Auto merge of rust-lang#126726 - matthiaskrgr:rollup-ppe8ve3, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - rust-lang#126620 (Actually taint InferCtxt when a fulfillment error is emitted)
 - rust-lang#126649 (Fix `feature = "nightly"` in the new trait solver)
 - rust-lang#126652 (Clarify that anonymous consts still do introduce a new scope)
 - rust-lang#126703 (reword the hint::blackbox non-guarantees)
 - rust-lang#126708 (Minimize `can_begin_literal_maybe_minus` usage)

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

Author: bors

Diff for: Cargo.lock

@@ -4905,6 +4905,7 @@ version = "0.0.0"
 dependencies = [
  "bitflags 2.5.0",
  "derivative",
+ "indexmap",
  "rustc_ast_ir",
  "rustc_data_structures",
  "rustc_index",

Diff for: compiler/rustc_ast/src/token.rs

@@ -558,9 +558,10 @@ impl Token {
     /// Returns `true` if the token can appear at the start of a const param.
     pub fn can_begin_const_arg(&self) -> bool {
         match self.kind {
-            OpenDelim(Delimiter::Brace) => true,
+            OpenDelim(Delimiter::Brace) | Literal(..) | BinOp(Minus) => true,
+            Ident(name, IdentIsRaw::No) if name.is_bool_lit() => true,
             Interpolated(ref nt) => matches!(&**nt, NtExpr(..) | NtBlock(..) | NtLiteral(..)),
-            _ => self.can_begin_literal_maybe_minus(),
+            _ => false,
         }
     }
 
@@ -620,6 +621,21 @@ impl Token {
         }
     }
 
+    pub fn can_begin_string_literal(&self) -> bool {
+        match self.uninterpolate().kind {
+            Literal(..) => true,
+            Interpolated(ref nt) => match &**nt {
+                NtLiteral(_) => true,
+                NtExpr(e) => match &e.kind {
+                    ast::ExprKind::Lit(_) => true,
+                    _ => false,
+                },
+                _ => false,
+            },
+            _ => false,
+        }
+    }
+
     /// A convenience function for matching on identifiers during parsing.
     /// Turns interpolated identifier (`$i: ident`) or lifetime (`$l: lifetime`) token
     /// into the regular identifier or lifetime token it refers to,

Diff for: compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -119,16 +119,7 @@ where
 
     let errors = wfcx.select_all_or_error();
     if !errors.is_empty() {
-        let err = infcx.err_ctxt().report_fulfillment_errors(errors);
-        if tcx.dcx().has_errors().is_some() {
-            return Err(err);
-        } else {
-            // HACK(oli-obk): tests/ui/specialization/min_specialization/specialize_on_type_error.rs
-            // causes an delayed bug during normalization, without reporting an error, so we need
-            // to act as if no error happened, in order to let our callers continue and report an
-            // error later in check_impl_items_against_trait.
-            return Ok(());
-        }
+        return Err(infcx.err_ctxt().report_fulfillment_errors(errors));
     }
 
     debug!(?assumed_wf_types);

Diff for: compiler/rustc_hir_typeck/src/writeback.rs

@@ -793,7 +793,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
     }
 
     fn report_error(&self, p: impl Into<ty::GenericArg<'tcx>>) -> ErrorGuaranteed {
-        if let Some(guar) = self.fcx.dcx().has_errors() {
+        if let Some(guar) = self.fcx.tainted_by_errors() {
             guar
         } else {
             self.fcx

Diff for: compiler/rustc_lint/messages.ftl

@@ -550,7 +550,7 @@ lint_non_local_definitions_impl = non-local `impl` definition, `impl` blocks sho
     .with_trait = an `impl` is never scoped, even when it is nested inside an item, as it may impact type checking outside of that item, which can be the case if neither the trait or the self type are at the same nesting level as the `impl`
     .bounds = `impl` may be usable in bounds, etc. from outside the expression, which might e.g. make something constructible that previously wasn't, because it's still on a publicly-visible type
     .doctest = make this doc-test a standalone test with its own `fn main() {"{"} ... {"}"}`
-    .exception = items in an anonymous const item (`const _: () = {"{"} ... {"}"}`) are treated as in the same scope as the anonymous const's declaration
+    .exception = items in an anonymous const item (`const _: () = {"{"} ... {"}"}`) are treated as in the same scope as the anonymous const's declaration for the purpose of this lint
     .const_anon = use a const-anon item to suppress this lint
     .macro_to_change = the {$macro_kind} `{$macro_to_change}` defines the non-local `impl`, and may need to be changed
 

Diff for: compiler/rustc_next_trait_solver/Cargo.toml

@@ -7,7 +7,7 @@ edition = "2021"
 # tidy-alphabetical-start
 bitflags = "2.4.1"
 derivative = "2.2.0"
-rustc_ast_ir = { path = "../rustc_ast_ir" }
+rustc_ast_ir = { path = "../rustc_ast_ir", default-features = false }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }

Diff for: compiler/rustc_next_trait_solver/src/lib.rs

@@ -4,8 +4,6 @@
 //! but were uplifted in the process of making the new trait solver generic.
 //! So if you got to this crate from the old solver, it's totally normal.
 
