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Rollup merge of #91416 - compiler-errors:infinite-ty-option-box, r=estebank

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Specialize infinite-type "insert some indirection" suggestion for Option

Suggest `Option<Box<_>>` instead of `Box<Option<_>>` for infinitely-recursive members of a struct.

Not sure if I can get the span of the generic subty of the Option so I can make this a `+++`-style suggestion. The current output is a tiny bit less fancy looking than the original suggestion.

Should I limit the specialization to just `Option<Box<TheOuterStruct>>`? Because right now it applies to all `Option` members in the struct that are returned by `Representability::SelfRecursive`.

Fixes #91402

r? `@estebank`
(since you wrote the original suggestion and are definitely most familiar with it!)
This commit is contained in:
Dylan DPC 2022-03-31 17:29:52 +02:00 committed by GitHub
commit 521c590c9f
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16 changed files with 256 additions and 63 deletions
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59
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View File

@ -2285,10 +2285,10 @@ impl<'v> Visitor<'v> for FindTypeParam {
}
}
pub fn recursive_type_with_infinite_size_error(
tcx: TyCtxt<'_>,
pub fn recursive_type_with_infinite_size_error<'tcx>(
tcx: TyCtxt<'tcx>,
type_def_id: DefId,
spans: Vec<Span>,
spans: Vec<(Span, Option<hir::HirId>)>,
) {
assert!(type_def_id.is_local());
let span = tcx.hir().span_if_local(type_def_id).unwrap();
@ -2297,7 +2297,7 @@ pub fn recursive_type_with_infinite_size_error(
let mut err =
struct_span_err!(tcx.sess, span, E0072, "recursive type `{}` has infinite size", path);
err.span_label(span, "recursive type has infinite size");
for &span in &spans {
for &(span, _) in &spans {
err.span_label(span, "recursive without indirection");
}
let msg = format!(
@ -2305,16 +2305,25 @@ pub fn recursive_type_with_infinite_size_error(
path,
);
if spans.len() <= 4 {
// FIXME(compiler-errors): This suggestion might be erroneous if Box is shadowed
err.multipart_suggestion(
&msg,
spans
.iter()
.flat_map(|&span| {
[
(span.shrink_to_lo(), "Box<".to_string()),
(span.shrink_to_hi(), ">".to_string()),
]
.into_iter()
.into_iter()
.flat_map(|(span, field_id)| {
if let Some(generic_span) = get_option_generic_from_field_id(tcx, field_id) {
// If we match an `Option` and can grab the span of the Option's generic, then
// suggest boxing the generic arg for a non-null niche optimization.
vec![
(generic_span.shrink_to_lo(), "Box<".to_string()),
(generic_span.shrink_to_hi(), ">".to_string()),
]
} else {
vec![
(span.shrink_to_lo(), "Box<".to_string()),
(span.shrink_to_hi(), ">".to_string()),
]
}
})
.collect(),
Applicability::HasPlaceholders,
@ -2325,6 +2334,34 @@ pub fn recursive_type_with_infinite_size_error(
err.emit();
}
/// Extract the span for the generic type `T` of `Option<T>` in a field definition
fn get_option_generic_from_field_id(tcx: TyCtxt<'_>, field_id: Option<hir::HirId>) -> Option<Span> {
let node = tcx.hir().find(field_id?);
// Expect a field from our field_id
let Some(hir::Node::Field(field_def)) = node
else { bug!("Expected HirId corresponding to FieldDef, found: {:?}", node) };
// Match a type that is a simple QPath with no Self
let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = &field_def.ty.kind
else { return None };
// Check if the path we're checking resolves to Option
let hir::def::Res::Def(_, did) = path.res
else { return None };
// Bail if this path doesn't describe `::core::option::Option`
if !tcx.is_diagnostic_item(sym::Option, did) {
return None;
}
// Match a single generic arg in the 0th path segment
let generic_arg = path.segments.last()?.args?.args.get(0)?;
// Take the span out of the type, if it's a type
if let hir::GenericArg::Type(generic_ty) = generic_arg { Some(generic_ty.span) } else { None }
}
/// Summarizes information
#[derive(Clone)]
pub enum ArgKind {

