Auto merge of rust-lang#117967 - adetaylor:fix-lifetime-elision-bug, …

…r=<try> Fix lifetime elision ```rust struct Concrete(u32); impl Concrete { fn m(self: &Box<Self>) -> &u32 { &self.0 } } ``` resulted in a confusing error. ```rust impl Concrete { fn n(self: &Box<&Self>) -> &u32 { &self.0 } } ``` resulted in no error or warning, despite apparent ambiguity over the elided lifetime. Fixes rust-lang#117715
rust-lang-ci · Jan 9, 2024 · e65790b · e65790b
2 parents ae9d24d + c46b820
commit e65790b
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diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
@@ -2105,13 +2105,17 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             // Handle `self` specially.
             if index == 0 && has_self {
                 let self_lifetime = self.find_lifetime_for_self(ty);
-                if let Set1::One(lifetime) = self_lifetime {
+                elision_lifetime = match self_lifetime {
                     // We found `self` elision.
-                    elision_lifetime = Elision::Self_(lifetime);
-                } else {
+                    Set1::One(lifetime) => Elision::Self_(lifetime),
+                    // `self` itself had ambiguous lifetimes, e.g.
+                    // &Box<&Self>. In this case we won't consider
+                    // taking an alternative parameter lifetime; just avoid elision
+                    // entirely.
+                    Set1::Many => Elision::Err,
                     // We do not have `self` elision: disregard the `Elision::Param` that we may
                     // have found.
-                    elision_lifetime = Elision::None;
+                    Set1::Empty => Elision::None,
                 }
             }
             debug!("(resolving function / closure) recorded parameter");
@@ -2135,6 +2139,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             r: &'r Resolver<'a, 'tcx>,
             impl_self: Option<Res>,
             lifetime: Set1<LifetimeRes>,
+            self_found: bool,
         }
 
         impl SelfVisitor<'_, '_, '_> {
@@ -2158,9 +2163,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
         impl<'a> Visitor<'a> for SelfVisitor<'_, '_, '_> {
             fn visit_ty(&mut self, ty: &'a Ty) {
                 trace!("SelfVisitor considering ty={:?}", ty);
-                if let TyKind::Ref(lt, ref mt) = ty.kind
-                    && self.is_self_ty(&mt.ty)
-                {
+                if self.is_self_ty(ty) {
+                    trace!("SelfVisitor found Self");
+                    self.self_found = true;
+                }
+                if let TyKind::Ref(lt, _) = ty.kind {
                     let lt_id = if let Some(lt) = lt {
                         lt.id
                     } else {
@@ -2201,10 +2208,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                     Res::Def(DefKind::Struct | DefKind::Union | DefKind::Enum, _,) | Res::PrimTy(_)
                 )
             });
-        let mut visitor = SelfVisitor { r: self.r, impl_self, lifetime: Set1::Empty };
+        let mut visitor =
+            SelfVisitor { r: self.r, impl_self, lifetime: Set1::Empty, self_found: false };
         visitor.visit_ty(ty);
-        trace!("SelfVisitor found={:?}", visitor.lifetime);
-        visitor.lifetime
+        trace!("SelfVisitor found={:?}, self_found={:?}", visitor.lifetime, visitor.self_found);
+        if visitor.self_found { visitor.lifetime } else { Set1::Empty }
     }
 
     /// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved

diff --git a/tests/ui/self/elision/multiple-ref-self-async.rs b/tests/ui/self/elision/multiple-ref-self-async.rs
@@ -1,4 +1,3 @@
-// check-pass
 // edition:2018
 
