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Rollup merge of #99651 - compiler-errors:fn-and-raw-ptr-in-const-generics, r=oli-obk

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Deeply deny fn and raw ptrs in const generics

I think this is right -- just because we wrap a fn ptr in a wrapper type does not mean we should allow it in a const parameter.

We now reject both of these in the same way:

```
#![feature(adt_const_params)]

#[derive(Eq, PartialEq)]
struct Wrapper();

fn foo<const W: Wrapper>() {}

fn foo2<const F: fn()>() {}
```

This does regress one test (`src/test/ui/consts/refs_check_const_eq-issue-88384.stderr`), but I'm not sure it should've passed in the first place.

cc: ``@b-naber`` who introduced that test^
fixes #99641
This commit is contained in:
Guillaume Gomez 2022-07-27 17:55:04 +02:00 • committed by GitHub
commit 9e7b7d5e1c
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GPG key ID: 4AEE18F83AFDEB23
18 changed files with 193 additions and 139 deletions
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2
compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
View file

@ -226,7 +226,7 @@ impl Qualif for CustomEq {
// because that component may be part of an enum variant (e.g.,
// `Option::<NonStructuralMatchTy>::Some`), in which case some values of this type may be
// structural-match (`Option::None`).
traits::search_for_structural_match_violation(cx.body.span, cx.tcx, ty, true).is_some()
traits::search_for_structural_match_violation(cx.body.span, cx.tcx, ty).is_some()
}
fn in_adt_inherently<'tcx>(

2
compiler/rustc_middle/src/ty/consts.rs
View file

@ -203,7 +203,7 @@ impl<'tcx> Const<'tcx> {
pub fn to_valtree(self) -> ty::ValTree<'tcx> {
match self.kind() {
ty::ConstKind::Value(valtree) => valtree,
_ => bug!("expected ConstKind::Value"),
_ => bug!("expected ConstKind::Value, got {:?}", self.kind()),
}
}

32
compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
View file

@ -120,37 +120,35 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
}
fn search_for_structural_match_violation(&self, ty: Ty<'tcx>) -> Option<String> {
traits::search_for_structural_match_violation(self.span, self.tcx(), ty, true).map(
|non_sm_ty| {
with_no_trimmed_paths!(match non_sm_ty.kind {
traits::NonStructuralMatchTyKind::Adt(adt) => self.adt_derive_msg(adt),
traits::NonStructuralMatchTyKind::Dynamic => {
traits::search_for_structural_match_violation(self.span, self.tcx(), ty).map(|non_sm_ty| {
with_no_trimmed_paths!(match non_sm_ty.kind() {
ty::Adt(adt, _) => self.adt_derive_msg(*adt),
ty::Dynamic(..) => {
"trait objects cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Opaque => {
ty::Opaque(..) => {
"opaque types cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Closure => {
ty::Closure(..) => {
"closures cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Generator => {
ty::Generator(..) | ty::GeneratorWitness(..) => {
"generators cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Float => {
ty::Float(..) => {
"floating-point numbers cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Param => {
bug!("use of a constant whose type is a parameter inside a pattern")
ty::FnPtr(..) => {
"function pointers cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Projection => {
bug!("use of a constant whose type is a projection inside a pattern")
ty::RawPtr(..) => {
"raw pointers cannot be used in patterns".to_string()
}
traits::NonStructuralMatchTyKind::Foreign => {
bug!("use of a value of a foreign type inside a pattern")
_ => {
bug!("use of a value of `{non_sm_ty}` inside a pattern")
}
})
},
)
})
}
fn type_marked_structural(&self, ty: Ty<'tcx>) -> bool {

