From d5354eb48ea8705d9f2d4f211b139b43ccdebd16 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Tue, 28 Jun 2022 19:45:15 +0200
Subject: [PATCH 1/2] Add known bug test.
---
.../lifetimes/bare-trait-object-borrowck.rs | 27 ++++++++++++
.../bare-trait-object-borrowck.stderr | 43 +++++++++++++++++++
src/test/ui/lifetimes/bare-trait-object.rs | 27 ++++++++++++
.../ui/lifetimes/bare-trait-object.stderr | 21 +++++++++
4 files changed, 118 insertions(+)
create mode 100644 src/test/ui/lifetimes/bare-trait-object-borrowck.rs
create mode 100644 src/test/ui/lifetimes/bare-trait-object-borrowck.stderr
create mode 100644 src/test/ui/lifetimes/bare-trait-object.rs
create mode 100644 src/test/ui/lifetimes/bare-trait-object.stderr
diff --git a/src/test/ui/lifetimes/bare-trait-object-borrowck.rs b/src/test/ui/lifetimes/bare-trait-object-borrowck.rs
new file mode 100644
index 0000000000000..ee2c61468cb60
--- /dev/null
+++ b/src/test/ui/lifetimes/bare-trait-object-borrowck.rs
@@ -0,0 +1,27 @@
+#![allow(bare_trait_objects)]
+
+pub struct FormatWith<'a, I, F> {
+ sep: &'a str,
+ /// FormatWith uses interior mutability because Display::fmt takes &self.
+ inner: RefCell<Option<(I, F)>>,
+}
+
+use std::cell::RefCell;
+use std::fmt;
+
+struct Layout;
+
+pub fn new_format<'a, I, F>(iter: I, separator: &'a str, f: F) -> FormatWith<'a, I, F>
+where
+ I: Iterator,
+ F: FnMut(I::Item, &mut FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result,
+{
+ FormatWith { sep: separator, inner: RefCell::new(Some((iter, f))) }
+}
+
+fn main() {
+ let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
+ //~^ ERROR temporary value dropped while borrowed
+ //~| ERROR temporary value dropped while borrowed
+ //~| ERROR `i` does not live long enough
+}
diff --git a/src/test/ui/lifetimes/bare-trait-object-borrowck.stderr b/src/test/ui/lifetimes/bare-trait-object-borrowck.stderr
new file mode 100644
index 0000000000000..d7b059019eb3b
--- /dev/null
+++ b/src/test/ui/lifetimes/bare-trait-object-borrowck.stderr
@@ -0,0 +1,43 @@
+error[E0716]: temporary value dropped while borrowed
+ --> $DIR/bare-trait-object-borrowck.rs:23:48
+ |
+LL | let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
+ | - ---^^^^^^^^^^^^^^^^^^^^^^^^^-
+ | | | | |
+ | | | | temporary value is freed at the end of this statement
+ | | | creates a temporary which is freed while still in use
+ | | argument requires that borrow lasts for `'1`
+ | has type `&mut dyn FnMut(&'1 (dyn std::fmt::Display + '1)) -> Result<(), std::fmt::Error>`
+ |
+ = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0716]: temporary value dropped while borrowed
+ --> $DIR/bare-trait-object-borrowck.rs:23:48
+ |
+LL | let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
+ | - ---^^^^^^^^^^^^^^^^^^^^^^^^^-
+ | | | | |
+ | | | | temporary value is freed at the end of this statement
+ | | | creates a temporary which is freed while still in use
+ | | argument requires that borrow lasts for `'1`
+ | has type `&mut dyn FnMut(&'1 (dyn std::fmt::Display + '1)) -> Result<(), std::fmt::Error>`
+ |
+ = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0597]: `i` does not live long enough
+ --> $DIR/bare-trait-object-borrowck.rs:23:71
+ |
+LL | let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
+ | - --------------------------^--
+ | | | | |
+ | | | | `i` dropped here while still borrowed
+ | | | borrowed value does not live long enough
+ | | argument requires that `i` is borrowed for `'1`
+ | has type `&mut dyn FnMut(&'1 (dyn std::fmt::Display + '1)) -> Result<(), std::fmt::Error>`
+ |
+ = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0597, E0716.
