
+error[E0698]: type inside `async fn` body must be known in this context
   --> $DIR/async-error-span.rs:12:9
    |
 LL |     let a;
    |         ^ cannot infer type
    |
-note: the type is part of the `async` object because of this `await`
+note: the type is part of the `async fn` body because of this `await`
   --> $DIR/async-error-span.rs:13:5
    |
 LL |     get_future().await;
diff --git a/src/test/ui/async-await/issues/issue-63388-1.rs b/src/test/ui/async-await/issues/issue-63388-1.rs
index 3cde5de2198..baecf49c798 100644
--- a/src/test/ui/async-await/issues/issue-63388-1.rs
+++ b/src/test/ui/async-await/issues/issue-63388-1.rs
@@ -9,9 +9,9 @@ trait Foo {}
 impl Xyz {
     async fn do_sth<'a>(
         &'a self, foo: &dyn Foo
-    ) -> &dyn Foo //~ ERROR lifetime mismatch
+    ) -> &dyn Foo
     {
-        foo
+        foo  //~ ERROR lifetime mismatch
     }
 }
 
diff --git a/src/test/ui/async-await/issues/issue-63388-1.stderr b/src/test/ui/async-await/issues/issue-63388-1.stderr
index a54cadb0cd2..2917fa9ccb7 100644
--- a/src/test/ui/async-await/issues/issue-63388-1.stderr
+++ b/src/test/ui/async-await/issues/issue-63388-1.stderr
@@ -1,12 +1,13 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/issue-63388-1.rs:12:10
+  --> $DIR/issue-63388-1.rs:14:9
    |
 LL |         &'a self, foo: &dyn Foo
    |         -------- this parameter and the return type are declared with different lifetimes...
 LL |     ) -> &dyn Foo
-   |          ^^^^^^^^
-   |          |
-   |          ...but data from `foo` is returned here
+   |          --------
+LL |     {
+LL |         foo
+   |         ^^^ ...but data from `foo` is returned here
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/async-await/issues/issue-63388-2.stderr b/src/test/ui/async-await/issues/issue-63388-2.stderr
index 1edeb3d5493..5099297fbeb 100644
--- a/src/test/ui/async-await/issues/issue-63388-2.stderr
+++ b/src/test/ui/async-await/issues/issue-63388-2.stderr
@@ -11,8 +11,9 @@ error: cannot infer an appropriate lifetime
    |
 LL |         foo: &dyn Foo, bar: &'a dyn Foo
    |         ^^^ ...but this borrow...
-LL |     ) -> &dyn Foo
-   |          -------- this return type evaluates to the `'static` lifetime...
+...
+LL |         foo
+   |         --- this return type evaluates to the `'static` lifetime...
    |
 note: ...can't outlive the lifetime '_ as defined on the method body at 11:14
   --> $DIR/issue-63388-2.rs:11:14
@@ -21,8 +22,8 @@ LL |         foo: &dyn Foo, bar: &'a dyn Foo
    |              ^
 help: you can add a constraint to the return type to make it last less than `'static` and match the lifetime '_ as defined on the method body at 11:14
    |
-LL |     ) -> &dyn Foo + '_
-   |          ^^^^^^^^^^^^^
+LL |         foo + '_
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/async-await/return-ty-raw-ptr-coercion.rs b/src/test/ui/async-await/return-ty-raw-ptr-coercion.rs
new file mode 100644
index 00000000000..9fe0869cad6
--- /dev/null
+++ b/src/test/ui/async-await/return-ty-raw-ptr-coercion.rs
@@ -0,0 +1,25 @@
+// Check that we apply unsizing coercions based on the return type.
+//
+// Also serves as a regression test for #60424.
+//
+// edition:2018
+// check-pass
+
+#![allow(warnings)]
+
+use std::fmt::Debug;
+
+const TMP: u32 = 22;
+
+// Coerce from `&u32` to `*const u32`
+fn raw_pointer_coercion() {
+    fn sync_example() -> *const u32 {
+        &TMP
+    }
+
+    async fn async_example() -> *const u32 {
+        &TMP
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/return-ty-unsize-coercion.rs b/src/test/ui/async-await/return-ty-unsize-coercion.rs
new file mode 100644
index 00000000000..93832ef7edd
--- /dev/null
+++ b/src/test/ui/async-await/return-ty-unsize-coercion.rs
@@ -0,0 +1,45 @@
+// Check that we apply unsizing coercions based on the return type.
+//
+// Also serves as a regression test for #60424.
+//
+// edition:2018
+// check-pass
+
+#![allow(warnings)]
+
+use std::fmt::Debug;
+
+// Unsizing coercion from `Box<&'static str>` to `Box<dyn Debug>`.
+fn unsize_trait_coercion() {
+    fn sync_example() -> Box<dyn Debug> {
+        Box::new("asdf")
+    }
+
+    async fn async_example() -> Box<dyn Debug> {
+        Box::new("asdf")
+    }
+}
+
+// Unsizing coercion from `Box<[u32; N]>` to `Box<[32]>`.
+fn unsize_slice_coercion() {
+    fn sync_example() -> Box<[u32]> {
+        Box::new([0])
+    }
+
+    async fn async_example() -> Box<[u32]> {
+        Box::new([0])
+    }
+}
+
+// Unsizing coercion from `&[&str; 1]` to `&[&str]`
+fn unsize_slice_str_coercion() {
+    fn sync_example() -> &'static [&'static str] {
+        &["hi"]
+    }
+
+    async fn async_example() -> &'static [&'static str] {
+        &["hi"]
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/unresolved_type_param.rs b/src/test/ui/async-await/unresolved_type_param.rs
index d8ea87d2775..2876f9fea0e 100644
--- a/src/test/ui/async-await/unresolved_type_param.rs
+++ b/src/test/ui/async-await/unresolved_type_param.rs
@@ -7,9 +7,9 @@ async fn bar<T>() -> () {}
 
