diff options
| -rw-r--r-- | compiler/rustc_hir_typeck/src/pat.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_hir_typeck/src/writeback.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/typeck_results.rs | 7 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs | 31 | ||||
| -rw-r--r-- | compiler/rustc_mir_build/src/thir/pattern/mod.rs | 38 | ||||
| -rw-r--r-- | tests/ui/consts/const_in_pattern/arrays-and-slices.rs | 53 | ||||
| -rw-r--r-- | tests/ui/consts/const_in_pattern/arrays-and-slices.stderr | 84 |
7 files changed, 172 insertions, 48 deletions
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs index f1f956779c9..5a2cead33de 100644 --- a/compiler/rustc_hir_typeck/src/pat.rs +++ b/compiler/rustc_hir_typeck/src/pat.rs @@ -632,10 +632,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { { let tcx = self.tcx; trace!(?lt.hir_id.local_id, "polymorphic byte string lit"); - self.typeck_results - .borrow_mut() - .treat_byte_string_as_slice - .insert(lt.hir_id.local_id); pat_ty = Ty::new_imm_ref(tcx, tcx.lifetimes.re_static, Ty::new_slice(tcx, tcx.types.u8)); } diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs index b63c0b6ab7e..109023c513e 100644 --- a/compiler/rustc_hir_typeck/src/writeback.rs +++ b/compiler/rustc_hir_typeck/src/writeback.rs @@ -81,9 +81,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports); wbcx.typeck_results.used_trait_imports = used_trait_imports; - wbcx.typeck_results.treat_byte_string_as_slice = - mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice); - debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results); self.tcx.arena.alloc(wbcx.typeck_results) diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs index 06054e22e76..3d3f4e2773a 100644 --- a/compiler/rustc_middle/src/ty/typeck_results.rs +++ b/compiler/rustc_middle/src/ty/typeck_results.rs @@ -197,12 +197,6 @@ pub struct TypeckResults<'tcx> { /// formatting modified file tests/ui/coroutine/retain-resume-ref.rs pub coroutine_stalled_predicates: FxIndexSet<(ty::Predicate<'tcx>, ObligationCause<'tcx>)>, - /// We sometimes treat byte string literals (which are of type `&[u8; N]`) - /// as `&[u8]`, depending on the pattern in which they are used. - /// This hashset records all instances where we behave - /// like this to allow `const_to_pat` to reliably handle this situation. - pub treat_byte_string_as_slice: ItemLocalSet, - /// Contains the data for evaluating the effect of feature `capture_disjoint_fields` /// on closure size. pub closure_size_eval: LocalDefIdMap<ClosureSizeProfileData<'tcx>>, @@ -237,7 +231,6 @@ impl<'tcx> TypeckResults<'tcx> { closure_fake_reads: Default::default(), rvalue_scopes: Default::default(), coroutine_stalled_predicates: Default::default(), - treat_byte_string_as_slice: Default::default(), closure_size_eval: Default::default(), offset_of_data: Default::default(), } diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs index 667d59d858e..372453688d2 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs @@ -58,25 +58,13 @@ struct ConstToPat<'tcx> { span: Span, id: hir::HirId, - treat_byte_string_as_slice: bool, - c: ty::Const<'tcx>, } impl<'tcx> ConstToPat<'tcx> { fn new(pat_ctxt: &PatCtxt<'_, 'tcx>, id: hir::HirId, span: Span, c: ty::Const<'tcx>) -> Self { trace!(?pat_ctxt.typeck_results.hir_owner); - ConstToPat { - tcx: pat_ctxt.tcx, - typing_env: pat_ctxt.typing_env, - span, - id, - treat_byte_string_as_slice: pat_ctxt - .typeck_results - .treat_byte_string_as_slice - .contains(&id.local_id), - c, - } + ConstToPat { tcx: pat_ctxt.tcx, typing_env: pat_ctxt.typing_env, span, id, c } } fn type_marked_structural(&self, ty: Ty<'tcx>) -> bool { @@ -108,8 +96,6 @@ impl<'tcx> ConstToPat<'tcx> { uv: ty::UnevaluatedConst<'tcx>, ty: Ty<'tcx>, ) -> Box<Pat<'tcx>> { - trace!(self.treat_byte_string_as_slice); - // It's not *technically* correct to be revealing opaque types here as borrowcheck has // not run yet. However, CTFE itself uses `TypingMode::PostAnalysis` unconditionally even // during typeck and not doing so has a lot of (undesirable) fallout (#101478, #119821). @@ -307,21 +293,8 @@ impl<'tcx> ConstToPat<'tcx> { ty, ); } else { - // `b"foo"` produces a `&[u8; 3]`, but you can't use constants of array type when - // matching against references, you can only use byte string literals. - // The typechecker has a special case for byte string literals, by treating them - // as slices. This means we turn `&[T; N]` constants into slice patterns, which - // has no negative effects on pattern matching, even if we're actually matching