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fmeasefmease
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Reject escaping generic params in the type of assoc const bindings
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5 files changed

+273
-4
lines changed

5 files changed

+273
-4
lines changed

‎compiler/rustc_hir_analysis/messages.ftl

+18
Original file line numberDiff line numberDiff line change
@@ -314,6 +314,22 @@ hir_analysis_only_current_traits_primitive = only traits defined in the current
314314
315315
hir_analysis_only_current_traits_ty = `{$ty}` is not defined in the current crate
316316
317+
hir_analysis_param_in_ty_of_assoc_const_binding =
318+
the type of the associated constant `{$assoc_const}` must not depend on {$param_category ->
319+
[self] `Self`
320+
[synthetic] `impl Trait`
321+
*[normal] generic parameters
322+
}
323+
.label = its type must not depend on {$param_category ->
324+
[self] `Self`
325+
[synthetic] `impl Trait`
326+
*[normal] the {$param_def_kind} `{$param_name}`
327+
}
328+
.param_defined_here_label = {$param_category ->
329+
[synthetic] the `impl Trait` is specified here
330+
*[normal] the {$param_def_kind} `{$param_name}` is defined here
331+
}
332+
317333
hir_analysis_paren_sugar_attribute = the `#[rustc_paren_sugar]` attribute is a temporary means of controlling which traits can use parenthetical notation
318334
.help = add `#![feature(unboxed_closures)]` to the crate attributes to use it
319335
@@ -424,6 +440,8 @@ hir_analysis_transparent_non_zero_sized_enum = the variant of a transparent {$de
424440
.label = needs at most one field with non-trivial size or alignment, but has {$field_count}
425441
.labels = this field has non-zero size or requires alignment
426442
443+
hir_analysis_ty_of_assoc_const_binding_note = `{$assoc_const}` has type `{$ty}`
444+
427445
hir_analysis_ty_param_first_local = type parameter `{$param_ty}` must be covered by another type when it appears before the first local type (`{$local_type}`)
428446
.label = type parameter `{$param_ty}` must be covered by another type when it appears before the first local type (`{$local_type}`)
429447
.note = implementing a foreign trait is only possible if at least one of the types for which it is implemented is local, and no uncovered type parameters appear before that first local type

‎compiler/rustc_hir_analysis/src/collect/type_of.rs

+101-4
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,6 @@
1+
use std::ops::ControlFlow;
2+
3+
use rustc_data_structures::fx::FxIndexSet;
14
use rustc_errors::{Applicability, StashKey};
25
use rustc_hir as hir;
36
use rustc_hir::def_id::{DefId, LocalDefId};
@@ -7,7 +10,8 @@ use rustc_middle::ty::print::with_forced_trimmed_paths;
710
use rustc_middle::ty::util::IntTypeExt;
811
use rustc_middle::ty::{self, ImplTraitInTraitData, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
912
use rustc_span::symbol::Ident;
10-
use rustc_span::{Span, DUMMY_SP};
13+
use rustc_span::{ErrorGuaranteed, Span, Symbol, DUMMY_SP};
14+
use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
1115

1216
use crate::errors::TypeofReservedKeywordUsed;
1317

@@ -78,10 +82,23 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
7882
.expect("const parameter types cannot be generic");
7983
}
8084

81-
Node::TypeBinding(&TypeBinding { hir_id, .. }) => {
82-
// FIXME(fmease): Reject “escaping” early-bound generic parameters.
85+
Node::TypeBinding(&TypeBinding { hir_id, ident, .. }) => {
86+
let ty = tcx.type_of_assoc_const_binding(hir_id);
87+
88+
// We can't possibly catch this in the resolver, therefore we need to handle it here.
89+
// FIXME(const_generics): Support generic const generics.
90+
let Some(ty) = ty.no_bound_vars() else {
91+
let reported = report_overly_generic_assoc_const_binding_type(
92+
tcx,
93+
ident,
94+
ty.skip_binder().skip_binder(),
95+
hir_id,
96+
);
97+
return Ty::new_error(tcx, reported);
98+
};
99+
83100
// FIXME(fmease): Reject escaping late-bound vars.
84-
return tcx.type_of_assoc_const_binding(hir_id).skip_binder().skip_binder();
101+
return ty.skip_binder();
85102
}
86103

