Auto merge of rust-lang#135402 - matthiaskrgr:rollup-cz7hs13, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - rust-lang#129259 (Add inherent versions of MaybeUninit methods for slices)
 - rust-lang#135374 (Suggest typo fix when trait path expression is typo'ed)
 - rust-lang#135377 (Make MIR cleanup for functions with impossible predicates into a real MIR pass)
 - rust-lang#135378 (Remove a bunch of diagnostic stashing that doesn't do anything)
 - rust-lang#135397 (compiletest: add erroneous variant to `string_enum`s conversions error)
 - rust-lang#135398 (add more crash tests)

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

Author: bors

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

@@ -78,7 +78,7 @@ impl<T> ArenaChunk<T> {
             // been initialized.
             unsafe {
                 let slice = self.storage.as_mut();
-                ptr::drop_in_place(MaybeUninit::slice_assume_init_mut(&mut slice[..len]));
+                slice[..len].assume_init_drop();
             }
         }
     }

Diff for: compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -152,7 +152,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                         let (Ok(e) | Err(e)) = prev
                             .build_mismatch_error(
                                 &OpaqueHiddenType { ty, span: concrete_type.span },
-                                opaque_type_key.def_id,
                                 infcx.tcx,
                             )
                             .map(|d| d.emit());

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

@@ -566,9 +566,7 @@ pub enum StashKey {
     /// FRU syntax
     MaybeFruTypo,
     CallAssocMethod,
-    TraitMissingMethod,
     AssociatedTypeSuggestion,
-    OpaqueHiddenTypeMismatch,
     MaybeForgetReturn,
     /// Query cycle detected, stashing in favor of a better error.
     Cycle,

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

@@ -575,7 +575,7 @@ fn sanity_check_found_hidden_type<'tcx>(
     } else {
         let span = tcx.def_span(key.def_id);
         let other = ty::OpaqueHiddenType { ty: hidden_ty, span };
-        Err(ty.build_mismatch_error(&other, key.def_id, tcx)?.emit())
+        Err(ty.build_mismatch_error(&other, tcx)?.emit())
     }
 }
 

Diff for: compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs

@@ -1,4 +1,3 @@
-use rustc_errors::StashKey;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
@@ -45,7 +44,7 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
         if !hidden.ty.references_error() {
             for concrete_type in locator.typeck_types {
                 if concrete_type.ty != tcx.erase_regions(hidden.ty) {
-                    if let Ok(d) = hidden.build_mismatch_error(&concrete_type, def_id, tcx) {
+                    if let Ok(d) = hidden.build_mismatch_error(&concrete_type, tcx) {
                         d.emit();
                     }
                 }
@@ -121,7 +120,7 @@ pub(super) fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: Local
         if !hidden.ty.references_error() {
             for concrete_type in locator.typeck_types {
                 if concrete_type.ty != tcx.erase_regions(hidden.ty) {
-                    if let Ok(d) = hidden.build_mismatch_error(&concrete_type, def_id, tcx) {
+                    if let Ok(d) = hidden.build_mismatch_error(&concrete_type, tcx) {
                         d.emit();
                     }
                 }
@@ -285,9 +284,8 @@ impl TaitConstraintLocator<'_> {
             debug!(?concrete_type, "found constraint");
             if let Some(prev) = &mut self.found {
                 if concrete_type.ty != prev.ty {
-                    let (Ok(guar) | Err(guar)) = prev
-                        .build_mismatch_error(&concrete_type, self.def_id, self.tcx)
-                        .map(|d| d.emit());
+                    let (Ok(guar) | Err(guar)) =
+                        prev.build_mismatch_error(&concrete_type, self.tcx).map(|d| d.emit());
                     prev.ty = Ty::new_error(self.tcx, guar);
                 }
             } else {
@@ -361,11 +359,8 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             );
             if let Some(prev) = &mut hir_opaque_ty {
                 if concrete_type.ty != prev.ty {
-                    if let Ok(d) = prev.build_mismatch_error(&concrete_type, def_id, tcx) {
-                        d.stash(
-                            tcx.def_span(opaque_type_key.def_id),
-                            StashKey::OpaqueHiddenTypeMismatch,
-                        );
+                    if let Ok(d) = prev.build_mismatch_error(&concrete_type, tcx) {
+                        d.emit();
                     }
                 }
             } else {
@@ -435,9 +430,7 @@ impl RpitConstraintChecker<'_> {
             debug!(?concrete_type, "found constraint");
 
             if concrete_type.ty != self.found.ty {
-                if let Ok(d) =
-                    self.found.build_mismatch_error(&concrete_type, self.def_id, self.tcx)
-                {
+                if let Ok(d) = self.found.build_mismatch_error(&concrete_type, self.tcx) {
                     d.emit();
                 }
             }

