diff options
Diffstat (limited to 'compiler/rustc_mir_build/src')
4 files changed, 43 insertions, 10 deletions
diff --git a/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs index a4ef6e92739..3a5839f2d40 100644 --- a/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs +++ b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs @@ -8,6 +8,7 @@ use rustc_middle::middle::region; use rustc_middle::mir::interpret::Scalar; use rustc_middle::mir::*; use rustc_middle::thir::*; +use rustc_middle::ty::adjustment::PointerCoercion; use rustc_middle::ty::cast::{CastTy, mir_cast_kind}; use rustc_middle::ty::util::IntTypeExt; use rustc_middle::ty::{self, Ty, UpvarArgs}; @@ -656,6 +657,27 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { block.and(rvalue) } + /// Recursively inspect a THIR expression and probe through unsizing + /// operations that can be const-folded today. + fn check_constness(&self, mut kind: &'a ExprKind<'tcx>) -> bool { + loop { + debug!(?kind, "check_constness"); + match kind { + &ExprKind::ValueTypeAscription { source: eid, user_ty: _, user_ty_span: _ } + | &ExprKind::Use { source: eid } + | &ExprKind::PointerCoercion { + cast: PointerCoercion::Unsize, + source: eid, + is_from_as_cast: _, + } + | &ExprKind::Scope { region_scope: _, lint_level: _, value: eid } => { + kind = &self.thir[eid].kind + } + _ => return matches!(Category::of(&kind), Some(Category::Constant)), + } + } + } + fn build_zero_repeat( &mut self, mut block: BasicBlock, @@ -666,7 +688,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> { let this = self; let value_expr = &this.thir[value]; let elem_ty = value_expr.ty; - if let Some(Category::Constant) = Category::of(&value_expr.kind) { + if this.check_constness(&value_expr.kind) { // Repeating a const does nothing } else { // For a non-const, we may need to generate an appropriate `Drop` diff --git a/compiler/rustc_mir_build/src/builder/mod.rs b/compiler/rustc_mir_build/src/builder/mod.rs index cdb2c5561ce..7ca94e655fb 100644 --- a/compiler/rustc_mir_build/src/builder/mod.rs +++ b/compiler/rustc_mir_build/src/builder/mod.rs @@ -395,12 +395,10 @@ enum NeedsTemporary { Maybe, } -/////////////////////////////////////////////////////////////////////////// /// The `BlockAnd` "monad" packages up the new basic block along with a /// produced value (sometimes just unit, of course). The `unpack!` /// macro (and methods below) makes working with `BlockAnd` much more /// convenient. - #[must_use = "if you don't use one of these results, you're leaving a dangling edge"] struct BlockAnd<T>(BasicBlock, T); @@ -438,9 +436,7 @@ macro_rules! unpack { }}; } -/////////////////////////////////////////////////////////////////////////// -/// the main entry point for building MIR for a function - +/// The main entry point for building MIR for a function. fn construct_fn<'tcx>( tcx: TyCtxt<'tcx>, fn_def: LocalDefId, diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs index b5e165c7517..195d45c2c4c 100644 --- a/compiler/rustc_mir_build/src/check_unsafety.rs +++ b/compiler/rustc_mir_build/src/check_unsafety.rs @@ -554,6 +554,21 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> { visit::walk_expr(self, &self.thir[arg]); return; } + + // Secondly, we allow raw borrows of union field accesses. Peel + // any of those off, and recurse normally on the LHS, which should + // reject any unsafe operations within. + let mut peeled = arg; + while let ExprKind::Scope { value: arg, .. } = self.thir[peeled].kind + && let ExprKind::Field { lhs, name: _, variant_index: _ } = self.thir[arg].kind + && let ty::Adt(def, _) = &self.thir[lhs].ty.kind() + && def.is_union() + { + peeled = lhs; + } + visit::walk_expr(self, &self.thir[peeled]); + // And return so we don't recurse directly onto the union field access(es). + return; } ExprKind::Deref { arg } => { if let ExprKind::StaticRef { def_id, .. } | ExprKind::ThreadLocalRef(def_id) = diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs index ae67bb5075e..3929a97eed8 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs @@ -1275,13 +1275,13 @@ fn report_non_exhaustive_match<'p, 'tcx>( if ty.is_ptr_sized_integral() { if ty.inner() == cx.tcx.types.usize { err.note(format!( - "`{ty}` does not have a fixed maximum value, so half-open ranges are \ - necessary to match exhaustively", + "`{ty}::MAX` is not treated as exhaustive, \ + so half-open ranges are necessary to match exhaustively", )); } else if ty.inner() == cx.tcx.types.isize { err.note(format!( - "`{ty}` does not have fixed minimum and maximum values, so half-open \ - ranges are necessary to match exhaustively", + "`{ty}::MIN` and `{ty}::MAX` are not treated as exhaustive, \ + so half-open ranges are necessary to match exhaustively", )); } } else if ty.inner() == cx.tcx.types.str_ { |