70
compiler/rustc_ty_utils/src/representability.rs
View File

@ -17,12 +17,20 @@ use std::cmp;
pub enum Representability {
Representable,
ContainsRecursive,
SelfRecursive(Vec<Span>),
/// Return a list of types that are included in themselves:
/// the spans where they are self-included, and (if found)
/// the HirId of the FieldDef that defines the self-inclusion.
SelfRecursive(Vec<(Span, Option<hir::HirId>)>),
}
/// Check whether a type is representable. This means it cannot contain unboxed
/// structural recursion. This check is needed for structs and enums.
pub fn ty_is_representable<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, sp: Span) -> Representability {
pub fn ty_is_representable<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
sp: Span,
field_id: Option<hir::HirId>,
) -> Representability {
debug!("is_type_representable: {:?}", ty);
// To avoid a stack overflow when checking an enum variant or struct that
// contains a different, structurally recursive type, maintain a stack of
@ -38,11 +46,12 @@ pub fn ty_is_representable<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, sp: Span) -> R
let mut force_result = false;
let r = is_type_structurally_recursive(
tcx,
sp,
&mut seen,
&mut shadow_seen,
&mut representable_cache,
ty,
sp,
field_id,
&mut force_result,
);
debug!("is_type_representable: {:?} is {:?}", ty, r);
@ -61,11 +70,12 @@ fn fold_repr<It: Iterator<Item = Representability>>(iter: It) -> Representabilit
fn are_inner_types_recursive<'tcx>(
tcx: TyCtxt<'tcx>,
sp: Span,
seen: &mut Vec<Ty<'tcx>>,
shadow_seen: &mut Vec<ty::AdtDef<'tcx>>,
representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
ty: Ty<'tcx>,
sp: Span,
field_id: Option<hir::HirId>,
force_result: &mut bool,
) -> Representability {
debug!("are_inner_types_recursive({:?}, {:?}, {:?})", ty, seen, shadow_seen);
@ -75,11 +85,12 @@ fn are_inner_types_recursive<'tcx>(
fold_repr(fields.iter().map(|ty| {
is_type_structurally_recursive(
tcx,
sp,
seen,
shadow_seen,
representable_cache,
ty,
sp,
field_id,
force_result,
)
}))
@ -88,20 +99,26 @@ fn are_inner_types_recursive<'tcx>(
// FIXME(#11924) Behavior undecided for zero-length vectors.
ty::Array(ty, _) => is_type_structurally_recursive(
tcx,
sp,
seen,
shadow_seen,
representable_cache,
*ty,
sp,
field_id,
force_result,
),
ty::Adt(def, substs) => {
// Find non representable fields with their spans
fold_repr(def.all_fields().map(|field| {
let ty = field.ty(tcx, substs);
let span = match field.did.as_local().and_then(|id| tcx.hir().find_by_def_id(id)) {
Some(hir::Node::Field(field)) => field.ty.span,
_ => sp,
let (sp, field_id) = match field
.did
.as_local()
.map(|id| tcx.hir().local_def_id_to_hir_id(id))
.and_then(|id| tcx.hir().find(id))
{
Some(hir::Node::Field(field)) => (field.ty.span, Some(field.hir_id)),
_ => (sp, field_id),
};
let mut result = None;
@ -130,7 +147,7 @@ fn are_inner_types_recursive<'tcx>(
// result without adjusting).
if shadow_seen.len() > seen.len() && shadow_seen.first() == Some(def) {
*force_result = true;