5
compiler/rustc_trait_selection/src/traits/mod.rs
View file

@ -60,8 +60,9 @@ pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError
pub use self::specialize::specialization_graph::FutureCompatOverlapError;
pub use self::specialize::specialization_graph::FutureCompatOverlapErrorKind;
pub use self::specialize::{specialization_graph, translate_substs, OverlapError};
pub use self::structural_match::search_for_structural_match_violation;
pub use self::structural_match::{NonStructuralMatchTy, NonStructuralMatchTyKind};
pub use self::structural_match::{
search_for_adt_const_param_violation, search_for_structural_match_violation,
};
pub use self::util::{
elaborate_obligations, elaborate_predicates, elaborate_predicates_with_span,
elaborate_trait_ref, elaborate_trait_refs,

133
compiler/rustc_trait_selection/src/traits/structural_match.rs
View file

@ -6,29 +6,10 @@ use rustc_data_structures::fx::FxHashSet;
use rustc_hir as hir;
use rustc_hir::lang_items::LangItem;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
use rustc_span::Span;
use std::ops::ControlFlow;
#[derive(Debug)]
pub struct NonStructuralMatchTy<'tcx> {
pub ty: Ty<'tcx>,
pub kind: NonStructuralMatchTyKind<'tcx>,
}
#[derive(Debug)]
pub enum NonStructuralMatchTyKind<'tcx> {
Adt(AdtDef<'tcx>),
Param,
Dynamic,
Foreign,
Opaque,
Closure,
Generator,
Projection,
Float,
}
/// This method traverses the structure of `ty`, trying to find an
/// instance of an ADT (i.e. struct or enum) that doesn't implement
/// the structural-match traits, or a generic type parameter
@ -54,15 +35,28 @@ pub enum NonStructuralMatchTyKind<'tcx> {
/// For more background on why Rust has this requirement, and issues
/// that arose when the requirement was not enforced completely, see
/// Rust RFC 1445, rust-lang/rust#61188, and rust-lang/rust#62307.
///
/// The floats_allowed flag is used to deny constants in floating point
pub fn search_for_structural_match_violation<'tcx>(
span: Span,
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
floats_allowed: bool,
) -> Option<NonStructuralMatchTy<'tcx>> {
ty.visit_with(&mut Search { tcx, span, seen: FxHashSet::default(), floats_allowed })
) -> Option<Ty<'tcx>> {
ty.visit_with(&mut Search { tcx, span, seen: FxHashSet::default(), adt_const_param: false })
.break_value()
}
/// This method traverses the structure of `ty`, trying to find any
/// types that are not allowed to be used in a const generic.
///
/// This is either because the type does not implement `StructuralEq`
/// and `StructuralPartialEq`, or because the type is intentionally
/// not supported in const generics (such as floats and raw pointers,
/// which are allowed in match blocks).
pub fn search_for_adt_const_param_violation<'tcx>(
span: Span,
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
) -> Option<Ty<'tcx>> {
ty.visit_with(&mut Search { tcx, span, seen: FxHashSet::default(), adt_const_param: true })
.break_value()
}
@ -125,7 +119,10 @@ struct Search<'tcx> {
/// we will not recur on them again.
seen: FxHashSet<hir::def_id::DefId>,
floats_allowed: bool,
// Additionally deny things that have been allowed in patterns,
// but are not allowed in adt const params, such as floats and
// fn ptrs.
adt_const_param: bool,
}
impl<'tcx> Search<'tcx> {
@ -135,7 +132,7 @@ impl<'tcx> Search<'tcx> {
}
impl<'tcx> TypeVisitor<'tcx> for Search<'tcx> {
type BreakTy = NonStructuralMatchTy<'tcx>;
type BreakTy = Ty<'tcx>;
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
debug!("Search visiting ty: {:?}", ty);
@ -143,51 +140,27 @@ impl<'tcx> TypeVisitor<'tcx> for Search<'tcx> {
let (adt_def, substs) = match *ty.kind() {
ty::Adt(adt_def, substs) => (adt_def, substs),
ty::Param(_) => {
let kind = NonStructuralMatchTyKind::Param;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::Dynamic(..) => {
let kind = NonStructuralMatchTyKind::Dynamic;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::Foreign(_) => {
let kind = NonStructuralMatchTyKind::Foreign;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::Opaque(..) => {
let kind = NonStructuralMatchTyKind::Opaque;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::Projection(..) => {
let kind = NonStructuralMatchTyKind::Projection;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::Closure(..) => {
let kind = NonStructuralMatchTyKind::Closure;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::Generator(..) | ty::GeneratorWitness(..) => {
let kind = NonStructuralMatchTyKind::Generator;
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
ty::RawPtr(..) => {
// structural-match ignores substructure of
// `*const _`/`*mut _`, so skip `super_visit_with`.
//
// For example, if you have:
// ```
// struct NonStructural;
// #[derive(PartialEq, Eq)]
// struct T(*const NonStructural);
// const C: T = T(std::ptr::null());
// ```
//
// Even though `NonStructural` does not implement `PartialEq`,
// structural equality on `T` does not recur into the raw
// pointer. Therefore, one can still use `C` in a pattern.
return ControlFlow::CONTINUE;
}
ty::FnDef(..) | ty::FnPtr(..) => {
ty::FnDef(..) => {
// Types of formals and return in `fn(_) -> _` are also irrelevant;
// so we do not recur into them via `super_visit_with`
return ControlFlow::CONTINUE;
@ -206,14 +179,41 @@ impl<'tcx> TypeVisitor<'tcx> for Search<'tcx> {
return ControlFlow::CONTINUE;
}
ty::Float(_) => {
if self.floats_allowed {
ty::FnPtr(..) => {
if !self.adt_const_param {
return ControlFlow::CONTINUE;
} else {
return ControlFlow::Break(NonStructuralMatchTy {
ty,
kind: NonStructuralMatchTyKind::Float,
});
return ControlFlow::Break(ty);
}
}
ty::RawPtr(..) => {
if !self.adt_const_param {
// structural-match ignores substructure of
// `*const _`/`*mut _`, so skip `super_visit_with`.
//
// For example, if you have:
// ```
// struct NonStructural;
// #[derive(PartialEq, Eq)]
// struct T(*const NonStructural);
// const C: T = T(std::ptr::null());
// ```
//
// Even though `NonStructural` does not implement `PartialEq`,
// structural equality on `T` does not recur into the raw
// pointer. Therefore, one can still use `C` in a pattern.
return ControlFlow::CONTINUE;
} else {
return ControlFlow::Break(ty);
}
}
ty::Float(_) => {
if !self.adt_const_param {
return ControlFlow::CONTINUE;
} else {
return ControlFlow::Break(ty);
}
}
@ -239,8 +239,7 @@ impl<'tcx> TypeVisitor<'tcx> for Search<'tcx> {
if !self.type_marked_structural(ty) {
debug!("Search found ty: {:?}", ty);
let kind = NonStructuralMatchTyKind::Adt(adt_def);
return ControlFlow::Break(NonStructuralMatchTy { ty, kind });
return ControlFlow::Break(ty);
}
// structural-match does not care about the

