Auto merge of rust-lang#123027 - matthiaskrgr:rollup-nng7h3z, r=matth…

…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#120557 (Add rust-lldb pretty printing for Path and PathBuf)
 - rust-lang#122802 (Provide structured suggestion for unconstrained generic constant)
 - rust-lang#122858 (Tweak `parse_dot_suffix_expr`)
 - rust-lang#122990 (Clarify transmute example)
 - rust-lang#122995 (Clean up unnecessary headers/flags in coverage mir-opt tests)
 - rust-lang#123003 (CFI: Handle dyn with no principal)
 - rust-lang#123005 (CFI: Support complex receivers)
 - rust-lang#123020 (Temporarily remove nnethercote from the review rotation.)

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

Cargo.lock

@@ -4634,6 +4634,7 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_target",
+ "rustc_trait_selection",
  "tracing",
  "twox-hash",
 ]

compiler/rustc_parse/src/parser/expr.rs

@@ -16,7 +16,6 @@ use core::mem;
 use core::ops::ControlFlow;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
-use rustc_ast::tokenstream::Spacing;
 use rustc_ast::util::case::Case;
 use rustc_ast::util::classify;
 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
@@ -999,13 +998,57 @@ impl<'a> Parser<'a> {
     }
 
     pub fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
+        // At this point we've consumed something like `expr.` and `self.token` holds the token
+        // after the dot.
         match self.token.uninterpolate().kind {
             token::Ident(..) => self.parse_dot_suffix(base, lo),
             token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
-                Ok(self.parse_expr_tuple_field_access(lo, base, symbol, suffix, None))
+                let ident_span = self.token.span;
+                self.bump();
+                Ok(self.mk_expr_tuple_field_access(lo, ident_span, base, symbol, suffix))
             }
             token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
-                Ok(self.parse_expr_tuple_field_access_float(lo, base, symbol, suffix))
+                Ok(match self.break_up_float(symbol, self.token.span) {
+                    // 1e2
+                    DestructuredFloat::Single(sym, _sp) => {
+                        // `foo.1e2`: a single complete dot access, fully consumed. We end up with
+                        // the `1e2` token in `self.prev_token` and the following token in
+                        // `self.token`.
+                        let ident_span = self.token.span;
+                        self.bump();
+                        self.mk_expr_tuple_field_access(lo, ident_span, base, sym, suffix)
+                    }
+                    // 1.
+                    DestructuredFloat::TrailingDot(sym, ident_span, dot_span) => {
+                        // `foo.1.`: a single complete dot access and the start of another.
+                        // We end up with the `sym` (`1`) token in `self.prev_token` and a dot in
+                        // `self.token`.
+                        assert!(suffix.is_none());
+                        self.token = Token::new(token::Ident(sym, IdentIsRaw::No), ident_span);
+                        self.bump_with((Token::new(token::Dot, dot_span), self.token_spacing));
+                        self.mk_expr_tuple_field_access(lo, ident_span, base, sym, None)
+                    }
+                    // 1.2 | 1.2e3
+                    DestructuredFloat::MiddleDot(
+                        sym1,
+                        ident1_span,
+                        _dot_span,
+                        sym2,
+                        ident2_span,
+                    ) => {
+                        // `foo.1.2` (or `foo.1.2e3`): two complete dot accesses. We end up with
+                        // the `sym2` (`2` or `2e3`) token in `self.prev_token` and the following
+                        // token in `self.token`.
+                        let next_token2 =
+                            Token::new(token::Ident(sym2, IdentIsRaw::No), ident2_span);
+                        self.bump_with((next_token2, self.token_spacing));
+                        self.bump();
+                        let base1 =
+                            self.mk_expr_tuple_field_access(lo, ident1_span, base, sym1, None);
+                        self.mk_expr_tuple_field_access(lo, ident2_span, base1, sym2, suffix)
+                    }
+                    DestructuredFloat::Error => base,
+                })
             }
             _ => {
                 self.error_unexpected_after_dot();
@@ -1119,41 +1162,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_expr_tuple_field_access_float(
-        &mut self,
-        lo: Span,
-        base: P<Expr>,
-        float: Symbol,
-        suffix: Option<Symbol>,
-    ) -> P<Expr> {
-        match self.break_up_float(float, self.token.span) {
-            // 1e2
-            DestructuredFloat::Single(sym, _sp) => {
-                self.parse_expr_tuple_field_access(lo, base, sym, suffix, None)
-            }
-            // 1.
-            DestructuredFloat::TrailingDot(sym, ident_span, dot_span) => {
-                assert!(suffix.is_none());
-                self.token = Token::new(token::Ident(sym, IdentIsRaw::No), ident_span);
-                let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
-                self.parse_expr_tuple_field_access(lo, base, sym, None, Some(next_token))
-            }
-            // 1.2 | 1.2e3
-            DestructuredFloat::MiddleDot(symbol1, ident1_span, dot_span, symbol2, ident2_span) => {
-                self.token = Token::new(token::Ident(symbol1, IdentIsRaw::No), ident1_span);
-                // This needs to be `Spacing::Alone` to prevent regressions.
-                // See issue #76399 and PR #76285 for more details
-                let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
-                let base1 =
-                    self.parse_expr_tuple_field_access(lo, base, symbol1, None, Some(next_token1));
-                let next_token2 = Token::new(token::Ident(symbol2, IdentIsRaw::No), ident2_span);
-                self.bump_with((next_token2, self.token_spacing)); // `.`
-                self.parse_expr_tuple_field_access(lo, base1, symbol2, suffix, None)
-            }
-            DestructuredFloat::Error => base,
-        }
-    }
-
     /// Parse the field access used in offset_of, matched by `$(e:expr)+`.
     /// Currently returns a list of idents. However, it should be possible in
     /// future to also do array indices, which might be arbitrary expressions.
@@ -1255,24 +1263,18 @@ impl<'a> Parser<'a> {
         Ok(fields.into_iter().collect())
     }
 