+For more information about an error, try `rustc --explain E0597`.
diff --git a/src/test/ui/lifetimes/bare-trait-object.rs b/src/test/ui/lifetimes/bare-trait-object.rs
new file mode 100644
index 0000000000000..dc8b611c03978
--- /dev/null
+++ b/src/test/ui/lifetimes/bare-trait-object.rs
@@ -0,0 +1,27 @@
+// Verify that lifetime resolution correctly accounts for `Fn` bare trait objects.
+
+#![allow(bare_trait_objects)]
+
+// This should work as: fn next_u32(fill_buf: &mut dyn FnMut(&mut [u8]))
+fn next_u32(fill_buf: &mut FnMut(&mut [u8])) {
+ let mut buf: [u8; 4] = [0; 4];
+ fill_buf(&mut buf);
+}
+
+fn explicit(fill_buf: &mut dyn FnMut(&mut [u8])) {
+ let mut buf: [u8; 4] = [0; 4];
+ fill_buf(&mut buf);
+}
+
+fn main() {
+ let _: fn(&mut FnMut(&mut [u8])) = next_u32;
+ //~^ ERROR mismatched types
+ let _: &dyn Fn(&mut FnMut(&mut [u8])) = &next_u32;
+ let _: fn(&mut FnMut(&mut [u8])) = explicit;
+ //~^ ERROR mismatched types
+ let _: &dyn Fn(&mut FnMut(&mut [u8])) = &explicit;
+ let _: fn(&mut dyn FnMut(&mut [u8])) = next_u32;
+ let _: &dyn Fn(&mut dyn FnMut(&mut [u8])) = &next_u32;
+ let _: fn(&mut dyn FnMut(&mut [u8])) = explicit;
+ let _: &dyn Fn(&mut dyn FnMut(&mut [u8])) = &explicit;
+}
diff --git a/src/test/ui/lifetimes/bare-trait-object.stderr b/src/test/ui/lifetimes/bare-trait-object.stderr
new file mode 100644
index 0000000000000..8f06410152e62
--- /dev/null
+++ b/src/test/ui/lifetimes/bare-trait-object.stderr
@@ -0,0 +1,21 @@
+error[E0308]: mismatched types
+ --> $DIR/bare-trait-object.rs:17:40
+ |
+LL | let _: fn(&mut FnMut(&mut [u8])) = next_u32;
+ | ^^^^^^^^ one type is more general than the other
+ |
+ = note: expected fn pointer `for<'r, 's> fn(&'r mut (dyn for<'s> FnMut(&'s mut [u8]) + 'r))`
+ found fn item `for<'r> fn(&'r mut (dyn for<'r> FnMut(&'r mut [u8]) + 'r)) {next_u32}`
+
+error[E0308]: mismatched types
+ --> $DIR/bare-trait-object.rs:20:40
+ |
+LL | let _: fn(&mut FnMut(&mut [u8])) = explicit;
+ | ^^^^^^^^ one type is more general than the other
+ |
+ = note: expected fn pointer `for<'r, 's> fn(&'r mut (dyn for<'s> FnMut(&'s mut [u8]) + 'r))`
+ found fn item `for<'r> fn(&'r mut (dyn for<'r> FnMut(&'r mut [u8]) + 'r)) {explicit}`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
From 21a12e8ab78f7e67a4ddc1d13d289a496f2f619d Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Sat, 25 Jun 2022 19:16:56 +0200
Subject: [PATCH 2/2] Handle fresh lifetimes on bare trait objects.
---
compiler/rustc_ast_lowering/src/lib.rs | 27 ++++++++++++
compiler/rustc_resolve/src/late.rs | 24 +++++++++++
.../lifetimes/bare-trait-object-borrowck.rs | 5 +--
.../bare-trait-object-borrowck.stderr | 43 -------------------
src/test/ui/lifetimes/bare-trait-object.rs | 4 +-
.../ui/lifetimes/bare-trait-object.stderr | 21 ---------
6 files changed, 53 insertions(+), 71 deletions(-)
delete mode 100644 src/test/ui/lifetimes/bare-trait-object-borrowck.stderr
delete mode 100644 src/test/ui/lifetimes/bare-trait-object.stderr
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index e8b92eaad5c8d..cab2de0ced87c 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1174,6 +1174,33 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
param_mode: ParamMode,
itctx: ImplTraitContext,
) -> hir::Ty<'hir> {
+ // Check whether we should interpret this as a bare trait object.
