Auto merge of rust-lang#123801 - cuviper:beta-next, r=cuviper

[beta] backports

- fix attribute validation on associated items in traits rust-lang#121545
- Only inspect user-written predicates for privacy concerns rust-lang#123377
- Check def id before calling `match_projection_projections` rust-lang#123471
- Restore `pred_known_to_hold_modulo_regions` rust-lang#123578
- Beta revert "Use OS thread name by default" rust-lang#123533

r? cuviper

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1527,6 +1527,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     generics,
                     body.as_deref(),
                 );
+                walk_list!(self, visit_attribute, &item.attrs);
                 self.visit_fn(kind, item.span, item.id);
             }
             AssocItemKind::Type(_) => {

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -119,16 +119,60 @@ pub fn predicates_for_generics<'tcx>(
 
 /// Determines whether the type `ty` is known to meet `bound` and
 /// returns true if so. Returns false if `ty` either does not meet
-/// `bound` or is not known to meet bound.
+/// `bound` or is not known to meet bound (note that this is
+/// conservative towards *no impl*, which is the opposite of the
+/// `evaluate` methods).
 pub fn type_known_to_meet_bound_modulo_regions<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     ty: Ty<'tcx>,
     def_id: DefId,
 ) -> bool {
     let trait_ref = ty::TraitRef::new(infcx.tcx, def_id, [ty]);
-    let obligation = Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, trait_ref);
-    infcx.predicate_must_hold_modulo_regions(&obligation)
+    pred_known_to_hold_modulo_regions(infcx, param_env, trait_ref)
+}
+
+/// FIXME(@lcnr): this function doesn't seem right and shouldn't exist?
+///
+/// Ping me on zulip if you want to use this method and need help with finding
+/// an appropriate replacement.
+#[instrument(level = "debug", skip(infcx, param_env, pred), ret)]
+fn pred_known_to_hold_modulo_regions<'tcx>(
+    infcx: &InferCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    pred: impl ToPredicate<'tcx>,
+) -> bool {
+    let obligation = Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, pred);
+
+    let result = infcx.evaluate_obligation_no_overflow(&obligation);
+    debug!(?result);
+
+    if result.must_apply_modulo_regions() {
+        true
+    } else if result.may_apply() {
+        // Sometimes obligations are ambiguous because the recursive evaluator
+        // is not smart enough, so we fall back to fulfillment when we're not certain
+        // that an obligation holds or not. Even still, we must make sure that
+        // the we do no inference in the process of checking this obligation.
+        let goal = infcx.resolve_vars_if_possible((obligation.predicate, obligation.param_env));
+        infcx.probe(|_| {
+            let ocx = ObligationCtxt::new(infcx);
+            ocx.register_obligation(obligation);
+
+            let errors = ocx.select_all_or_error();
+            match errors.as_slice() {
+                // Only known to hold if we did no inference.
+                [] => infcx.shallow_resolve(goal) == goal,
+
+                errors => {
+                    debug!(?errors);
+                    false
+                }
+            }
+        })
+    } else {
+        false
+    }
 }
 
 #[instrument(level = "debug", skip(tcx, elaborated_env))]

compiler/rustc_trait_selection/src/traits/project.rs

@@ -794,6 +794,9 @@ fn assemble_candidates_from_trait_def<'cx, 'tcx>(
             let Some(clause) = clause.as_projection_clause() else {
                 return ControlFlow::Continue(());
             };
+            if clause.projection_def_id() != obligation.predicate.def_id {
+                return ControlFlow::Continue(());
+            }
 
             let is_match =
                 selcx.infcx.probe(|_| selcx.match_projection_projections(obligation, clause, true));

compiler/rustc_ty_utils/src/sig_types.rs

@@ -13,6 +13,7 @@ pub trait SpannedTypeVisitor<'tcx> {
     fn visit(&mut self, span: Span, value: impl TypeVisitable<TyCtxt<'tcx>>) -> Self::Result;
 }
 
+#[instrument(level = "trace", skip(tcx, visitor))]
 pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
     tcx: TyCtxt<'tcx>,
     item: LocalDefId,
@@ -36,7 +37,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
             for (hir, ty) in hir_sig.inputs.iter().zip(ty_sig.inputs().iter()) {
                 try_visit!(visitor.visit(hir.span, ty.map_bound(|x| *x)));
             }
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
@@ -54,7 +55,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 // Associated types in traits don't necessarily have a type that we can visit
                 try_visit!(visitor.visit(ty.span, tcx.type_of(item).instantiate_identity()));
             }
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
@@ -76,7 +77,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 let ty = field.ty(tcx, args);
                 try_visit!(visitor.visit(span, ty));
             }
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
@@ -95,12 +96,12 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 _ => tcx.def_span(item),
             };
             try_visit!(visitor.visit(span, tcx.type_of(item).instantiate_identity()));
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
         DefKind::TraitAlias | DefKind::Trait => {
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }

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, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -71,10 +71,6 @@ 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, CString},
+    ffi::CStr,
     hint, io,
     mem::ManuallyDrop,
     num::NonZero,
@@ -204,10 +204,6 @@ 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, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -133,10 +133,6 @@ 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, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -101,10 +101,6 @@ 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, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
 use crate::ptr::NonNull;
@@ -23,10 +23,6 @@ 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();

library/std/src/sys/pal/unix/thread.rs

@@ -1,5 +1,5 @@
 use crate::cmp;
-use crate::ffi::{CStr, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -225,44 +225,6 @@ 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();

library/std/src/sys/pal/unsupported/thread.rs

@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::{CStr, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -22,10 +22,6 @@ impl Thread {
         // nope
     }
 
-    pub fn get_name() -> Option<CString> {
-        None
-    }
-
     pub fn sleep(_dur: Duration) {
         panic!("can't sleep");
     }

library/std/src/sys/pal/wasi/thread.rs

@@ -1,4 +1,4 @@
-use crate::ffi::{CStr, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -134,10 +134,6 @@ 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);

library/std/src/sys/pal/wasm/atomics/thread.rs

@@ -1,5 +1,4 @@
 use crate::ffi::CStr;
-use crate::ffi::CString;
 use crate::io;
 use crate::num::NonZero;
 use crate::sys::unsupported;
@@ -18,9 +17,6 @@ impl Thread {
     pub fn yield_now() {}
 
     pub fn set_name(_name: &CStr) {}
-    pub fn get_name() -> Option<CString> {
-        None
-    }
 
     pub fn sleep(dur: Duration) {
         use crate::arch::wasm32;

library/std/src/sys/pal/windows/thread.rs

@@ -9,7 +9,6 @@ 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;
@@ -68,29 +67,6 @@ 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 {

library/std/src/sys/pal/xous/thread.rs

@@ -1,4 +1,4 @@
-use crate::ffi::{CStr, CString};
+use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
 use crate::os::xous::ffi::{
@@ -113,10 +113,6 @@ 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