-    fn parse_expr_tuple_field_access(
+    fn mk_expr_tuple_field_access(
         &mut self,
         lo: Span,
+        ident_span: Span,
         base: P<Expr>,
         field: Symbol,
         suffix: Option<Symbol>,
-        next_token: Option<(Token, Spacing)>,
     ) -> P<Expr> {
-        match next_token {
-            Some(next_token) => self.bump_with(next_token),
-            None => self.bump(),
-        }
-        let span = self.prev_token.span;
-        let field = ExprKind::Field(base, Ident::new(field, span));
         if let Some(suffix) = suffix {
-            self.expect_no_tuple_index_suffix(span, suffix);
+            self.expect_no_tuple_index_suffix(ident_span, suffix);
         }
-        self.mk_expr(lo.to(span), field)
+        self.mk_expr(lo.to(ident_span), ExprKind::Field(base, Ident::new(field, ident_span)))
     }
 
     /// Parse a function call expression, `expr(...)`.

compiler/rustc_symbol_mangling/Cargo.toml

@@ -15,6 +15,7 @@ rustc_middle = { path = "../rustc_middle" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
+rustc_trait_selection = { path = "../rustc_trait_selection" }
 tracing = "0.1"
 twox-hash = "1.6.3"
 # tidy-alphabetical-end

compiler/rustc_symbol_mangling/src/lib.rs

@@ -90,6 +90,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
+#![feature(let_chains)]
 #![allow(internal_features)]
 
 #[macro_use]

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -11,6 +11,7 @@ use rustc_data_structures::base_n;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
 use rustc_middle::ty::layout::IntegerExt;
+use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{
     self, Const, ExistentialPredicate, FloatTy, FnSig, Instance, IntTy, List, Region, RegionKind,
     TermKind, Ty, TyCtxt, UintTy,
@@ -21,7 +22,9 @@ use rustc_span::sym;
 use rustc_target::abi::call::{Conv, FnAbi, PassMode};
 use rustc_target::abi::Integer;
 use rustc_target::spec::abi::Abi;
+use rustc_trait_selection::traits;
 use std::fmt::Write as _;
+use std::iter;
 
 use crate::typeid::TypeIdOptions;
 
@@ -747,9 +750,8 @@ fn transform_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
     predicates: &List<ty::PolyExistentialPredicate<'tcx>>,
 ) -> &'tcx List<ty::PolyExistentialPredicate<'tcx>> {
-    let predicates: Vec<ty::PolyExistentialPredicate<'tcx>> = predicates
-        .iter()
-        .filter_map(|predicate| match predicate.skip_binder() {
+    tcx.mk_poly_existential_predicates_from_iter(predicates.iter().filter_map(|predicate| {
+        match predicate.skip_binder() {
             ty::ExistentialPredicate::Trait(trait_ref) => {
                 let trait_ref = ty::TraitRef::identity(tcx, trait_ref.def_id);
                 Some(ty::Binder::dummy(ty::ExistentialPredicate::Trait(
@@ -758,9 +760,8 @@ fn transform_predicates<'tcx>(
             }
             ty::ExistentialPredicate::Projection(..) => None,
             ty::ExistentialPredicate::AutoTrait(..) => Some(predicate),
-        })
-        .collect();
-    tcx.mk_poly_existential_predicates(&predicates)
+        }
+    }))
 }
 
