Auto merge of #112465 - GuillaumeGomez:rollup-gyh5buc, r=GuillaumeGomez

Rollup of 3 pull requests

Successful merges:

 - #112260 (Improve document of `unsafe_code` lint)
 - #112429 ([rustdoc] List matching impls on type aliases)
 - #112442 (Deduplicate identical region constraints in new solver)

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

compiler/rustc_lint/src/builtin.rs

@@ -286,7 +286,9 @@ impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
 }
 
 declare_lint! {
-    /// The `unsafe_code` lint catches usage of `unsafe` code.
+    /// The `unsafe_code` lint catches usage of `unsafe` code and other
+    /// potentially unsound constructs like `no_mangle`, `export_name`,
+    /// and `link_section`.
     ///
     /// ### Example
     ///
@@ -297,17 +299,29 @@ declare_lint! {
     ///
     ///     }
     /// }
+    ///
+    /// #[no_mangle]
+    /// fn func_0() { }
+    ///
+    /// #[export_name = "exported_symbol_name"]
+    /// pub fn name_in_rust() { }
+    ///
+    /// #[no_mangle]
+    /// #[link_section = ".example_section"]
+    /// pub static VAR1: u32 = 1;
     /// ```
     ///
     /// {{produces}}
     ///
     /// ### Explanation
     ///
-    /// This lint is intended to restrict the usage of `unsafe`, which can be
-    /// difficult to use correctly.
+    /// This lint is intended to restrict the usage of `unsafe` blocks and other
+    /// constructs (including, but not limited to `no_mangle`, `link_section`
+    /// and `export_name` attributes) wrong usage of which causes undefined
+    /// behavior.
     UNSAFE_CODE,
     Allow,
-    "usage of `unsafe` code"
+    "usage of `unsafe` code and other potentially unsound constructs"
 }
 
 declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -11,6 +11,7 @@
 use super::{CanonicalInput, Certainty, EvalCtxt, Goal};
 use crate::solve::canonicalize::{CanonicalizeMode, Canonicalizer};
 use crate::solve::{CanonicalResponse, QueryResult, Response};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_index::IndexVec;
 use rustc_infer::infer::canonical::query_response::make_query_region_constraints;
 use rustc_infer::infer::canonical::CanonicalVarValues;
@@ -147,7 +148,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         // Cannot use `take_registered_region_obligations` as we may compute the response
         // inside of a `probe` whenever we have multiple choices inside of the solver.
         let region_obligations = self.infcx.inner.borrow().region_obligations().to_owned();
-        let region_constraints = self.infcx.with_region_constraints(|region_constraints| {
+        let mut region_constraints = self.infcx.with_region_constraints(|region_constraints| {
             make_query_region_constraints(
                 self.tcx(),
                 region_obligations
@@ -157,6 +158,9 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             )
         });
 
+        let mut seen = FxHashSet::default();
+        region_constraints.outlives.retain(|outlives| seen.insert(*outlives));
+
         let mut opaque_types = self.infcx.clone_opaque_types_for_query_response();
         // Only return opaque type keys for newly-defined opaques
         opaque_types.retain(|(a, _)| {

