Auto merge of #121904 - matthiaskrgr:rollup-qcq0d3h, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #121666 (Use the OS thread name by default if `THREAD_INFO` has not been initialized)
 - #121758 (Move thread local implementation to `sys`)
 - #121759 (attempt to further clarify addr_of docs)
 - #121855 (Correctly generate item info of trait items)
 - #121888 (style library/core/src/error.rs)
 - #121892 (The ordinary lowering of `thir::ExprKind::Let` is unreachable)
 - #121895 (avoid collecting into vecs in some places)

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

33 files changed, 269 insertions, 107 deletions

diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
index 6116a6fd222..c45787f35aa 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
@@ -357,31 +357,27 @@ fn add_unused_functions(cx: &CodegenCx<'_, '_>) {
 
     let ignore_unused_generics = tcx.sess.instrument_coverage_except_unused_generics();
 
-    let eligible_def_ids: Vec<DefId> = tcx
-        .mir_keys(())
-        .iter()
-        .filter_map(|local_def_id| {
-            let def_id = local_def_id.to_def_id();
-            let kind = tcx.def_kind(def_id);
-            // `mir_keys` will give us `DefId`s for all kinds of things, not
-            // just "functions", like consts, statics, etc. Filter those out.
-            // If `ignore_unused_generics` was specified, filter out any
-            // generic functions from consideration as well.
-            if !matches!(kind, DefKind::Fn | DefKind::AssocFn | DefKind::Closure) {
-                return None;
-            }
-            if ignore_unused_generics && tcx.generics_of(def_id).requires_monomorphization(tcx) {
-                return None;
-            }
-            Some(local_def_id.to_def_id())
-        })
-        .collect();
+    let eligible_def_ids = tcx.mir_keys(()).iter().filter_map(|local_def_id| {
+        let def_id = local_def_id.to_def_id();
+        let kind = tcx.def_kind(def_id);
+        // `mir_keys` will give us `DefId`s for all kinds of things, not
+        // just "functions", like consts, statics, etc. Filter those out.
+        // If `ignore_unused_generics` was specified, filter out any
+        // generic functions from consideration as well.
+        if !matches!(kind, DefKind::Fn | DefKind::AssocFn | DefKind::Closure) {
+            return None;
+        }
+        if ignore_unused_generics && tcx.generics_of(def_id).requires_monomorphization(tcx) {
+            return None;
+        }
+        Some(local_def_id.to_def_id())
+    });
 
     let codegenned_def_ids = codegenned_and_inlined_items(tcx);
 
