diff --git a/src/liballoc/alloc/tests.rs b/src/liballoc/alloc/tests.rs index 1ad40eca93b69..1c003983df989 100644 --- a/src/liballoc/alloc/tests.rs +++ b/src/liballoc/alloc/tests.rs @@ -23,7 +23,7 @@ fn allocate_zeroed() { } #[bench] -#[cfg_attr(miri, ignore)] // Miri does not support benchmarks +#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks fn alloc_owned_small(b: &mut Bencher) { b.iter(|| { let _: Box<_> = box 10; diff --git a/src/liballoc/collections/linked_list/tests.rs b/src/liballoc/collections/linked_list/tests.rs index 085f734ed916a..b8c93a28bba81 100644 --- a/src/liballoc/collections/linked_list/tests.rs +++ b/src/liballoc/collections/linked_list/tests.rs @@ -182,7 +182,6 @@ fn test_insert_prev() { #[test] #[cfg_attr(target_os = "emscripten", ignore)] -#[cfg_attr(miri, ignore)] // Miri does not support threads fn test_send() { let n = list_from(&[1, 2, 3]); thread::spawn(move || { diff --git a/src/liballoc/collections/vec_deque/tests.rs b/src/liballoc/collections/vec_deque/tests.rs index 0a3f33003233f..fc2ec7908e823 100644 --- a/src/liballoc/collections/vec_deque/tests.rs +++ b/src/liballoc/collections/vec_deque/tests.rs @@ -3,7 +3,7 @@ use super::*; use test; #[bench] -#[cfg_attr(miri, ignore)] // Miri does not support benchmarks +#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks fn bench_push_back_100(b: &mut test::Bencher) { let mut deq = VecDeque::with_capacity(101); b.iter(|| { @@ -16,7 +16,7 @@ fn bench_push_back_100(b: &mut test::Bencher) { } #[bench] -#[cfg_attr(miri, ignore)] // Miri does not support benchmarks +#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks fn bench_push_front_100(b: &mut test::Bencher) { let mut deq = VecDeque::with_capacity(101); b.iter(|| { @@ -29,7 +29,7 @@ fn bench_push_front_100(b: &mut test::Bencher) { } #[bench] -#[cfg_attr(miri, ignore)] // Miri does not support benchmarks +#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks fn bench_pop_back_100(b: &mut test::Bencher) { let mut deq = VecDeque::::with_capacity(101); @@ -43,7 +43,7 @@ fn bench_pop_back_100(b: &mut test::Bencher) { } #[bench] -#[cfg_attr(miri, ignore)] // Miri does not support benchmarks +#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks fn bench_pop_front_100(b: &mut test::Bencher) { let mut deq = VecDeque::::with_capacity(101); diff --git a/src/liballoc/sync/tests.rs b/src/liballoc/sync/tests.rs index edc2820ee22f1..a2bb651e2b778 100644 --- a/src/liballoc/sync/tests.rs +++ b/src/liballoc/sync/tests.rs @@ -32,7 +32,6 @@ impl Drop for Canary { #[test] #[cfg_attr(target_os = "emscripten", ignore)] -#[cfg_attr(miri, ignore)] // Miri does not support threads fn manually_share_arc() { let v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; let arc_v = Arc::new(v); @@ -337,12 +336,13 @@ fn test_ptr_eq() { #[test] #[cfg_attr(target_os = "emscripten", ignore)] -#[cfg_attr(miri, ignore)] // Miri does not support threads fn test_weak_count_locked() { let mut a = Arc::new(atomic::AtomicBool::new(false)); let a2 = a.clone(); let t = thread::spawn(move || { - for _i in 0..1000000 { + // Miri is too slow + let count = if cfg!(miri) { 1000 } else { 1000000 }; + for _i in 0..count { Arc::get_mut(&mut a); } a.store(true, SeqCst); @@ -351,6 +351,8 @@ fn test_weak_count_locked() { while !a2.load(SeqCst) { let n = Arc::weak_count(&a2); assert!(n < 2, "bad weak count: {}", n); + #[cfg(miri)] // Miri's scheduler does not guarantee liveness, and thus needs this hint. + atomic::spin_loop_hint(); } t.join().unwrap(); } diff --git a/src/librustc_middle/mir/visit.rs b/src/librustc_middle/mir/visit.rs index 2f3d89dc02980..1f097f24942de 100644 --- a/src/librustc_middle/mir/visit.rs +++ b/src/librustc_middle/mir/visit.rs @@ -427,13 +427,29 @@ macro_rules! make_mir_visitor { TerminatorKind::Goto { .. } | TerminatorKind::Resume | TerminatorKind::Abort | - TerminatorKind::Return | TerminatorKind::GeneratorDrop | TerminatorKind::Unreachable | TerminatorKind::FalseEdges { .. } | TerminatorKind::FalseUnwind { .. } => { } + TerminatorKind::Return => { + // `return` logically moves from the return place `_0`. Note that the place + // cannot be changed by any visitor, though. + let $($mutability)? local = RETURN_PLACE; + self.visit_local( + & $($mutability)? local, + PlaceContext::NonMutatingUse(NonMutatingUseContext::Move), + source_location, + ); + + assert_eq!