on - // arrays. - let pointee_ty = match *pointee_ty.kind() { - ty::Array(elem_ty, _) if self.treat_byte_string_as_slice => { - Ty::new_slice(tcx, elem_ty) - } - _ => *pointee_ty, - }; // References have the same valtree representation as their pointee. - let subpattern = self.valtree_to_pat(cv, pointee_ty); - PatKind::Deref { subpattern } + PatKind::Deref { subpattern: self.valtree_to_pat(cv, *pointee_ty) } } } }, diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs index 4bfeab44bf4..d20e051548b 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs @@ -11,7 +11,7 @@ use rustc_abi::{FieldIdx, Integer}; use rustc_errors::codes::*; use rustc_hir::def::{CtorOf, DefKind, Res}; use rustc_hir::pat_util::EnumerateAndAdjustIterator; -use rustc_hir::{self as hir, RangeEnd}; +use rustc_hir::{self as hir, LangItem, RangeEnd}; use rustc_index::Idx; use rustc_middle::mir::interpret::LitToConstInput; use rustc_middle::thir::{ @@ -130,7 +130,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> { // Lower the endpoint into a temporary `PatKind` that will then be // deconstructed to obtain the constant value and other data. - let mut kind: PatKind<'tcx> = self.lower_pat_expr(expr); + let mut kind: PatKind<'tcx> = self.lower_pat_expr(expr, None); // Unpeel any ascription or inline-const wrapper nodes. loop { @@ -294,7 +294,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> { hir::PatKind::Never => PatKind::Never, - hir::PatKind::Expr(value) => self.lower_pat_expr(value), + hir::PatKind::Expr(value) => self.lower_pat_expr(value, Some(ty)), hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => { let (lo_expr, hi_expr) = (lo_expr.as_deref(), hi_expr.as_deref()); @@ -630,7 +630,11 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> { /// - Paths (e.g. `FOO`, `foo::BAR`, `Option::None`) /// - Inline const blocks (e.g. `const { 1 + 1 }`) /// - Literals, possibly negated (e.g. `-128u8`, `"hello"`) - fn lower_pat_expr(&mut self, expr: &'tcx hir::PatExpr<'tcx>) -> PatKind<'tcx> { + fn lower_pat_expr( + &mut self, + expr: &'tcx hir::PatExpr<'tcx>, + pat_ty: Option<Ty<'tcx>>, + ) -> PatKind<'tcx> { let (lit, neg) = match &expr.kind { hir::PatExprKind::Path(qpath) => { return self.lower_path(qpath, expr.hir_id, expr.span).kind; @@ -641,7 +645,31 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> { hir::PatExprKind::Lit { lit, negated } => (lit, *negated), }; - let ct_ty = self.typeck_results.node_type(expr.hir_id); + // We handle byte string literal patterns by using the pattern's type instead of the + // literal's type in `const_to_pat`: if the literal `b"..."` matches on a slice reference, + // the pattern's type will be `&[u8]` whereas the literal's type is `&[u8; 3]`; using the + // pattern's type means we'll properly translate it to a slice reference pattern. This works + // because slices and arrays have the same valtree representation. + // HACK: As an exception, use the literal's type if `pat_ty` is `String`; this can happen if + // `string_deref_patterns` is enabled. There's a special case for that when lowering to MIR. + // FIXME(deref_patterns): This hack won't be necessary once `string_deref_patterns` is + // superseded by a more general implementation of deref patterns. + let ct_ty = match pat_ty { + Some(pat_ty) + if let ty::Adt(def, _) = *pat_ty.kind() + && self.tcx.is_lang_item(def.did(), LangItem::String) => + { + if !self.tcx.features().string_deref_patterns() { + span_bug!( + expr.span, + "matching on `String` went through without enabling string_deref_patterns" + ); + } + self.typeck_results.node_type(expr.hir_id) + } + Some(pat_ty) => pat_ty, + None => self.typeck_results.node_type(expr.hir_id), + }; let lit_input = LitToConstInput { lit: &lit.node, ty: ct_ty, neg }; let constant = self.tcx.at(expr.span).lit_to_const(lit_input); self.const_to_pat(constant, ct_ty, expr.hir_id, lit.span).kind diff --git a/tests/ui/consts/const_in_pattern/arrays-and-slices.rs b/tests/ui/consts/const_in_pattern/arrays-and-slices.rs new file mode 100644 index 00000000000..bb38490206b --- /dev/null +++ b/tests/ui/consts/const_in_pattern/arrays-and-slices.rs @@ -0,0 +1,53 @@ +//! Tests that arrays and slices in constants aren't interchangeable when used as patterns. + +#[derive(PartialEq, Eq)] +struct SomeStruct<T: ?Sized>(T); + +const BSTR_SIZED: &'static [u8; 3] = b"012"; +const BSTR_UNSIZED: &'static [u8] = BSTR_SIZED; +const STRUCT_SIZED: &'static SomeStruct<[u8; 3]> = &SomeStruct(*BSTR_SIZED); +const STRUCT_UNSIZED: &'static SomeStruct<[u8]> = STRUCT_SIZED; + +fn