     // For each `DefId` that should have coverage instrumentation but wasn't
     // codegenned, add it to the function coverage map as an unused function.
-    for def_id in eligible_def_ids.into_iter().filter(|id| !codegenned_def_ids.contains(id)) {
+    for def_id in eligible_def_ids.filter(|id| !codegenned_def_ids.contains(id)) {
         // Skip any function that didn't have coverage data added to it by the
         // coverage instrumentor.
         let body = tcx.instance_mir(ty::InstanceDef::Item(def_id));
diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index 218891a7c67..b8cf72c2c73 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -860,10 +860,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                              traits with associated type `{name}`, you could use the \
                              fully-qualified path",
                         ),
-                        traits
-                            .iter()
-                            .map(|trait_str| format!("<Example as {trait_str}>::{name}"))
-                            .collect::<Vec<_>>(),
+                        traits.iter().map(|trait_str| format!("<Example as {trait_str}>::{name}")),
                         Applicability::HasPlaceholders,
                     );
                 }
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 054be89a7c4..b8cceebe103 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2156,10 +2156,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     err.span_suggestions(
                         span.shrink_to_hi().with_hi(expr_span.hi()),
                         "you might have meant to use an associated function to build this type",
-                        items
-                            .iter()
-                            .map(|(_, name, args)| suggestion(name, *args))
-                            .collect::<Vec<String>>(),
+                        items.iter().map(|(_, name, args)| suggestion(name, *args)),
                         Applicability::MaybeIncorrect,
                     );
                 }
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs
index 2978491d646..f2cf6fe613c 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/build/expr/into.rs
@@ -109,38 +109,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 this.cfg.goto(else_blk, source_info, join_block);
                 join_block.unit()
             }
-            ExprKind::Let { expr, ref pat } => {
-                let scope = this.local_scope();
-                let (true_block, false_block) = this.in_if_then_scope(scope, expr_span, |this| {
-                    this.lower_let_expr(block, expr, pat, scope, None, expr_span, true)
-                });
-
-                this.cfg.push_assign_constant(
-                    true_block,
-                    source_info,
-                    destination,
-                    ConstOperand {
-                        span: expr_span,
-                        user_ty: None,
-                        const_: Const::from_bool(this.tcx, true),
-                    },
-                );
-
-                this.cfg.push_assign_constant(
-                    false_block,
-                    source_info,
-                    destination,
-                    ConstOperand {
-                        span: expr_span,
-                        user_ty: None,
-                        const_: Const::from_bool(this.tcx, false),
-                    },
-                );
-
-                let join_block = this.cfg.start_new_block();
-                this.cfg.goto(true_block, source_info, join_block);
-                this.cfg.goto(false_block, source_info, join_block);
-                join_block.unit()
+            ExprKind::Let { .. } => {
+                // After desugaring, `let` expressions should only appear inside `if`
+                // expressions or `match` guards, possibly nested within a let-chain.
+                // In both cases they are specifically handled by the lowerings of
+                // those expressions, so this case is currently unreachable.
+                span_bug!(expr_span, "unexpected let expression outside of if or match-guard");
             }
             ExprKind::NeverToAny { source } => {
                 let source_expr = &this.thir[source];
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 327884c8414..d008346af69 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1884,10 +1884,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 err.span_suggestions_with_style(
                     path_span.shrink_to_hi().with_hi(call_span.hi()),
                     "you might have meant to use an associated function to build this type",
-                    items
-                        .iter()
-                        .map(|(_, name, len)| suggestion(name, *len))
-                        .collect::<Vec<String>>(),
+                    items.iter().map(|(_, name, len)| suggestion(name, *len)),
                     Applicability::MaybeIncorrect,
                     SuggestionStyle::ShowAlways,
                 );
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index bc2bae9da61..3fa409eefff 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -57,7 +57,7 @@ impl<'tcx> ObligationStorage<'tcx> {
 
     fn take_pending(&mut self) -> Vec<PredicateObligation<'tcx>> {
         let mut obligations = mem::take(&mut self.pending);
-        obligations.extend(self.overflowed.drain(..));
+        obligations.append(&mut self.overflowed);
         obligations
     }
 