87104
// This match arm is for when the def_id appears in a GAT whose
@@ -302,6 +319,86 @@ pub(super) fn type_of_assoc_const_binding<'tcx>(
302319
ty::EarlyBinder::bind(ty::Binder::dummy(Ty::new_error(tcx, reported)))
303320
}
304321

322+
fn report_overly_generic_assoc_const_binding_type<'tcx>(
323+
tcx: TyCtxt<'tcx>,
324+
assoc_const: Ident,
325+
ty: Ty<'tcx>,
326+
hir_id: HirId,
327+
) -> ErrorGuaranteed {
328+
let mut collector = GenericParamCollector { params: Default::default() };
329+
ty.visit_with(&mut collector);
330+
331+
let mut reported = None;
332+
333+
let ty_note = ty
334+
.make_suggestable(tcx, false)
335+
.map(|ty| crate::errors::TyOfAssocConstBindingNote { assoc_const, ty });
336+
337+
// FIXME(fmease): Consider delaying a bug instead of unwrapping since maybe this could trigger
338+
// if we encountered some malformed code, dunno?
339+
let enclosing_item_owner_id = tcx
340+
.hir()
341+
.parent_owner_iter(hir_id)
342+
.find_map(|(owner_id, parent)| parent.generics().map(|_| owner_id))
343+
.unwrap();
344+
let generics = tcx.generics_of(enclosing_item_owner_id);
345+
for (param_index, param_name) in collector.params {
346+
let param_def = generics.param_at(param_index as _, tcx);
347+
let is_self_param = param_def.name == rustc_span::symbol::kw::SelfUpper;
348+
reported.get_or_insert(tcx.dcx().emit_err(crate::errors::ParamInTyOfAssocConstBinding {
349+
span: assoc_const.span,
350+
assoc_const,
351+
param_name,
352+
param_def_kind: tcx.def_descr(param_def.def_id),
353+
// FIXME(fmease): Yeah, I don't like this stringly-typed stuff either.
354+
param_category: if is_self_param {
355+
"self"
356+
} else if param_def.kind.is_synthetic() {
357+
"synthetic"
358+
} else {
359+
"normal"
360+
},
361+
param_defined_here_label:
362+
(!is_self_param).then(|| tcx.def_ident_span(param_def.def_id).unwrap()),
363+
ty_note,
364+
}));
365+
}
366+
367+
struct GenericParamCollector {
368+
params: FxIndexSet<(u32, Symbol)>,
369+
}
370+
371+
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for GenericParamCollector {
372+
type BreakTy = !;
373+
374+
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
375+
if let ty::Param(param) = ty.kind() {
376+
self.params.insert((param.index, param.name));
377+
return ControlFlow::Continue(());
378+
}
379+
ty.super_visit_with(self)
380+
}
381+
382+
fn visit_region(&mut self, re: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
383+
if let ty::ReEarlyParam(param) = re.kind() {
384+
self.params.insert((param.index, param.name));
385+
return ControlFlow::Continue(());
386+
}
387+
ControlFlow::Continue(())
388+
}
389+
390+
fn visit_const(&mut self, ct: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
391+
if let ty::ConstKind::Param(param) = ct.kind() {
392+
self.params.insert((param.index, param.name));
393+
return ControlFlow::Continue(());
394+
}
395+
ct.super_visit_with(self)
396+
}
397+
}
398+
399+
reported.unwrap_or_else(|| bug!("failed to find gen params in ty"))
400+
}
401+
305402
fn get_path_containing_arg_in_pat<'hir>(
306403
pat: &'hir hir::Pat<'hir>,
307404
arg_id: HirId,

‎compiler/rustc_hir_analysis/src/errors.rs

+23
Original file line numberDiff line numberDiff line change
@@ -295,6 +295,29 @@ pub struct AssocTypeBindingNotAllowed {
295295
pub fn_trait_expansion: Option<ParenthesizedFnTraitExpansion>,
296296
}
297297