 async fn foo() {
     bar().await;
-    //~^ ERROR type inside `async` object must be known in this context
+    //~^ ERROR type inside `async fn` body must be known in this context
     //~| NOTE cannot infer type for `T`
-    //~| NOTE the type is part of the `async` object because of this `await`
+    //~| NOTE the type is part of the `async fn` body because of this `await`
     //~| NOTE in this expansion of desugaring of `await`
 }
 fn main() {}
diff --git a/src/test/ui/async-await/unresolved_type_param.stderr b/src/test/ui/async-await/unresolved_type_param.stderr
index f3090a2b980..c7866fc7744 100644
--- a/src/test/ui/async-await/unresolved_type_param.stderr
+++ b/src/test/ui/async-await/unresolved_type_param.stderr
@@ -1,10 +1,10 @@
-error[E0698]: type inside `async` object must be known in this context
+error[E0698]: type inside `async fn` body must be known in this context
   --> $DIR/unresolved_type_param.rs:9:5
    |
 LL |     bar().await;
    |     ^^^ cannot infer type for `T`
    |
-note: the type is part of the `async` object because of this `await`
+note: the type is part of the `async fn` body because of this `await`
   --> $DIR/unresolved_type_param.rs:9:5
    |
 LL |     bar().await;
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.nll.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.nll.stderr
index e53d91c3604..7eec31d36e3 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.nll.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.nll.stderr
@@ -7,19 +7,19 @@ LL |     async fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:8:50
+  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:8:52
    |
 LL |     async fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
-   |                          -                       ^^^^^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+   |                          -                         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
    |                          |
    |                          lifetime `'_` defined here
    |                          lifetime `'_` defined here
 
 error: lifetime may not live long enough
-  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:11:73
+  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:11:75
    |
 LL |     async fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) }
-   |                          -                                              ^^^^^^^^^^^^^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+   |                          -                                                ^^^^^^^^^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
    |                          |
    |                          lifetime `'_` defined here
    |                          lifetime `'_` defined here
@@ -33,12 +33,11 @@ LL |     async fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:17:62
+  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:17:64
    |
 LL |     async fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
-   |                  --              -                           ^^^^^^^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'a`
-   |                  |               |
-   |                  |               lifetime `'_` defined here
+   |                  --              - lifetime `'_` defined here  ^^^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'a`
+   |                  |
    |                  lifetime `'a` defined here
 
 error: aborting due to 5 previous errors
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
index 57ad026bdcf..e3c261576e6 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
@@ -1,28 +1,25 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:8:45
+  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:8:52
    |
 LL |     async fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
-   |                          ----               ^^^^
-   |                          |                  |
-   |                          |                  ...but data from `f` is returned here
+   |                          ----               ----   ^ ...but data from `f` is returned here
+   |                          |
    |                          this parameter and the return type are declared with different lifetimes...
 
 error[E0623]: lifetime mismatch
-  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:11:55
+  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:11:82
    |
 LL |     async fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) }
-   |                          -----                        ^^^^^^^^^^^^^^^^^
-   |                          |                            |
-   |                          |                            ...but data from `f` is returned here
+   |                          -----                        -----------------          ^ ...but data from `f` is returned here
+   |                          |
    |                          this parameter and the return type are declared with different lifetimes...
 
 error[E0623]: lifetime mismatch
-  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:17:58
+  --> $DIR/arbitrary_self_types_pin_lifetime_mismatch-async.rs:17:64
    |
 LL |     async fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
-   |                                  -----                   ^^^
-   |                                  |                       |
-   |                                  |                       ...but data from `arg` is returned here
+   |                                  -----                   ---   ^^^ ...but data from `arg` is returned here
+   |                                  |
    |                                  this parameter and the return type are declared with different lifetimes...
 
 error: aborting due to 3 previous errors
diff --git a/src/test/ui/self/elision/lt-ref-self-async.nll.stderr b/src/test/ui/self/elision/lt-ref-self-async.nll.stderr
index 998178dde1d..b4f8ff6001d 100644
--- a/src/test/ui/self/elision/lt-ref-self-async.nll.stderr
+++ b/src/test/ui/self/elision/lt-ref-self-async.nll.stderr
@@ -7,16 +7,15 @@ LL |     async fn ref_self(&self, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#23r
 
 error: lifetime may not live long enough
-  --> $DIR/lt-ref-self-async.rs:13:47
-   |
-LL |       async fn ref_self(&self, f: &u32) -> &u32 {
-   |  _______________________-_______________________^
-   | |                       |
-   | |                       lifetime `'_` defined here
-   | |                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/lt-ref-self-async.rs:14:9
+   |
+LL |     async fn ref_self(&self, f: &u32) -> &u32 {
+   |                       -
+   |                       |
+   |                       lifetime `'_` defined here
+   |                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/lt-ref-self-async.rs:19:48
@@ -27,16 +26,15 @@ LL |     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#23r
 
