Auto merge of #123628 - matthiaskrgr:rollup-6otgb94, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #115984 (extending filesystem support for Hermit)
 - #120144 (privacy: Stabilize lint `unnameable_types`)
 - #122807 (Add consistency with phrases "meantime" and "mean time")
 - #123089 (Add invariant to VecDeque::pop_* that len < cap if pop successful)
 - #123595 (Documentation fix)
 - #123625 (Stop exporting `TypeckRootCtxt` and `FnCtxt`.)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_driver_impl/messages.ftl

@@ -2,7 +2,7 @@ driver_impl_ice = the compiler unexpectedly panicked. this is a bug.
 driver_impl_ice_bug_report = we would appreciate a bug report: {$bug_report_url}
 driver_impl_ice_bug_report_internal_feature = using internal features is not supported and expected to cause internal compiler errors when used incorrectly
 driver_impl_ice_bug_report_outdated =
-    it seems that this compiler `{$version}` is outdated, a newer nightly should have been released in the mean time
+    it seems that this compiler `{$version}` is outdated, a newer nightly should have been released in the meantime
     .update = please consider running `rustup update nightly` to update the nightly channel and check if this problem still persists
     .url = if the problem still persists, we would appreciate a bug report: {$bug_report_url}
 driver_impl_ice_exclude_cargo_defaults = some of the compiler flags provided by cargo are hidden

compiler/rustc_feature/src/accepted.rs

@@ -355,6 +355,8 @@ declare_features! (
     (accepted, type_alias_enum_variants, "1.37.0", Some(49683)),
     /// Allows macros to appear in the type position.
     (accepted, type_macros, "1.13.0", Some(27245)),
+    /// Allows using type privacy lints (`private_interfaces`, `private_bounds`, `unnameable_types`).
+    (accepted, type_privacy_lints, "CURRENT_RUSTC_VERSION", Some(48054)),
     /// Allows `const _: TYPE = VALUE`.
     (accepted, underscore_const_names, "1.37.0", Some(54912)),
     /// Allows `use path as _;` and `extern crate c as _;`.

compiler/rustc_feature/src/unstable.rs

@@ -615,8 +615,6 @@ declare_features! (
     /// Allows creation of instances of a struct by moving fields that have
     /// not changed from prior instances of the same struct (RFC #2528)
     (unstable, type_changing_struct_update, "1.58.0", Some(86555)),
-    /// Allows using type privacy lints (`private_interfaces`, `private_bounds`, `unnameable_types`).
-    (unstable, type_privacy_lints, "1.72.0", Some(48054)),
     /// Enables rustc to generate code that instructs libstd to NOT ignore SIGPIPE.
     (unstable, unix_sigpipe, "1.65.0", Some(97889)),
     /// Allows unnamed fields of struct and union type

compiler/rustc_hir_typeck/src/cast.rs

@@ -40,17 +40,19 @@ use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::cast::{CastKind, CastTy};
 use rustc_middle::ty::error::TypeError;
+use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::{self, Ty, TypeAndMut, TypeVisitableExt, VariantDef};
 use rustc_session::lint;
 use rustc_span::def_id::{DefId, LOCAL_CRATE};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
+use rustc_span::DUMMY_SP;
 use rustc_trait_selection::infer::InferCtxtExt;
 
 /// Reifies a cast check to be checked once we have full type information for
 /// a function context.
 #[derive(Debug)]
-pub struct CastCheck<'tcx> {
+pub(crate) struct CastCheck<'tcx> {
     /// The expression whose value is being casted
     expr: &'tcx hir::Expr<'tcx>,
     /// The source type for the cast expression
@@ -60,8 +62,6 @@ pub struct CastCheck<'tcx> {
     cast_ty: Ty<'tcx>,
     cast_span: Span,
     span: Span,
-    /// whether the cast is made in a const context or not.
-    pub constness: hir::Constness,
 }
 
 /// The kind of pointer and associated metadata (thin, length or vtable) - we
@@ -194,18 +194,45 @@ fn make_invalid_casting_error<'a, 'tcx>(
     )
 }
 
