Rollup of 8 pull requests

Cargo.lock

@@ -4728,6 +4728,7 @@ version = "0.0.0"
 dependencies = [
  "arrayvec",
  "askama",
+ "atty",
  "expect-test",
  "itertools 0.9.0",
  "minifier",

compiler/rustc_feature/src/builtin_attrs.rs

@@ -623,6 +623,11 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, lang_items,
         "language items are subject to change",
     ),
+    rustc_attr!(
+        rustc_pass_by_value, Normal,
+        template!(Word), WarnFollowing,
+        "#[rustc_pass_by_value] is used to mark types that must be passed by value instead of reference."
+    ),
     BuiltinAttribute {
         name: sym::rustc_diagnostic_item,
         type_: Normal,

compiler/rustc_index/src/lib.rs

@@ -9,7 +9,3 @@
 pub mod bit_set;
 pub mod interval;
 pub mod vec;
-
-// FIXME(#56935): Work around ICEs during cross-compilation.
-#[allow(unused)]
-extern crate rustc_macros;

compiler/rustc_infer/src/infer/outlives/obligations.rs

@@ -164,7 +164,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
             "cannot process registered region obligations in a snapshot"
         );
 
-        debug!("process_registered_region_obligations()");
+        debug!(?param_env, "process_registered_region_obligations()");
 
         let my_region_obligations = self.take_registered_region_obligations();
 
@@ -356,6 +356,8 @@ where
         let trait_bounds: Vec<_> =
             self.verify_bound.projection_declared_bounds_from_trait(projection_ty).collect();
 
+        debug!(?trait_bounds);
+
         // Compute the bounds we can derive from the environment. This
         // is an "approximate" match -- in some cases, these bounds
         // may not apply.

compiler/rustc_infer/src/traits/util.rs

@@ -241,10 +241,19 @@ impl<'tcx> Elaborator<'tcx> {
 
                             Component::UnresolvedInferenceVariable(_) => None,
 
-                            Component::Projection(_) | Component::EscapingProjection(_) => {
-                                // We can probably do more here. This
-                                // corresponds to a case like `<T as
-                                // Foo<'a>>::U: 'b`.
+                            Component::Projection(projection) => {
+                                // We might end up here if we have `Foo<<Bar as Baz>::Assoc>: 'a`.
+                                // With this, we can deduce that `<Bar as Baz>::Assoc: 'a`.
+                                let ty =
+                                    tcx.mk_projection(projection.item_def_id, projection.substs);
+                                Some(ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
+                                    ty, r_min,
+                                )))
+                            }
+
+                            Component::EscapingProjection(_) => {
+                                // We might be able to do more here, but we don't
+                                // want to deal with escaping vars right now.
                                 None
                             }
                         })

compiler/rustc_lint/src/internal.rs

@@ -5,10 +5,7 @@ use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext}
 use rustc_ast as ast;
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
-use rustc_hir::{
-    GenericArg, HirId, Item, ItemKind, MutTy, Mutability, Node, Path, PathSegment, QPath, Ty,
-    TyKind,
-};
+use rustc_hir::{GenericArg, HirId, Item, ItemKind, Node, Path, PathSegment, QPath, Ty, TyKind};
 use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::hygiene::{ExpnKind, MacroKind};
@@ -58,13 +55,6 @@ declare_tool_lint! {
     report_in_external_macro: true
 }
 
-declare_tool_lint! {
-    pub rustc::TY_PASS_BY_REFERENCE,
-    Allow,
-    "passing `Ty` or `TyCtxt` by reference",
-    report_in_external_macro: true
-}
-
 declare_tool_lint! {
     pub rustc::USAGE_OF_QUALIFIED_TY,
     Allow,
@@ -74,7 +64,6 @@ declare_tool_lint! {
 
 declare_lint_pass!(TyTyKind => [
     USAGE_OF_TY_TYKIND,
-    TY_PASS_BY_REFERENCE,
     USAGE_OF_QUALIFIED_TY,
 ]);
 
@@ -131,26 +120,6 @@ impl<'tcx> LateLintPass<'tcx> for TyTyKind {
                     }
                 }
             }
-            TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
-                if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
-                    if cx.tcx.impl_trait_ref(impl_did).is_some() {
-                        return;
-                    }
-                }
-                if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
-                    cx.struct_span_lint(TY_PASS_BY_REFERENCE, ty.span, |lint| {
-                        lint.build(&format!("passing `{}` by reference", t))
-                            .span_suggestion(
-                                ty.span,
-                                "try passing by value",
-                                t,
-                                // Changing type of function argument
-                                Applicability::MaybeIncorrect,
-                            )
-                            .emit();
-                    })
-                }
-            }
             _ => {}
         }
     }