 error: lifetime may not live long enough
-  --> $DIR/lt-ref-self-async.rs:19:53
-   |
-LL |       async fn ref_Self(self: &Self, f: &u32) -> &u32 {
-   |  _____________________________-_______________________^
-   | |                             |
-   | |                             lifetime `'_` defined here
-   | |                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/lt-ref-self-async.rs:20:9
+   |
+LL |     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
+   |                             -
+   |                             |
+   |                             lifetime `'_` defined here
+   |                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/lt-ref-self-async.rs:23:57
@@ -47,16 +45,15 @@ LL |     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#23r
 
 error: lifetime may not live long enough
-  --> $DIR/lt-ref-self-async.rs:23:62
-   |
-LL |       async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
-   |  _____________________________________-________________________^
-   | |                                     |
-   | |                                     lifetime `'_` defined here
-   | |                                     lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/lt-ref-self-async.rs:24:9
+   |
+LL |     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
+   |                                     -
+   |                                     |
+   |                                     lifetime `'_` defined here
+   |                                     lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/lt-ref-self-async.rs:27:57
@@ -67,16 +64,15 @@ LL |     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#23r
 
 error: lifetime may not live long enough
-  --> $DIR/lt-ref-self-async.rs:27:62
-   |
-LL |       async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
-   |  _____________________________________-________________________^
-   | |                                     |
-   | |                                     lifetime `'_` defined here
-   | |                                     lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/lt-ref-self-async.rs:28:9
+   |
+LL |     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
+   |                                     -
+   |                                     |
+   |                                     lifetime `'_` defined here
+   |                                     lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/lt-ref-self-async.rs:31:66
@@ -87,16 +83,15 @@ LL |     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#23r
 
 error: lifetime may not live long enough
-  --> $DIR/lt-ref-self-async.rs:31:71
-   |
-LL |       async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
-   |  _____________________________________________-_________________________^
-   | |                                             |
-   | |                                             lifetime `'_` defined here
-   | |                                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/lt-ref-self-async.rs:32:9
+   |
+LL |     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
+   |                                             -
+   |                                             |
+   |                                             lifetime `'_` defined here
+   |                                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/lt-ref-self-async.rs:35:62
@@ -107,16 +102,15 @@ LL |     async fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#23r
 
 error: lifetime may not live long enough
-  --> $DIR/lt-ref-self-async.rs:35:67
-   |
-LL |       async fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
-   |  _________________________________________-_________________________^
-   | |                                         |
-   | |                                         lifetime `'_` defined here
-   | |                                         lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/lt-ref-self-async.rs:36:9
+   |
+LL |     async fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
+   |                                         -
+   |                                         |
+   |                                         lifetime `'_` defined here
+   |                                         lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error: aborting due to 12 previous errors
 
diff --git a/src/test/ui/self/elision/lt-ref-self-async.rs b/src/test/ui/self/elision/lt-ref-self-async.rs
index e3ca0c2e2dd..5aba7cfcf29 100644
--- a/src/test/ui/self/elision/lt-ref-self-async.rs
+++ b/src/test/ui/self/elision/lt-ref-self-async.rs
@@ -11,29 +11,29 @@ impl<'a> Struct<'a> {
     // Test using `&self` sugar:
 
     async fn ref_self(&self, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     // Test using `&Self` explicitly:
 