type_mismatches() { + // Test that array consts can't be used where a slice pattern is expected. This helps ensure + // that `const_to_pat` won't produce irrefutable `thir::PatKind::Array` patterns when matching + // on slices, which would result in missing length checks. + // See also `tests/ui/match/pattern-deref-miscompile.rs`, which tests that byte string literal + // patterns check slices' length appropriately when matching on slices. + match BSTR_UNSIZED { + BSTR_SIZED => {} + //~^ ERROR: mismatched types + _ => {} + } + match STRUCT_UNSIZED { + STRUCT_SIZED => {} + //~^ ERROR: mismatched types + _ => {} + } + + // Test that slice consts can't be used where an array pattern is expected. + match BSTR_UNSIZED { + BSTR_SIZED => {} + //~^ ERROR: mismatched types + _ => {} + } + // If the types matched here, this would still error, since unsized structs aren't permitted in + // constant patterns. See the `invalid_patterns` test below. + match STRUCT_UNSIZED { + STRUCT_SIZED => {} + //~^ ERROR: mismatched types + _ => {} + } +} + +fn invalid_patterns() { + // Test that unsized structs containing slices can't be used as patterns. + // See `tests/ui/consts/issue-87046.rs` for an example with `str`. + match STRUCT_UNSIZED { + STRUCT_UNSIZED => {} + //~^ ERROR: cannot use unsized non-slice type `SomeStruct<[u8]>` in constant patterns + _ => {} + } +} + +fn main() {} diff --git a/tests/ui/consts/const_in_pattern/arrays-and-slices.stderr b/tests/ui/consts/const_in_pattern/arrays-and-slices.stderr new file mode 100644 index 00000000000..412caf60f7d --- /dev/null +++ b/tests/ui/consts/const_in_pattern/arrays-and-slices.stderr @@ -0,0 +1,84 @@ +error[E0308]: mismatched types + --> $DIR/arrays-and-slices.rs:18:9 + | +LL | const BSTR_SIZED: &'static [u8; 3] = b"012"; + | ---------------------------------- constant defined here +... +LL | match BSTR_UNSIZED { + | ------------ this expression has type `&[u8]` +LL | BSTR_SIZED => {} + | ^^^^^^^^^^ + | | + | expected `&[u8]`, found `&[u8; 3]` + | `BSTR_SIZED` is interpreted as a constant, not a new binding + | help: introduce a new binding instead: `other_bstr_sized` + | + = note: expected reference `&[u8]` + found reference `&'static [u8; 3]` + +error[E0308]: mismatched types + --> $DIR/arrays-and-slices.rs:23:9 + | +LL | const STRUCT_SIZED: &'static SomeStruct<[u8; 3]> = &SomeStruct(*BSTR_SIZED); + | ------------------------------------------------ constant defined here +... +LL | match STRUCT_UNSIZED { + | -------------- this expression has type `&SomeStruct<[u8]>` +LL | STRUCT_SIZED => {} + | ^^^^^^^^^^^^ + | | + | expected `&SomeStruct<[u8]>`, found `&SomeStruct<[u8; 3]>` + | `STRUCT_SIZED` is interpreted as a constant, not a new binding + | help: introduce a new binding instead: `other_struct_sized` + | + = note: expected reference `&SomeStruct<[u8]>` + found reference `&'static SomeStruct<[u8; 3]>` + +error[E0308]: mismatched types + --> $DIR/arrays-and-slices.rs:30:9 + | +LL | const BSTR_SIZED: &'static [u8; 3] = b"012"; + | ---------------------------------- constant defined here +... +LL | match BSTR_UNSIZED { + | ------------ this expression has type `&[u8]` +LL | BSTR_SIZED => {} + | ^^^^^^^^^^ + | | + | expected `&[u8]`, found `&[u8; 3]` + | `BSTR_SIZED` is interpreted as a constant, not a new binding + | help: introduce a new binding instead: `other_bstr_sized` + | + = note: expected reference `&[u8]` + found reference `&'static [u8; 3]` + +error[E0308]: mismatched types + --> $DIR/arrays-and-slices.rs:37:9 + | +LL | const STRUCT_SIZED: &'static SomeStruct<[u8; 3]> = &SomeStruct(*BSTR_SIZED); + | ------------------------------------------------ constant defined here +... +LL | match STRUCT_UNSIZED { + | -------------- this expression has type `&SomeStruct<[u8]>` +LL | STRUCT_SIZED => {} + | ^^^^^^^^^^^^ + | | + | expected `&SomeStruct<[u8]>`, found `&SomeStruct<[u8; 3]>` + | `STRUCT_SIZED` is interpreted as a constant, not a new binding + | help: introduce a new binding instead: `other_struct_sized` + | + = note: expected reference `&SomeStruct<[u8]>` + found reference `&'static SomeStruct<[u8; 3]>` + +error: cannot use unsized non-slice type `SomeStruct<[u8]>` in constant patterns + --> $DIR/arrays-and-slices.rs:47:9 + | +LL | const STRUCT_UNSIZED: &'static SomeStruct<[u8]> = STRUCT_SIZED; + | ----------------------------------------------- constant defined here +... +LL | STRUCT_UNSIZED => {} + | ^^^^^^^^^^^^^^ + +error: aborting due to 5 previous errors + +For more information about this error, try `rustc --explain E0308`. |