+/// If a cast from `from_ty` to `to_ty` is valid, returns a `Some` containing the kind
+/// of the cast.
+///
+/// This is a helper used from clippy.
+pub fn check_cast<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    e: &'tcx hir::Expr<'tcx>,
+    from_ty: Ty<'tcx>,
+    to_ty: Ty<'tcx>,
+) -> Option<CastKind> {
+    let hir_id = e.hir_id;
+    let local_def_id = hir_id.owner.def_id;
+
+    let root_ctxt = crate::TypeckRootCtxt::new(tcx, local_def_id);
+    let fn_ctxt = FnCtxt::new(&root_ctxt, param_env, local_def_id);
+
+    if let Ok(check) = CastCheck::new(
+        &fn_ctxt, e, from_ty, to_ty,
+        // We won't show any errors to the user, so the span is irrelevant here.
+        DUMMY_SP, DUMMY_SP,
+    ) {
+        check.do_check(&fn_ctxt).ok()
+    } else {
+        None
+    }
+}
+
 impl<'a, 'tcx> CastCheck<'tcx> {
-    pub fn new(
+    pub(crate) fn new(
         fcx: &FnCtxt<'a, 'tcx>,
         expr: &'tcx hir::Expr<'tcx>,
         expr_ty: Ty<'tcx>,
         cast_ty: Ty<'tcx>,
         cast_span: Span,
         span: Span,
-        constness: hir::Constness,
     ) -> Result<CastCheck<'tcx>, ErrorGuaranteed> {
         let expr_span = expr.span.find_ancestor_inside(span).unwrap_or(expr.span);
-        let check = CastCheck { expr, expr_ty, expr_span, cast_ty, cast_span, span, constness };
+        let check = CastCheck { expr, expr_ty, expr_span, cast_ty, cast_span, span };
 
         // For better error messages, check for some obviously unsized
         // cases now. We do a more thorough check at the end, once
@@ -644,7 +671,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
     /// Checks a cast, and report an error if one exists. In some cases, this
     /// can return Ok and create type errors in the fcx rather than returning
     /// directly. coercion-cast is handled in check instead of here.
-    pub fn do_check(&self, fcx: &FnCtxt<'a, 'tcx>) -> Result<CastKind, CastError> {
+    fn do_check(&self, fcx: &FnCtxt<'a, 'tcx>) -> Result<CastKind, CastError> {
         use rustc_middle::ty::cast::CastTy::*;
         use rustc_middle::ty::cast::IntTy::*;
 

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1318,6 +1318,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 }
 
+/// Check whether `ty` can be coerced to `output_ty`.
+/// Used from clippy.
+pub fn can_coerce<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    body_id: LocalDefId,
+    ty: Ty<'tcx>,
+    output_ty: Ty<'tcx>,
+) -> bool {
+    let root_ctxt = crate::typeck_root_ctxt::TypeckRootCtxt::new(tcx, body_id);
+    let fn_ctxt = FnCtxt::new(&root_ctxt, param_env, body_id);
+    fn_ctxt.can_coerce(ty, output_ty)
+}
+
 /// CoerceMany encapsulates the pattern you should use when you have
 /// many expressions that are all getting coerced to a common
 /// type. This arises, for example, when you have a match (the result

compiler/rustc_hir_typeck/src/expr.rs

@@ -1390,15 +1390,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else {
             // Defer other checks until we're done type checking.
             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
-            match cast::CastCheck::new(
-                self,
-                e,
-                t_expr,
-                t_cast,
-                t.span,
-                expr.span,
-                hir::Constness::NotConst,
-            ) {
+            match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
                 Ok(cast_check) => {
                     debug!(
                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -38,7 +38,7 @@ use std::ops::Deref;
 ///
 /// [`ItemCtxt`]: rustc_hir_analysis::collect::ItemCtxt
 /// [`InferCtxt`]: infer::InferCtxt
-pub struct FnCtxt<'a, 'tcx> {
+pub(crate) struct FnCtxt<'a, 'tcx> {
     pub(super) body_id: LocalDefId,
 
     /// The parameter environment used for proving trait obligations

compiler/rustc_hir_typeck/src/lib.rs

@@ -42,8 +42,9 @@ mod typeck_root_ctxt;
 mod upvar;
 mod writeback;
 
-pub use fn_ctxt::FnCtxt;
-pub use typeck_root_ctxt::TypeckRootCtxt;
+pub use coercion::can_coerce;
+use fn_ctxt::FnCtxt;
+use typeck_root_ctxt::TypeckRootCtxt;
 
 use crate::check::check_fn;
 use crate::coercion::DynamicCoerceMany;

compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs

@@ -27,7 +27,7 @@ use std::ops::Deref;
 /// `bar()` will each have their own `FnCtxt`, but they will
 /// share the inference context, will process obligations together,
 /// can access each other's local types (scoping permitted), etc.
-pub struct TypeckRootCtxt<'tcx> {
+pub(crate) struct TypeckRootCtxt<'tcx> {
     pub(super) infcx: InferCtxt<'tcx>,
 