298+
#[derive(Diagnostic)]
299+
#[diag(hir_analysis_param_in_ty_of_assoc_const_binding)]
300+
pub(crate) struct ParamInTyOfAssocConstBinding<'tcx> {
301+
#[primary_span]
302+
#[label]
303+
pub span: Span,
304+
pub assoc_const: Ident,
305+
pub param_name: Symbol,
306+
pub param_def_kind: &'static str,
307+
pub param_category: &'static str,
308+
#[label(hir_analysis_param_defined_here_label)]
309+
pub param_defined_here_label: Option<Span>,
310+
#[subdiagnostic]
311+
pub ty_note: Option<TyOfAssocConstBindingNote<'tcx>>,
312+
}
313+
314+
#[derive(Subdiagnostic, Clone, Copy)]
315+
#[note(hir_analysis_ty_of_assoc_const_binding_note)]
316+
pub(crate) struct TyOfAssocConstBindingNote<'tcx> {
317+
pub assoc_const: Ident,
318+
pub ty: Ty<'tcx>,
319+
}
320+
298321
#[derive(Subdiagnostic)]
299322
#[help(hir_analysis_parenthesized_fn_trait_expansion)]
300323
pub struct ParenthesizedFnTraitExpansion {

‎tests/ui/associated-consts/assoc-const-eq-param-in-ty.rs

+55
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,55 @@
1+
// Regression test for issue #108271.
2+
// Detect and reject generic params in the type of assoc consts used in an equality bound.
3+
#![feature(associated_const_equality)]
4+
5+
trait Trait<'a, T: 'a, const N: usize> {
6+
const K: &'a [T; N];
7+
}
8+
9+
fn take0<'r, A: 'r, const Q: usize>(_: impl Trait<'r, A, Q, K = { loop {} }>) {}
10+
//~^ ERROR the type of the associated constant `K` must not depend on generic parameters
11+
//~| NOTE its type must not depend on the lifetime parameter `'r`
12+
//~| NOTE the lifetime parameter `'r` is defined here
13+
//~| NOTE `K` has type `&'r [A; Q]`
14+
//~| ERROR the type of the associated constant `K` must not depend on generic parameters
15+
//~| NOTE its type must not depend on the type parameter `A`
16+
//~| NOTE the type parameter `A` is defined here
17+
//~| NOTE `K` has type `&'r [A; Q]`
18+
//~| ERROR the type of the associated constant `K` must not depend on generic parameters
19+
//~| NOTE its type must not depend on the const parameter `Q`
20+
//~| NOTE the const parameter `Q` is defined here
21+
//~| NOTE `K` has type `&'r [A; Q]`
22+
23+
trait Project {
24+
const SELF: Self;
25+
}
26+
27+
fn take1(_: impl Project<SELF = {}>) {}
28+
//~^ ERROR the type of the associated constant `SELF` must not depend on `impl Trait`
29+
//~| NOTE its type must not depend on `impl Trait`
30+
//~| NOTE the `impl Trait` is specified here
31+
32+
fn take2<P: Project<SELF = {}>>(_: P) {}
33+
//~^ ERROR the type of the associated constant `SELF` must not depend on generic parameters
34+
//~| NOTE its type must not depend on the type parameter `P`
35+
//~| NOTE the type parameter `P` is defined here
36+
//~| NOTE `SELF` has type `P`
37+
38+
trait Iface<'r> {
39+
//~^ NOTE the lifetime parameter `'r` is defined here
40+
type Assoc<const Q: usize>: Trait<'r, Self, Q, K = { loop {} }>
41+
//~^ ERROR the type of the associated constant `K` must not depend on generic parameters
42+
//~| NOTE its type must not depend on the lifetime parameter `'r`
43+
//~| NOTE `K` has type `&'r [Self; Q]`
44+
//~| ERROR the type of the associated constant `K` must not depend on `Self`
45+
//~| NOTE its type must not depend on `Self`
46+
//~| NOTE `K` has type `&'r [Self; Q]`
47+
//~| ERROR the type of the associated constant `K` must not depend on generic parameters
48+
//~| NOTE its type must not depend on the const parameter `Q`
49+
//~| NOTE the const parameter `Q` is defined here
50+
//~| NOTE `K` has type `&'r [Self; Q]`
51+
where
52+
Self: Sized + 'r;
53+
}
54+
55+
fn main() {}