compiler/rustc_lint/src/lib.rs

@@ -56,6 +56,7 @@ mod non_ascii_idents;
 mod non_fmt_panic;
 mod nonstandard_style;
 mod noop_method_call;
+mod pass_by_value;
 mod passes;
 mod redundant_semicolon;
 mod traits;
@@ -85,6 +86,7 @@ use non_ascii_idents::*;
 use non_fmt_panic::NonPanicFmt;
 use nonstandard_style::*;
 use noop_method_call::*;
+use pass_by_value::*;
 use redundant_semicolon::*;
 use traits::*;
 use types::*;
@@ -490,15 +492,17 @@ fn register_internals(store: &mut LintStore) {
     store.register_late_pass(|| Box::new(ExistingDocKeyword));
     store.register_lints(&TyTyKind::get_lints());
     store.register_late_pass(|| Box::new(TyTyKind));
+    store.register_lints(&PassByValue::get_lints());
+    store.register_late_pass(|| Box::new(PassByValue));
     store.register_group(
         false,
         "rustc::internal",
         None,
         vec![
             LintId::of(DEFAULT_HASH_TYPES),
             LintId::of(USAGE_OF_TY_TYKIND),
+            LintId::of(PASS_BY_VALUE),
             LintId::of(LINT_PASS_IMPL_WITHOUT_MACRO),
-            LintId::of(TY_PASS_BY_REFERENCE),
             LintId::of(USAGE_OF_QUALIFIED_TY),
             LintId::of(EXISTING_DOC_KEYWORD),
         ],

compiler/rustc_lint/src/pass_by_value.rs

@@ -0,0 +1,94 @@
+use crate::{LateContext, LateLintPass, LintContext};
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_hir::def::Res;
+use rustc_hir::{GenericArg, PathSegment, QPath, TyKind};
+use rustc_middle::ty;
+use rustc_span::symbol::sym;
+
+declare_tool_lint! {
+    /// The `rustc_pass_by_value` lint marks a type with `#[rustc_pass_by_value]` requiring it to always be passed by value.
+    /// This is usually used for types that are thin wrappers around references, so there is no benefit to an extra
+    /// layer of indirection. (Example: `Ty` which is a reference to a `TyS`)
+    pub rustc::PASS_BY_VALUE,
+    Warn,
+    "pass by reference of a type flagged as `#[rustc_pass_by_value]`",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(PassByValue => [PASS_BY_VALUE]);
+
+impl<'tcx> LateLintPass<'tcx> for PassByValue {
+    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx hir::Ty<'tcx>) {
+        match &ty.kind {
+            TyKind::Rptr(_, hir::MutTy { ty: inner_ty, mutbl: hir::Mutability::Not }) => {
+                if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
+                    if cx.tcx.impl_trait_ref(impl_did).is_some() {
+                        return;
+                    }
+                }
+                if let Some(t) = path_for_pass_by_value(cx, &inner_ty) {
+                    cx.struct_span_lint(PASS_BY_VALUE, ty.span, |lint| {
+                        lint.build(&format!("passing `{}` by reference", t))
+                            .span_suggestion(
+                                ty.span,
+                                "try passing by value",
+                                t,
+                                // Changing type of function argument
+                                Applicability::MaybeIncorrect,
+                            )
+                            .emit();
+                    })
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+fn path_for_pass_by_value(cx: &LateContext<'_>, ty: &hir::Ty<'_>) -> Option<String> {
+    if let TyKind::Path(QPath::Resolved(_, path)) = &ty.kind {
+        match path.res {
+            Res::Def(_, def_id) if cx.tcx.has_attr(def_id, sym::rustc_pass_by_value) => {
+                let name = cx.tcx.item_name(def_id).to_ident_string();
+                let path_segment = path.segments.last().unwrap();
+                return Some(format!("{}{}", name, gen_args(cx, path_segment)));
+            }
+            Res::SelfTy(None, Some((did, _))) => {
+                if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
+                    if cx.tcx.has_attr(adt.did, sym::rustc_pass_by_value) {
+                        return Some(cx.tcx.def_path_str_with_substs(adt.did, substs));
+                    }
+                }
+            }
+            _ => (),
+        }
+    }
+
+    None
+}
+
+fn gen_args(cx: &LateContext<'_>, segment: &PathSegment<'_>) -> String {
+    if let Some(args) = &segment.args {
+        let params = args
+            .args
+            .iter()
+            .map(|arg| match arg {
+                GenericArg::Lifetime(lt) => lt.name.ident().to_string(),
+                GenericArg::Type(ty) => {
+                    cx.tcx.sess.source_map().span_to_snippet(ty.span).unwrap_or_default()
+                }
+                GenericArg::Const(c) => {
+                    cx.tcx.sess.source_map().span_to_snippet(c.span).unwrap_or_default()
+                }
+                GenericArg::Infer(_) => String::from("_"),
+            })
+            .collect::<Vec<_>>();
+
+        if !params.is_empty() {
+            return format!("<{}>", params.join(", "));
+        }
+    }
+
+    String::new()
+}