     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 }
 
diff --git a/src/test/ui/self/elision/lt-ref-self-async.stderr b/src/test/ui/self/elision/lt-ref-self-async.stderr
index 2bc64bdf1f7..6b668d9f1f6 100644
--- a/src/test/ui/self/elision/lt-ref-self-async.stderr
+++ b/src/test/ui/self/elision/lt-ref-self-async.stderr
@@ -1,56 +1,62 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/lt-ref-self-async.rs:13:42
+  --> $DIR/lt-ref-self-async.rs:14:9
    |
 LL |     async fn ref_self(&self, f: &u32) -> &u32 {
-   |                       -----              ^^^^
-   |                       |                  |
-   |                       |                  ...but data from `f` is returned here
+   |                       -----              ----
+   |                       |
    |                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/lt-ref-self-async.rs:19:48
+  --> $DIR/lt-ref-self-async.rs:20:9
    |
 LL |     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
-   |                             -----              ^^^^
-   |                             |                  |
-   |                             |                  ...but data from `f` is returned here
+   |                             -----              ----
+   |                             |
    |                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/lt-ref-self-async.rs:23:57
+  --> $DIR/lt-ref-self-async.rs:24:9
    |
 LL |     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
-   |                                     -----               ^^^^
-   |                                     |                   |
-   |                                     |                   ...but data from `f` is returned here
+   |                                     -----               ----
+   |                                     |
    |                                     this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/lt-ref-self-async.rs:27:57
+  --> $DIR/lt-ref-self-async.rs:28:9
    |
 LL |     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
-   |                                     -----               ^^^^
-   |                                     |                   |
-   |                                     |                   ...but data from `f` is returned here
+   |                                     -----               ----
+   |                                     |
    |                                     this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/lt-ref-self-async.rs:31:66
+  --> $DIR/lt-ref-self-async.rs:32:9
    |
 LL |     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
-   |                                             -----                ^^^^
-   |                                             |                    |
-   |                                             |                    ...but data from `f` is returned here
+   |                                             -----                ----
+   |                                             |
    |                                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/lt-ref-self-async.rs:35:62
+  --> $DIR/lt-ref-self-async.rs:36:9
    |
 LL |     async fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
-   |                                         -----                ^^^^
-   |                                         |                    |
-   |                                         |                    ...but data from `f` is returned here
+   |                                         -----                ----
+   |                                         |
    |                                         this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/self/elision/ref-mut-self-async.nll.stderr b/src/test/ui/self/elision/ref-mut-self-async.nll.stderr
index 97bc80509df..b6f2b63f093 100644
--- a/src/test/ui/self/elision/ref-mut-self-async.nll.stderr
+++ b/src/test/ui/self/elision/ref-mut-self-async.nll.stderr
@@ -7,16 +7,15 @@ LL |     async fn ref_self(&mut self, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-self-async.rs:13:51
-   |
-LL |       async fn ref_self(&mut self, f: &u32) -> &u32 {
-   |  _______________________-___________________________^
-   | |                       |
-   | |                       lifetime `'_` defined here
-   | |                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-mut-self-async.rs:14:9
+   |
+LL |     async fn ref_self(&mut self, f: &u32) -> &u32 {
+   |                       -
+   |                       |
+   |                       lifetime `'_` defined here
+   |                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-self-async.rs:19:52
@@ -27,16 +26,15 @@ LL |     async fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-self-async.rs:19:57
-   |
-LL |       async fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
-   |  _____________________________-___________________________^
-   | |                             |
-   | |                             lifetime `'_` defined here
-   | |                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-mut-self-async.rs:20:9
+   |
+LL |     async fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
+   |                             -
+   |                             |
+   |                             lifetime `'_` defined here
+   |                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-self-async.rs:23:61
@@ -47,16 +45,15 @@ LL |     async fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-self-async.rs:23:66
-   |
-LL |       async fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
-   |  _____________________________________-____________________________^
-   | |                                     |
-   | |                                     lifetime `'_` defined here
-   | |                                     lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-mut-self-async.rs:24:9
+   |
+LL |     async fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
+   |                                     -
+   |                                     |
+   |                                     lifetime `'_` defined here
+   |                                     lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-self-async.rs:27:61
@@ -67,16 +64,15 @@ LL |     async fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-self-async.rs:27:66
-   |
-LL |       async fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
-   |  _____________________________________-____________________________^
-   | |                                     |
-   | |                                     lifetime `'_` defined here
-   | |                                     lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-mut-self-async.rs:28:9
+   |
+LL |     async fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
+   |                                     -
+   |                                     |
+   |                                     lifetime `'_` defined here
+   |                                     lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-self-async.rs:31:70
@@ -87,16 +83,15 @@ LL |     async fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-self-async.rs:31:75
-   |
-LL |       async fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
-   |  _____________________________________________-_____________________________^
-   | |                                             |
-   | |                                             lifetime `'_` defined here
-   | |                                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-mut-self-async.rs:32:9
+   |
+LL |     async fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
+   |                                             -
+   |                                             |
+   |                                             lifetime `'_` defined here
+   |                                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-self-async.rs:35:70
@@ -107,16 +102,15 @@ LL |     async fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-self-async.rs:35:75
-   |
-LL |       async fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
-   |  _____________________________________________-_____________________________^
-   | |                                             |
-   | |                                             lifetime `'_` defined here
-   | |                                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-mut-self-async.rs:36:9
+   |
+LL |     async fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
+   |                                             -
+   |                                             |
+   |                                             lifetime `'_` defined here
+   |                                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error: aborting due to 12 previous errors
 
diff --git a/src/test/ui/self/elision/ref-mut-self-async.rs b/src/test/ui/self/elision/ref-mut-self-async.rs
index 2ca14800a75..b8eb416d904 100644
--- a/src/test/ui/self/elision/ref-mut-self-async.rs
+++ b/src/test/ui/self/elision/ref-mut-self-async.rs
@@ -10,30 +10,30 @@ struct Struct { }
 impl Struct {
     // Test using `&mut self` sugar:
 
-    async fn ref_self(&mut self, f: &u32) -> &u32 { //~ ERROR lifetime mismatch
-        f
+    async fn ref_self(&mut self, f: &u32) -> &u32 {
+        f //~ ERROR lifetime mismatch
     }
 
     // Test using `&mut Self` explicitly:
 
