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Add a method to create an arbitrary OpTy from outside rustc_mir #61718

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Add a method to create an arbitrary OpTy from outside rustc_mir #61718

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19 changes: 14 additions & 5 deletions src/librustc_mir/interpret/operand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,7 @@ use rustc::mir::interpret::{
InterpResult, InterpError, InboundsCheck,
sign_extend, truncate,
};
use super::{
InterpretCx, Machine,
MemPlace, MPlaceTy, PlaceTy, Place,
};
use super::{InterpretCx, Machine, MemPlace, MPlaceTy, PlaceTy, Place};
pub use rustc::mir::interpret::ScalarMaybeUndef;

/// A `Value` represents a single immediate self-contained Rust value.
Expand Down Expand Up @@ -190,6 +187,19 @@ impl<'tcx, Tag: Copy> ImmTy<'tcx, Tag>
}
}

impl<'tcx, Tag> OpTy<'tcx, Tag>
{
/// This is used by [priroda](https://github.com/oli-obk/priroda) to create an `OpTy`.
///
/// Do not use this from inside rustc.
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Can you expand a bit on why this shouldn't be used from inside rustc? Is it just that this operation is unchecked or does it violate some other assumption?

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I thought that somebody wanted to prevent having a method like this to prevent accidental misusage or something like that, but in #55179 I can really find anything like that except for "I wanted to have something like an abstraction here" by @RalfJung.

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The *Ty types have successfully found and prevent several bugs. Currently the only "hole" in the scheme is ImmTy, you can construct arbitrary immediates from the outside. I was very happy when I managed to make OpTy private and only expose ImmTy instead, having to un-do this would be very sad. :(

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Really the advice here should be "do not use this, period". This is not an inside-rustc vs outside-rustc distinction.

pub fn from_op_and_layout_unchecked(op: Operand<Tag>, layout: TyLayout<'tcx>) -> Self {
OpTy {
op,
layout,
}
}
}

// Use the existing layout if given (but sanity check in debug mode),
// or compute the layout.
#[inline(always)]
Expand Down Expand Up @@ -395,7 +405,6 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
})
}

/// This is used by [priroda](https://github.com/oli-obk/priroda) to get an OpTy from a local
pub fn access_local(
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Does that mean we can make the method private?

&self,
frame: &super::Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>,
Expand Down