     pub(super) typeck_results: RefCell<ty::TypeckResults<'tcx>>,

compiler/rustc_lint/src/builtin.rs

@@ -1337,8 +1337,9 @@ impl<'tcx> LateLintPass<'tcx> for UngatedAsyncFnTrackCaller {
 }
 
 declare_lint! {
-    /// The `unreachable_pub` lint triggers for `pub` items not reachable from
-    /// the crate root.
+    /// The `unreachable_pub` lint triggers for `pub` items not reachable from other crates - that
+    /// means neither directly accessible, nor reexported, nor leaked through things like return
+    /// types.
     ///
     /// ### Example
     ///

compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs

@@ -20,7 +20,7 @@ declare_lint! {
     /// This functionality was removed in #97346, but then rolled back in #99860
     /// because it caused regressions.
     ///
-    /// We plan on reintroducing this as a hard error, but in the mean time,
+    /// We plan on reintroducing this as a hard error, but in the meantime,
     /// this lint serves to warn and suggest fixes for any use-cases which rely
     /// on this behavior.
     ///

compiler/rustc_lint_defs/src/builtin.rs

@@ -4311,7 +4311,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust,compile_fail
-    /// # #![feature(type_privacy_lints)]
     /// # #![allow(unused)]
     /// #![deny(unnameable_types)]
     /// mod m {
@@ -4328,10 +4327,14 @@ declare_lint! {
     ///
     /// It is often expected that if you can obtain an object of type `T`, then
     /// you can name the type `T` as well, this lint attempts to enforce this rule.
+    /// The recommended action is to either reexport the type properly to make it nameable,
+    /// or document that users are not supposed to be able to name it for one reason or another.
+    ///
+    /// Besides types, this lint applies to traits because traits can also leak through signatures,
+    /// and you may obtain objects of their `dyn Trait` or `impl Trait` types.
     pub UNNAMEABLE_TYPES,
     Allow,
     "effective visibility of a type is larger than the area in which it can be named",
-    @feature_gate = sym::type_privacy_lints;
 }
 
 declare_lint! {

compiler/rustc_llvm/llvm-wrapper/ArchiveWrapper.cpp

@@ -147,7 +147,7 @@ LLVMRustArchiveChildName(LLVMRustArchiveChildConstRef Child, size_t *Size) {
   Expected<StringRef> NameOrErr = Child->getName();
   if (!NameOrErr) {
     // rustc_codegen_llvm currently doesn't use this error string, but it might be
-    // useful in the future, and in the mean time this tells LLVM that the
+    // useful in the future, and in the meantime this tells LLVM that the
     // error was not ignored and that it shouldn't abort the process.
     LLVMRustSetLastError(toString(NameOrErr.takeError()).c_str());
     return nullptr;

library/alloc/src/collections/vec_deque/mod.rs

@@ -1614,7 +1614,10 @@ impl<T, A: Allocator> VecDeque<T, A> {
             let old_head = self.head;
             self.head = self.to_physical_idx(1);
             self.len -= 1;
-            Some(unsafe { self.buffer_read(old_head) })
+            unsafe {
+                core::hint::assert_unchecked(self.len < self.capacity());
+                Some(self.buffer_read(old_head))
+            }
         }
     }
 
@@ -1638,7 +1641,10 @@ impl<T, A: Allocator> VecDeque<T, A> {
             None
         } else {
             self.len -= 1;
-            Some(unsafe { self.buffer_read(self.to_physical_idx(self.len)) })
+            unsafe {
+                core::hint::assert_unchecked(self.len < self.capacity());
+                Some(self.buffer_read(self.to_physical_idx(self.len)))
+            }
         }
     }
 

library/core/src/ops/try_trait.rs

@@ -310,7 +310,7 @@ pub trait FromResidual<R = <Self as Try>::Residual> {
     /// This should be implemented consistently with the `branch` method such
     /// that applying the `?` operator will get back an equivalent residual:
     /// `FromResidual::from_residual(r).branch() --> ControlFlow::Break(r)`.
-    /// (It must not be an *identical* residual when interconversion is involved.)
+    /// (The residual is not mandated to be *identical* when interconversion is involved.)
     ///
     /// # Examples
     ///

library/std/src/sys/pal/hermit/fd.rs

@@ -48,6 +48,11 @@ impl FileDesc {
     pub fn set_nonblocking(&self, _nonblocking: bool) -> io::Result<()> {
         unsupported()
     }
+
+    pub fn fstat(&self, stat: *mut abi::stat) -> io::Result<()> {
+        cvt(unsafe { abi::fstat(self.fd.as_raw_fd(), stat) })?;
+        Ok(())
+    }
 }
 
 impl<'a> Read for &'a FileDesc {