     async fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 }
 
diff --git a/src/test/ui/self/elision/ref-mut-self-async.stderr b/src/test/ui/self/elision/ref-mut-self-async.stderr
index 39a1b30ca53..29fbec9fa7a 100644
--- a/src/test/ui/self/elision/ref-mut-self-async.stderr
+++ b/src/test/ui/self/elision/ref-mut-self-async.stderr
@@ -1,56 +1,62 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-self-async.rs:13:46
+  --> $DIR/ref-mut-self-async.rs:14:9
    |
 LL |     async fn ref_self(&mut self, f: &u32) -> &u32 {
-   |                       ---------              ^^^^
-   |                       |                      |
-   |                       |                      ...but data from `f` is returned here
+   |                       ---------              ----
+   |                       |
    |                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-self-async.rs:19:52
+  --> $DIR/ref-mut-self-async.rs:20:9
    |
 LL |     async fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
-   |                             ---------              ^^^^
-   |                             |                      |
-   |                             |                      ...but data from `f` is returned here
+   |                             ---------              ----
+   |                             |
    |                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-self-async.rs:23:61
+  --> $DIR/ref-mut-self-async.rs:24:9
    |
 LL |     async fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
-   |                                     ---------               ^^^^
-   |                                     |                       |
-   |                                     |                       ...but data from `f` is returned here
+   |                                     ---------               ----
+   |                                     |
    |                                     this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-self-async.rs:27:61
+  --> $DIR/ref-mut-self-async.rs:28:9
    |
 LL |     async fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
-   |                                     ---------               ^^^^
-   |                                     |                       |
-   |                                     |                       ...but data from `f` is returned here
+   |                                     ---------               ----
+   |                                     |
    |                                     this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-self-async.rs:31:70
+  --> $DIR/ref-mut-self-async.rs:32:9
    |
 LL |     async fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
-   |                                             ---------                ^^^^
-   |                                             |                        |
-   |                                             |                        ...but data from `f` is returned here
+   |                                             ---------                ----
+   |                                             |
    |                                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-self-async.rs:35:70
+  --> $DIR/ref-mut-self-async.rs:36:9
    |
 LL |     async fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
-   |                                             ---------                ^^^^
-   |                                             |                        |
-   |                                             |                        ...but data from `f` is returned here
+   |                                             ---------                ----
+   |                                             |
    |                                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/self/elision/ref-mut-struct-async.nll.stderr b/src/test/ui/self/elision/ref-mut-struct-async.nll.stderr
index 2905a022e5d..fa78543bd87 100644
--- a/src/test/ui/self/elision/ref-mut-struct-async.nll.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct-async.nll.stderr
@@ -7,16 +7,15 @@ LL |     async fn ref_Struct(self: &mut Struct, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-struct-async.rs:13:61
+  --> $DIR/ref-mut-struct-async.rs:14:9
    |
-LL |       async fn ref_Struct(self: &mut Struct, f: &u32) -> &u32 {
-   |  _______________________________-_____________________________^
-   | |                               |
-   | |                               lifetime `'_` defined here
-   | |                               lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn ref_Struct(self: &mut Struct, f: &u32) -> &u32 {
+   |                               -
+   |                               |
+   |                               lifetime `'_` defined here
+   |                               lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-struct-async.rs:17:65
@@ -27,16 +26,15 @@ LL |     async fn box_ref_Struct(self: Box<&mut Struct>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-struct-async.rs:17:70
+  --> $DIR/ref-mut-struct-async.rs:18:9
    |
-LL |       async fn box_ref_Struct(self: Box<&mut Struct>, f: &u32) -> &u32 {
-   |  _______________________________________-______________________________^
-   | |                                       |
-   | |                                       lifetime `'_` defined here
-   | |                                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn box_ref_Struct(self: Box<&mut Struct>, f: &u32) -> &u32 {
+   |                                       -
+   |                                       |
+   |                                       lifetime `'_` defined here
+   |                                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-struct-async.rs:21:65
@@ -47,16 +45,15 @@ LL |     async fn pin_ref_Struct(self: Pin<&mut Struct>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-struct-async.rs:21:70
+  --> $DIR/ref-mut-struct-async.rs:22:9
    |
-LL |       async fn pin_ref_Struct(self: Pin<&mut Struct>, f: &u32) -> &u32 {
-   |  _______________________________________-______________________________^
-   | |                                       |
-   | |                                       lifetime `'_` defined here
-   | |                                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn pin_ref_Struct(self: Pin<&mut Struct>, f: &u32) -> &u32 {
+   |                                       -
+   |                                       |
+   |                                       lifetime `'_` defined here
+   |                                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-struct-async.rs:25:74
@@ -67,16 +64,15 @@ LL |     async fn box_box_ref_Struct(self: Box<Box<&mut Struct>>, f: &u32) -> &u
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-struct-async.rs:25:79
+  --> $DIR/ref-mut-struct-async.rs:26:9
    |
-LL |       async fn box_box_ref_Struct(self: Box<Box<&mut Struct>>, f: &u32) -> &u32 {
-   |  _______________________________________________-_______________________________^
-   | |                                               |
-   | |                                               lifetime `'_` defined here
-   | |                                               lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn box_box_ref_Struct(self: Box<Box<&mut Struct>>, f: &u32) -> &u32 {
+   |                                               -
+   |                                               |
+   |                                               lifetime `'_` defined here
+   |                                               lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-mut-struct-async.rs:29:74
@@ -87,16 +83,15 @@ LL |     async fn box_pin_ref_Struct(self: Box<Pin<&mut Struct>>, f: &u32) -> &u
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-mut-struct-async.rs:29:79
+  --> $DIR/ref-mut-struct-async.rs:30:9
    |
-LL |       async fn box_pin_ref_Struct(self: Box<Pin<&mut Struct>>, f: &u32) -> &u32 {
-   |  _______________________________________________-_______________________________^
-   | |                                               |
-   | |                                               lifetime `'_` defined here
-   | |                                               lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn box_pin_ref_Struct(self: Box<Pin<&mut Struct>>, f: &u32) -> &u32 {
+   |                                               -
+   |                                               |
+   |                                               lifetime `'_` defined here
+   |                                               lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error: aborting due to 10 previous errors
 
diff --git a/src/test/ui/self/elision/ref-mut-struct-async.rs b/src/test/ui/self/elision/ref-mut-struct-async.rs
index a671116de25..1822a9a468b 100644
--- a/src/test/ui/self/elision/ref-mut-struct-async.rs
+++ b/src/test/ui/self/elision/ref-mut-struct-async.rs
@@ -11,23 +11,23 @@ impl Struct {
     // Test using `&mut Struct` explicitly:
 
     async fn ref_Struct(self: &mut Struct, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_ref_Struct(self: Box<&mut Struct>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn pin_ref_Struct(self: Pin<&mut Struct>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_box_ref_Struct(self: Box<Box<&mut Struct>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_pin_ref_Struct(self: Box<Pin<&mut Struct>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 }
 