 /// Transforms args for being encoded and used in the substitution dictionary.
@@ -1115,51 +1116,46 @@ pub fn typeid_for_instance<'tcx>(
         instance.args = strip_receiver_auto(tcx, instance.args)
     }
 
+    if let Some(impl_id) = tcx.impl_of_method(instance.def_id())
+        && let Some(trait_ref) = tcx.impl_trait_ref(impl_id)
+    {
+        let impl_method = tcx.associated_item(instance.def_id());
+        let method_id = impl_method
+            .trait_item_def_id
+            .expect("Part of a trait implementation, but not linked to the def_id?");
+        let trait_method = tcx.associated_item(method_id);
+        if traits::is_vtable_safe_method(tcx, trait_ref.skip_binder().def_id, trait_method) {
+            // Trait methods will have a Self polymorphic parameter, where the concreteized
+            // implementatation will not. We need to walk back to the more general trait method
+            let trait_ref = tcx.instantiate_and_normalize_erasing_regions(
+                instance.args,
+                ty::ParamEnv::reveal_all(),
+                trait_ref,
+            );
+            let invoke_ty = trait_object_ty(tcx, ty::Binder::dummy(trait_ref));
+
+            // At the call site, any call to this concrete function through a vtable will be
+            // `Virtual(method_id, idx)` with appropriate arguments for the method. Since we have the
+            // original method id, and we've recovered the trait arguments, we can make the callee
+            // instance we're computing the alias set for match the caller instance.
+            //
+            // Right now, our code ignores the vtable index everywhere, so we use 0 as a placeholder.
+            // If we ever *do* start encoding the vtable index, we will need to generate an alias set
+            // based on which vtables we are putting this method into, as there will be more than one
+            // index value when supertraits are involved.
+            instance.def = ty::InstanceDef::Virtual(method_id, 0);
+            let abstract_trait_args =
+                tcx.mk_args_trait(invoke_ty, trait_ref.args.into_iter().skip(1));
+            instance.args = instance.args.rebase_onto(tcx, impl_id, abstract_trait_args);
+        }
+    }
+
     let fn_abi = tcx
         .fn_abi_of_instance(tcx.param_env(instance.def_id()).and((instance, ty::List::empty())))
         .unwrap_or_else(|instance| {
             bug!("typeid_for_instance: couldn't get fn_abi of instance {:?}", instance)
         });
 
-    // If this instance is a method and self is a reference, get the impl it belongs to
-    let impl_def_id = tcx.impl_of_method(instance.def_id());
-    if impl_def_id.is_some() && !fn_abi.args.is_empty() && fn_abi.args[0].layout.ty.is_ref() {
-        // If this impl is not an inherent impl, get the trait it implements
-        if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id.unwrap()) {
-            // Transform the concrete self into a reference to a trait object
-            let existential_predicate = trait_ref.map_bound(|trait_ref| {
-                ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef::erase_self_ty(
-                    tcx, trait_ref,
-                ))
-            });
-            let existential_predicates = tcx.mk_poly_existential_predicates(&[ty::Binder::dummy(
-                existential_predicate.skip_binder(),
-            )]);
-            // Is the concrete self mutable?
-            let self_ty = if fn_abi.args[0].layout.ty.is_mutable_ptr() {
-                Ty::new_mut_ref(
-                    tcx,
-                    tcx.lifetimes.re_erased,
-                    Ty::new_dynamic(tcx, existential_predicates, tcx.lifetimes.re_erased, ty::Dyn),
-                )
-            } else {
-                Ty::new_imm_ref(
-                    tcx,
-                    tcx.lifetimes.re_erased,
-                    Ty::new_dynamic(tcx, existential_predicates, tcx.lifetimes.re_erased, ty::Dyn),
-                )
-            };
-
-            // Replace the concrete self in an fn_abi clone by the reference to a trait object
-            let mut fn_abi = fn_abi.clone();
-            // HACK(rcvalle): It is okay to not replace or update the entire ArgAbi here because the
-            //   other fields are never used.
-            fn_abi.args[0].layout.ty = self_ty;
-
-            return typeid_for_fnabi(tcx, &fn_abi, options);
-        }
-    }
-
     typeid_for_fnabi(tcx, fn_abi, options)
 }
 
