Auto merge of rust-lang#121904 - matthiaskrgr:rollup-qcq0d3h, r=matth…

…iaskrgr

Rollup of 7 pull requests

Successful merges:

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

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

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));

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,
                     );
                 }

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,
                     );
                 }

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];

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,
                 );

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
     }
 

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.

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)]

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.

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;

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 {

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");

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);
     }

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();

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();