diff --git a/src/test/ui/self/elision/ref-mut-struct-async.stderr b/src/test/ui/self/elision/ref-mut-struct-async.stderr
index fe4a636ada6..46591bfc958 100644
--- a/src/test/ui/self/elision/ref-mut-struct-async.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct-async.stderr
@@ -1,47 +1,52 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-struct-async.rs:13:56
+  --> $DIR/ref-mut-struct-async.rs:14:9
    |
 LL |     async fn ref_Struct(self: &mut Struct, f: &u32) -> &u32 {
-   |                               -----------              ^^^^
-   |                               |                        |
-   |                               |                        ...but data from `f` is returned here
+   |                               -----------              ----
+   |                               |
    |                               this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-struct-async.rs:17:65
+  --> $DIR/ref-mut-struct-async.rs:18:9
    |
 LL |     async fn box_ref_Struct(self: Box<&mut Struct>, f: &u32) -> &u32 {
-   |                                       -----------               ^^^^
-   |                                       |                         |
-   |                                       |                         ...but data from `f` is returned here
+   |                                       -----------               ----
+   |                                       |
    |                                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-struct-async.rs:21:65
+  --> $DIR/ref-mut-struct-async.rs:22:9
    |
 LL |     async fn pin_ref_Struct(self: Pin<&mut Struct>, f: &u32) -> &u32 {
-   |                                       -----------               ^^^^
-   |                                       |                         |
-   |                                       |                         ...but data from `f` is returned here
+   |                                       -----------               ----
+   |                                       |
    |                                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-struct-async.rs:25:74
+  --> $DIR/ref-mut-struct-async.rs:26:9
    |
 LL |     async fn box_box_ref_Struct(self: Box<Box<&mut Struct>>, f: &u32) -> &u32 {
-   |                                               -----------                ^^^^
-   |                                               |                          |
-   |                                               |                          ...but data from `f` is returned here
+   |                                               -----------                ----
+   |                                               |
    |                                               this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-mut-struct-async.rs:29:74
+  --> $DIR/ref-mut-struct-async.rs:30:9
    |
 LL |     async fn box_pin_ref_Struct(self: Box<Pin<&mut Struct>>, f: &u32) -> &u32 {
-   |                                               -----------                ^^^^
-   |                                               |                          |
-   |                                               |                          ...but data from `f` is returned here
+   |                                               -----------                ----
+   |                                               |
    |                                               this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/self/elision/ref-self-async.nll.stderr b/src/test/ui/self/elision/ref-self-async.nll.stderr
index 0eee56654f7..88fd2101bc6 100644
--- a/src/test/ui/self/elision/ref-self-async.nll.stderr
+++ b/src/test/ui/self/elision/ref-self-async.nll.stderr
@@ -7,16 +7,15 @@ LL |     async fn ref_self(&self, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:22:47
-   |
-LL |       async fn ref_self(&self, f: &u32) -> &u32 {
-   |  _______________________-_______________________^
-   | |                       |
-   | |                       lifetime `'_` defined here
-   | |                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:23:9
+   |
+LL |     async fn ref_self(&self, f: &u32) -> &u32 {
+   |                       -
+   |                       |
+   |                       lifetime `'_` defined here
+   |                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-self-async.rs:28:48
@@ -27,16 +26,15 @@ LL |     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:28:53
-   |
-LL |       async fn ref_Self(self: &Self, f: &u32) -> &u32 {
-   |  _____________________________-_______________________^
-   | |                             |
-   | |                             lifetime `'_` defined here
-   | |                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:29:9
+   |
+LL |     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
+   |                             -
+   |                             |
+   |                             lifetime `'_` defined here
+   |                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-self-async.rs:32:57
@@ -47,16 +45,15 @@ LL |     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:32:62
-   |
-LL |       async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
-   |  _____________________________________-________________________^
-   | |                                     |
-   | |                                     lifetime `'_` defined here
-   | |                                     lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:33:9
+   |
+LL |     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
+   |                                     -
+   |                                     |
+   |                                     lifetime `'_` defined here
+   |                                     lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-self-async.rs:36:57
@@ -67,16 +64,15 @@ LL |     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:36:62
-   |
-LL |       async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
-   |  _____________________________________-________________________^
-   | |                                     |
-   | |                                     lifetime `'_` defined here
-   | |                                     lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:37:9
+   |
+LL |     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
+   |                                     -
+   |                                     |
+   |                                     lifetime `'_` defined here
+   |                                     lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-self-async.rs:40:66
@@ -87,16 +83,15 @@ LL |     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:40:71
-   |
-LL |       async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
-   |  _____________________________________________-_________________________^
-   | |                                             |
-   | |                                             lifetime `'_` defined here
-   | |                                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:41:9
+   |
+LL |     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
+   |                                             -
+   |                                             |
+   |                                             lifetime `'_` defined here
+   |                                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-self-async.rs:44:66
@@ -107,16 +102,15 @@ LL |     async fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:44:71
-   |
-LL |       async fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
-   |  _____________________________________________-_________________________^
-   | |                                             |
-   | |                                             lifetime `'_` defined here
-   | |                                             lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:45:9
+   |
+LL |     async fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
+   |                                             -
+   |                                             |
+   |                                             lifetime `'_` defined here
+   |                                             lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-self-async.rs:48:69
@@ -127,16 +121,15 @@ LL |     async fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-self-async.rs:48:73
-   |
-LL |       async fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
-   |  ____________________________________________-____________________________^
-   | |                                            |
-   | |                                            lifetime `'_` defined here
-   | |                                            lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+  --> $DIR/ref-self-async.rs:49:9
+   |
+LL |     async fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
+   |                                            -
+   |                                            |
+   |                                            lifetime `'_` defined here
+   |                                            lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error: aborting due to 14 previous errors
 
diff --git a/src/test/ui/self/elision/ref-self-async.rs b/src/test/ui/self/elision/ref-self-async.rs
index 06f3b127b21..9425fbfca8f 100644
--- a/src/test/ui/self/elision/ref-self-async.rs
+++ b/src/test/ui/self/elision/ref-self-async.rs
@@ -19,34 +19,34 @@ impl<T, P> Deref for Wrap<T, P> {
 impl Struct {
     // Test using `&self` sugar:
 
