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Normalize consts in writeback when GCE is enabled #130645

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Sep 21, 2024
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13 changes: 1 addition & 12 deletions compiler/rustc_hir_typeck/src/pat.rs
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,6 @@ use rustc_hir::def::{CtorKind, DefKind, Res};
use rustc_hir::pat_util::EnumerateAndAdjustIterator;
use rustc_hir::{self as hir, BindingMode, ByRef, HirId, LangItem, Mutability, Pat, PatKind};
use rustc_infer::infer;
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::ty::{self, Ty, TypeVisitableExt};
use rustc_middle::{bug, span_bug};
use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
Expand Down Expand Up @@ -2413,17 +2412,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
len: ty::Const<'tcx>,
min_len: u64,
) -> (Option<Ty<'tcx>>, Ty<'tcx>) {
let len = match len.eval(self.tcx, self.param_env, span) {
Ok((_, val)) => val
.try_to_scalar()
.and_then(|scalar| scalar.try_to_scalar_int().ok())
.map(|int| int.to_target_usize(self.tcx)),
Err(ErrorHandled::Reported(..)) => {
let guar = self.error_scrutinee_unfixed_length(span);
return (Some(Ty::new_error(self.tcx, guar)), arr_ty);
}
Err(ErrorHandled::TooGeneric(..)) => None,
};
let len = len.try_eval_target_usize(self.tcx, self.param_env);

let guar = if let Some(len) = len {
// Now we know the length...
Expand Down
37 changes: 33 additions & 4 deletions compiler/rustc_hir_typeck/src/writeback.rs
Original file line number Diff line number Diff line change
Expand Up @@ -803,7 +803,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
// We must deeply normalize in the new solver, since later lints
// expect that types that show up in the typeck are fully
// normalized.
let value = if self.should_normalize {
let mut value = if self.should_normalize {
let body_id = tcx.hir().body_owner_def_id(self.body.id());
let cause = ObligationCause::misc(self.span.to_span(tcx), body_id);
let at = self.fcx.at(&cause, self.fcx.param_env);
Expand All @@ -818,12 +818,27 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
value
};

// Bail if there are any non-region infer.
if value.has_non_region_infer() {
let guar = self.report_error(value);
new_err(tcx, guar)
} else {
tcx.fold_regions(value, |_, _| tcx.lifetimes.re_erased)
value = new_err(tcx, guar);
}

// Erase the regions from the ty, since it's not really meaningful what
// these region values are; there's not a trivial correspondence between
// regions in the HIR and MIR, so when we turn the body into MIR, there's
// no reason to keep regions around. They will be repopulated during MIR
// borrowck, and specifically region constraints will be populated during
// MIR typeck which is run on the new body.
value = tcx.fold_regions(value, |_, _| tcx.lifetimes.re_erased);

// Normalize consts in writeback, because GCE doesn't normalize eagerly.
if tcx.features().generic_const_exprs {
value =
value.fold_with(&mut EagerlyNormalizeConsts { tcx, param_env: self.fcx.param_env });
}

value
}
}

Expand Down Expand Up @@ -858,3 +873,17 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Resolver<'cx, 'tcx> {
predicate
}
}

struct EagerlyNormalizeConsts<'tcx> {
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for EagerlyNormalizeConsts<'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.tcx
}

fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
self.tcx.try_normalize_erasing_regions(self.param_env, ct).unwrap_or(ct)
}
}
3 changes: 1 addition & 2 deletions tests/ui/const-generics/generic_const_exprs/issue-109141.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@

impl EntriesBuffer {
fn a(&self) -> impl Iterator {
self.0.iter_mut() //~ ERROR: cannot borrow `*self.0` as mutable, as it is behind a `&` reference
//~| ERROR captures lifetime that does not appear in bounds
self.0.iter_mut()
}
}

