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Do not assert in op_to_const. #117441

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merged 6 commits into from
Nov 2, 2023
Merged

Do not assert in op_to_const. #117441

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c2f49e9
Do not assert in op_to_const.
cjgillot Oct 31, 2023
a2e151c
Make ui into mir-opt test.
cjgillot Oct 31, 2023
3a55c28
Rename hook.
cjgillot Oct 31, 2023
0f8f77f
Rebase fallout.
cjgillot Nov 1, 2023
224e290
Specify diagnostic path.
cjgillot Nov 1, 2023
f512f91
Comment `for_diagnostics` flag.
cjgillot Nov 1, 2023
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13 changes: 10 additions & 3 deletions compiler/rustc_const_eval/src/const_eval/eval_queries.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,7 @@ pub(crate) fn mk_eval_cx<'mir, 'tcx>(
pub(super) fn op_to_const<'tcx>(
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Please extend the doc comment (sadly github doesn't let me put a suggestion there...)

/// The `for_diagnostics` flag turns the usual rules for returning `ConstValue::Scalar` into a best-effort
/// attempt. This is not okay for use in const-eval sine it breaks invariants rustc relies on, but
/// it is okay for diagnostics which will just give up gracefully when they encounter an `Indirect` they
/// cannot handle.

ecx: &CompileTimeEvalContext<'_, 'tcx>,
op: &OpTy<'tcx>,
for_diagnostics: bool,
) -> ConstValue<'tcx> {
// Handle ZST consistently and early.
if op.layout.is_zst() {
Expand All @@ -132,8 +133,14 @@ pub(super) fn op_to_const<'tcx>(
// functionality.)
_ => false,
};
let immediate = if force_as_immediate && let Ok(imm) = ecx.read_immediate(op) {
Right(imm)
let immediate = if force_as_immediate {
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I wonder, would it work to just say if !force_as_immediate && force_as_immediate here? Then we could avoid "catching" entirely.

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I tried it. This would degrade diagnostics significantly, as we wont be able to output an Option<u32> as a Some(99_usize), just Some(Indirect { stuff }), which IMO is much harder to use.

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@RalfJung RalfJung Nov 1, 2023 •
edited
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This could be alleviated by equipping the diagnostic code with support for printing integers that are Indirect. Not sure if that's worth it though.

match ecx.read_immediate(op) {
Ok(imm) => Right(imm),
Err(err) if !for_diagnostics => {
panic!("normalization works on validated constants: {err:?}")
}
_ => op.as_mplace_or_imm(),
}
} else {
op.as_mplace_or_imm()
};
Expand Down Expand Up @@ -205,7 +212,7 @@ pub(crate) fn turn_into_const_value<'tcx>(
);

// Turn this into a proper constant.
op_to_const(&ecx, &mplace.into())
op_to_const(&ecx, &mplace.into(), /* for diagnostics */ false)
}

#[instrument(skip(tcx), level = "debug")]
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_const_eval/src/const_eval/mod.rs
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Expand Up @@ -99,7 +99,7 @@ pub(crate) fn try_destructure_mir_constant_for_user_output<'tcx>(
let fields_iter = (0..field_count)
.map(|i| {
let field_op = ecx.project_field(&down, i).ok()?;
let val = op_to_const(&ecx, &field_op);
let val = op_to_const(&ecx, &field_op, /* for diagnostics */ true);
Some((val, field_op.layout.ty))
})
.collect::<Option<Vec<_>>>()?;
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_const_eval/src/const_eval/valtrees.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -232,7 +232,7 @@ pub fn valtree_to_const_value<'tcx>(
let mut ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, CanAccessStatics::No);
let imm = valtree_to_ref(&mut ecx, valtree, *inner_ty);
let imm = ImmTy::from_immediate(imm, tcx.layout_of(param_env_ty).unwrap());
op_to_const(&ecx, &imm.into())
op_to_const(&ecx, &imm.into(), /* for diagnostics */ false)
}
ty::Tuple(_) | ty::Array(_, _) | ty::Adt(..) => {
let layout = tcx.layout_of(param_env_ty).unwrap();
Expand Down Expand Up @@ -265,7 +265,7 @@ pub fn valtree_to_const_value<'tcx>(
dump_place(&ecx, &place);
intern_const_alloc_recursive(&mut ecx, InternKind::Constant, &place).unwrap();

op_to_const(&ecx, &place.into())
op_to_const(&ecx, &place.into(), /* for diagnostics */ false)
}
ty::Never
| ty::Error(_)
Expand Down
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