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Rollup merge of #138962 - xizheyin:issue-138836, r=compiler-errors

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Expect an array when expected and acutal types are both arrays during cast

Closes #138836
This commit is contained in:
Jacob Pratt 2025-04-13 17:37:52 -04:00 committed by GitHub
commit 60c76b9dfd
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5 changed files with 37 additions and 22 deletions
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37
compiler/rustc_hir_typeck/src/cast.rs
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@ -1042,30 +1042,31 @@ impl<'a, 'tcx> CastCheck<'tcx> {
m_cast: ty::TypeAndMut<'tcx>,
) -> Result<CastKind, CastError<'tcx>> {
// array-ptr-cast: allow mut-to-mut, mut-to-const, const-to-const
if m_expr.mutbl >= m_cast.mutbl {
if let ty::Array(ety, _) = m_expr.ty.kind() {
// Due to the limitations of LLVM global constants,
// region pointers end up pointing at copies of
// vector elements instead of the original values.
// To allow raw pointers to work correctly, we
// need to special-case obtaining a raw pointer
// from a region pointer to a vector.
if m_expr.mutbl >= m_cast.mutbl
&& let ty::Array(ety, _) = m_expr.ty.kind()
&& fcx.can_eq(fcx.param_env, *ety, m_cast.ty)
{
// Due to the limitations of LLVM global constants,
// region pointers end up pointing at copies of
// vector elements instead of the original values.
// To allow raw pointers to work correctly, we
// need to special-case obtaining a raw pointer
// from a region pointer to a vector.
// Coerce to a raw pointer so that we generate RawPtr in MIR.
let array_ptr_type = Ty::new_ptr(fcx.tcx, m_expr.ty, m_expr.mutbl);
fcx.coerce(self.expr, self.expr_ty, array_ptr_type, AllowTwoPhase::No, None)
.unwrap_or_else(|_| {
bug!(
// Coerce to a raw pointer so that we generate RawPtr in MIR.
let array_ptr_type = Ty::new_ptr(fcx.tcx, m_expr.ty, m_expr.mutbl);
fcx.coerce(self.expr, self.expr_ty, array_ptr_type, AllowTwoPhase::No, None)
.unwrap_or_else(|_| {
bug!(
"could not cast from reference to array to pointer to array ({:?} to {:?})",
self.expr_ty,
array_ptr_type,
)
});
});
// this will report a type mismatch if needed
fcx.demand_eqtype(self.span, *ety, m_cast.ty);
return Ok(CastKind::ArrayPtrCast);
}
// this will report a type mismatch if needed
fcx.demand_eqtype(self.span, *ety, m_cast.ty);
return Ok(CastKind::ArrayPtrCast);
}
Err(CastError::IllegalCast)

5
tests/ui/cast/cast-array-issue-138836.rs Normal file
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@ -0,0 +1,5 @@
fn main() {
let a: [u8; 3] = [1,2,3];
let b = &a;
let c = b as *const [u32; 3]; //~ ERROR casting `&[u8; 3]` as `*const [u32; 3]` is invalid
}

9
tests/ui/cast/cast-array-issue-138836.stderr Normal file
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@ -0,0 +1,9 @@
error[E0606]: casting `&[u8; 3]` as `*const [u32; 3]` is invalid
--> $DIR/cast-array-issue-138836.rs:4:13
|
LL | let c = b as *const [u32; 3];
| ^^^^^^^^^^^^^^^^^^^^
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0606`.

2
tests/ui/consts/const-cast-wrong-type.rs
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@ -1,5 +1,5 @@
const a: [u8; 3] = ['h' as u8, 'i' as u8, 0 as u8];
const b: *const i8 = &a as *const i8; //~ ERROR mismatched types
const b: *const i8 = &a as *const i8; //~ ERROR casting `&[u8; 3]` as `*const i8` is invalid
fn main() {
}

6
tests/ui/consts/const-cast-wrong-type.stderr
View File

@ -1,9 +1,9 @@
error[E0308]: mismatched types
error[E0606]: casting `&[u8; 3]` as `*const i8` is invalid
--> $DIR/const-cast-wrong-type.rs:2:22
|
LL | const b: *const i8 = &a as *const i8;
| ^^^^^^^^^^^^^^^ expected `u8`, found `i8`
| ^^^^^^^^^^^^^^^
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0308`.
For more information about this error, try `rustc --explain E0606`.