diff --git a/library/core/src/error.rs b/library/core/src/error.rs
index ded17e69bd9..a3f2b767054 100644
--- a/library/core/src/error.rs
+++ b/library/core/src/error.rs
@@ -183,6 +183,7 @@ pub trait Error: Debug + Display {
     #[allow(unused_variables)]
     fn provide<'a>(&'a self, request: &mut Request<'a>) {}
 }
+
 mod private {
     // This is a hack to prevent `type_id` from being overridden by `Error`
     // implementations, since that can enable unsound downcasting.
diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs
index fc5b08c9801..018efd4b9b3 100644
--- a/library/core/src/ptr/mod.rs
+++ b/library/core/src/ptr/mod.rs
@@ -2071,11 +2071,16 @@ impl<F: FnPtr> fmt::Debug for F {
 /// as all other references. This macro can create a raw pointer *without* creating
 /// a reference first.
 ///
-/// The `expr` in `addr_of!(expr)` is evaluated as a place expression, but never loads
-/// from the place or requires the place to be dereferenceable. This means that
-/// `addr_of!(*ptr)` is defined behavior even if `ptr` is null, dangling, or misaligned.
-/// Note however that `addr_of!((*ptr).field)` still requires the projection to
-/// `field` to be in-bounds, using the same rules as [`offset`].
+/// See [`addr_of_mut`] for how to create a pointer to uninitialized data.
+/// Doing that with `addr_of` would not make much sense since one could only
+/// read the data, and that would be Undefined Behavior.
+///
+/// # Safety
+///
+/// The `expr` in `addr_of!(expr)` is evaluated as a place expression, but never loads from the
+/// place or requires the place to be dereferenceable. This means that `addr_of!((*ptr).field)`
+/// still requires the projection to `field` to be in-bounds, using the same rules as [`offset`].
+/// However, `addr_of!(*ptr)` is defined behavior even if `ptr` is null, dangling, or misaligned.
 ///
 /// Note that `Deref`/`Index` coercions (and their mutable counterparts) are applied inside
 /// `addr_of!` like everywhere else, in which case a reference is created to call `Deref::deref` or
@@ -2086,6 +2091,8 @@ impl<F: FnPtr> fmt::Debug for F {
 ///
 /// # Example
 ///
+/// **Correct usage: Creating a pointer to unaligned data**
+///
 /// ```
 /// use std::ptr;
 ///
@@ -2101,9 +2108,27 @@ impl<F: FnPtr> fmt::Debug for F {
 /// assert_eq!(unsafe { raw_f2.read_unaligned() }, 2);
 /// ```
 ///
-/// See [`addr_of_mut`] for how to create a pointer to uninitialized data.
-/// Doing that with `addr_of` would not make much sense since one could only
-/// read the data, and that would be Undefined Behavior.
+/// **Incorrect usage: Out-of-bounds fields projection**
+///
+/// ```rust,no_run
+/// use std::ptr;
+///
+/// #[repr(C)]
+/// struct MyStruct {
+///     field1: i32,
+///     field2: i32,
+/// }
+///
+/// let ptr: *const MyStruct = ptr::null();
+/// let fieldptr = unsafe { ptr::addr_of!((*ptr).field2) }; // Undefined Behavior ⚠️
+/// ```
+///
+/// The field projection `.field2` would offset the pointer by 4 bytes,
+/// but the pointer is not in-bounds of an allocation for 4 bytes,
+/// so this offset is Undefined Behavior.
+/// See the [`offset`] docs for a full list of requirements for inbounds pointer arithmetic; the
+/// same requirements apply to field projections, even inside `addr_of!`. (In particular, it makes
+/// no difference whether the pointer is null or dangling.)
 #[stable(feature = "raw_ref_macros", since = "1.51.0")]
 #[rustc_macro_transparency = "semitransparent"]
 #[allow_internal_unstable(raw_ref_op)]
@@ -2120,11 +2145,12 @@ pub macro addr_of($place:expr) {
 /// as all other references. This macro can create a raw pointer *without* creating
 /// a reference first.
 ///
-/// The `expr` in `addr_of_mut!(expr)` is evaluated as a place expression, but never loads
-/// from the place or requires the place to be dereferenceable. This means that
-/// `addr_of_mut!(*ptr)` is defined behavior even if `ptr` is null, dangling, or misaligned.
-/// Note however that `addr_of_mut!((*ptr).field)` still requires the projection to
-/// `field` to be in-bounds, using the same rules as [`offset`].
+/// # Safety
+///
+/// The `expr` in `addr_of_mut!(expr)` is evaluated as a place expression, but never loads from the
+/// place or requires the place to be dereferenceable. This means that `addr_of_mut!((*ptr).field)`
+/// still requires the projection to `field` to be in-bounds, using the same rules as [`offset`].
+/// However, `addr_of_mut!(*ptr)` is defined behavior even if `ptr` is null, dangling, or misaligned.
 ///
 /// Note that `Deref`/`Index` coercions (and their mutable counterparts) are applied inside
 /// `addr_of_mut!` like everywhere else, in which case a reference is created to call `Deref::deref`
@@ -2135,7 +2161,7 @@ pub macro addr_of($place:expr) {
 ///
 /// # Examples
 ///
-/// **Creating a pointer to unaligned data:**
+/// **Correct usage: Creating a pointer to unaligned data**
 ///
 /// ```
 /// use std::ptr;
@@ -2153,7 +2179,7 @@ pub macro addr_of($place:expr) {
 /// assert_eq!({packed.f2}, 42); // `{...}` forces copying the field instead of creating a reference.
 /// ```
 ///
-/// **Creating a pointer to uninitialized data:**
+/// **Correct usage: Creating a pointer to uninitialized data**
 ///
 /// ```rust
 /// use std::{ptr, mem::MaybeUninit};
@@ -2169,6 +2195,28 @@ pub macro addr_of($place:expr) {
 /// unsafe { f1_ptr.write(true); }
 /// let init = unsafe { uninit.assume_init() };
 /// ```
+///
+/// **Incorrect usage: Out-of-bounds fields projection**
+///
+/// ```rust,no_run
+/// use std::ptr;
+///
+/// #[repr(C)]
+/// struct MyStruct {
+///     field1: i32,
+///     field2: i32,
+/// }
+///
+/// let ptr: *mut MyStruct = ptr::null_mut();
+/// let fieldptr = unsafe { ptr::addr_of_mut!((*ptr).field2) }; // Undefined Behavior ⚠️
+/// ```
+///
+/// The field projection `.field2` would offset the pointer by 4 bytes,
+/// but the pointer is not in-bounds of an allocation for 4 bytes,
+/// so this offset is Undefined Behavior.
+/// See the [`offset`] docs for a full list of requirements for inbounds pointer arithmetic; the
+/// same requirements apply to field projections, even inside `addr_of_mut!`. (In particular, it
+/// makes no difference whether the pointer is null or dangling.)
 #[stable(feature = "raw_ref_macros", since = "1.51.0")]
 #[rustc_macro_transparency = "semitransparent"]
 #[allow_internal_unstable(raw_ref_op)]
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index d77ac7eb027..81200e0061e 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -9,6 +9,9 @@ pub mod cmath;
 pub mod locks;
 pub mod os_str;
 pub mod path;
+#[allow(dead_code)]
+#[allow(unused_imports)]
+pub mod thread_local;
 