compiler/rustc_middle/src/ty/context.rs

@@ -961,6 +961,7 @@ pub struct FreeRegionInfo {
 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/ty.html
 #[derive(Copy, Clone)]
 #[rustc_diagnostic_item = "TyCtxt"]
+#[cfg_attr(not(bootstrap), rustc_pass_by_value)]
 pub struct TyCtxt<'tcx> {
     gcx: &'tcx GlobalCtxt<'tcx>,
 }

compiler/rustc_middle/src/ty/mod.rs

@@ -464,6 +464,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> {
 }
 
 #[rustc_diagnostic_item = "Ty"]
+#[cfg_attr(not(bootstrap), rustc_pass_by_value)]
 pub type Ty<'tcx> = &'tcx TyS<'tcx>;
 
 impl ty::EarlyBoundRegion {

compiler/rustc_passes/src/check_attr.rs

@@ -114,6 +114,7 @@ impl CheckAttrVisitor<'_> {
                 }
                 sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target),
                 sym::must_use => self.check_must_use(hir_id, &attr, span, target),
+                sym::rustc_pass_by_value => self.check_pass_by_value(&attr, span, target),
                 sym::rustc_const_unstable
                 | sym::rustc_const_stable
                 | sym::unstable
@@ -1066,6 +1067,24 @@ impl CheckAttrVisitor<'_> {
         is_valid
     }
 
+    /// Warns against some misuses of `#[pass_by_value]`
+    fn check_pass_by_value(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
+        match target {
+            Target::Struct | Target::Enum | Target::TyAlias => true,
+            _ => {
+                self.tcx
+                    .sess
+                    .struct_span_err(
+                        attr.span,
+                        "`pass_by_value` attribute should be applied to a struct, enum or type alias.",
+                    )
+                    .span_label(*span, "is not a struct, enum or type alias")
+                    .emit();
+                false
+            }
+        }
+    }
+
     /// Warns against some misuses of `#[must_use]`
     fn check_must_use(
         &self,

compiler/rustc_span/src/symbol.rs

@@ -1147,6 +1147,7 @@ symbols! {
         rustc_paren_sugar,
         rustc_partition_codegened,
         rustc_partition_reused,
+        rustc_pass_by_value,
         rustc_peek,
         rustc_peek_definite_init,
         rustc_peek_liveness,

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -206,7 +206,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             })?);
 
             if let ty::Projection(..) = placeholder_self_ty.kind() {
-                for predicate in tcx.predicates_of(def_id).instantiate_own(tcx, substs).predicates {
+                let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs).predicates;
+                debug!(?predicates, "projection predicates");
+                for predicate in predicates {
                     let normalized = normalize_with_depth_to(
                         self,
                         obligation.param_env,

library/alloc/tests/lib.rs

@@ -38,6 +38,7 @@
 #![feature(const_trait_impl)]
 #![feature(const_str_from_utf8)]
 #![feature(nonnull_slice_from_raw_parts)]
+#![feature(panic_update_hook)]
 
 use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};

library/alloc/tests/slice.rs

@@ -1783,12 +1783,11 @@ thread_local!(static SILENCE_PANIC: Cell<bool> = Cell::new(false));
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)] // no threads
 fn panic_safe() {
-    let prev = panic::take_hook();
-    panic::set_hook(Box::new(move |info| {
+    panic::update_hook(move |prev, info| {
         if !SILENCE_PANIC.with(|s| s.get()) {
             prev(info);
         }
-    }));
+    });
 
     let mut rng = thread_rng();
 

library/proc_macro/src/bridge/client.rs

@@ -310,16 +310,15 @@ impl Bridge<'_> {
         // NB. the server can't do this because it may use a different libstd.
         static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
         HIDE_PANICS_DURING_EXPANSION.call_once(|| {
-            let prev = panic::take_hook();
-            panic::set_hook(Box::new(move |info| {
+            panic::update_hook(move |prev, info| {
                 let show = BridgeState::with(|state| match state {
                     BridgeState::NotConnected => true,
                     BridgeState::Connected(_) | BridgeState::InUse => force_show_panics,
                 });
                 if show {
                     prev(info)
                 }
-            }));
+            });
         });
 
         BRIDGE_STATE.with(|state| state.set(BridgeState::Connected(self), f))

library/proc_macro/src/lib.rs

@@ -30,6 +30,7 @@
 #![feature(restricted_std)]
 #![feature(rustc_attrs)]
 #![feature(min_specialization)]
+#![feature(panic_update_hook)]
 #![recursion_limit = "256"]
 
 #[unstable(feature = "proc_macro_internals", issue = "27812")]

library/std/src/panic.rs

@@ -36,6 +36,9 @@ pub use core::panic::panic_2021;
 #[stable(feature = "panic_hooks", since = "1.10.0")]
 pub use crate::panicking::{set_hook, take_hook};
 
+#[unstable(feature = "panic_update_hook", issue = "92649")]
+pub use crate::panicking::update_hook;
+
 #[stable(feature = "panic_hooks", since = "1.10.0")]
 pub use core::panic::{Location, PanicInfo};