library/core/src/ptr/mut_ptr.rs

@@ -106,7 +106,7 @@ impl<T: ?Sized> *mut T {
     /// with [`cast_mut`] on `*const T` and may have documentation value if used instead of implicit
     /// coercion.
     ///
-    /// [`cast_mut`]: #method.cast_mut
+    /// [`cast_mut`]: pointer::cast_mut
     #[stable(feature = "ptr_const_cast", since = "1.65.0")]
     #[rustc_const_stable(feature = "ptr_const_cast", since = "1.65.0")]
     #[inline(always)]
@@ -117,7 +117,7 @@ impl<T: ?Sized> *mut T {
     /// Casts a pointer to its raw bits.
     ///
     /// This is equivalent to `as usize`, but is more specific to enhance readability.
-    /// The inverse method is [`from_bits`](#method.from_bits-1).
+    /// The inverse method is [`from_bits`](pointer#method.from_bits-1).
     ///
     /// In particular, `*p as usize` and `p as usize` will both compile for
     /// pointers to numeric types but do very different things, so using this
@@ -153,7 +153,7 @@ impl<T: ?Sized> *mut T {
     /// Creates a pointer from its raw bits.
     ///
     /// This is equivalent to `as *mut T`, but is more specific to enhance readability.
-    /// The inverse method is [`to_bits`](#method.to_bits-1).
+    /// The inverse method is [`to_bits`](pointer#method.to_bits-1).
     ///
     /// # Examples
     ///
@@ -303,7 +303,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// For the mutable counterpart see [`as_mut`].
     ///
-    /// [`as_uninit_ref`]: #method.as_uninit_ref-1
+    /// [`as_uninit_ref`]: pointer#method.as_uninit_ref-1
     /// [`as_mut`]: #method.as_mut
     ///
     /// # Safety
@@ -369,7 +369,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// For the mutable counterpart see [`as_uninit_mut`].
     ///
-    /// [`as_ref`]: #method.as_ref-1
+    /// [`as_ref`]: pointer#method.as_ref-1
     /// [`as_uninit_mut`]: #method.as_uninit_mut
     ///
     /// # Safety
@@ -624,7 +624,7 @@ impl<T: ?Sized> *mut T {
     /// For the shared counterpart see [`as_ref`].
     ///
     /// [`as_uninit_mut`]: #method.as_uninit_mut
-    /// [`as_ref`]: #method.as_ref-1
+    /// [`as_ref`]: pointer#method.as_ref-1
     ///
     /// # Safety
     ///
@@ -689,7 +689,7 @@ impl<T: ?Sized> *mut T {
     /// For the shared counterpart see [`as_uninit_ref`].
     ///
     /// [`as_mut`]: #method.as_mut
-    /// [`as_uninit_ref`]: #method.as_uninit_ref-1
+    /// [`as_uninit_ref`]: pointer#method.as_uninit_ref-1
     ///
     /// # Safety
     ///
@@ -779,7 +779,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// This function is the inverse of [`offset`].
     ///
-    /// [`offset`]: #method.offset-1
+    /// [`offset`]: pointer#method.offset-1
     ///
     /// # Safety
     ///
@@ -2051,7 +2051,7 @@ impl<T> *mut [T] {
     ///
     /// For the mutable counterpart see [`as_uninit_slice_mut`].
     ///
-    /// [`as_ref`]: #method.as_ref-1
+    /// [`as_ref`]: pointer#method.as_ref-1
     /// [`as_uninit_slice_mut`]: #method.as_uninit_slice_mut
     ///
     /// # Safety

src/librustdoc/html/render/mod.rs

@@ -53,12 +53,15 @@ use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::{DefId, DefIdSet};
 use rustc_hir::Mutability;
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::traits::{Obligation, ObligationCause};
 use rustc_middle::middle::stability;
-use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{ParamEnv, TyCtxt};
 use rustc_span::{
     symbol::{sym, Symbol},
     BytePos, FileName, RealFileName,
 };
+use rustc_trait_selection::traits::ObligationCtxt;
 use serde::ser::{SerializeMap, SerializeSeq};
 use serde::{Serialize, Serializer};
 
@@ -1112,28 +1115,76 @@ fn render_assoc_items<'a, 'cx: 'a>(
     containing_item: &'a clean::Item,
     it: DefId,
     what: AssocItemRender<'a>,
+    aliased_type: Option<DefId>,
 ) -> impl fmt::Display + 'a + Captures<'cx> {
     let mut derefs = DefIdSet::default();
     derefs.insert(it);
     display_fn(move |f| {
-        render_assoc_items_inner(f, cx, containing_item, it, what, &mut derefs);
+        render_assoc_items_inner(f, cx, containing_item, it, what, &mut derefs, aliased_type);
         Ok(())
     })
 }
 
