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Rollup merge of #111100 - BoxyUwU:array_repeat_expr_wf, r=compiler-er…
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…rors

check array type of repeat exprs is wf

Fixes #111091

Also makes sure that we actually renumber regions in the length of repeat exprs which we previously weren't doing and would cause ICEs in `adt_const_params` + `generic_const_exprs` from attempting to prove the wf goals when the length was an unevaluated constant with `'erased` in the `ty` field of `Const`

The duplicate errors are caused by the fact that `const_arg_to_const`/`array_len_to_const` in `FnCtxt` adds a `WellFormed` goal for the created `Const` which is also checked by the added `WellFormed(array_ty)`. I don't want to change this to just emit a `T: Sized` goal for the element type since that would ignore `ConstArgHasType` wf requirements and generally uncomfortable with the idea of trying to sync up `wf::obligations` for arrays and the code in hir typeck for repeat exprs.

r? `@compiler-errors`
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matthiaskrgr authored May 4, 2023
2 parents ea0b650 + 7d9130f commit c0ca84b
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Showing 10 changed files with 94 additions and 6 deletions.
8 changes: 8 additions & 0 deletions compiler/rustc_borrowck/src/renumber.rs
Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,14 @@ impl<'a, 'tcx> MutVisitor<'tcx> for RegionRenumberer<'a, 'tcx> {
debug!(?region);
}

#[instrument(skip(self), level = "debug")]
fn visit_ty_const(&mut self, ct: &mut ty::Const<'tcx>, location: Location) {
let old_ct = *ct;
*ct = self.renumber_regions(old_ct, || RegionCtxt::Location(location));

debug!(?ct);
}

#[instrument(skip(self), level = "debug")]
fn visit_constant(&mut self, constant: &mut Constant<'tcx>, location: Location) {
let literal = constant.literal;
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7 changes: 7 additions & 0 deletions compiler/rustc_borrowck/src/type_check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1801,6 +1801,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
Rvalue::Repeat(operand, len) => {
self.check_operand(operand, location);

let array_ty = rvalue.ty(body.local_decls(), tcx);
self.prove_predicate(
ty::PredicateKind::WellFormed(array_ty.into()),
Locations::Single(location),
ConstraintCategory::Boring,
);

// If the length cannot be evaluated we must assume that the length can be larger
// than 1.
// If the length is larger than 1, the repeat expression will need to copy the
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6 changes: 6 additions & 0 deletions compiler/rustc_hir_typeck/src/expr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1426,6 +1426,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

self.check_repeat_element_needs_copy_bound(element, count, element_ty);

self.register_wf_obligation(
tcx.mk_array_with_const_len(t, count).into(),
expr.span,
traits::WellFormed(None),
);

tcx.mk_array_with_const_len(t, count)
}

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21 changes: 19 additions & 2 deletions compiler/rustc_middle/src/mir/visit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,14 @@ macro_rules! make_mir_visitor {
self.super_constant(constant, location);
}

fn visit_ty_const(
&mut self,
ct: $( & $mutability)? ty::Const<'tcx>,
location: Location,
) {
self.super_ty_const(ct, location);
}

fn visit_span(
&mut self,
span: $(& $mutability)? Span,
Expand Down Expand Up @@ -625,8 +633,9 @@ macro_rules! make_mir_visitor {
self.visit_operand(operand, location);
}

Rvalue::Repeat(value, _) => {
Rvalue::Repeat(value, ct) => {
self.visit_operand(value, location);
self.visit_ty_const($(&$mutability)? *ct, location);
}

Rvalue::ThreadLocalRef(_) => {}
Expand Down Expand Up @@ -878,12 +887,20 @@ macro_rules! make_mir_visitor {
self.visit_span($(& $mutability)? *span);
drop(user_ty); // no visit method for this
match literal {
ConstantKind::Ty(_) => {}
ConstantKind::Ty(ct) => self.visit_ty_const($(&$mutability)? *ct, location),
ConstantKind::Val(_, ty) => self.visit_ty($(& $mutability)? *ty, TyContext::Location(location)),
ConstantKind::Unevaluated(_, ty) => self.visit_ty($(& $mutability)? *ty, TyContext::Location(location)),
}
}

fn super_ty_const(
&mut self,
_ct: $(& $mutability)? ty::Const<'tcx>,
_location: Location,
) {