+ // This check mirrors the one in late resolution. We only introduce this special case in
+ // the rare occurence we need to lower `Fresh` anonymous lifetimes.
+ // The other cases when a qpath should be opportunistically made a trait object are handled
+ // by `ty_path`.
+ if qself.is_none()
+ && let Some(partial_res) = self.resolver.get_partial_res(t.id)
+ && partial_res.unresolved_segments() == 0
+ && let Res::Def(DefKind::Trait | DefKind::TraitAlias, _) = partial_res.base_res()
+ {
+ let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
+ let bound = this.lower_poly_trait_ref(
+ &PolyTraitRef {
+ bound_generic_params: vec![],
+ trait_ref: TraitRef { path: path.clone(), ref_id: t.id },
+ span: t.span
+ },
+ itctx,
+ );
+ let bounds = this.arena.alloc_from_iter([bound]);
+ let lifetime_bound = this.elided_dyn_bound(t.span);
+ (bounds, lifetime_bound)
+ });
+ let kind = hir::TyKind::TraitObject(bounds, lifetime_bound, TraitObjectSyntax::None);
+ return hir::Ty { kind, span: self.lower_span(t.span), hir_id: self.next_id() };
+ }
+
let id = self.lower_node_id(t.id);
let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
self.ty_path(id, t.span, qpath)
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 640d13ea43547..ced32904c0acb 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -611,6 +611,30 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
TyKind::Path(ref qself, ref path) => {
self.diagnostic_metadata.current_type_path = Some(ty);
self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
+
+ // Check whether we should interpret this as a bare trait object.
+ if qself.is_none()
+ && let Some(partial_res) = self.r.partial_res_map.get(&ty.id)
+ && partial_res.unresolved_segments() == 0
+ && let Res::Def(DefKind::Trait | DefKind::TraitAlias, _) = partial_res.base_res()
+ {
+ // This path is actually a bare trait object. In case of a bare `Fn`-trait
+ // object with anonymous lifetimes, we need this rib to correctly place the
+ // synthetic lifetimes.
+ let span = ty.span.shrink_to_lo().to(path.span.shrink_to_lo());
+ self.with_generic_param_rib(
+ &[],
+ NormalRibKind,
+ LifetimeRibKind::Generics {
+ binder: ty.id,
+ kind: LifetimeBinderKind::PolyTrait,
+ span,
+ },
+ |this| this.visit_path(&path, ty.id),
+ );
+ self.diagnostic_metadata.current_type_path = prev_ty;
+ return;
+ }
}
TyKind::ImplicitSelf => {
let self_ty = Ident::with_dummy_span(kw::SelfUpper);
diff --git a/src/test/ui/lifetimes/bare-trait-object-borrowck.rs b/src/test/ui/lifetimes/bare-trait-object-borrowck.rs
index ee2c61468cb60..45f5e4ae129a1 100644
--- a/src/test/ui/lifetimes/bare-trait-object-borrowck.rs
+++ b/src/test/ui/lifetimes/bare-trait-object-borrowck.rs
@@ -1,5 +1,5 @@
#![allow(bare_trait_objects)]
-
+// check-pass
pub struct FormatWith<'a, I, F> {
sep: &'a str,
/// FormatWith uses interior mutability because Display::fmt takes &self.