 #![feature(arbitrary_self_types)]
@@ -21,23 +20,33 @@ impl Struct {
     // Test using multiple `&Self`:
 
     async fn wrap_ref_Self_ref_Self(self: Wrap<&Self, &Self>, f: &u8) -> &u8 {
+        //~^ ERROR missing lifetime specifier
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn box_wrap_ref_Self_ref_Self(self: Box<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn pin_wrap_ref_Self_ref_Self(self: Pin<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn box_box_wrap_ref_Self_ref_Self(self: Box<Box<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn box_pin_wrap_ref_Self_ref_Self(self: Box<Pin<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
+        //~^ ERROR lifetime may not live long enough
     }
 }
 

diff --git a/tests/ui/self/elision/multiple-ref-self-async.stderr b/tests/ui/self/elision/multiple-ref-self-async.stderr
@@ -0,0 +1,108 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self-async.rs:22:74
+   |
+LL |     async fn wrap_ref_Self_ref_Self(self: Wrap<&Self, &Self>, f: &u8) -> &u8 {
+   |                                           ------------------     ---     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     async fn wrap_ref_Self_ref_Self<'a>(self: Wrap<&'a Self, &'a Self>, f: &'a u8) -> &'a u8 {
+   |                                    ++++             ++        ++            ++         ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self-async.rs:28:84
+   |
+LL |     async fn box_wrap_ref_Self_ref_Self(self: Box<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+   |                                               -----------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     async fn box_wrap_ref_Self_ref_Self<'a>(self: Box<Wrap<&'a Self, &'a Self>>, f: &'a u32) -> &'a u32 {
+   |                                        ++++                 ++        ++             ++          ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self-async.rs:34:84
+   |
+LL |     async fn pin_wrap_ref_Self_ref_Self(self: Pin<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+   |                                               -----------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     async fn pin_wrap_ref_Self_ref_Self<'a>(self: Pin<Wrap<&'a Self, &'a Self>>, f: &'a u32) -> &'a u32 {
+   |                                        ++++                 ++        ++             ++          ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self-async.rs:40:93
+   |
+LL |     async fn box_box_wrap_ref_Self_ref_Self(self: Box<Box<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+   |                                                   ----------------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     async fn box_box_wrap_ref_Self_ref_Self<'a>(self: Box<Box<Wrap<&'a Self, &'a Self>>>, f: &'a u32) -> &'a u32 {
+   |                                            ++++                     ++        ++              ++          ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self-async.rs:46:93
+   |
+LL |     async fn box_pin_wrap_ref_Self_ref_Self(self: Box<Pin<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+   |                                                   ----------------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     async fn box_pin_wrap_ref_Self_ref_Self<'a>(self: Box<Pin<Wrap<&'a Self, &'a Self>>>, f: &'a u32) -> &'a u32 {
+   |                                            ++++                     ++        ++              ++          ++
+
+error: lifetime may not live long enough
+  --> $DIR/multiple-ref-self-async.rs:24:9
+   |
+LL |     async fn wrap_ref_Self_ref_Self(self: Wrap<&Self, &Self>, f: &u8) -> &u8 {
+   |                                                                  - let's call the lifetime of this reference `'1`
+LL |
+LL |         f
+   |         ^ returning this value requires that `'1` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/multiple-ref-self-async.rs:30:9
+   |
+LL |     async fn box_wrap_ref_Self_ref_Self(self: Box<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+   |                                                                           - let's call the lifetime of this reference `'1`
+LL |
+LL |         f
+   |         ^ returning this value requires that `'1` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/multiple-ref-self-async.rs:36:9
+   |
+LL |     async fn pin_wrap_ref_Self_ref_Self(self: Pin<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+   |                                                                           - let's call the lifetime of this reference `'1`
+LL |
+LL |         f
+   |         ^ returning this value requires that `'1` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/multiple-ref-self-async.rs:42:9
+   |
+LL |     async fn box_box_wrap_ref_Self_ref_Self(self: Box<Box<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+   |                                                                                    - let's call the lifetime of this reference `'1`
+LL |
+LL |         f
+   |         ^ returning this value requires that `'1` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/multiple-ref-self-async.rs:48:9
+   |
+LL |     async fn box_pin_wrap_ref_Self_ref_Self(self: Box<Pin<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+   |                                                                                    - let's call the lifetime of this reference `'1`
+LL |
+LL |         f
+   |         ^ returning this value requires that `'1` must outlive `'static`
+
+error: aborting due to 10 previous errors
+
+For more information about this error, try `rustc --explain E0106`.
diff --git a/tests/ui/self/elision/multiple-ref-self.rs b/tests/ui/self/elision/multiple-ref-self.rs
@@ -1,5 +1,3 @@
-// check-pass
-
 #![feature(arbitrary_self_types)]
 #![allow(non_snake_case)]
 
