Check for array lengths that aren't actually usize · rust-lang/rust@43a79a0 (original) (raw)
`@@ -647,13 +647,31 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
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`match place_ty.kind() {
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` ty::Array(_elem_ty, len_const) => {
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// We know how long an array is, so just use that as a constant
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// directly -- no locals needed. We do need one statement so
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// that borrow- and initialization-checking consider it used,
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// though. FIXME: Do we really need to count this as a use?
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// Could partial array tracking work off something else instead?
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self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
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let const_ = Const::from_ty_const(*len_const, usize_ty, self.tcx);
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let ty_const = if let Some((_, len_ty)) = len_const.try_to_valtree()
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&& len_ty != self.tcx.types.usize
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{
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// Bad const generics can give us a constant from the type that's
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// not actually a usize, so in that case give an error instead.
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// FIXME: It'd be nice if the type checker made sure this wasn't
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// possible, instead.
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let err = self.tcx.dcx().span_delayed_bug(
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span,
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format!(
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"Array length should have already been a type error, as it's {len_ty:?}"
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),
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);
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ty::Const::new_error(self.tcx, err)
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} else {
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// We know how long an array is, so just use that as a constant
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// directly -- no locals needed. We do need one statement so
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// that borrow- and initialization-checking consider it used,
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``
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// though. FIXME: Do we really need to count this as a use?
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// Could partial array tracking work off something else instead?
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self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
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*len_const
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};
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let const_ = Const::from_ty_const(ty_const, usize_ty, self.tcx);
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`Operand::Constant(Box::new(ConstOperand { span, user_ty: None, const_ }))
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`}
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` ty::Slice(_elem_ty) => {
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