-    async fn ref_self(&self, f: &u32) -> &u32 { //~ ERROR lifetime mismatch
-        f
+    async fn ref_self(&self, f: &u32) -> &u32 {
+        f //~ ERROR lifetime mismatch
     }
 
     // Test using `&Self` explicitly:
 
     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 }
 
diff --git a/src/test/ui/self/elision/ref-self-async.stderr b/src/test/ui/self/elision/ref-self-async.stderr
index 2f9e2a01e34..c255d189363 100644
--- a/src/test/ui/self/elision/ref-self-async.stderr
+++ b/src/test/ui/self/elision/ref-self-async.stderr
@@ -1,65 +1,72 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:22:42
+  --> $DIR/ref-self-async.rs:23:9
    |
 LL |     async fn ref_self(&self, f: &u32) -> &u32 {
-   |                       -----              ^^^^
-   |                       |                  |
-   |                       |                  ...but data from `f` is returned here
+   |                       -----              ----
+   |                       |
    |                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:28:48
+  --> $DIR/ref-self-async.rs:29:9
    |
 LL |     async fn ref_Self(self: &Self, f: &u32) -> &u32 {
-   |                             -----              ^^^^
-   |                             |                  |
-   |                             |                  ...but data from `f` is returned here
+   |                             -----              ----
+   |                             |
    |                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:32:57
+  --> $DIR/ref-self-async.rs:33:9
    |
 LL |     async fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
-   |                                     -----               ^^^^
-   |                                     |                   |
-   |                                     |                   ...but data from `f` is returned here
+   |                                     -----               ----
+   |                                     |
    |                                     this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:36:57
+  --> $DIR/ref-self-async.rs:37:9
    |
 LL |     async fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
-   |                                     -----               ^^^^
-   |                                     |                   |
-   |                                     |                   ...but data from `f` is returned here
+   |                                     -----               ----
+   |                                     |
    |                                     this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:40:66
+  --> $DIR/ref-self-async.rs:41:9
    |
 LL |     async fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
-   |                                             -----                ^^^^
-   |                                             |                    |
-   |                                             |                    ...but data from `f` is returned here
+   |                                             -----                ----
+   |                                             |
    |                                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:44:66
+  --> $DIR/ref-self-async.rs:45:9
    |
 LL |     async fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
-   |                                             -----                ^^^^
-   |                                             |                    |
-   |                                             |                    ...but data from `f` is returned here
+   |                                             -----                ----
+   |                                             |
    |                                             this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-self-async.rs:48:69
+  --> $DIR/ref-self-async.rs:49:9
    |
 LL |     async fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
-   |                                            -----                    ^^^
-   |                                            |                        |
-   |                                            |                        ...but data from `f` is returned here
+   |                                            -----                    ---
+   |                                            |
    |                                            this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error: aborting due to 7 previous errors
 
diff --git a/src/test/ui/self/elision/ref-struct-async.nll.stderr b/src/test/ui/self/elision/ref-struct-async.nll.stderr
index 8508e42264b..93fec69ec34 100644
--- a/src/test/ui/self/elision/ref-struct-async.nll.stderr
+++ b/src/test/ui/self/elision/ref-struct-async.nll.stderr
@@ -7,16 +7,15 @@ LL |     async fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-struct-async.rs:13:57
+  --> $DIR/ref-struct-async.rs:14:9
    |
-LL |       async fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
-   |  _______________________________-_________________________^
-   | |                               |
-   | |                               lifetime `'_` defined here
-   | |                               lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
+   |                               -
+   |                               |
+   |                               lifetime `'_` defined here
+   |                               lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-struct-async.rs:17:61
@@ -27,16 +26,15 @@ LL |     async fn box_ref_Struct(self: Box<&Struct>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-struct-async.rs:17:66
+  --> $DIR/ref-struct-async.rs:18:9
    |
-LL |       async fn box_ref_Struct(self: Box<&Struct>, f: &u32) -> &u32 {
-   |  _______________________________________-__________________________^
-   | |                                       |
-   | |                                       lifetime `'_` defined here
-   | |                                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn box_ref_Struct(self: Box<&Struct>, f: &u32) -> &u32 {
+   |                                       -
+   |                                       |
+   |                                       lifetime `'_` defined here
+   |                                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-struct-async.rs:21:61
@@ -47,16 +45,15 @@ LL |     async fn pin_ref_Struct(self: Pin<&Struct>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-struct-async.rs:21:66
+  --> $DIR/ref-struct-async.rs:22:9
    |
-LL |       async fn pin_ref_Struct(self: Pin<&Struct>, f: &u32) -> &u32 {
-   |  _______________________________________-__________________________^
-   | |                                       |
-   | |                                       lifetime `'_` defined here
-   | |                                       lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn pin_ref_Struct(self: Pin<&Struct>, f: &u32) -> &u32 {
+   |                                       -
+   |                                       |
+   |                                       lifetime `'_` defined here
+   |                                       lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-struct-async.rs:25:70
@@ -67,16 +64,15 @@ LL |     async fn box_box_ref_Struct(self: Box<Box<&Struct>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-struct-async.rs:25:75
+  --> $DIR/ref-struct-async.rs:26:9
    |
-LL |       async fn box_box_ref_Struct(self: Box<Box<&Struct>>, f: &u32) -> &u32 {
-   |  _______________________________________________-___________________________^
-   | |                                               |
-   | |                                               lifetime `'_` defined here
-   | |                                               lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn box_box_ref_Struct(self: Box<Box<&Struct>>, f: &u32) -> &u32 {
+   |                                               -
+   |                                               |
+   |                                               lifetime `'_` defined here
+   |                                               lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ref-struct-async.rs:29:66
@@ -87,16 +83,15 @@ LL |     async fn box_pin_Struct(self: Box<Pin<&Struct>>, f: &u32) -> &u32 {
    = note: hidden type `impl std::future::Future` captures lifetime '_#15r
 