@@ -1171,14 +1167,50 @@ fn strip_receiver_auto<'tcx>(
     let ty::Dynamic(preds, lifetime, kind) = ty.kind() else {
         bug!("Tried to strip auto traits from non-dynamic type {ty}");
     };
-    let filtered_preds =
-        if preds.principal().is_some() {
+    let new_rcvr = if preds.principal().is_some() {
+        let filtered_preds =
             tcx.mk_poly_existential_predicates_from_iter(preds.into_iter().filter(|pred| {
                 !matches!(pred.skip_binder(), ty::ExistentialPredicate::AutoTrait(..))
-            }))
-        } else {
-            ty::List::empty()
-        };
-    let new_rcvr = Ty::new_dynamic(tcx, filtered_preds, *lifetime, *kind);
+            }));
+        Ty::new_dynamic(tcx, filtered_preds, *lifetime, *kind)
+    } else {
+        // If there's no principal type, re-encode it as a unit, since we don't know anything
+        // about it. This technically discards the knowledge that it was a type that was made
+        // into a trait object at some point, but that's not a lot.
+        tcx.types.unit
+    };
     tcx.mk_args_trait(new_rcvr, args.into_iter().skip(1))
 }
+
+fn trait_object_ty<'tcx>(tcx: TyCtxt<'tcx>, poly_trait_ref: ty::PolyTraitRef<'tcx>) -> Ty<'tcx> {
+    assert!(!poly_trait_ref.has_non_region_param());
+    let principal_pred = poly_trait_ref.map_bound(|trait_ref| {
+        ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref))
+    });
+    let mut assoc_preds: Vec<_> = traits::supertraits(tcx, poly_trait_ref)
+        .flat_map(|super_poly_trait_ref| {
+            tcx.associated_items(super_poly_trait_ref.def_id())
+                .in_definition_order()
+                .filter(|item| item.kind == ty::AssocKind::Type)
+                .map(move |assoc_ty| {
+                    super_poly_trait_ref.map_bound(|super_trait_ref| {
+                        let alias_ty = ty::AliasTy::new(tcx, assoc_ty.def_id, super_trait_ref.args);
+                        let resolved = tcx.normalize_erasing_regions(
+                            ty::ParamEnv::reveal_all(),
+                            alias_ty.to_ty(tcx),
+                        );
+                        ty::ExistentialPredicate::Projection(ty::ExistentialProjection {
+                            def_id: assoc_ty.def_id,
+                            args: ty::ExistentialTraitRef::erase_self_ty(tcx, super_trait_ref).args,
+                            term: resolved.into(),
+                        })
+                    })
+                })
+        })
+        .collect();
+    assoc_preds.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder()));
+    let preds = tcx.mk_poly_existential_predicates_from_iter(
+        iter::once(principal_pred).chain(assoc_preds.into_iter()),
+    );
+    Ty::new_dynamic(tcx, preds, tcx.lifetimes.re_erased, ty::Dyn)
+}

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -3536,12 +3536,39 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     let mut err =
                         self.dcx().struct_span_err(span, "unconstrained generic constant");
                     let const_span = self.tcx.def_span(uv.def);
+
+                    let const_ty = self.tcx.type_of(uv.def).instantiate(self.tcx, uv.args);
+                    let cast = if const_ty != self.tcx.types.usize { " as usize" } else { "" };
+                    let msg = "try adding a `where` bound";
                     match self.tcx.sess.source_map().span_to_snippet(const_span) {
-                            Ok(snippet) => err.help(format!(
-                                "try adding a `where` bound using this expression: `where [(); {snippet}]:`"
-                            )),
-                            _ => err.help("consider adding a `where` bound using this expression"),
-                        };
+                        Ok(snippet) => {
+                            let code = format!("[(); {snippet}{cast}]:");
+                            let def_id = if let ObligationCauseCode::CompareImplItemObligation {
+                                trait_item_def_id,
+                                ..
+                            } = obligation.cause.code()
+                            {
+                                trait_item_def_id.as_local()
+                            } else {
+                                Some(obligation.cause.body_id)
+                            };
+                            if let Some(def_id) = def_id
+                                && let Some(generics) = self.tcx.hir().get_generics(def_id)
+                            {
+                                err.span_suggestion_verbose(
+                                    generics.tail_span_for_predicate_suggestion(),
+                                    msg,
+                                    format!("{} {code}", generics.add_where_or_trailing_comma()),
+                                    Applicability::MaybeIncorrect,
+                                );
+                            } else {
+                                err.help(format!("{msg}: where {code}"));
+                            };
+                        }
+                        _ => {
+                            err.help(msg);
+                        }
+                    };
                     Ok(err)
                 }
                 ty::ConstKind::Expr(_) => {