( + local, + RETURN_PLACE, + "`MutVisitor` tried to mutate return place of `return` terminator" + ); + } + TerminatorKind::SwitchInt { discr, switch_ty, diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs index d3ab7df817b38..a3ee49651ba7b 100644 --- a/src/librustc_mir/borrow_check/mod.rs +++ b/src/librustc_mir/borrow_check/mod.rs @@ -209,7 +209,7 @@ fn do_mir_borrowck<'a, 'tcx>( nll_errors, } = nll::compute_regions( infcx, - def_id.to_def_id(), + def_id, free_regions, body, &promoted, diff --git a/src/librustc_mir/borrow_check/nll.rs b/src/librustc_mir/borrow_check/nll.rs index 29636a067092b..b820b79c47fe8 100644 --- a/src/librustc_mir/borrow_check/nll.rs +++ b/src/librustc_mir/borrow_check/nll.rs @@ -2,7 +2,7 @@ use rustc_data_structures::fx::FxHashMap; use rustc_errors::Diagnostic; -use rustc_hir::def_id::DefId; +use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_index::vec::IndexVec; use rustc_infer::infer::InferCtxt; use rustc_middle::mir::{ @@ -157,7 +157,7 @@ fn populate_polonius_move_facts( /// This may result in errors being reported. pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>( infcx: &InferCtxt<'cx, 'tcx>, - def_id: DefId, + def_id: LocalDefId, universal_regions: UniversalRegions<'tcx>, body: &Body<'tcx>, promoted: &IndexVec>, @@ -272,7 +272,7 @@ pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>( // Dump facts if requested. let polonius_output = all_facts.and_then(|all_facts| { if infcx.tcx.sess.opts.debugging_opts.nll_facts { - let def_path = infcx.tcx.def_path(def_id); + let def_path = infcx.tcx.def_path(def_id.to_def_id()); let dir_path = PathBuf::from("nll-facts").join(def_path.to_filename_friendly_no_crate()); all_facts.write_to_dir(dir_path, location_table).unwrap(); @@ -292,7 +292,7 @@ pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>( // Solve the region constraints. let (closure_region_requirements, nll_errors) = - regioncx.solve(infcx, &body, def_id, polonius_output.clone()); + regioncx.solve(infcx, &body, def_id.to_def_id(), polonius_output.clone()); if !nll_errors.is_empty() { // Suppress unhelpful extra errors in `infer_opaque_types`. diff --git a/src/librustc_mir/borrow_check/type_check/input_output.rs b/src/librustc_mir/borrow_check/type_check/input_output.rs index 894a997ea7a4d..edd2dc3c2de55 100644 --- a/src/librustc_mir/borrow_check/type_check/input_output.rs +++ b/src/librustc_mir/borrow_check/type_check/input_output.rs @@ -33,35 +33,37 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { // // e.g., `|x: FxHashMap<_, &'static u32>| ...` let user_provided_sig; - if !self.tcx().is_closure(self.mir_def_id) { + if !self.tcx().is_closure(self.mir_def_id.to_def_id()) { user_provided_sig = None; } else { - let typeck_tables = self.tcx().typeck_tables_of(self.mir_def_id.expect_local()); - user_provided_sig = match typeck_tables.user_provided_sigs.get(&self.mir_def_id) { - None => None, - Some(user_provided_poly_sig) => { - // Instantiate the canonicalized variables from - // user-provided signature (e.g., the `_` in the code - // above) with fresh variables. - let (poly_sig, _) = self.infcx.instantiate_canonical_with_fresh_inference_vars( - body.span, - &user_provided_poly_sig, - ); - - // Replace the bound items in the fn sig with fresh - // variables, so that they represent the view from - // "inside" the closure. - Some( - self.infcx - .replace_bound_vars_with_fresh_vars( + let typeck_tables = self.tcx().typeck_tables_of(self.mir_def_id); + user_provided_sig = + match typeck_tables.user_provided_sigs.get(&self.mir_def_id.to_def_id()) { + None => None, + Some(user_provided_poly_sig) => { + // Instantiate the canonicalized variables from + // user-provided signature (e.g., the `_` in the code + // above) with fresh variables. + let (poly_sig, _) = + self.infcx.instantiate_canonical_with_fresh_inference_vars( body.span, - LateBoundRegionConversionTime::FnCall, - &poly_sig, - ) - .0, - ) + &user_provided_poly_sig, + ); + + // Replace the bound items in the fn sig with fresh + // variables, so that they represent the view from + // "inside" the closure. + Some( + self.infcx + .replace_bound_vars_with_fresh_vars( + body.span, + LateBoundRegionConversionTime::FnCall, + &poly_sig, + ) + .0, + ) + } } - } }; debug!