 // FIXME(117276): remove this, move feature implementations into individual
 //                submodules.
diff --git a/library/std/src/sys/pal/common/mod.rs b/library/std/src/sys/pal/common/mod.rs
index b35c5d30b41..29fc0835d76 100644
--- a/library/std/src/sys/pal/common/mod.rs
+++ b/library/std/src/sys/pal/common/mod.rs
@@ -12,8 +12,6 @@
 
 pub mod alloc;
 pub mod small_c_string;
-#[allow(unused_imports)]
-pub mod thread_local;
 
 #[cfg(test)]
 mod tests;
diff --git a/library/std/src/sys/pal/hermit/thread.rs b/library/std/src/sys/pal/hermit/thread.rs
index fee80c02d4a..cf45b9c2396 100644
--- a/library/std/src/sys/pal/hermit/thread.rs
+++ b/library/std/src/sys/pal/hermit/thread.rs
@@ -2,7 +2,7 @@
 
 use super::abi;
 use super::thread_local_dtor::run_dtors;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -71,6 +71,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     #[inline]
     pub fn sleep(dur: Duration) {
         unsafe {
diff --git a/library/std/src/sys/pal/itron/thread.rs b/library/std/src/sys/pal/itron/thread.rs
index 9c1387bf408..814a102dd09 100644
--- a/library/std/src/sys/pal/itron/thread.rs
+++ b/library/std/src/sys/pal/itron/thread.rs
@@ -8,7 +8,7 @@ use super::{
 };
 use crate::{
     cell::UnsafeCell,
-    ffi::CStr,
+    ffi::{CStr, CString},
     hint, io,
     mem::ManuallyDrop,
     num::NonZero,
@@ -204,6 +204,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         for timeout in dur2reltims(dur) {
             expect_success(unsafe { abi::dly_tsk(timeout) }, &"dly_tsk");
diff --git a/library/std/src/sys/pal/sgx/thread.rs b/library/std/src/sys/pal/sgx/thread.rs
index c797fde7fbd..77f68bf7334 100644
--- a/library/std/src/sys/pal/sgx/thread.rs
+++ b/library/std/src/sys/pal/sgx/thread.rs
@@ -1,6 +1,6 @@
 #![cfg_attr(test, allow(dead_code))] // why is this necessary?
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -133,6 +133,10 @@ impl Thread {
         // which succeeds as-is with the SGX target.
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         usercalls::wait_timeout(0, dur, || true);
     }
diff --git a/library/std/src/sys/pal/teeos/thread.rs b/library/std/src/sys/pal/teeos/thread.rs
index 77f9040ead5..b76bcf9bbb0 100644
--- a/library/std/src/sys/pal/teeos/thread.rs
+++ b/library/std/src/sys/pal/teeos/thread.rs
@@ -1,7 +1,7 @@
 use core::convert::TryInto;
 
