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Fix const eval of ZST index operations to make the static assertion work

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This commit is contained in:
Oliver Schneider 2018-09-10 17:46:30 +02:00
parent 24dca6aeca
commit d1b5231aa7
2 changed files with 15 additions and 4 deletions
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14
src/librustc_mir/interpret/operand.rs
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@ -340,7 +340,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
let field = field.try_into().unwrap(); let field = field.try_into().unwrap();
let field_layout = op.layout.field(self, field)?; let field_layout = op.layout.field(self, field)?;
if field_layout.size.bytes() == 0 { if field_layout.is_zst() {
let val = Value::Scalar(Scalar::zst().into()); let val = Value::Scalar(Scalar::zst().into());
return Ok(OpTy { op: Operand::Immediate(val), layout: field_layout }); return Ok(OpTy { op: Operand::Immediate(val), layout: field_layout });
} }
@ -397,9 +397,15 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
Field(field, _) => self.operand_field(base, field.index() as u64)?, Field(field, _) => self.operand_field(base, field.index() as u64)?,
Downcast(_, variant) => self.operand_downcast(base, variant)?, Downcast(_, variant) => self.operand_downcast(base, variant)?,
Deref => self.deref_operand(base)?.into(), Deref => self.deref_operand(base)?.into(),
// The rest should only occur as mplace, we do not use Immediates for types Subslice { .. } | ConstantIndex { .. } | Index(_) => if base.layout.is_zst() {
// allowing such operations. This matches place_projection forcing an allocation. OpTy {
Subslice { .. } | ConstantIndex { .. } | Index(_) => { op: Operand::Immediate(Value::Scalar(Scalar::zst().into())),
// the actual index doesn't matter, so we just pick a convenient one like 0
layout: base.layout.field(self, 0)?,
}
} else {
// The rest should only occur as mplace, we do not use Immediates for types
// allowing such operations. This matches place_projection forcing an allocation.
let mplace = base.to_mem_place(); let mplace = base.to_mem_place();
self.mplace_projection(mplace, proj_elem)?.into() self.mplace_projection(mplace, proj_elem)?.into()
} }

5
src/test/ui/consts/const-eval/zst_operand_eval.rs Normal file
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@ -0,0 +1,5 @@
// compile-pass
static ASSERT: () = [()][(std::mem::size_of::<u32>() != 4) as usize];
fn main() {}