42
compiler/rustc_typeck/src/check/wfcheck.rs
View file

@ -848,29 +848,13 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
let ty = tcx.type_of(tcx.hir().local_def_id(param.hir_id));
if tcx.features().adt_const_params {
let err = match ty.peel_refs().kind() {
ty::FnPtr(_) => Some("function pointers"),
ty::RawPtr(_) => Some("raw pointers"),
_ => None,
};
if let Some(unsupported_type) = err {
tcx.sess.span_err(
hir_ty.span,
&format!(
"using {} as const generic parameters is forbidden",
unsupported_type
),
);
}
if let Some(non_structural_match_ty) =
traits::search_for_structural_match_violation(param.span, tcx, ty, false)
traits::search_for_adt_const_param_violation(param.span, tcx, ty)
{
// We use the same error code in both branches, because this is really the same
// issue: we just special-case the message for type parameters to make it
// clearer.
match ty.peel_refs().kind() {
match non_structural_match_ty.kind() {
ty::Param(_) => {
// Const parameters may not have type parameters as their types,
// because we cannot be sure that the type parameter derives `PartialEq`
@ -902,6 +886,24 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
.note("floats do not derive `Eq` or `Ord`, which are required for const parameters")
.emit();
}
ty::FnPtr(_) => {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"using function pointers as const generic parameters is forbidden",
)
.emit();
}
ty::RawPtr(_) => {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"using raw pointers as const generic parameters is forbidden",
)
.emit();
}
_ => {
let mut diag = struct_span_err!(
tcx.sess,
@ -909,10 +911,10 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
E0741,
"`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \
the type of a const parameter",
non_structural_match_ty.ty,
non_structural_match_ty,
);
if ty == non_structural_match_ty.ty {
if ty == non_structural_match_ty {
diag.span_label(
hir_ty.span,
format!("`{ty}` doesn't derive both `PartialEq` and `Eq`"),