+/// Check whether `impl_def_id` may apply to *some instantiation* of `item_def_id`.
+fn is_valid_impl_for(tcx: TyCtxt<'_>, item_def_id: DefId, impl_def_id: DefId) -> bool {
+    let infcx = tcx.infer_ctxt().intercrate(true).build();
+    let ocx = ObligationCtxt::new(&infcx);
+    let param_env = ParamEnv::empty();
+
+    let alias_substs = infcx.fresh_substs_for_item(rustc_span::DUMMY_SP, item_def_id);
+    let alias_ty = tcx.type_of(item_def_id).subst(tcx, alias_substs);
+    let alias_bounds = tcx.predicates_of(item_def_id).instantiate(tcx, alias_substs);
+
+    let impl_substs = infcx.fresh_substs_for_item(rustc_span::DUMMY_SP, impl_def_id);
+    let impl_self_ty = tcx.type_of(impl_def_id).subst(tcx, impl_substs);
+    let impl_bounds = tcx.predicates_of(impl_def_id).instantiate(tcx, impl_substs);
+
+    if ocx.eq(&ObligationCause::dummy(), param_env, impl_self_ty, alias_ty).is_err() {
+        return false;
+    }
+    ocx.register_obligations(
+        alias_bounds
+            .iter()
+            .chain(impl_bounds)
+            .map(|(p, _)| Obligation::new(tcx, ObligationCause::dummy(), param_env, p)),
+    );
+
+    let errors = ocx.select_where_possible();
+    errors.is_empty()
+}
+
+// If `aliased_type` is `Some`, it means `it` is a type alias and `aliased_type` is the "actual"
+// type aliased behind `it`. It is used to check whether or not the implementation of the aliased
+// type can be displayed on the alias doc page.
 fn render_assoc_items_inner(
     mut w: &mut dyn fmt::Write,
     cx: &mut Context<'_>,
     containing_item: &clean::Item,
     it: DefId,
     what: AssocItemRender<'_>,
     derefs: &mut DefIdSet,
+    aliased_type: Option<DefId>,
 ) {
     info!("Documenting associated items of {:?}", containing_item.name);
     let shared = Rc::clone(&cx.shared);
     let cache = &shared.cache;
-    let Some(v) = cache.impls.get(&it) else { return };
-    let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
+    let empty = Vec::new();
+    let v = match cache.impls.get(&it) {
+        Some(v) => v,
+        None => &empty,
+    };
+    let v2 = match aliased_type {
+        Some(aliased_type) => cache.impls.get(&aliased_type).unwrap_or(&empty),
+        None => &empty,
+    };
+    if v.is_empty() && v2.is_empty() {
+        return;
+    }
+    let mut saw_impls = FxHashSet::default();
+    let (non_trait, traits): (Vec<_>, _) =
+        v.iter().chain(v2).partition(|i| i.inner_impl().trait_.is_none());
+    let tcx = cx.tcx();
+    let is_alias = aliased_type.is_some();
     if !non_trait.is_empty() {
         let mut tmp_buf = Buffer::html();
         let (render_mode, id, class_html) = match what {
@@ -1165,6 +1216,12 @@ fn render_assoc_items_inner(
         };
         let mut impls_buf = Buffer::html();
         for i in &non_trait {
+            if !saw_impls.insert(i.def_id()) {
+                continue;
+            }
+            if is_alias && !is_valid_impl_for(tcx, it, i.def_id()) {
+                continue;
+            }
             render_impl(
                 &mut impls_buf,
                 cx,
@@ -1193,9 +1250,14 @@ fn render_assoc_items_inner(
     if !traits.is_empty() {
         let deref_impl =
             traits.iter().find(|t| t.trait_did() == cx.tcx().lang_items().deref_trait());
-        if let Some(impl_) = deref_impl {
+        if let Some(impl_) = deref_impl &&
+            (!is_alias || is_valid_impl_for(tcx, it, impl_.def_id()))
+        {
             let has_deref_mut =
-                traits.iter().any(|t| t.trait_did() == cx.tcx().lang_items().deref_mut_trait());
+                traits.iter().any(|t| {
+                    t.trait_did() == cx.tcx().lang_items().deref_mut_trait() &&
+                    (!is_alias || is_valid_impl_for(tcx, it, t.def_id()))
+                });
             render_deref_methods(&mut w, cx, impl_, containing_item, has_deref_mut, derefs);
         }
 
@@ -1205,10 +1267,14 @@ fn render_assoc_items_inner(
             return;
         }
 
-        let (synthetic, concrete): (Vec<&Impl>, Vec<&Impl>) =
-            traits.into_iter().partition(|t| t.inner_impl().kind.is_auto());
-        let (blanket_impl, concrete): (Vec<&Impl>, _) =
-            concrete.into_iter().partition(|t| t.inner_impl().kind.is_blanket());
+        let (synthetic, concrete): (Vec<&Impl>, Vec<&Impl>) = traits
+            .into_iter()
+            .filter(|t| saw_impls.insert(t.def_id()))
+            .partition(|t| t.inner_impl().kind.is_auto());
+        let (blanket_impl, concrete): (Vec<&Impl>, _) = concrete
+            .into_iter()
+            .filter(|t| !is_alias || is_valid_impl_for(tcx, it, t.def_id()))
+            .partition(|t| t.inner_impl().kind.is_blanket());
 
         render_all_impls(w, cx, containing_item, &concrete, &synthetic, &blanket_impl);
     }
@@ -1247,10 +1313,10 @@ fn render_deref_methods(
                 return;
             }
         }
-        render_assoc_items_inner(&mut w, cx, container_item, did, what, derefs);
+        render_assoc_items_inner(&mut w, cx, container_item, did, what, derefs, None);
     } else if let Some(prim) = target.primitive_type() {
         if let Some(&did) = cache.primitive_locations.get(&prim) {
-            render_assoc_items_inner(&mut w, cx, container_item, did, what, derefs);
+            render_assoc_items_inner(&mut w, cx, container_item, did, what, derefs, None);
         }
     }
 }