Diff for: compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -2,10 +2,12 @@ use rustc_ast::TraitObjectSyntax;
 use rustc_errors::codes::*;
 use rustc_errors::{Diag, EmissionGuarantee, ErrorGuaranteed, StashKey, Suggestions};
 use rustc_hir as hir;
-use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def::{DefKind, Namespace, Res};
+use rustc_hir::def_id::DefId;
 use rustc_lint_defs::Applicability;
 use rustc_lint_defs::builtin::BARE_TRAIT_OBJECTS;
 use rustc_span::Span;
+use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_trait_selection::error_reporting::traits::suggestions::NextTypeParamName;
 
 use super::HirTyLowerer;
@@ -86,7 +88,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             // Check if the impl trait that we are considering is an impl of a local trait.
             self.maybe_suggest_blanket_trait_impl(self_ty, &mut diag);
             self.maybe_suggest_assoc_ty_bound(self_ty, &mut diag);
-            // In case there is an associate type with the same name
+            self.maybe_suggest_typoed_method(
+                self_ty,
+                poly_trait_ref.trait_ref.trait_def_id(),
+                &mut diag,
+            );
+            // In case there is an associated type with the same name
             // Add the suggestion to this error
             if let Some(mut sugg) =
                 tcx.dcx().steal_non_err(self_ty.span, StashKey::AssociatedTypeSuggestion)
@@ -96,7 +103,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 s1.append(s2);
                 sugg.cancel();
             }
-            diag.stash(self_ty.span, StashKey::TraitMissingMethod)
+            Some(diag.emit())
         } else {
             tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, |lint| {
                 lint.primary_message("trait objects without an explicit `dyn` are deprecated");
@@ -343,4 +350,44 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             );
         }
     }
+
+    fn maybe_suggest_typoed_method(
+        &self,
+        self_ty: &hir::Ty<'_>,
+        trait_def_id: Option<DefId>,
+        diag: &mut Diag<'_>,
+    ) {
+        let tcx = self.tcx();
+        let Some(trait_def_id) = trait_def_id else {
+            return;
+        };
+        let hir::Node::Expr(hir::Expr {
+            kind: hir::ExprKind::Path(hir::QPath::TypeRelative(path_ty, segment)),
+            ..
+        }) = tcx.parent_hir_node(self_ty.hir_id)
+        else {
+            return;
+        };
+        if path_ty.hir_id != self_ty.hir_id {
+            return;
+        }
+        let names: Vec<_> = tcx
+            .associated_items(trait_def_id)
+            .in_definition_order()
+            .filter(|assoc| assoc.kind.namespace() == Namespace::ValueNS)
+            .map(|cand| cand.name)
+            .collect();
+        if let Some(typo) = find_best_match_for_name(&names, segment.ident.name, None) {
+            diag.span_suggestion_verbose(
+                segment.ident.span,
+                format!(
+                    "you may have misspelled this associated item, causing `{}` \
+                    to be interpreted as a type rather than a trait",
+                    tcx.item_name(trait_def_id),
+                ),
+                typo,
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
 }

Diff for: compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -3,7 +3,7 @@ use std::slice;
 
 use rustc_abi::FieldIdx;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan, StashKey};
+use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan};
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
@@ -806,17 +806,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let item_name = item_segment.ident;
         let result = self
             .resolve_fully_qualified_call(span, item_name, ty.normalized, qself.span, hir_id)
-            .map(|r| {
-                // lint bare trait if the method is found in the trait
-                if span.edition().at_least_rust_2021() {
-                    self.dcx().try_steal_modify_and_emit_err(
-                        qself.span,
-                        StashKey::TraitMissingMethod,
-                        |_err| {},
-                    );
-                }
-                r
-            })
             .or_else(|error| {
                 let guar = self
                     .dcx()
@@ -840,17 +829,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     );
                 }
 
-                // Emit the diagnostic for bare traits. (We used to cancel for slightly better
-                // error messages, but cancelling stashed diagnostics is no longer allowed because
-                // it causes problems when tracking whether errors have actually occurred.)
-                if span.edition().at_least_rust_2021() {
-                    self.dcx().try_steal_modify_and_emit_err(
-                        qself.span,
-                        StashKey::TraitMissingMethod,
-                        |_err| {},
-                    );
-                }
-
                 if item_name.name != kw::Empty {
                     self.report_method_error(
                         hir_id,

