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Do not consider traits that have unsatisfied const conditions to be conditionally const

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This commit is contained in:
Michael Goulet 2025-01-13 02:03:41 +00:00
parent 8c39ce5b4f
commit 2669f2a7c7
6 changed files with 34 additions and 26 deletions
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26
compiler/rustc_const_eval/src/check_consts/check.rs
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@ -35,6 +35,12 @@ use crate::errors;
type QualifResults<'mir, 'tcx, Q> =
rustc_mir_dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'mir, 'mir, 'tcx, Q>>;
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
enum ConstConditionsHold {
Yes,
No,
}
#[derive(Default)]
pub(crate) struct Qualifs<'mir, 'tcx> {
has_mut_interior: Option<QualifResults<'mir, 'tcx, HasMutInterior>>,
@ -376,15 +382,15 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
callee: DefId,
callee_args: ty::GenericArgsRef<'tcx>,
call_span: Span,
) -> bool {
) -> Option<ConstConditionsHold> {
let tcx = self.tcx;
if !tcx.is_conditionally_const(callee) {
return false;
return None;
}
let const_conditions = tcx.const_conditions(callee).instantiate(tcx, callee_args);
if const_conditions.is_empty() {
return false;
return None;
}
let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(self.body.typing_env(tcx));
@ -413,12 +419,13 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
}));
let errors = ocx.select_all_or_error();
if !errors.is_empty() {
if errors.is_empty() {
Some(ConstConditionsHold::Yes)
} else {
tcx.dcx()
.span_delayed_bug(call_span, "this should have reported a ~const error in HIR");
Some(ConstConditionsHold::No)
}
true
}
pub fn check_drop_terminator(
@ -706,7 +713,10 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
trace!("attempting to call a trait method");
let trait_is_const = tcx.is_const_trait(trait_did);
if trait_is_const {
// Only consider a trait to be const if the const conditions hold.
// Otherwise, it's really misleading to call something "conditionally"
// const when it's very obviously not conditionally const.
if trait_is_const && has_const_conditions == Some(ConstConditionsHold::Yes) {
// Trait calls are always conditionally-const.
self.check_op(ops::ConditionallyConstCall {
callee,
@ -730,7 +740,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
}
// Even if we know the callee, ensure we can use conditionally-const calls.
if has_const_conditions {
if has_const_conditions.is_some() {
self.check_op(ops::ConditionallyConstCall {
callee,
args: fn_args,