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-rw-r--r--src/librustc/hir/intravisit.rs1
-rw-r--r--src/librustc/hir/lowering.rs19
-rw-r--r--src/librustc/hir/mod.rs21
-rw-r--r--src/librustc/middle/resolve_lifetime.rs17
-rw-r--r--src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs3
-rw-r--r--src/test/ui/async-await/issues/issue-62517-1.rs23
-rw-r--r--src/test/ui/async-await/issues/issue-62517-2.rs16
-rw-r--r--src/test/ui/async-await/issues/issue-62517-2.stderr11
-rw-r--r--src/test/ui/impl-trait/dyn-trait-elided-two-inputs-assoc.rs16
-rw-r--r--src/test/ui/impl-trait/dyn-trait-elided-two-inputs-param.rs11
-rw-r--r--src/test/ui/impl-trait/dyn-trait-elided-two-inputs-ref-param.rs23
-rw-r--r--src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs2
-rw-r--r--src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr10
13 files changed, 163 insertions, 10 deletions
diff --git a/src/librustc/hir/intravisit.rs b/src/librustc/hir/intravisit.rs
index 2c6373bdfa4..fa274f831b7 100644
--- a/src/librustc/hir/intravisit.rs
+++ b/src/librustc/hir/intravisit.rs
@@ -433,6 +433,7 @@ pub fn walk_lifetime<'v, V: Visitor<'v>>(visitor: &mut V, lifetime: &'v Lifetime
         LifetimeName::Static |
         LifetimeName::Error |
         LifetimeName::Implicit |
+        LifetimeName::ImplicitObjectLifetimeDefault |
         LifetimeName::Underscore => {}
     }
 }
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index cd127177e9f..e04e45e5fbc 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -1560,6 +1560,11 @@ impl<'a> LoweringContext<'a> {
                         }
                     }
                     hir::LifetimeName::Param(_) => lifetime.name,
+
+                    // Refers to some other lifetime that is "in
+                    // scope" within the type.
+                    hir::LifetimeName::ImplicitObjectLifetimeDefault => return,
+
                     hir::LifetimeName::Error | hir::LifetimeName::Static => return,
                 };
 
@@ -2550,6 +2555,12 @@ impl<'a> LoweringContext<'a> {
                     hir::LifetimeName::Implicit
                         | hir::LifetimeName::Underscore
                         | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
+                    hir::LifetimeName::ImplicitObjectLifetimeDefault => {
+                        span_bug!(
+                            param.ident.span,
+                            "object-lifetime-default should not occur here",
+                        );
+                    }
                     hir::LifetimeName::Error => ParamName::Error,
                 };
 
@@ -3293,7 +3304,13 @@ impl<'a> LoweringContext<'a> {
             AnonymousLifetimeMode::PassThrough => {}
         }
 
-        self.new_implicit_lifetime(span)
+        let r = hir::Lifetime {
+            hir_id: self.next_id(),
+            span,
+            name: hir::LifetimeName::ImplicitObjectLifetimeDefault,
+        };
+        debug!("elided_dyn_bound: r={:?}", r);
+        r
     }
 
     fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index b469b7016be..98304818852 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -221,6 +221,19 @@ pub enum LifetimeName {
     /// User wrote nothing (e.g., the lifetime in `&u32`).
     Implicit,
 
+    /// Implicit lifetime in a context like `dyn Foo`. This is
+    /// distinguished from implicit lifetimes elsewhere because the
+    /// lifetime that they default to must appear elsewhere within the
+    /// enclosing type.  This means that, in an `impl Trait` context, we
+    /// don't have to create a parameter for them. That is, `impl
+    /// Trait<Item = &u32>` expands to an opaque type like `type
+    /// Foo<'a> = impl Trait<Item = &'a u32>`, but `impl Trait<item =
+    /// dyn Bar>` expands to `type Foo = impl Trait<Item = dyn Bar +
+    /// 'static>`. The latter uses `ImplicitObjectLifetimeDefault` so
+    /// that surrounding code knows not to create a lifetime
+    /// parameter.
+    ImplicitObjectLifetimeDefault,
+
     /// Indicates an error during lowering (usually `'_` in wrong place)
     /// that was already reported.
     Error,
@@ -235,7 +248,9 @@ pub enum LifetimeName {
 impl LifetimeName {
     pub fn ident(&self) -> Ident {
         match *self {
-            LifetimeName::Implicit | LifetimeName::Error => Ident::invalid(),
+            LifetimeName::ImplicitObjectLifetimeDefault
+                | LifetimeName::Implicit
+                | LifetimeName::Error => Ident::invalid(),
             LifetimeName::Underscore => Ident::with_dummy_span(kw::UnderscoreLifetime),
             LifetimeName::Static => Ident::with_dummy_span(kw::StaticLifetime),
             LifetimeName::Param(param_name) => param_name.ident(),
@@ -244,7 +259,9 @@ impl LifetimeName {
 