-#![feature(let_chains)]
-
 pub mod canonicalizer;
 pub mod infcx;
 pub mod resolve;

Diff for: compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -2,7 +2,7 @@
 //! traits, `Copy`/`Clone`.
 
 use rustc_ast_ir::{Movability, Mutability};
-use rustc_data_structures::fx::FxHashMap;
+use rustc_type_ir::data_structures::HashMap;
 use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
@@ -304,9 +304,10 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<I: Intern
             let kind_ty = args.kind_ty();
             let sig = args.coroutine_closure_sig().skip_binder();
 
-            let coroutine_ty = if let Some(closure_kind) = kind_ty.to_opt_closure_kind()
-                && !args.tupled_upvars_ty().is_ty_var()
-            {
+            // FIXME: let_chains
+            let kind = kind_ty.to_opt_closure_kind();
+            let coroutine_ty = if kind.is_some() && !args.tupled_upvars_ty().is_ty_var() {
+                let closure_kind = kind.unwrap();
                 if !closure_kind.extends(goal_kind) {
                     return Err(NoSolution);
                 }
@@ -411,10 +412,11 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<I:
             let kind_ty = args.kind_ty();
             let sig = args.coroutine_closure_sig().skip_binder();
             let mut nested = vec![];
-            let coroutine_ty = if let Some(closure_kind) = kind_ty.to_opt_closure_kind()
-                && !args.tupled_upvars_ty().is_ty_var()
-            {
-                if !closure_kind.extends(goal_kind) {
+
+            // FIXME: let_chains
+            let kind = kind_ty.to_opt_closure_kind();
+            let coroutine_ty = if kind.is_some() && !args.tupled_upvars_ty().is_ty_var() {
+                if !kind.unwrap().extends(goal_kind) {
                     return Err(NoSolution);
                 }
 
@@ -683,7 +685,7 @@ where
         );
     }
 
-    let mut replace_projection_with = FxHashMap::default();
+    let mut replace_projection_with = HashMap::default();
     for bound in object_bounds {
         if let ty::ExistentialPredicate::Projection(proj) = bound.skip_binder() {
             let proj = proj.with_self_ty(tcx, trait_ref.self_ty());
@@ -713,7 +715,7 @@ where
 struct ReplaceProjectionWith<'a, Infcx: SolverDelegate<Interner = I>, I: Interner> {
     ecx: &'a EvalCtxt<'a, Infcx>,
     param_env: I::ParamEnv,
-    mapping: FxHashMap<I::DefId, ty::Binder<I, ty::ProjectionPredicate<I>>>,
+    mapping: HashMap<I::DefId, ty::Binder<I, ty::ProjectionPredicate<I>>>,
     nested: Vec<Goal<I, I::Predicate>>,
 }
 
@@ -725,24 +727,28 @@ impl<Infcx: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I>
     }
 
     fn fold_ty(&mut self, ty: I::Ty) -> I::Ty {
-        if let ty::Alias(ty::Projection, alias_ty) = ty.kind()
-            && let Some(replacement) = self.mapping.get(&alias_ty.def_id)
-        {
-            // We may have a case where our object type's projection bound is higher-ranked,
-            // but the where clauses we instantiated are not. We can solve this by instantiating
-            // the binder at the usage site.
-            let proj = self.ecx.instantiate_binder_with_infer(*replacement);
-            // FIXME: Technically this equate could be fallible...
-            self.nested.extend(
-                self.ecx
-                    .eq_and_get_goals(
-                        self.param_env,
-                        alias_ty,
-                        proj.projection_term.expect_ty(self.ecx.interner()),
-                    )
-                    .expect("expected to be able to unify goal projection with dyn's projection"),
-            );
-            proj.term.expect_ty()
+        if let ty::Alias(ty::Projection, alias_ty) = ty.kind() {
+            if let Some(replacement) = self.mapping.get(&alias_ty.def_id) {
+                // We may have a case where our object type's projection bound is higher-ranked,
+                // but the where clauses we instantiated are not. We can solve this by instantiating
+                // the binder at the usage site.
+                let proj = self.ecx.instantiate_binder_with_infer(*replacement);
+                // FIXME: Technically this equate could be fallible...
+                self.nested.extend(
+                    self.ecx
+                        .eq_and_get_goals(
+                            self.param_env,
+                            alias_ty,
+                            proj.projection_term.expect_ty(self.ecx.interner()),
+                        )
+                        .expect(
+                            "expected to be able to unify goal projection with dyn's projection",
+                        ),
+                );
+                proj.term.expect_ty()
+            } else {
+                ty.super_fold_with(self)
+            }
         } else {
             ty.super_fold_with(self)
         }