result = Some(Representability::SelfRecursive(vec![span]));
result = Some(Representability::SelfRecursive(vec![(sp, field_id)]));
}
if result == None {
@ -161,16 +178,17 @@ fn are_inner_types_recursive<'tcx>(
result = Some(
match is_type_structurally_recursive(
tcx,
span,
&mut nested_seen,
shadow_seen,
representable_cache,
raw_adt_ty,
sp,
field_id,
force_result,
) {
Representability::SelfRecursive(_) => {
if *force_result {
Representability::SelfRecursive(vec![span])
Representability::SelfRecursive(vec![(sp, field_id)])
} else {
Representability::ContainsRecursive
}
@ -208,15 +226,16 @@ fn are_inner_types_recursive<'tcx>(
result = Some(
match is_type_structurally_recursive(
tcx,
span,
seen,
shadow_seen,
representable_cache,
ty,
sp,
field_id,
force_result,
) {
Representability::SelfRecursive(_) => {
Representability::SelfRecursive(vec![span])
Representability::SelfRecursive(vec![(sp, field_id)])
}
x => x,
},
@ -247,29 +266,31 @@ fn same_adt<'tcx>(ty: Ty<'tcx>, def: ty::AdtDef<'tcx>) -> bool {
// contain any types on stack `seen`?
fn is_type_structurally_recursive<'tcx>(
tcx: TyCtxt<'tcx>,
sp: Span,
seen: &mut Vec<Ty<'tcx>>,
shadow_seen: &mut Vec<ty::AdtDef<'tcx>>,
representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
ty: Ty<'tcx>,
sp: Span,
field_id: Option<hir::HirId>,
force_result: &mut bool,
) -> Representability {
debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp);
debug!("is_type_structurally_recursive: {:?} {:?} {:?}", ty, sp, field_id);
if let Some(representability) = representable_cache.get(&ty) {
debug!(
"is_type_structurally_recursive: {:?} {:?} - (cached) {:?}",
ty, sp, representability
"is_type_structurally_recursive: {:?} {:?} {:?} - (cached) {:?}",
ty, sp, field_id, representability
);
return representability.clone();
}
let representability = is_type_structurally_recursive_inner(
tcx,
sp,
seen,
shadow_seen,
representable_cache,
ty,
sp,
field_id,
force_result,
);
@ -279,11 +300,12 @@ fn is_type_structurally_recursive<'tcx>(
fn is_type_structurally_recursive_inner<'tcx>(
tcx: TyCtxt<'tcx>,
sp: Span,
seen: &mut Vec<Ty<'tcx>>,
shadow_seen: &mut Vec<ty::AdtDef<'tcx>>,
representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>,
ty: Ty<'tcx>,
sp: Span,
field_id: Option<hir::HirId>,
force_result: &mut bool,
) -> Representability {
match ty.kind() {
@ -305,7 +327,7 @@ fn is_type_structurally_recursive_inner<'tcx>(
if let Some(&seen_adt) = iter.next() {
if same_adt(seen_adt, *def) {
debug!("SelfRecursive: {:?} contains {:?}", seen_adt, ty);
return Representability::SelfRecursive(vec![sp]);
return Representability::SelfRecursive(vec![(sp, field_id)]);
}
}
@ -335,11 +357,12 @@ fn is_type_structurally_recursive_inner<'tcx>(
shadow_seen.push(*def);
let out = are_inner_types_recursive(
tcx,
sp,
seen,
shadow_seen,
representable_cache,
ty,
sp,
field_id,
force_result,
);
shadow_seen.pop();
@ -350,11 +373,12 @@ fn is_type_structurally_recursive_inner<'tcx>(
// No need to push in other cases.
are_inner_types_recursive(
tcx,
sp,
seen,
shadow_seen,
representable_cache,
ty,
sp,
field_id,
force_result,
)
}

