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use super::QueryCtxt;
use rustc_middle::ty::{self, AdtSizedConstraint, Ty};
pub(super) trait Value<'tcx>: Sized {
fn from_cycle_error(tcx: QueryCtxt<'tcx>) -> Self;
}
impl<'tcx, T> Value<'tcx> for T {
default fn from_cycle_error(tcx: QueryCtxt<'tcx>) -> T {
tcx.sess.abort_if_errors();
bug!("Value::from_cycle_error called without errors");
}
}
impl<'tcx> Value<'tcx> for Ty<'_> {
fn from_cycle_error(tcx: QueryCtxt<'tcx>) -> Self {
// SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(tcx.ty_error()) }
}
}
impl<'tcx> Value<'tcx> for ty::SymbolName<'_> {
fn from_cycle_error(tcx: QueryCtxt<'tcx>) -> Self {
// SAFETY: This is never called when `Self` is not `SymbolName<'tcx>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe {
std::mem::transmute::<ty::SymbolName<'tcx>, ty::SymbolName<'_>>(ty::SymbolName::new(
*tcx, "<error>",
))
}
}
}
impl<'tcx> Value<'tcx> for AdtSizedConstraint<'_> {
fn from_cycle_error(tcx: QueryCtxt<'tcx>) -> Self {
// SAFETY: This is never called when `Self` is not `AdtSizedConstraint<'tcx>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe {
std::mem::transmute::<AdtSizedConstraint<'tcx>, AdtSizedConstraint<'_>>(
AdtSizedConstraint(tcx.intern_type_list(&[tcx.ty_error()])),
)
}
}
}
impl<'tcx> Value<'tcx> for ty::Binder<'_, ty::FnSig<'_>> {
fn from_cycle_error(tcx: QueryCtxt<'tcx>) -> Self {
let err = tcx.ty_error();
// FIXME(compiler-errors): It would be nice if we could get the
// query key, so we could at least generate a fn signature that
// has the right arity.
let fn_sig = ty::Binder::dummy(tcx.mk_fn_sig(
[].into_iter(),
err,
false,
rustc_hir::Unsafety::Normal,
rustc_target::spec::abi::Abi::Rust,
));
// SAFETY: This is never called when `Self` is not `ty::Binder<'tcx, ty::FnSig<'tcx>>`.
// FIXME: Represent the above fact in the trait system somehow.
unsafe { std::mem::transmute::<ty::PolyFnSig<'tcx>, ty::Binder<'_, ty::FnSig<'_>>>(fn_sig) }
}
}
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