     pub fn is_elided(&self) -> bool {
         match self {
-            LifetimeName::Implicit | LifetimeName::Underscore => true,
+            LifetimeName::ImplicitObjectLifetimeDefault
+            | LifetimeName::Implicit
+            | LifetimeName::Underscore => true,
 
             // It might seem surprising that `Fresh(_)` counts as
             // *not* elided -- but this is because, as far as the code
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index 74031541f56..3b604bef78e 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -5,6 +5,8 @@
 //! used between functions, and they operate in a purely top-down
 //! way. Therefore, we break lifetime name resolution into a separate pass.
 
+// ignore-tidy-filelength
+
 use crate::hir::def::{Res, DefKind};
 use crate::hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use crate::hir::map::Map;
@@ -591,6 +593,14 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 }
                 match lifetime.name {
                     LifetimeName::Implicit => {
+                        // For types like `dyn Foo`, we should
+                        // generate a special form of elided.
+                        span_bug!(
+                            ty.span,
+                            "object-lifetime-default expected, not implict",
+                        );
+                    }
+                    LifetimeName::ImplicitObjectLifetimeDefault => {
                         // If the user does not write *anything*, we
                         // use the object lifetime defaulting
                         // rules. So e.g., `Box<dyn Debug>` becomes
@@ -2643,6 +2653,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                         hir::LifetimeName::Param(_) | hir::LifetimeName::Implicit => {
                             self.resolve_lifetime_ref(lt);
                         }
+                        hir::LifetimeName::ImplicitObjectLifetimeDefault => {
+                            self.tcx.sess.delay_span_bug(
+                                lt.span,
+                                "lowering generated `ImplicitObjectLifetimeDefault` \
+                                 outside of an object type",
+                            )
+                        }
                         hir::LifetimeName::Error => {
                             // No need to do anything, error already reported.
                         }
diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
index 3f5b2f4bce7..ca68b9e31b6 100644
--- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
+++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
@@ -578,7 +578,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 })
             }
 
