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Fix the reporting of layout normalization failures in transmute checks #159456

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Fix the reporting of layout normalization failures in transmute checks #159456

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20 changes: 8 additions & 12 deletions compiler/rustc_hir_typeck/src/intrinsicck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,20 +75,16 @@ fn check_transmute<'tcx>(
hir_id: HirId,
) -> Result<(), ErrorGuaranteed> {
let span = tcx.hir_span(hir_id);
let normalize = |ty| {
if let Ok(ty) = tcx.try_normalize_erasing_regions(typing_env, Unnormalized::new_wip(ty)) {
ty
} else {
Ty::new_error_with_message(
tcx,
span,
format!("tried to normalize non-wf type {ty:#?} in check_transmute"),
)
}
let normalize = |ty| -> Result<Ty<'tcx>, ErrorGuaranteed> {
tcx.try_normalize_erasing_regions(typing_env, Unnormalized::new_wip(ty)).map_err(|err| {
tcx.dcx()
.struct_span_err(span, LayoutError::NormalizationFailure(ty, err).to_string())
.emit()
})
};

let from = normalize(from);
let to = normalize(to);
let from = normalize(from)?;
let to = normalize(to)?;
trace!(?from, ?to);

// Transmutes that are only changing lifetimes are always ok.
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4 changes: 1 addition & 3 deletions tests/ui/layout/normalization-failure.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,9 +48,7 @@ fn opaque<T>() -> impl Project2 {
fn check<T: Project1>() {
unsafe {
std::mem::transmute::<_, ()>(opaque::<T>().get());
//~^ ERROR: cannot transmute
//~| NOTE: source type: `{type error}` (the type has an unknown layout)
//~| NOTE: target type: `()` (0 bits)
//~^ ERROR: unable to determine layout
}
}

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6 changes: 1 addition & 5 deletions tests/ui/layout/normalization-failure.stderr
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Original file line number Diff line number Diff line change
@@ -1,12 +1,8 @@
error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
error: unable to determine layout for `<impl Project2 as Project2>::Assoc2` because `<impl Project2 as Project2>::Assoc2` cannot be normalized
--> $DIR/normalization-failure.rs:50:9
|
LL | std::mem::transmute::<_, ()>(opaque::<T>().get());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: source type: `{type error}` (the type has an unknown layout)
= note: target type: `()` (0 bits)

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0512`.
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