2
compiler/rustc_typeck/src/check/check.rs
View File

@ -1045,7 +1045,7 @@ pub(super) fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: LocalD
// recursive type. It is only necessary to throw an error on those that
// contain themselves. For case 2, there must be an inner type that will be
// caught by case 1.
match representability::ty_is_representable(tcx, rty, sp) {
match representability::ty_is_representable(tcx, rty, sp, None) {
Representability::SelfRecursive(spans) => {
recursive_type_with_infinite_size_error(tcx, item_def_id.to_def_id(), spans);
return false;

4
src/test/ui/issues/issue-17431-1.stderr
View File

@ -8,8 +8,8 @@ LL | struct Foo { foo: Option<Option<Foo>> }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Foo` representable
|
LL | struct Foo { foo: Box<Option<Option<Foo>>> }
| ++++ +
LL | struct Foo { foo: Option<Box<Option<Foo>>> }
| ++++ +
error: aborting due to previous error

8
src/test/ui/issues/issue-17431-2.stderr
View File

@ -8,8 +8,8 @@ LL | struct Baz { q: Option<Foo> }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Baz` representable
|
LL | struct Baz { q: Box<Option<Foo>> }
| ++++ +
LL | struct Baz { q: Option<Box<Foo>> }
| ++++ +
error[E0072]: recursive type `Foo` has infinite size
--> $DIR/issue-17431-2.rs:4:1
@ -21,8 +21,8 @@ LL | struct Foo { q: Option<Baz> }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Foo` representable
|
LL | struct Foo { q: Box<Option<Baz>> }
| ++++ +
LL | struct Foo { q: Option<Box<Baz>> }
| ++++ +
error: aborting due to 2 previous errors

4
src/test/ui/issues/issue-17431-4.stderr
View File

@ -8,8 +8,8 @@ LL | struct Foo<T> { foo: Option<Option<Foo<T>>>, marker: marker::PhantomData<T>
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Foo` representable
|
LL | struct Foo<T> { foo: Box<Option<Option<Foo<T>>>>, marker: marker::PhantomData<T> }
| ++++ +
LL | struct Foo<T> { foo: Option<Box<Option<Foo<T>>>>, marker: marker::PhantomData<T> }
| ++++ +
error: aborting due to previous error

4
src/test/ui/issues/issue-17431-7.stderr
View File

@ -8,8 +8,8 @@ LL | enum Foo { Voo(Option<Option<Foo>>) }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Foo` representable
|
LL | enum Foo { Voo(Box<Option<Option<Foo>>>) }
| ++++ +
LL | enum Foo { Voo(Option<Box<Option<Foo>>>) }
| ++++ +
error: aborting due to previous error

4
src/test/ui/issues/issue-3779.stderr
View File

@ -9,8 +9,8 @@ LL | element: Option<S>
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `S` representable
|
LL | element: Box<Option<S>>
| ++++ +
LL | element: Option<Box<S>>
| ++++ +
error: aborting due to previous error

8
src/test/ui/sized-cycle-note.stderr
View File

@ -8,8 +8,8 @@ LL | struct Baz { q: Option<Foo> }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Baz` representable
|
LL | struct Baz { q: Box<Option<Foo>> }
| ++++ +
LL | struct Baz { q: Option<Box<Foo>> }
| ++++ +
error[E0072]: recursive type `Foo` has infinite size
--> $DIR/sized-cycle-note.rs:11:1
@ -21,8 +21,8 @@ LL | struct Foo { q: Option<Baz> }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Foo` representable
|
LL | struct Foo { q: Box<Option<Baz>> }
| ++++ +
LL | struct Foo { q: Option<Box<Baz>> }
| ++++ +
error: aborting due to 2 previous errors

4
src/test/ui/span/E0072.stderr
View File

@ -9,8 +9,8 @@ LL | tail: Option<ListNode>,
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `ListNode` representable
|
LL | tail: Box<Option<ListNode>>,
| ++++ +
LL | tail: Option<Box<ListNode>>,
| ++++ +
error: aborting due to previous error

4
src/test/ui/span/multiline-span-E0072.stderr
View File

@ -12,8 +12,8 @@ LL | | }
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `ListNode` representable
|
LL | tail: Box<Option<ListNode>>,
| ++++ +
LL | tail: Option<Box<ListNode>>,
| ++++ +
error: aborting due to previous error

8
src/test/ui/structs-enums/struct-rec/mutual-struct-recursion.stderr
View File

@ -37,8 +37,8 @@ LL | y: Option<Option<D<T>>>,
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `C` representable
|
LL | y: Box<Option<Option<D<T>>>>,
| ++++ +
LL | y: Option<Box<Option<D<T>>>>,
| ++++ +
error[E0072]: recursive type `D` has infinite size
--> $DIR/mutual-struct-recursion.rs:18:1
@ -51,8 +51,8 @@ LL | z: Option<Option<C<T>>>,
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `D` representable
|
LL | z: Box<Option<Option<C<T>>>>,
| ++++ +
LL | z: Option<Box<Option<C<T>>>>,
| ++++ +
error: aborting due to 4 previous errors