 use crate::cmp;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -101,6 +101,10 @@ impl Thread {
         // contact the teeos rustzone team.
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     /// only main thread could wait for sometime in teeos
     pub fn sleep(dur: Duration) {
         let sleep_millis = dur.as_millis();
diff --git a/library/std/src/sys/pal/uefi/thread.rs b/library/std/src/sys/pal/uefi/thread.rs
index 3d8fa27251f..b3a4f9c53e3 100644
--- a/library/std/src/sys/pal/uefi/thread.rs
+++ b/library/std/src/sys/pal/uefi/thread.rs
@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::ptr::NonNull;
@@ -23,6 +23,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         let boot_services: NonNull<r_efi::efi::BootServices> =
             crate::os::uefi::env::boot_services().expect("can't sleep").cast();
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index 864de31c6eb..2af6382f3da 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -1,5 +1,5 @@
 use crate::cmp;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -225,6 +225,44 @@ impl Thread {
         // Newlib, Emscripten, and VxWorks have no way to set a thread name.
     }
 
+    #[cfg(target_os = "linux")]
+    pub fn get_name() -> Option<CString> {
+        const TASK_COMM_LEN: usize = 16;
+        let mut name = vec![0u8; TASK_COMM_LEN];
+        let res = unsafe {
+            libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
+        };
+        if res != 0 {
+            return None;
+        }
+        name.truncate(name.iter().position(|&c| c == 0)?);
+        CString::new(name).ok()
+    }
+
+    #[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos"))]
+    pub fn get_name() -> Option<CString> {
+        let mut name = vec![0u8; libc::MAXTHREADNAMESIZE];
+        let res = unsafe {
+            libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
+        };
+        if res != 0 {
+            return None;
+        }
+        name.truncate(name.iter().position(|&c| c == 0)?);
+        CString::new(name).ok()
+    }
+
+    #[cfg(not(any(
+        target_os = "linux",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "tvos",
+        target_os = "watchos"
+    )))]
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     #[cfg(not(target_os = "espidf"))]
     pub fn sleep(dur: Duration) {
         let mut secs = dur.as_secs();
diff --git a/library/std/src/sys/pal/unsupported/thread.rs b/library/std/src/sys/pal/unsupported/thread.rs
index cd1ae7f7d11..b3a91ee1d4c 100644
--- a/library/std/src/sys/pal/unsupported/thread.rs
+++ b/library/std/src/sys/pal/unsupported/thread.rs
@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -22,6 +22,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(_dur: Duration) {
         panic!("can't sleep");
     }
diff --git a/library/std/src/sys/pal/wasi/thread.rs b/library/std/src/sys/pal/wasi/thread.rs
index 77d8b4378e7..4b116052f8f 100644
--- a/library/std/src/sys/pal/wasi/thread.rs
+++ b/library/std/src/sys/pal/wasi/thread.rs
@@ -1,4 +1,4 @@
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -134,6 +134,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         let nanos = dur.as_nanos();
         assert!(nanos <= u64::MAX as u128);
diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/windows/c.rs
index b007796722b..afa92409404 100644
--- a/library/std/src/sys/pal/windows/c.rs
+++ b/library/std/src/sys/pal/windows/c.rs
@@ -344,6 +344,12 @@ compat_fn_with_fallback! {
         SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
     }
 