Diff for: compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -1,7 +1,8 @@
 use std::ops::ControlFlow;
 
-use rustc_data_structures::stack::ensure_sufficient_stack;
+#[cfg(feature = "nightly")]
 use rustc_macros::{HashStable_NoContext, TyDecodable, TyEncodable};
+use rustc_type_ir::data_structures::ensure_sufficient_stack;
 use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::relate::Relate;
@@ -88,7 +89,7 @@ where
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = ""), Debug(bound = ""), Default(bound = ""))]
 #[derive(TypeVisitable_Generic, TypeFoldable_Generic, Lift_Generic)]
-#[derive(TyDecodable, TyEncodable, HashStable_NoContext)]
+#[cfg_attr(feature = "nightly", derive(TyDecodable, TyEncodable, HashStable_NoContext))]
 // FIXME: This can be made crate-private once `EvalCtxt` also lives in this crate.
 pub struct NestedGoals<I: Interner> {
     /// These normalizes-to goals are treated specially during the evaluation
@@ -116,7 +117,8 @@ impl<I: Interner> NestedGoals<I> {
     }
 }
 
-#[derive(PartialEq, Eq, Debug, Hash, HashStable_NoContext, Clone, Copy)]
+#[derive(PartialEq, Eq, Debug, Hash, Clone, Copy)]
+#[cfg_attr(feature = "nightly", derive(HashStable_NoContext))]
 pub enum GenerateProofTree {
     Yes,
     No,
@@ -689,14 +691,15 @@ where
             fn visit_ty(&mut self, t: I::Ty) -> Self::Result {
                 match t.kind() {
                     ty::Infer(ty::TyVar(vid)) => {
-                        if let ty::TermKind::Ty(term) = self.term.kind()
-                            && let ty::Infer(ty::TyVar(term_vid)) = term.kind()
-                            && self.infcx.root_ty_var(vid) == self.infcx.root_ty_var(term_vid)
-                        {
-                            ControlFlow::Break(())
-                        } else {
-                            self.check_nameable(self.infcx.universe_of_ty(vid).unwrap())
+                        if let ty::TermKind::Ty(term) = self.term.kind() {
+                            if let ty::Infer(ty::TyVar(term_vid)) = term.kind() {
+                                if self.infcx.root_ty_var(vid) == self.infcx.root_ty_var(term_vid) {
+                                    return ControlFlow::Break(());
+                                }
+                            }
                         }
+
+                        self.check_nameable(self.infcx.universe_of_ty(vid).unwrap())
                     }
                     ty::Placeholder(p) => self.check_nameable(p.universe()),
                     _ => {
@@ -712,14 +715,18 @@ where
             fn visit_const(&mut self, c: I::Const) -> Self::Result {
                 match c.kind() {
                     ty::ConstKind::Infer(ty::InferConst::Var(vid)) => {
-                        if let ty::TermKind::Const(term) = self.term.kind()
-                            && let ty::ConstKind::Infer(ty::InferConst::Var(term_vid)) = term.kind()
-                            && self.infcx.root_const_var(vid) == self.infcx.root_const_var(term_vid)
-                        {
-                            ControlFlow::Break(())
-                        } else {
-                            self.check_nameable(self.infcx.universe_of_ct(vid).unwrap())
+                        if let ty::TermKind::Const(term) = self.term.kind() {
+                            if let ty::ConstKind::Infer(ty::InferConst::Var(term_vid)) = term.kind()
+                            {
+                                if self.infcx.root_const_var(vid)
+                                    == self.infcx.root_const_var(term_vid)
+                                {
+                                    return ControlFlow::Break(());
+                                }
+                            }
                         }
+
+                        self.check_nameable(self.infcx.universe_of_ct(vid).unwrap())
                     }
                     ty::ConstKind::Placeholder(p) => self.check_nameable(p.universe()),
                     _ => {

Diff for: compiler/rustc_next_trait_solver/src/solve/search_graph.rs

@@ -1,7 +1,7 @@
 use std::mem;
 