5
src/test/ui/const-generics/fn-const-param-call.full.stderr
View file

@ -1,10 +1,10 @@
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/fn-const-param-call.rs:11:25
|
LL | struct Wrapper<const F: fn() -> u32>;
| ^^^^^^^^^^^
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/fn-const-param-call.rs:13:15
|
LL | impl<const F: fn() -> u32> Wrapper<F> {
@ -12,3 +12,4 @@ LL | impl<const F: fn() -> u32> Wrapper<F> {
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0741`.

3
src/test/ui/const-generics/fn-const-param-infer.full.stderr
View file

@ -1,4 +1,4 @@
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/fn-const-param-infer.rs:6:25
|
LL | struct Checked<const F: fn(usize) -> bool>;
@ -6,3 +6,4 @@ LL | struct Checked<const F: fn(usize) -> bool>;
error: aborting due to previous error
For more information about this error, try `rustc --explain E0741`.

7
src/test/ui/const-generics/issues/issue-71381.full.stderr
View file

@ -10,13 +10,13 @@ error[E0770]: the type of const parameters must not depend on other generic para
LL | const FN: unsafe extern "C" fn(Args),
| ^^^^ the type must not depend on the parameter `Args`
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-71381.rs:14:61
|
LL | pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-71381.rs:23:19
|
LL | const FN: unsafe extern "C" fn(Args),
@ -24,4 +24,5 @@ LL | const FN: unsafe extern "C" fn(Args),
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0770`.
Some errors have detailed explanations: E0741, E0770.
For more information about an error, try `rustc --explain E0741`.

3
src/test/ui/const-generics/issues/issue-71382.full.stderr
View file

@ -1,4 +1,4 @@
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-71382.rs:16:23
|
LL | fn test<const FN: fn()>(&self) {
@ -6,3 +6,4 @@ LL | fn test<const FN: fn()>(&self) {
error: aborting due to previous error
For more information about this error, try `rustc --explain E0741`.

5
src/test/ui/const-generics/issues/issue-71611.full.stderr
View file

@ -4,7 +4,7 @@ error[E0770]: the type of const parameters must not depend on other generic para
LL | fn func<A, const F: fn(inner: A)>(outer: A) {
| ^ the type must not depend on the parameter `A`
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-71611.rs:5:21
|
LL | fn func<A, const F: fn(inner: A)>(outer: A) {
@ -12,4 +12,5 @@ LL | fn func<A, const F: fn(inner: A)>(outer: A) {
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0770`.
Some errors have detailed explanations: E0741, E0770.
For more information about an error, try `rustc --explain E0741`.

3
src/test/ui/const-generics/issues/issue-72352.full.stderr
View file

@ -1,4 +1,4 @@
error: using function pointers as const generic parameters is forbidden
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-72352.rs:7:42
|
LL | unsafe fn unsafely_do_the_thing<const F: fn(&CStr) -> usize>(ptr: *const i8) -> usize {
@ -6,3 +6,4 @@ LL | unsafe fn unsafely_do_the_thing<const F: fn(&CStr) -> usize>(ptr: *const i8
error: aborting due to previous error
For more information about this error, try `rustc --explain E0741`.