 error: lifetime may not live long enough
-  --> $DIR/ref-struct-async.rs:29:71
+  --> $DIR/ref-struct-async.rs:30:9
    |
-LL |       async fn box_pin_Struct(self: Box<Pin<&Struct>>, f: &u32) -> &u32 {
-   |  ___________________________________________-___________________________^
-   | |                                           |
-   | |                                           lifetime `'_` defined here
-   | |                                           lifetime `'_` defined here
-LL | |         f
-LL | |     }
-   | |_____^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
+LL |     async fn box_pin_Struct(self: Box<Pin<&Struct>>, f: &u32) -> &u32 {
+   |                                           -
+   |                                           |
+   |                                           lifetime `'_` defined here
+   |                                           lifetime `'_` defined here
+LL |         f
+   |         ^ function was supposed to return data with lifetime `'_` but it is returning data with lifetime `'_`
 
 error: aborting due to 10 previous errors
 
diff --git a/src/test/ui/self/elision/ref-struct-async.rs b/src/test/ui/self/elision/ref-struct-async.rs
index 94eaeedc734..64c84c4cd2e 100644
--- a/src/test/ui/self/elision/ref-struct-async.rs
+++ b/src/test/ui/self/elision/ref-struct-async.rs
@@ -11,23 +11,23 @@ impl Struct {
     // Test using `&Struct` explicitly:
 
     async fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_ref_Struct(self: Box<&Struct>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn pin_ref_Struct(self: Pin<&Struct>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_box_ref_Struct(self: Box<Box<&Struct>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 
     async fn box_pin_Struct(self: Box<Pin<&Struct>>, f: &u32) -> &u32 {
-        f //~^ ERROR lifetime mismatch
+        f //~ ERROR lifetime mismatch
     }
 }
 
diff --git a/src/test/ui/self/elision/ref-struct-async.stderr b/src/test/ui/self/elision/ref-struct-async.stderr
index 222e27ebf0d..c70facc931e 100644
--- a/src/test/ui/self/elision/ref-struct-async.stderr
+++ b/src/test/ui/self/elision/ref-struct-async.stderr
@@ -1,47 +1,52 @@
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-struct-async.rs:13:52
+  --> $DIR/ref-struct-async.rs:14:9
    |
 LL |     async fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
-   |                               -------              ^^^^
-   |                               |                    |
-   |                               |                    ...but data from `f` is returned here
+   |                               -------              ----
+   |                               |
    |                               this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-struct-async.rs:17:61
+  --> $DIR/ref-struct-async.rs:18:9
    |
 LL |     async fn box_ref_Struct(self: Box<&Struct>, f: &u32) -> &u32 {
-   |                                       -------               ^^^^
-   |                                       |                     |
-   |                                       |                     ...but data from `f` is returned here
+   |                                       -------               ----
+   |                                       |
    |                                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-struct-async.rs:21:61
+  --> $DIR/ref-struct-async.rs:22:9
    |
 LL |     async fn pin_ref_Struct(self: Pin<&Struct>, f: &u32) -> &u32 {
-   |                                       -------               ^^^^
-   |                                       |                     |
-   |                                       |                     ...but data from `f` is returned here
+   |                                       -------               ----
+   |                                       |
    |                                       this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-struct-async.rs:25:70
+  --> $DIR/ref-struct-async.rs:26:9
    |
 LL |     async fn box_box_ref_Struct(self: Box<Box<&Struct>>, f: &u32) -> &u32 {
-   |                                               -------                ^^^^
-   |                                               |                      |
-   |                                               |                      ...but data from `f` is returned here
+   |                                               -------                ----
+   |                                               |
    |                                               this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error[E0623]: lifetime mismatch
-  --> $DIR/ref-struct-async.rs:29:66
+  --> $DIR/ref-struct-async.rs:30:9
    |
 LL |     async fn box_pin_Struct(self: Box<Pin<&Struct>>, f: &u32) -> &u32 {
-   |                                           -------                ^^^^
-   |                                           |                      |
-   |                                           |                      ...but data from `f` is returned here
+   |                                           -------                ----
+   |                                           |
    |                                           this parameter and the return type are declared with different lifetimes...
+LL |         f
+   |         ^ ...but data from `f` is returned here
 
 error: aborting due to 5 previous errors