+    // >= Win10 1607
+    // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getthreaddescription
+    pub fn GetThreadDescription(hthread: HANDLE, lpthreaddescription: *mut PWSTR) -> HRESULT {
+        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
+    }
+
     // >= Win8 / Server 2012
     // https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime
     pub fn GetSystemTimePreciseAsFileTime(lpsystemtimeasfiletime: *mut FILETIME) -> () {
diff --git a/library/std/src/sys/pal/windows/c/bindings.txt b/library/std/src/sys/pal/windows/c/bindings.txt
index ab2a8caf5df..d0081411530 100644
--- a/library/std/src/sys/pal/windows/c/bindings.txt
+++ b/library/std/src/sys/pal/windows/c/bindings.txt
@@ -1923,6 +1923,7 @@ Windows.Win32.Foundation.HANDLE_FLAG_INHERIT
 Windows.Win32.Foundation.HANDLE_FLAG_PROTECT_FROM_CLOSE
 Windows.Win32.Foundation.HANDLE_FLAGS
 Windows.Win32.Foundation.HMODULE
+Windows.Win32.Foundation.LocalFree
 Windows.Win32.Foundation.MAX_PATH
 Windows.Win32.Foundation.NO_ERROR
 Windows.Win32.Foundation.NTSTATUS
diff --git a/library/std/src/sys/pal/windows/c/windows_sys.rs b/library/std/src/sys/pal/windows/c/windows_sys.rs
index 8eb779373f7..96773d91e99 100644
--- a/library/std/src/sys/pal/windows/c/windows_sys.rs
+++ b/library/std/src/sys/pal/windows/c/windows_sys.rs
@@ -380,6 +380,10 @@ extern "system" {
 }
 #[link(name = "kernel32")]
 extern "system" {
+    pub fn LocalFree(hmem: HLOCAL) -> HLOCAL;
+}
+#[link(name = "kernel32")]
+extern "system" {
     pub fn MoveFileExW(
         lpexistingfilename: PCWSTR,
         lpnewfilename: PCWSTR,
@@ -3441,6 +3445,7 @@ pub type HANDLE_FLAGS = u32;
 pub const HANDLE_FLAG_INHERIT: HANDLE_FLAGS = 1u32;
 pub const HANDLE_FLAG_PROTECT_FROM_CLOSE: HANDLE_FLAGS = 2u32;
 pub const HIGH_PRIORITY_CLASS: PROCESS_CREATION_FLAGS = 128u32;
+pub type HLOCAL = *mut ::core::ffi::c_void;
 pub type HMODULE = *mut ::core::ffi::c_void;
 pub type HRESULT = i32;
 pub const IDLE_PRIORITY_CLASS: PROCESS_CREATION_FLAGS = 64u32;
diff --git a/library/std/src/sys/pal/windows/thread.rs b/library/std/src/sys/pal/windows/thread.rs
index 0f709e2ec7b..a8f1e9b726b 100644
--- a/library/std/src/sys/pal/windows/thread.rs
+++ b/library/std/src/sys/pal/windows/thread.rs
@@ -9,7 +9,7 @@ use crate::sys::handle::Handle;
 use crate::sys::stack_overflow;
 use crate::sys_common::FromInner;
 use crate::time::Duration;
-
+use alloc::ffi::CString;
 use core::ffi::c_void;
 
 use super::time::WaitableTimer;
@@ -71,6 +71,29 @@ impl Thread {
         };
     }
 