@@ -20,22 +18,27 @@ impl Struct {
     // Test using multiple `&Self`:
 
     fn wrap_ref_Self_ref_Self(self: Wrap<&Self, &Self>, f: &u8) -> &u8 {
+        //~^ ERROR missing lifetime specifier
         f
     }
 
     fn box_wrap_ref_Self_ref_Self(self: Box<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
     }
 
     fn pin_wrap_ref_Self_ref_Self(self: Pin<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
     }
 
     fn box_box_wrap_ref_Self_ref_Self(self: Box<Box<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
     }
 
     fn box_pin_wrap_ref_Self_ref_Self(self: Box<Pin<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+        //~^ ERROR missing lifetime specifier
         f
     }
 }

diff --git a/tests/ui/self/elision/multiple-ref-self.stderr b/tests/ui/self/elision/multiple-ref-self.stderr
@@ -0,0 +1,63 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self.rs:20:68
+   |
+LL |     fn wrap_ref_Self_ref_Self(self: Wrap<&Self, &Self>, f: &u8) -> &u8 {
+   |                                     ------------------     ---     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn wrap_ref_Self_ref_Self<'a>(self: Wrap<&'a Self, &'a Self>, f: &'a u8) -> &'a u8 {
+   |                              ++++             ++        ++            ++         ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self.rs:25:78
+   |
+LL |     fn box_wrap_ref_Self_ref_Self(self: Box<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+   |                                         -----------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn box_wrap_ref_Self_ref_Self<'a>(self: Box<Wrap<&'a Self, &'a Self>>, f: &'a u32) -> &'a u32 {
+   |                                  ++++                 ++        ++             ++          ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self.rs:30:78
+   |
+LL |     fn pin_wrap_ref_Self_ref_Self(self: Pin<Wrap<&Self, &Self>>, f: &u32) -> &u32 {
+   |                                         -----------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn pin_wrap_ref_Self_ref_Self<'a>(self: Pin<Wrap<&'a Self, &'a Self>>, f: &'a u32) -> &'a u32 {
+   |                                  ++++                 ++        ++             ++          ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self.rs:35:87
+   |
+LL |     fn box_box_wrap_ref_Self_ref_Self(self: Box<Box<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+   |                                             ----------------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn box_box_wrap_ref_Self_ref_Self<'a>(self: Box<Box<Wrap<&'a Self, &'a Self>>>, f: &'a u32) -> &'a u32 {
+   |                                      ++++                     ++        ++              ++          ++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/multiple-ref-self.rs:40:87
+   |
+LL |     fn box_pin_wrap_ref_Self_ref_Self(self: Box<Pin<Wrap<&Self, &Self>>>, f: &u32) -> &u32 {
+   |                                             ----------------------------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `self`'s 2 lifetimes or `f`
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn box_pin_wrap_ref_Self_ref_Self<'a>(self: Box<Pin<Wrap<&'a Self, &'a Self>>>, f: &'a u32) -> &'a u32 {
+   |                                      ++++                     ++        ++              ++          ++
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0106`.
diff --git a/tests/ui/self/elision/ref-assoc-async.rs b/tests/ui/self/elision/ref-assoc-async.rs
@@ -1,5 +1,4 @@
 // edition:2018
-// check-pass
 
 #![allow(non_snake_case)]
 
@@ -18,22 +17,27 @@ impl Trait for Struct {
 impl Struct {
     async fn ref_AssocType(self: &<Struct as Trait>::AssocType, f: &u32) -> &u32 {
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn box_ref_AssocType(self: Box<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn pin_ref_AssocType(self: Pin<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn box_box_ref_AssocType(self: Box<Box<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
         f
+        //~^ ERROR lifetime may not live long enough
     }
 
     async fn box_pin_ref_AssocType(self: Box<Pin<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
         f
+        //~^ ERROR lifetime may not live long enough
     }
 }