( @@ -120,7 +122,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { if let Err(terr) = self.eq_opaque_type_and_type( mir_output_ty, normalized_output_ty, - self.mir_def_id, + self.mir_def_id.to_def_id(), Locations::All(output_span), ConstraintCategory::BoringNoLocation, ) { @@ -143,7 +145,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { if let Err(err) = self.eq_opaque_type_and_type( mir_output_ty, user_provided_output_ty, - self.mir_def_id, + self.mir_def_id.to_def_id(), Locations::All(output_span), ConstraintCategory::BoringNoLocation, ) { diff --git a/src/librustc_mir/borrow_check/type_check/mod.rs b/src/librustc_mir/borrow_check/type_check/mod.rs index ee8a4358147cf..9282a0a06b480 100644 --- a/src/librustc_mir/borrow_check/type_check/mod.rs +++ b/src/librustc_mir/borrow_check/type_check/mod.rs @@ -108,26 +108,22 @@ mod relate_tys; /// /// - `infcx` -- inference context to use /// - `param_env` -- parameter environment to use for trait solving -/// - `mir` -- MIR to type-check -/// - `mir_def_id` -- DefId from which the MIR is derived (must be local) -/// - `region_bound_pairs` -- the implied outlives obligations between type parameters -/// and lifetimes (e.g., `&'a T` implies `T: 'a`) -/// - `implicit_region_bound` -- a region which all generic parameters are assumed -/// to outlive; should represent the fn body -/// - `input_tys` -- fully liberated, but **not** normalized, expected types of the arguments; -/// the types of the input parameters found in the MIR itself will be equated with these -/// - `output_ty` -- fully liberated, but **not** normalized, expected return type; -/// the type for the RETURN_PLACE will be equated with this -/// - `liveness` -- results of a liveness computation on the MIR; used to create liveness -/// constraints for the regions in the types of variables +/// - `body` -- MIR body to type-check +/// - `promoted` -- map of promoted constants within `body` +/// - `mir_def_id` -- `LocalDefId` from which the MIR is derived +/// - `universal_regions` -- the universal regions from `body`s function signature +/// - `location_table` -- MIR location map of `body` +/// - `borrow_set` -- information about borrows occurring in `body` +/// - `all_facts` -- when using Polonius, this is the generated set of Polonius facts /// - `flow_inits` -- results of a maybe-init dataflow analysis /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis +/// - `elements` -- MIR region map pub(crate) fn type_check<'mir, 'tcx>( infcx: &InferCtxt<'_, 'tcx>, param_env: ty::ParamEnv<'tcx>, body: &Body<'tcx>, promoted: &IndexVec>, - mir_def_id: DefId, + mir_def_id: LocalDefId, universal_regions: &Rc>, location_table: &LocationTable, borrow_set: &BorrowSet<'tcx>, @@ -191,7 +187,7 @@ pub(crate) fn type_check<'mir, 'tcx>( fn type_check_internal<'a, 'tcx, R>( infcx: &'a InferCtxt<'a, 'tcx>, - mir_def_id: DefId, + mir_def_id: LocalDefId, param_env: ty::ParamEnv<'tcx>, body: &'a Body<'tcx>, promoted: &'a IndexVec>, @@ -271,7 +267,7 @@ struct TypeVerifier<'a, 'b, 'tcx> { body: &'b Body<'tcx>, promoted: &'b IndexVec>, last_span: Span, - mir_def_id: DefId, + mir_def_id: LocalDefId, errors_reported: bool, } @@ -815,7 +811,7 @@ struct TypeChecker<'a, 'tcx> { /// User type annotations are shared between the main MIR and the MIR of /// all of the promoted items. user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>, - mir_def_id: DefId, + mir_def_id: LocalDefId, region_bound_pairs: &'a RegionBoundPairs<'tcx>, implicit_region_bound: ty::Region<'tcx>, reported_errors: FxHashSet<(Ty<'tcx>, Span)>, @@ -963,7 +959,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { fn new( infcx: &'a InferCtxt<'a, 'tcx>, body: &'a Body<'tcx>, - mir_def_id: DefId, + mir_def_id: LocalDefId, param_env: ty::ParamEnv<'tcx>, region_bound_pairs: &'a RegionBoundPairs<'tcx>, implicit_region_bound: ty::Region<'tcx>, @@ -1142,7 +1138,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { // When you have `let x: impl Foo = ...