‎tests/ui/associated-consts/assoc-const-eq-param-in-ty.stderr

+76
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
1+
error: the type of the associated constant `K` must not depend on generic parameters
2+
--> $DIR/assoc-const-eq-param-in-ty.rs:9:61
3+
|
4+
LL | fn take0<'r, A: 'r, const Q: usize>(_: impl Trait<'r, A, Q, K = { loop {} }>) {}
5+
| -- the lifetime parameter `'r` is defined here ^ its type must not depend on the lifetime parameter `'r`
6+
|
7+
= note: `K` has type `&'r [A; Q]`
8+
9+
error: the type of the associated constant `K` must not depend on generic parameters
10+
--> $DIR/assoc-const-eq-param-in-ty.rs:9:61
11+
|
12+
LL | fn take0<'r, A: 'r, const Q: usize>(_: impl Trait<'r, A, Q, K = { loop {} }>) {}
13+
| - the type parameter `A` is defined here ^ its type must not depend on the type parameter `A`
14+
|
15+
= note: `K` has type `&'r [A; Q]`
16+
17+
error: the type of the associated constant `K` must not depend on generic parameters
18+
--> $DIR/assoc-const-eq-param-in-ty.rs:9:61
19+
|
20+
LL | fn take0<'r, A: 'r, const Q: usize>(_: impl Trait<'r, A, Q, K = { loop {} }>) {}
21+
| - ^ its type must not depend on the const parameter `Q`
22+
| |
23+
| the const parameter `Q` is defined here
24+
|
25+
= note: `K` has type `&'r [A; Q]`
26+
27+
error: the type of the associated constant `SELF` must not depend on `impl Trait`
28+
--> $DIR/assoc-const-eq-param-in-ty.rs:27:26
29+
|
30+
LL | fn take1(_: impl Project<SELF = {}>) {}
31+
| -------------^^^^------
32+
| | |
33+
| | its type must not depend on `impl Trait`
34+
| the `impl Trait` is specified here
35+
36+
error: the type of the associated constant `SELF` must not depend on generic parameters
37+
--> $DIR/assoc-const-eq-param-in-ty.rs:32:21
38+
|
39+
LL | fn take2<P: Project<SELF = {}>>(_: P) {}
40+
| - ^^^^ its type must not depend on the type parameter `P`
41+
| |
42+
| the type parameter `P` is defined here
43+
|
44+
= note: `SELF` has type `P`
45+
46+
error: the type of the associated constant `K` must not depend on generic parameters
47+
--> $DIR/assoc-const-eq-param-in-ty.rs:40:52
48+
|
49+
LL | trait Iface<'r> {
50+
| -- the lifetime parameter `'r` is defined here
51+
LL |
52+
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = { loop {} }>
53+
| ^ its type must not depend on the lifetime parameter `'r`
54+
|
55+
= note: `K` has type `&'r [Self; Q]`
56+
57+
error: the type of the associated constant `K` must not depend on `Self`
58+
--> $DIR/assoc-const-eq-param-in-ty.rs:40:52
59+
|
60+
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = { loop {} }>
61+
| ^ its type must not depend on `Self`
62+
|
63+
= note: `K` has type `&'r [Self; Q]`
64+
65+
error: the type of the associated constant `K` must not depend on generic parameters
66+
--> $DIR/assoc-const-eq-param-in-ty.rs:40:52
67+
|
68+
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = { loop {} }>
69+
| - ^ its type must not depend on the const parameter `Q`
70+
| |
71+
| the const parameter `Q` is defined here
72+
|
73+
= note: `K` has type `&'r [Self; Q]`
74+
75+
error: aborting due to 8 previous errors
76+

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