18
src/test/ui/const-generics/issues/issue-99641.rs Normal file
View file

@ -0,0 +1,18 @@
#![feature(adt_const_params)]
#![allow(incomplete_features)]
fn main() {
pub struct Color<const WHITE: (fn(),)>;
//~^ ERROR using function pointers
impl<const WHITE: (fn(),)> Color<WHITE> {
//~^ ERROR using function pointers
pub fn new() -> Self {
Color::<WHITE>
}
}
pub const D65: (fn(),) = (|| {},);
Color::<D65>::new();
}

15
src/test/ui/const-generics/issues/issue-99641.stderr Normal file
View file

@ -0,0 +1,15 @@
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-99641.rs:5:35
|
LL | pub struct Color<const WHITE: (fn(),)>;
| ^^^^^^^
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/issue-99641.rs:8:23
|
LL | impl<const WHITE: (fn(),)> Color<WHITE> {
| ^^^^^^^
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0741`.

5
src/test/ui/const-generics/raw-ptr-const-param-deref.full.stderr
View file

@ -1,10 +1,10 @@
error: using raw pointers as const generic parameters is forbidden
error[E0741]: using raw pointers as const generic parameters is forbidden
--> $DIR/raw-ptr-const-param-deref.rs:9:23
|
LL | struct Const<const P: *const u32>;
| ^^^^^^^^^^
error: using raw pointers as const generic parameters is forbidden
error[E0741]: using raw pointers as const generic parameters is forbidden
--> $DIR/raw-ptr-const-param-deref.rs:11:15
|
LL | impl<const P: *const u32> Const<P> {
@ -12,3 +12,4 @@ LL | impl<const P: *const u32> Const<P> {
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0741`.

3
src/test/ui/const-generics/raw-ptr-const-param.full.stderr
View file

@ -1,4 +1,4 @@
error: using raw pointers as const generic parameters is forbidden
error[E0741]: using raw pointers as const generic parameters is forbidden
--> $DIR/raw-ptr-const-param.rs:6:23
|
LL | struct Const<const P: *const u32>;
@ -6,3 +6,4 @@ LL | struct Const<const P: *const u32>;
error: aborting due to previous error
For more information about this error, try `rustc --explain E0741`.

4
src/test/ui/consts/refs_check_const_eq-issue-88384.rs
View file

@ -1,5 +1,3 @@
// check-pass
#![feature(fn_traits)]
#![feature(adt_const_params)]
//~^ WARNING the feature `adt_const_params` is incomplete
@ -10,8 +8,10 @@ struct CompileTimeSettings{
}
struct Foo<const T: CompileTimeSettings>;
//~^ ERROR using function pointers as const generic parameters is forbidden
impl<const T: CompileTimeSettings> Foo<T> {
//~^ ERROR using function pointers as const generic parameters is forbidden
fn call_hooks(){
}
}

17
src/test/ui/consts/refs_check_const_eq-issue-88384.stderr
View file

@ -1,5 +1,5 @@
warning: the feature `adt_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/refs_check_const_eq-issue-88384.rs:4:12
--> $DIR/refs_check_const_eq-issue-88384.rs:2:12
|
LL | #![feature(adt_const_params)]
| ^^^^^^^^^^^^^^^^
@ -7,5 +7,18 @@ LL | #![feature(adt_const_params)]
= note: `#[warn(incomplete_features)]` on by default
= note: see issue #95174 <https://github.com/rust-lang/rust/issues/95174> for more information
warning: 1 warning emitted
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/refs_check_const_eq-issue-88384.rs:10:21
|
LL | struct Foo<const T: CompileTimeSettings>;
| ^^^^^^^^^^^^^^^^^^^
error[E0741]: using function pointers as const generic parameters is forbidden
--> $DIR/refs_check_const_eq-issue-88384.rs:13:15
|
LL | impl<const T: CompileTimeSettings> Foo<T> {
| ^^^^^^^^^^^^^^^^^^^
error: aborting due to 2 previous errors; 1 warning emitted
For more information about this error, try `rustc --explain E0741`.