}

fn super_span(&mut self, _span: $(& $mutability)? Span) {
}

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2 changes: 2 additions & 0 deletions tests/ui/const-generics/sneaky-array-repeat-expr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ impl<const N: usize> Trait<N> for () {
pub const fn foo<const N: usize>() where (): Trait<N> {
let bar = [(); <()>::Assoc];
//~^ error: constant expression depends on a generic parameter
//~| error: constant expression depends on a generic parameter
}

trait Trait2<const N: usize> {
Expand All @@ -24,6 +25,7 @@ impl<const N: usize> Trait2<N> for () {
pub const fn foo2<const N: usize>() where (): Trait2<N> {
let bar2 = [(); <()>::Assoc2];
//~^ error: constant expression depends on a generic parameter
//~| error: constant expression depends on a generic parameter
}

fn main() {
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20 changes: 18 additions & 2 deletions tests/ui/const-generics/sneaky-array-repeat-expr.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -7,12 +7,28 @@ LL | let bar = [(); <()>::Assoc];
= note: this may fail depending on what value the parameter takes

error: constant expression depends on a generic parameter
--> $DIR/sneaky-array-repeat-expr.rs:25:21
--> $DIR/sneaky-array-repeat-expr.rs:11:15
|
LL | let bar = [(); <()>::Assoc];
| ^^^^^^^^^^^^^^^^^
|
= note: this may fail depending on what value the parameter takes

error: constant expression depends on a generic parameter
--> $DIR/sneaky-array-repeat-expr.rs:26:21
|
LL | let bar2 = [(); <()>::Assoc2];
| ^^^^^^^^^^^^
|
= note: this may fail depending on what value the parameter takes

error: aborting due to 2 previous errors
error: constant expression depends on a generic parameter
--> $DIR/sneaky-array-repeat-expr.rs:26:16
|
LL | let bar2 = [(); <()>::Assoc2];
| ^^^^^^^^^^^^^^^^^^
|
= note: this may fail depending on what value the parameter takes

error: aborting due to 4 previous errors

4 changes: 3 additions & 1 deletion tests/ui/consts/issue-50439.rs
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,9 @@ impl<T: Sized> PinDropInternal for Bears<T> {
where
Self: ReflectDrop,
{
let _ = [(); 0 - !!(<Bears<T> as ReflectDrop>::REFLECT_DROP) as usize]; //~ ERROR constant expression depends on a generic parameter
let _ = [(); 0 - !!(<Bears<T> as ReflectDrop>::REFLECT_DROP) as usize];
//~^ ERROR constant expression depends on a generic parameter
//~| ERROR constant expression depends on a generic parameter
}
}

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10 changes: 9 additions & 1 deletion tests/ui/consts/issue-50439.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -6,5 +6,13 @@ LL | let _ = [(); 0 - !!(<Bears<T> as ReflectDrop>::REFLECT_DROP) as usi
|
= note: this may fail depending on what value the parameter takes

error: aborting due to previous error
error: constant expression depends on a generic parameter
--> $DIR/issue-50439.rs:25:17
|
LL | let _ = [(); 0 - !!(<Bears<T> as ReflectDrop>::REFLECT_DROP) as usize];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: this may fail depending on what value the parameter takes

error: aborting due to 2 previous errors

10 changes: 10 additions & 0 deletions tests/ui/typeck/repeat-expr-checks-wf.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
trait Foo {
const ASSOC: [u8];
}

fn bar<T: Foo>() {
let a = [T::ASSOC; 2];
//~^ ERROR: the size for values of type `[u8]` cannot be known at compilation time
}

fn main() {}
12 changes: 12 additions & 0 deletions tests/ui/typeck/repeat-expr-checks-wf.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/repeat-expr-checks-wf.rs:6:13
|
LL | let a = [T::ASSOC; 2];
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `[u8]`
= note: slice and array elements must have `Sized` type

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.

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