+    pub fn get_name() -> Option<CString> {
+        unsafe {
+            let mut ptr = core::ptr::null_mut();
+            let result = c::GetThreadDescription(c::GetCurrentThread(), &mut ptr);
+            if result < 0 {
+                return None;
+            }
+            let name = String::from_utf16_lossy({
+                let mut len = 0;
+                while *ptr.add(len) != 0 {
+                    len += 1;
+                }
+                core::slice::from_raw_parts(ptr, len)
+            })
+            .into_bytes();
+            // Attempt to free the memory.
+            // This should never fail but if it does then there's not much we can do about it.
+            let result = c::LocalFree(ptr.cast::<c_void>());
+            debug_assert!(result.is_null());
+            if name.is_empty() { None } else { Some(CString::from_vec_unchecked(name)) }
+        }
+    }
+
     pub fn join(self) {
         let rc = unsafe { c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE) };
         if rc == c::WAIT_FAILED {
diff --git a/library/std/src/sys/pal/xous/thread.rs b/library/std/src/sys/pal/xous/thread.rs
index 21f5954d6e2..f95ceb7343b 100644
--- a/library/std/src/sys/pal/xous/thread.rs
+++ b/library/std/src/sys/pal/xous/thread.rs
@@ -1,4 +1,4 @@
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::os::xous::ffi::{
@@ -113,6 +113,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         // Because the sleep server works on units of `usized milliseconds`, split
         // the messages up into these chunks. This means we may run into issues
diff --git a/library/std/src/sys/pal/common/thread_local/fast_local.rs b/library/std/src/sys/thread_local/fast_local.rs
index 646dcd7f3a3..646dcd7f3a3 100644
--- a/library/std/src/sys/pal/common/thread_local/fast_local.rs
+++ b/library/std/src/sys/thread_local/fast_local.rs
diff --git a/library/std/src/sys/pal/common/thread_local/mod.rs b/library/std/src/sys/thread_local/mod.rs
index 8b2c839f837..8b2c839f837 100644
--- a/library/std/src/sys/pal/common/thread_local/mod.rs
+++ b/library/std/src/sys/thread_local/mod.rs
diff --git a/library/std/src/sys/pal/common/thread_local/os_local.rs b/library/std/src/sys/thread_local/os_local.rs
index 3edffd7e443..3edffd7e443 100644
--- a/library/std/src/sys/pal/common/thread_local/os_local.rs
+++ b/library/std/src/sys/thread_local/os_local.rs
diff --git a/library/std/src/sys/pal/common/thread_local/static_local.rs b/library/std/src/sys/thread_local/static_local.rs
index 4f2b6868962..4f2b6868962 100644
--- a/library/std/src/sys/pal/common/thread_local/static_local.rs
+++ b/library/std/src/sys/thread_local/static_local.rs
diff --git a/library/std/src/sys_common/thread_info.rs b/library/std/src/sys_common/thread_info.rs
index 8d51732e035..ec1428ea40e 100644
--- a/library/std/src/sys_common/thread_info.rs
+++ b/library/std/src/sys_common/thread_info.rs
@@ -1,6 +1,7 @@
 #![allow(dead_code)] // stack_guard isn't used right now on all platforms
 
 use crate::cell::OnceCell;
+use crate::sys;
 use crate::sys::thread::guard::Guard;
 use crate::thread::Thread;
 
@@ -23,7 +24,8 @@ impl ThreadInfo {
     {
         THREAD_INFO
             .try_with(move |thread_info| {
-                let thread = thread_info.thread.get_or_init(|| Thread::new(None));
+                let thread =
+                    thread_info.thread.get_or_init(|| Thread::new(sys::thread::Thread::get_name()));
                 f(thread, &thread_info.stack_guard)
             })
             .ok()
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index 76af7fec926..85de2980133 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -205,7 +205,7 @@ cfg_if::cfg_if! {
         #[doc(hidden)]
         #[unstable(feature = "thread_local_internals", issue = "none")]
         pub mod local_impl {
-            pub use crate::sys::common::thread_local::{thread_local_inner, Key, abort_on_dtor_unwind};
+            pub use crate::sys::thread_local::{thread_local_inner, Key, abort_on_dtor_unwind};
         }
     }
 }
diff --git a/library/std/src/thread/tests.rs b/library/std/src/thread/tests.rs
index 5d6b9e94ee9..efd06c8df6e 100644
--- a/library/std/src/thread/tests.rs
+++ b/library/std/src/thread/tests.rs
@@ -69,6 +69,25 @@ fn test_named_thread_truncation() {
     result.unwrap().join().unwrap();
 }
 