` in a closure, // the resulting inferend values are stored with the // def-id of the base function. - let parent_def_id = self.tcx().closure_base_def_id(self.mir_def_id); + let parent_def_id = self.tcx().closure_base_def_id(self.mir_def_id.to_def_id()); return self.eq_opaque_type_and_type(sub, sup, parent_def_id, locations, category); } else { return Err(terr); @@ -1994,7 +1990,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span) { let ccx = ConstCx::new_with_param_env( tcx, - self.mir_def_id.expect_local(), + self.mir_def_id, body, self.param_env, ); @@ -2010,9 +2006,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> { &traits::Obligation::new( ObligationCause::new( span, - self.tcx() - .hir() - .local_def_id_to_hir_id(self.mir_def_id.expect_local()), + self.tcx().hir().local_def_id_to_hir_id(self.mir_def_id), traits::ObligationCauseCode::RepeatVec(should_suggest), ), self.param_env, diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs index 4f90f83b735d1..7eb05ba2d2c54 100644 --- a/src/librustc_mir/interpret/validity.rs +++ b/src/librustc_mir/interpret/validity.rs @@ -15,7 +15,7 @@ use rustc_middle::mir::interpret::{InterpError, InterpErrorInfo}; use rustc_middle::ty; use rustc_middle::ty::layout::TyAndLayout; use rustc_span::symbol::{sym, Symbol}; -use rustc_target::abi::{Abi, LayoutOf, Scalar, VariantIdx, Variants}; +use rustc_target::abi::{Abi, LayoutOf, Scalar, Size, VariantIdx, Variants}; use std::hash::Hash; @@ -744,10 +744,11 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M> match op.layout.ty.kind { ty::Str => { let mplace = op.assert_mem_place(self.ecx); // strings are never immediate + let len = mplace.len(self.ecx)?; try_validation!( - self.ecx.read_str(mplace), + self.ecx.memory.read_bytes(mplace.ptr, Size::from_bytes(len)), self.path, - err_ub!(InvalidStr(..)) => { "uninitialized or non-UTF-8 data in str" }, + err_ub!(InvalidUninitBytes(..)) => { "uninitialized data in `str`" }, ); } ty::Array(tys, ..) | ty::Slice(tys) diff --git a/src/librustc_mir/transform/copy_prop.rs b/src/librustc_mir/transform/copy_prop.rs index b9eb58f800e5c..ba406c72df848 100644 --- a/src/librustc_mir/transform/copy_prop.rs +++ b/src/librustc_mir/transform/copy_prop.rs @@ -73,7 +73,12 @@ impl<'tcx> MirPass<'tcx> for CopyPropagation { } // Conservatively gives up if the dest is an argument, // because there may be uses of the original argument value. - if body.local_kind(dest_local) == LocalKind::Arg { + // Also gives up on the return place, as we cannot propagate into its implicit + // use by `return`. + if matches!( + body.local_kind(dest_local), + LocalKind::Arg | LocalKind::ReturnPointer + ) { debug!(" Can't copy-propagate local: dest {:?} (argument)", dest_local); continue; } diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs index d334006d7b528..bfc872be653a5 100644 --- a/src/librustc_mir/transform/generator.rs +++ b/src/librustc_mir/transform/generator.rs @@ -91,6 +91,16 @@ impl<'tcx> MutVisitor<'tcx> for RenameLocalVisitor<'tcx> { *local = self.to; } } + + fn visit_terminator_kind(&mut self, kind: &mut TerminatorKind<'tcx>, location: Location) { + match kind { + TerminatorKind::Return => { + // Do not replace the implicit `_0` access here, as that's not possible. The + // transform already handles `return` correctly. + } + _ => self.super_terminator_kind(kind, location), + } + } } struct DerefArgVisitor<'tcx> { diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs index a8e949ecb3144..632408fde749f 100644 --- a/src/librustc_mir/transform/inline.rs +++ b/src/librustc_mir/transform/inline.rs @@ -732,7 +732,11 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> { } fn visit_terminator_kind(&mut self, kind: &mut TerminatorKind<'tcx>, loc: Location) { - self.super_terminator_kind(kind, loc); + // Don't try to modify the implicit `_0` access on return (`return` terminators are + // replaced down below anyways). + if !matches!