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Do not panic in ty::consts::Const::try_to_target_usize() in case of size mismatch #126382

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Do not panic in ty::consts::Const::try_to_target_usize() in case of size mismatch #126382

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20 changes: 19 additions & 1 deletion compiler/rustc_hir_typeck/src/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1402,13 +1402,31 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
expr: &'tcx hir::Expr<'tcx>,
) -> Ty<'tcx> {
let element_ty = if !args.is_empty() {
let mut size_ct = None;
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@compiler-errors compiler-errors Oct 24, 2024 •
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This isn't a sufficient fix. The expectation may always be None, typically by just separating the expression from the place that gives that expectation. For example, I believe this still ICEs:

struct OppOrder<const N: u8 = 3, T = u32> {
    arr: [T; N],
}

fn main() {
    let arr = [0, 0, 0];
    let _ = OppOrder::<3, u32> { arr };
}

let coerce_to = expected
.to_option(self)
.and_then(|uty| match *uty.kind() {
ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
ty::Array(ty, sz_ct) => {
size_ct = Some(sz_ct);
Some(ty)
}
ty::Slice(ty) => Some(ty),
_ => None,
})
.unwrap_or_else(|| self.next_ty_var(expr.span));

// Check if the expected type of array size is something
// other than `usize` which is clearly wrong. Fixes ICE #126359
if let Some(size_ct) = size_ct
&& let ty::ConstKind::Value(size_ty, _) = size_ct.kind()
&& !matches!(size_ty.kind(), ty::Uint(ty::UintTy::Usize))
{
let guar = self.dcx().span_delayed_bug(expr.span, "array size type is not `usize`");
self.set_tainted_by_errors(guar);

return Ty::new_error(self.tcx, guar);
}

let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
assert_eq!(self.diverges.get(), Diverges::Maybe);
for e in args {
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9 changes: 0 additions & 9 deletions tests/crashes/126359.rs
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14 changes: 14 additions & 0 deletions tests/ui/consts/ice-const-size-relate-126359.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
// Regression test for ICE #126359

// Tests that there is no ICE when the generic const
// specifying the size of an array is of a non-usize type

struct OppOrder<const N: u8 = 3, T = u32> {
arr: [T; N],
//~^ ERROR the constant `N` is not of type `usize`
}

fn main() {
let _ = OppOrder::<3, u32> { arr: [0, 0, 0] };
//~^ ERROR the constant `3` is not of type `usize`
}
14 changes: 14 additions & 0 deletions tests/ui/consts/ice-const-size-relate-126359.stderr
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@@ -0,0 +1,14 @@
error: the constant `N` is not of type `usize`
--> $DIR/ice-const-size-relate-126359.rs:7:10
|
LL | arr: [T; N],
| ^^^^^^ expected `usize`, found `u8`

error: the constant `3` is not of type `usize`
--> $DIR/ice-const-size-relate-126359.rs:12:39
|
LL | let _ = OppOrder::<3, u32> { arr: [0, 0, 0] };
| ^^^^^^^^^ expected `usize`, found `u8`

error: aborting due to 2 previous errors

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