+#[cfg(any(
+    target_os = "windows",
+    target_os = "linux",
+    target_os = "macos",
+    target_os = "ios",
+    target_os = "tvos",
+    target_os = "watchos"
+))]
+#[test]
+fn test_get_os_named_thread() {
+    use crate::sys::thread::Thread;
+    let handler = thread::spawn(|| {
+        let name = c"test me please";
+        Thread::set_name(name);
+        assert_eq!(name, Thread::get_name().unwrap().as_c_str());
+    });
+    handler.join().unwrap();
+}
+
 #[test]
 #[should_panic]
 fn test_invalid_named_thread() {
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index ac7ae291d29..fe83095f944 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -1680,7 +1680,7 @@ fn render_impl(
                 write!(
                     &mut doc_buffer,
                     "{}",
-                    document_short(item, cx, link, parent, rendering_params.show_def_docs,)
+                    document_short(item, cx, link, parent, rendering_params.show_def_docs)
                 );
             }
         }
@@ -2043,15 +2043,13 @@ pub(crate) fn render_impl_summary(
     w.write_str("</h3>");
 
     let is_trait = inner_impl.trait_.is_some();
-    if is_trait {
-        if let Some(portability) = portability(&i.impl_item, Some(parent)) {
-            write!(
-                w,
-                "<span class=\"item-info\">\
-                     <div class=\"stab portability\">{portability}</div>\
-                 </span>",
-            );
-        }
+    if is_trait && let Some(portability) = portability(&i.impl_item, Some(parent)) {
+        write!(
+            w,
+            "<span class=\"item-info\">\
+                 <div class=\"stab portability\">{portability}</div>\
+             </span>",
+        );
     }
 
     w.write_str("</section>");
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 71186319e07..d588f219739 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -33,6 +33,7 @@ use crate::html::format::{
 };
 use crate::html::layout::Page;
 use crate::html::markdown::{HeadingOffset, MarkdownSummaryLine};
+use crate::html::render::{document_full, document_item_info};
 use crate::html::url_parts_builder::UrlPartsBuilder;
 use crate::html::{highlight, static_files};
 
@@ -818,8 +819,10 @@ fn item_trait(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean:
         info!("Documenting {name} on {ty_name:?}", ty_name = t.name);
         let item_type = m.type_();
         let id = cx.derive_id(format!("{item_type}.{name}"));
+
         let mut content = Buffer::empty_from(w);
-        write!(&mut content, "{}", document(cx, m, Some(t), HeadingOffset::H5));
+        write!(content, "{}", document_full(m, cx, HeadingOffset::H5));
+
         let toggled = !content.is_empty();
         if toggled {
             let method_toggle_class = if item_type.is_method() { " method-toggle" } else { "" };
@@ -836,8 +839,8 @@ fn item_trait(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean:
             cx,
             RenderMode::Normal,
         );
-        w.write_str("</h4>");
-        w.write_str("</section>");
+        w.write_str("</h4></section>");
+        document_item_info(cx, m, Some(t)).render_into(w).unwrap();
         if toggled {
             write!(w, "</summary>");
             w.push_buffer(content);
diff --git a/tests/rustdoc/trait-item-info.rs b/tests/rustdoc/trait-item-info.rs
new file mode 100644
index 00000000000..53a4c6917b9
--- /dev/null
+++ b/tests/rustdoc/trait-item-info.rs
@@ -0,0 +1,24 @@
+// This is a regression test for <https://github.com/rust-lang/rust/issues/121772>.
+// The goal is to ensure that the item information is always part of the `<summary>`
+// if there is one.
+
+#![crate_name = "foo"]
+#![feature(staged_api)]
+
+#![unstable(feature = "test", issue = "none")]
+
+// @has 'foo/trait.Foo.html'
+
+#[stable(feature = "rust2", since = "2.2.2")]
+pub trait Foo {
+    // @has - '//div[@class="methods"]/span[@class="item-info"]' 'bla'
+    // Should not be in a `<details>` because there is no doc.
+    #[unstable(feature = "bla", reason = "bla", issue = "111")]
+    fn bla() {}
+
+    // @has - '//details[@class="toggle method-toggle"]/summary/span[@class="item-info"]' 'bar'
+    // Should have a `<summary>` in the `<details>` containing the unstable info.
+    /// doc
+    #[unstable(feature = "bar", reason = "bla", issue = "222")]
+    fn bar() {}
+}