(kind, TerminatorKind::Return) { + self.super_terminator_kind(kind, loc); + } match *kind { TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => bug!(), diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs index 550f672ed4cf6..c129e54c0f28a 100644 --- a/src/librustdoc/html/markdown.rs +++ b/src/librustdoc/html/markdown.rs @@ -44,7 +44,7 @@ use pulldown_cmark::{html, CodeBlockKind, CowStr, Event, Options, Parser, Tag}; mod tests; fn opts() -> Options { - Options::ENABLE_TABLES | Options::ENABLE_FOOTNOTES + Options::ENABLE_TABLES | Options::ENABLE_FOOTNOTES | Options::ENABLE_STRIKETHROUGH } /// When `to_string` is called, this struct will emit the HTML corresponding to @@ -933,7 +933,11 @@ impl MarkdownSummaryLine<'_> { } }; - let p = Parser::new_with_broken_link_callback(md, Options::empty(), Some(&replacer)); + let p = Parser::new_with_broken_link_callback( + md, + Options::ENABLE_STRIKETHROUGH, + Some(&replacer), + ); let mut s = String::new(); @@ -975,7 +979,11 @@ pub fn plain_summary_line(md: &str) -> String { } } let mut s = String::with_capacity(md.len() * 3 / 2); - let p = ParserWrapper { inner: Parser::new(md), is_in: 0, is_first: true }; + let p = ParserWrapper { + inner: Parser::new_ext(md, Options::ENABLE_STRIKETHROUGH), + is_in: 0, + is_first: true, + }; p.filter(|t| !t.is_empty()).for_each(|i| s.push_str(&i)); s } diff --git a/src/test/rustdoc/test-strikethrough.rs b/src/test/rustdoc/test-strikethrough.rs new file mode 100644 index 0000000000000..c7855729a98ee --- /dev/null +++ b/src/test/rustdoc/test-strikethrough.rs @@ -0,0 +1,6 @@ +#![crate_name = "foo"] + +// @has foo/fn.f.html +// @has - //del "Y" +/// ~~Y~~ +pub fn f() {} diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.rs b/src/test/ui/consts/const-eval/ub-wide-ptr.rs index 29ac32fcf2204..f69f6a1109f76 100644 --- a/src/test/ui/consts/const-eval/ub-wide-ptr.rs +++ b/src/test/ui/consts/const-eval/ub-wide-ptr.rs @@ -42,11 +42,11 @@ const MY_STR_LENGTH_PTR: &MyStr = unsafe { mem::transmute((&42u8, &3)) }; const MY_STR_MUCH_TOO_LONG: &MyStr = unsafe { mem::transmute((&42u8, usize::MAX)) }; //~^ ERROR it is undefined behavior to use this value -// invalid UTF-8 -const STR_NO_UTF8: &str = unsafe { mem::transmute::<&[u8], _>(&[0xFF]) }; +// uninitialized byte +const STR_NO_INIT: &str = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit:: { uninit: () }]) }; //~^ ERROR it is undefined behavior to use this value -// invalid UTF-8 in user-defined str-like -const MYSTR_NO_UTF8: &MyStr = unsafe { mem::transmute::<&[u8], _>(&[0xFF]) }; +// uninitialized byte in user-defined str-like +const MYSTR_NO_INIT: &MyStr = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit:: { uninit: () }]) }; //~^ ERROR it is undefined behavior to use this value // # slice diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr index 063ea81036b69..47d29ffc9b3c1 100644 --- a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr +++ b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr @@ -41,16 +41,16 @@ LL | const MY_STR_MUCH_TOO_LONG: &MyStr = unsafe { mem::transmute((&42u8, usize: error[E0080]: it is undefined behavior to use this value --> $DIR/ub-wide-ptr.rs:46:1 | -LL | const STR_NO_UTF8: &str = unsafe { mem::transmute::<&[u8], _>(&[0xFF]) }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized or non-UTF-8 data in str at . +LL | const STR_NO_INIT: &str = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit:: { uninit: () }]) }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized data in `str` at . | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. error[E0080]: it is undefined behavior to use this value --> $DIR/ub-wide-ptr.rs:49:1 | -LL | const MYSTR_NO_UTF8: &MyStr = unsafe { mem::transmute::<&[u8], _>(&[0xFF]) }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized or non-UTF-8 data in str at ..0 +LL | const MYSTR_NO_INIT: &MyStr = unsafe { mem::transmute::<&[_], _>(&[MaybeUninit:: { uninit: () }]) }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized data in `str` at ..0 | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.