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

@@ -5,7 +5,7 @@
 use std::mem;
 
 use rustc_data_structures::unord::ExtendUnord;
-use rustc_errors::{ErrorGuaranteed, StashKey};
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::HirId;
 use rustc_hir::intravisit::{self, Visitor};
@@ -582,15 +582,8 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 && last_opaque_ty.ty != hidden_type.ty
             {
                 assert!(!self.fcx.next_trait_solver());
-                if let Ok(d) = hidden_type.build_mismatch_error(
-                    &last_opaque_ty,
-                    opaque_type_key.def_id,
-                    self.tcx(),
-                ) {
-                    d.stash(
-                        self.tcx().def_span(opaque_type_key.def_id),
-                        StashKey::OpaqueHiddenTypeMismatch,
-                    );
+                if let Ok(d) = hidden_type.build_mismatch_error(&last_opaque_ty, self.tcx()) {
+                    d.emit();
                 }
             }
         }

Diff for: compiler/rustc_middle/src/ty/mod.rs

@@ -32,7 +32,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
-use rustc_errors::{Diag, ErrorGuaranteed, StashKey};
+use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::LangItem;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
@@ -782,18 +782,8 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
     pub fn build_mismatch_error(
         &self,
         other: &Self,
-        opaque_def_id: LocalDefId,
         tcx: TyCtxt<'tcx>,
     ) -> Result<Diag<'tcx>, ErrorGuaranteed> {
-        // We used to cancel here for slightly better error messages, but
-        // cancelling stashed diagnostics is no longer allowed because it
-        // causes problems when tracking whether errors have actually
-        // occurred.
-        tcx.sess.dcx().try_steal_modify_and_emit_err(
-            tcx.def_span(opaque_def_id),
-            StashKey::OpaqueHiddenTypeMismatch,
-            |_err| {},
-        );
         (self.ty, other.ty).error_reported()?;
         // Found different concrete types for the opaque type.
         let sub_diag = if self.span == other.span {

Diff for: compiler/rustc_mir_transform/src/impossible_predicates.rs

@@ -0,0 +1,56 @@
+//! Check if it's even possible to satisfy the 'where' clauses
+//! for this item.
+//!
+//! It's possible to `#!feature(trivial_bounds)]` to write
+//! a function with impossible to satisfy clauses, e.g.:
+//! `fn foo() where String: Copy {}`.
+//!
+//! We don't usually need to worry about this kind of case,
+//! since we would get a compilation error if the user tried
+//! to call it. However, since we optimize even without any
+//! calls to the function, we need to make sure that it even
+//! makes sense to try to evaluate the body.
+//!
+//! If there are unsatisfiable where clauses, then all bets are
+//! off, and we just give up.
+//!
+//! We manually filter the predicates, skipping anything that's not
+//! "global". We are in a potentially generic context
+//! (e.g. we are evaluating a function without instantiating generic
+//! parameters, so this filtering serves two purposes:
+//!
+//! 1. We skip evaluating any predicates that we would
+//! never be able prove are unsatisfiable (e.g. `<T as Foo>`
+//! 2. We avoid trying to normalize predicates involving generic
+//! parameters (e.g. `<T as Foo>::MyItem`). This can confuse
+//! the normalization code (leading to cycle errors), since
+//! it's usually never invoked in this way.
+
+use rustc_middle::mir::{Body, START_BLOCK, TerminatorKind};
+use rustc_middle::ty::{TyCtxt, TypeVisitableExt};
+use rustc_trait_selection::traits;
+use tracing::trace;
+
+use crate::pass_manager::MirPass;
+
+pub(crate) struct ImpossiblePredicates;
+
+impl<'tcx> MirPass<'tcx> for ImpossiblePredicates {
+    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        let predicates = tcx
+            .predicates_of(body.source.def_id())
+            .predicates
+            .iter()
+            .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None });
+        if traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect()) {
+            trace!("found unsatisfiable predicates for {:?}", body.source);
+            // Clear the body to only contain a single `unreachable` statement.
+            let bbs = body.basic_blocks.as_mut();
+            bbs.raw.truncate(1);
+            bbs[START_BLOCK].statements.clear();
+            bbs[START_BLOCK].terminator_mut().kind = TerminatorKind::Unreachable;
+            body.var_debug_info.clear();
+            body.local_decls.raw.truncate(body.arg_count + 1);
+        }
+    }
+}