@@ -21,7 +21,4 @@ where
fn main() {
let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
- //~^ ERROR temporary value dropped while borrowed
- //~| ERROR temporary value dropped while borrowed
- //~| ERROR `i` does not live long enough
}
diff --git a/src/test/ui/lifetimes/bare-trait-object-borrowck.stderr b/src/test/ui/lifetimes/bare-trait-object-borrowck.stderr
deleted file mode 100644
index d7b059019eb3b..0000000000000
--- a/src/test/ui/lifetimes/bare-trait-object-borrowck.stderr
+++ /dev/null
@@ -1,43 +0,0 @@
-error[E0716]: temporary value dropped while borrowed
- --> $DIR/bare-trait-object-borrowck.rs:23:48
- |
-LL | let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
- | - ---^^^^^^^^^^^^^^^^^^^^^^^^^-
- | | | | |
- | | | | temporary value is freed at the end of this statement
- | | | creates a temporary which is freed while still in use
- | | argument requires that borrow lasts for `'1`
- | has type `&mut dyn FnMut(&'1 (dyn std::fmt::Display + '1)) -> Result<(), std::fmt::Error>`
- |
- = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0716]: temporary value dropped while borrowed
- --> $DIR/bare-trait-object-borrowck.rs:23:48
- |
-LL | let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
- | - ---^^^^^^^^^^^^^^^^^^^^^^^^^-
- | | | | |
- | | | | temporary value is freed at the end of this statement
- | | | creates a temporary which is freed while still in use
- | | argument requires that borrow lasts for `'1`
- | has type `&mut dyn FnMut(&'1 (dyn std::fmt::Display + '1)) -> Result<(), std::fmt::Error>`
- |
- = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0597]: `i` does not live long enough
- --> $DIR/bare-trait-object-borrowck.rs:23:71
- |
-LL | let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
- | - --------------------------^--
- | | | | |
- | | | | `i` dropped here while still borrowed
- | | | borrowed value does not live long enough
- | | argument requires that `i` is borrowed for `'1`
- | has type `&mut dyn FnMut(&'1 (dyn std::fmt::Display + '1)) -> Result<(), std::fmt::Error>`
- |
- = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: aborting due to 3 previous errors
-
-Some errors have detailed explanations: E0597, E0716.
-For more information about an error, try `rustc --explain E0597`.
diff --git a/src/test/ui/lifetimes/bare-trait-object.rs b/src/test/ui/lifetimes/bare-trait-object.rs
index dc8b611c03978..9eff618c734d5 100644
--- a/src/test/ui/lifetimes/bare-trait-object.rs
+++ b/src/test/ui/lifetimes/bare-trait-object.rs
@@ -1,5 +1,5 @@
// Verify that lifetime resolution correctly accounts for `Fn` bare trait objects.
-
+// check-pass
#![allow(bare_trait_objects)]
// This should work as: fn next_u32(fill_buf: &mut dyn FnMut(&mut [u8]))
@@ -15,10 +15,8 @@ fn explicit(fill_buf: &mut dyn FnMut(&mut [u8])) {
fn main() {
let _: fn(&mut FnMut(&mut [u8])) = next_u32;
- //~^ ERROR mismatched types
let _: &dyn Fn(&mut FnMut(&mut [u8])) = &next_u32;
let _: fn(&mut FnMut(&mut [u8])) = explicit;
- //~^ ERROR mismatched types
let _: &dyn Fn(&mut FnMut(&mut [u8])) = &explicit;
let _: fn(&mut dyn FnMut(&mut [u8])) = next_u32;
let _: &dyn Fn(&mut dyn FnMut(&mut [u8])) = &next_u32;
diff --git a/src/test/ui/lifetimes/bare-trait-object.stderr b/src/test/ui/lifetimes/bare-trait-object.stderr
deleted file mode 100644
index 8f06410152e62..0000000000000
--- a/src/test/ui/lifetimes/bare-trait-object.stderr
+++ /dev/null
@@ -1,21 +0,0 @@
-error[E0308]: mismatched types
- --> $DIR/bare-trait-object.rs:17:40
- |
-LL | let _: fn(&mut FnMut(&mut [u8])) = next_u32;
- | ^^^^^^^^ one type is more general than the other
- |
- = note: expected fn pointer `for<'r, 's> fn(&'r mut (dyn for<'s> FnMut(&'s mut [u8]) + 'r))`
- found fn item `for<'r> fn(&'r mut (dyn for<'r> FnMut(&'r mut [u8]) + 'r)) {next_u32}`
-
-error[E0308]: mismatched types
- --> $DIR/bare-trait-object.rs:20:40
- |
-LL | let _: fn(&mut FnMut(&mut [u8])) = explicit;
- | ^^^^^^^^ one type is more general than the other
- |
- = note: expected fn pointer `for<'r, 's> fn(&'r mut (dyn for<'s> FnMut(&'s mut [u8]) + 'r))`
- found fn item `for<'r> fn(&'r mut (dyn for<'r> FnMut(&'r mut [u8]) + 'r)) {explicit}`
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0308`.