Expand Down
33 changes: 3 additions & 30 deletions tests/ui/const-generics/generic_const_exprs/issue-109141.stderr
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error[E0425]: cannot find value `HashesEntryLEN` in this scope
--> $DIR/issue-109141.rs:11:32
--> $DIR/issue-109141.rs:10:32
|
LL | struct EntriesBuffer(Box<[[u8; HashesEntryLEN]; 5]>);
| ^^^^^^^^^^^^^^ not found in this scope
Expand All @@ -9,33 +9,6 @@ help: you might be missing a const parameter
LL | struct EntriesBuffer<const HashesEntryLEN: /* Type */>(Box<[[u8; HashesEntryLEN]; 5]>);
| ++++++++++++++++++++++++++++++++++

error[E0596]: cannot borrow `*self.0` as mutable, as it is behind a `&` reference
--> $DIR/issue-109141.rs:6:9
|
LL | self.0.iter_mut()
| ^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
|
help: consider changing this to be a mutable reference
|
LL | fn a(&mut self) -> impl Iterator {
| ~~~~~~~~~

error[E0700]: hidden type for `impl Iterator` captures lifetime that does not appear in bounds
--> $DIR/issue-109141.rs:6:9
|
LL | fn a(&self) -> impl Iterator {
| ----- ------------- opaque type defined here
| |
| hidden type `std::slice::IterMut<'_, [u8; {const error}]>` captures the anonymous lifetime defined here
LL | self.0.iter_mut()
| ^^^^^^^^^^^^^^^^^
|
help: add a `use<...>` bound to explicitly capture `'_`
|
LL | fn a(&self) -> impl Iterator + use<'_> {
| +++++++++

error: aborting due to 3 previous errors
error: aborting due to 1 previous error

Some errors have detailed explanations: E0425, E0596, E0700.
For more information about an error, try `rustc --explain E0425`.
For more information about this error, try `rustc --explain E0425`.
1 change: 0 additions & 1 deletion tests/ui/const-generics/generic_const_exprs/opaque_type.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@
#![allow(incomplete_features)]

type Foo = impl Sized;
//~^ ERROR: unconstrained opaque type

fn with_bound<const N: usize>() -> Foo
where
Expand Down
14 changes: 3 additions & 11 deletions tests/ui/const-generics/generic_const_exprs/opaque_type.stderr
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error[E0308]: mismatched types
--> $DIR/opaque_type.rs:11:17
--> $DIR/opaque_type.rs:10:17
|
LL | type Foo = impl Sized;
| ---------- the found opaque type
Expand All @@ -11,20 +11,12 @@ LL | let _: [u8; (N / 2) as Foo] = [0; (N / 2) as usize];
found opaque type `Foo`

error[E0605]: non-primitive cast: `usize` as `Foo`
--> $DIR/opaque_type.rs:11:17
--> $DIR/opaque_type.rs:10:17
|
LL | let _: [u8; (N / 2) as Foo] = [0; (N / 2) as usize];
| ^^^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object

error: unconstrained opaque type
--> $DIR/opaque_type.rs:4:12
|
LL | type Foo = impl Sized;
| ^^^^^^^^^^
|
= note: `Foo` must be used in combination with a concrete type within the same module

error: aborting due to 3 previous errors
error: aborting due to 2 previous errors

Some errors have detailed explanations: E0308, E0605.
For more information about an error, try `rustc --explain E0308`.
2 changes: 1 addition & 1 deletion tests/ui/consts/issue-116186.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
fn something(path: [usize; N]) -> impl Clone {
//~^ ERROR cannot find value `N` in this scope
match path {
[] => 0, //~ ERROR cannot pattern-match on an array without a fixed length
[] => 0,
_ => 1,
};
}
Expand Down
11 changes: 2 additions & 9 deletions tests/ui/consts/issue-116186.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,6 @@ help: you might be missing a const parameter
LL | fn something<const N: /* Type */>(path: [usize; N]) -> impl Clone {
| +++++++++++++++++++++

error[E0730]: cannot pattern-match on an array without a fixed length
--> $DIR/issue-116186.rs:7:9
|
LL | [] => 0,
| ^^

error: aborting due to 2 previous errors
error: aborting due to 1 previous error

Some errors have detailed explanations: E0425, E0730.
For more information about an error, try `rustc --explain E0425`.
For more information about this error, try `rustc --explain E0425`.
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