-            hir::LifetimeName::Implicit => {
+            hir::LifetimeName::ImplicitObjectLifetimeDefault
+            | hir::LifetimeName::Implicit => {
                 // In this case, the user left off the lifetime; so
                 // they wrote something like:
                 //
diff --git a/src/test/ui/async-await/issues/issue-62517-1.rs b/src/test/ui/async-await/issues/issue-62517-1.rs
new file mode 100644
index 00000000000..5955d9751af
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-62517-1.rs
@@ -0,0 +1,23 @@
+// Regression test for #62517. We used to ICE when you had an `async
+// fn` with an `impl Trait` return that mentioned a `dyn Bar` with no
+// explicit lifetime bound.
+//
+// edition:2018
+// check-pass
+
+#![feature(async_await)]
+
+trait FirstTrait {}
+trait SecondTrait {
+    type Item: ?Sized;
+}
+
+async fn foo(x: &str) -> impl SecondTrait<Item = dyn FirstTrait> {
+}
+
+
+impl<T> SecondTrait for T {
+    type Item = dyn FirstTrait;
+}
+
+fn main() { }
diff --git a/src/test/ui/async-await/issues/issue-62517-2.rs b/src/test/ui/async-await/issues/issue-62517-2.rs
new file mode 100644
index 00000000000..72dae58e516
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-62517-2.rs
@@ -0,0 +1,16 @@
+// Regression test for #62517. We used to ICE when you had an `async
+// fn` with an `impl Trait` return that mentioned a `dyn Bar` with no
+// explicit lifetime bound.
+//
+// edition:2018
+
+#![feature(async_await)]
+
+trait Object {}
+
+trait Alpha<Param> {}
+
+async fn foo<'a>(_: &'a ()) -> impl Alpha<dyn Object> {}
+//~^ ERROR not satisfied
+
+fn main() { }
diff --git a/src/test/ui/async-await/issues/issue-62517-2.stderr b/src/test/ui/async-await/issues/issue-62517-2.stderr
new file mode 100644
index 00000000000..4f9b3047bfe
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-62517-2.stderr
@@ -0,0 +1,11 @@
+error[E0277]: the trait bound `(): Alpha<(dyn Object + 'static)>` is not satisfied
+  --> $DIR/issue-62517-2.rs:13:32
+   |
+LL | async fn foo<'a>(_: &'a ()) -> impl Alpha<dyn Object> {}
+   |                                ^^^^^^^^^^^^^^^^^^^^^^ the trait `Alpha<(dyn Object + 'static)>` is not implemented for `()`
+   |
+   = note: the return type of a function must have a statically known size
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-assoc.rs b/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-assoc.rs
new file mode 100644
index 00000000000..3b714157384
--- /dev/null
+++ b/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-assoc.rs
@@ -0,0 +1,16 @@
+// Test that we don't get an error with `dyn Bar` in an impl Trait
+// when there are multiple inputs.  The `dyn Bar` should default to `+
+// 'static`. This used to erroneously generate an error (cc #62517).
+//
+// check-pass
+
+trait Foo { type Item: ?Sized; }
+trait Bar { }
+
+impl<T> Foo for T {
+    type Item = dyn Bar;
+}
+
+fn foo(x: &str, y: &str) -> impl Foo<Item = dyn Bar> { () }
+
+fn main() { }
diff --git a/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-param.rs b/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-param.rs
new file mode 100644
index 00000000000..e8da52aad0e
--- /dev/null
+++ b/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-param.rs
@@ -0,0 +1,11 @@
+// Test that we don't get an error with `dyn Object` in an impl Trait
+// when there are multiple inputs.  The `dyn Object` should default to `+
+// 'static`. This used to erroneously generate an error (cc #62517).
+//
+// check-pass
+
+trait Alpha<Item: ?Sized> {}
+trait Object {}
+impl<T> Alpha<dyn Object> for T {}
+fn alpha(x: &str, y: &str) -> impl Alpha<dyn Object> { () }
+fn main() { }
diff --git a/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-ref-param.rs b/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-ref-param.rs
new file mode 100644
index 00000000000..8d34c1b6c2a
--- /dev/null
+++ b/src/test/ui/impl-trait/dyn-trait-elided-two-inputs-ref-param.rs
@@ -0,0 +1,23 @@
+// Test that `impl Alpha<dyn Object>` resets the object-lifetime
+// default to `'static`.
+//
+// check-pass
+
+trait Alpha<Item: ?Sized> {
+    fn item(&self) -> Box<Item> {
+        panic!()
+    }
+}
+
+trait Object {}
+impl<T> Alpha<dyn Object> for T {}
+fn alpha(x: &str, y: &str) -> impl Alpha<dyn Object> { () }
+fn is_static<T>(_: T) where T: 'static { }
+
+fn bar(x: &str) -> &impl Alpha<dyn Object> { &() }
+
+fn main() {
+    let s = format!("foo");
+    let r = bar(&s);
+    is_static(r.item());
+}
diff --git a/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs
index 2370084b072..ea0d0ccbc55 100644
--- a/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs
+++ b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs
@@ -6,7 +6,7 @@ trait Future {
 use std::error::Error;
 
 fn foo() -> impl Future<Item=(), Error=Box<dyn Error>> {
-//~^ ERROR missing lifetime
+//~^ ERROR not satisfied
     Ok(())
 }
 
diff --git a/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr
index 06b317ce952..228582d0001 100644
--- a/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr
+++ b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr
@@ -1,11 +1,11 @@
-error[E0106]: missing lifetime specifier
-  --> $DIR/lifetime-elision-return-type-trait.rs:8:44
+error[E0277]: the trait bound `std::result::Result<(), _>: Future` is not satisfied
+  --> $DIR/lifetime-elision-return-type-trait.rs:8:13
    |
 LL | fn foo() -> impl Future<Item=(), Error=Box<dyn Error>> {
-   |                                            ^^^^^^^^^ help: consider giving it a 'static lifetime: `dyn Error + 'static`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Future` is not implemented for `std::result::Result<(), _>`
    |
-   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+   = note: the return type of a function must have a statically known size
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0106`.
+For more information about this error, try `rustc --explain E0277`.
generated by cgit-pink 1.4.1-3-g733a5 (git 2.37.1) at 2025-11-04 04:01:29 +0000