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_index::{Idx, IndexVec};
+use rustc_type_ir::data_structures::{HashMap, HashSet};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::Interner;
 use tracing::debug;
@@ -17,6 +17,7 @@ pub struct SolverLimit(usize);
 
 rustc_index::newtype_index! {
     #[orderable]
+    #[gate_rustc_only]
     pub struct StackDepth {}
 }
 
@@ -70,7 +71,7 @@ struct StackEntry<I: Interner> {
     /// C :- D
     /// D :- C
     /// ```
-    cycle_participants: FxHashSet<CanonicalInput<I>>,
+    cycle_participants: HashSet<CanonicalInput<I>>,
     /// Starts out as `None` and gets set when rerunning this
     /// goal in case we encounter a cycle.
     provisional_result: Option<QueryResult<I>>,
@@ -126,7 +127,7 @@ pub(super) struct SearchGraph<I: Interner> {
     ///
     /// An element is *deeper* in the stack if its index is *lower*.
     stack: IndexVec<StackDepth, StackEntry<I>>,
-    provisional_cache: FxHashMap<CanonicalInput<I>, ProvisionalCacheEntry<I>>,
+    provisional_cache: HashMap<CanonicalInput<I>, ProvisionalCacheEntry<I>>,
 }
 
 impl<I: Interner> SearchGraph<I> {
@@ -227,13 +228,17 @@ impl<I: Interner> SearchGraph<I> {
     }
 
     fn clear_dependent_provisional_results(
-        provisional_cache: &mut FxHashMap<CanonicalInput<I>, ProvisionalCacheEntry<I>>,
+        provisional_cache: &mut HashMap<CanonicalInput<I>, ProvisionalCacheEntry<I>>,
         head: StackDepth,
     ) {
         #[allow(rustc::potential_query_instability)]
         provisional_cache.retain(|_, entry| {
-            entry.with_coinductive_stack.take_if(|p| p.head == head);
-            entry.with_inductive_stack.take_if(|p| p.head == head);
+            if entry.with_coinductive_stack.as_ref().is_some_and(|p| p.head == head) {
+                entry.with_coinductive_stack.take();
+            }
+            if entry.with_inductive_stack.as_ref().is_some_and(|p| p.head == head) {
+                entry.with_inductive_stack.take();
+            }
             !entry.is_empty()
         });
     }

Diff for: compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -1,7 +1,7 @@
 //! Dealing with trait goals, i.e. `T: Trait<'a, U>`.
 
 use rustc_ast_ir::Movability;
-use rustc_data_structures::fx::FxIndexSet;
+use rustc_type_ir::data_structures::IndexSet;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::visit::TypeVisitableExt as _;
@@ -821,7 +821,7 @@ where
         // We may upcast to auto traits that are either explicitly listed in
         // the object type's bounds, or implied by the principal trait ref's
         // supertraits.
-        let a_auto_traits: FxIndexSet<I::DefId> = a_data
+        let a_auto_traits: IndexSet<I::DefId> = a_data
             .auto_traits()
             .into_iter()
             .chain(a_data.principal_def_id().into_iter().flat_map(|principal_def_id| {

Diff for: compiler/rustc_parse/src/parser/item.rs

@@ -1259,7 +1259,7 @@ impl<'a> Parser<'a> {
         self.token.is_keyword(kw::Unsafe)
             && self.is_keyword_ahead(1, &[kw::Extern])
             && self.look_ahead(
-                2 + self.look_ahead(2, |t| t.can_begin_literal_maybe_minus() as usize),
+                2 + self.look_ahead(2, |t| t.can_begin_string_literal() as usize),
                 |t| t.kind == token::OpenDelim(Delimiter::Brace),
             )
     }
@@ -2448,7 +2448,7 @@ impl<'a> Parser<'a> {
                 })
             // `extern ABI fn`
             || self.check_keyword_case(kw::Extern, case)
-                && self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
+                && self.look_ahead(1, |t| t.can_begin_string_literal())
                 && (self.look_ahead(2, |t| t.is_keyword_case(kw::Fn, case)) ||
                     // this branch is only for better diagnostic in later, `pub` is not allowed here
                     (self.may_recover()

Diff for: compiler/rustc_parse/src/parser/pat.rs

@@ -939,7 +939,8 @@ impl<'a> Parser<'a> {
             || self.look_ahead(dist, |t| {
                 t.is_path_start() // e.g. `MY_CONST`;
                 || t.kind == token::Dot // e.g. `.5` for recovery;
-                || t.can_begin_literal_maybe_minus() // e.g. `42`.
+                || matches!(t.kind, token::Literal(..) | token::BinOp(token::Minus))
+                || t.is_bool_lit()
                 || t.is_whole_expr()
                 || t.is_lifetime() // recover `'a` instead of `'a'`
                 || (self.may_recover() // recover leading `(`