12
src/test/ui/type/type-recursive-box-shadowed.rs Normal file
View File

@ -0,0 +1,12 @@
//FIXME(compiler-errors): This fixup should suggest the full box path, not just `Box`
struct Box<T> {
t: T,
}
struct Foo {
//~^ ERROR recursive type `Foo` has infinite size
inner: Foo,
}
fn main() {}

17
src/test/ui/type/type-recursive-box-shadowed.stderr Normal file
View File

@ -0,0 +1,17 @@
error[E0072]: recursive type `Foo` has infinite size
--> $DIR/type-recursive-box-shadowed.rs:7:1
|
LL | struct Foo {
| ^^^^^^^^^^ recursive type has infinite size
LL |
LL | inner: Foo,
| --- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Foo` representable
|
LL | inner: Box<Foo>,
| ++++ +
error: aborting due to previous error
For more information about this error, try `rustc --explain E0072`.

26
src/test/ui/type/type-recursive.rs
View File

@ -1,6 +1,30 @@
struct T1 { //~ ERROR E0072
foo: isize,
foolish: T1
foolish: T1,
}
struct T2 { //~ ERROR E0072
inner: Option<T2>,
}
type OptionT3 = Option<T3>;
struct T3 { //~ ERROR E0072
inner: OptionT3,
}
struct T4(Option<T4>); //~ ERROR E0072
enum T5 { //~ ERROR E0072
Variant(Option<T5>),
}
enum T6 { //~ ERROR E0072
Variant{ field: Option<T6> },
}
struct T7 { //~ ERROR E0072
foo: std::cell::Cell<Option<T7>>,
}
fn main() { }

85
src/test/ui/type/type-recursive.stderr
View File

@ -4,14 +4,93 @@ error[E0072]: recursive type `T1` has infinite size
LL | struct T1 {
| ^^^^^^^^^ recursive type has infinite size
LL | foo: isize,
LL | foolish: T1
LL | foolish: T1,
| -- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T1` representable
|
LL | foolish: Box<T1>
LL | foolish: Box<T1>,
| ++++ +
error: aborting due to previous error
error[E0072]: recursive type `T2` has infinite size
--> $DIR/type-recursive.rs:6:1
|
LL | struct T2 {
| ^^^^^^^^^ recursive type has infinite size
LL | inner: Option<T2>,
| ---------- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T2` representable
|
LL | inner: Option<Box<T2>>,
| ++++ +
error[E0072]: recursive type `T3` has infinite size
--> $DIR/type-recursive.rs:12:1
|
LL | struct T3 {
| ^^^^^^^^^ recursive type has infinite size
LL | inner: OptionT3,
| -------- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T3` representable
|
LL | inner: Box<OptionT3>,
| ++++ +
error[E0072]: recursive type `T4` has infinite size
--> $DIR/type-recursive.rs:16:1
|
LL | struct T4(Option<T4>);
| ^^^^^^^^^^----------^^
| | |
| | recursive without indirection
| recursive type has infinite size
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T4` representable
|
LL | struct T4(Option<Box<T4>>);
| ++++ +
error[E0072]: recursive type `T5` has infinite size
--> $DIR/type-recursive.rs:18:1
|
LL | enum T5 {
| ^^^^^^^ recursive type has infinite size
LL | Variant(Option<T5>),
| ---------- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T5` representable
|
LL | Variant(Option<Box<T5>>),
| ++++ +
error[E0072]: recursive type `T6` has infinite size
--> $DIR/type-recursive.rs:22:1
|
LL | enum T6 {
| ^^^^^^^ recursive type has infinite size
LL | Variant{ field: Option<T6> },
| ---------- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T6` representable
|
LL | Variant{ field: Option<Box<T6>> },
| ++++ +
error[E0072]: recursive type `T7` has infinite size
--> $DIR/type-recursive.rs:26:1
|
LL | struct T7 {
| ^^^^^^^^^ recursive type has infinite size
LL | foo: std::cell::Cell<Option<T7>>,
| --------------------------- recursive without indirection
|
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `T7` representable
|
LL | foo: Box<std::cell::Cell<Option<T7>>>,
| ++++ +
error: aborting due to 7 previous errors
For more information about this error, try `rustc --explain E0072`.