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Allow defining opaques in statics and consts #138911

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Mar 26, 2025
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Allow defining opaques in statics and consts #138911

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2bf0c2d
Make printing define_opaque less goofy
compiler-errors Mar 24, 2025
f8df298
Allow defining opaques in statics and consts
compiler-errors Mar 24, 2025
0827f76
Test define opaques in extern items
compiler-errors Mar 24, 2025
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2 changes: 2 additions & 0 deletions compiler/rustc_ast/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3535,6 +3535,7 @@ pub struct StaticItem {
pub safety: Safety,
pub mutability: Mutability,
pub expr: Option<P<Expr>>,
pub define_opaque: Option<ThinVec<(NodeId, Path)>>,
}

#[derive(Clone, Encodable, Decodable, Debug)]
Expand All @@ -3543,6 +3544,7 @@ pub struct ConstItem {
pub generics: Generics,
pub ty: P<Ty>,
pub expr: Option<P<Expr>>,
pub define_opaque: Option<ThinVec<(NodeId, Path)>>,
}

// Adding a new variant? Please update `test_item` in `tests/ui/macros/stringify.rs`.
Expand Down
54 changes: 38 additions & 16 deletions compiler/rustc_ast/src/mut_visit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -987,10 +987,7 @@ fn walk_fn<T: MutVisitor>(vis: &mut T, kind: FnKind<'_>) {
}
vis.visit_span(span);

for (id, path) in define_opaque.iter_mut().flatten() {
vis.visit_id(id);
vis.visit_path(path)
}
walk_define_opaques(vis, define_opaque);
}
FnKind::Closure(binder, coroutine_kind, decl, body) => {
vis.visit_closure_binder(binder);
Expand Down Expand Up @@ -1258,12 +1255,19 @@ impl WalkItemKind for ItemKind {
match self {
ItemKind::ExternCrate(_orig_name) => {}
ItemKind::Use(use_tree) => vis.visit_use_tree(use_tree),
ItemKind::Static(box StaticItem { ty, safety: _, mutability: _, expr }) => {
ItemKind::Static(box StaticItem {
ty,
safety: _,
mutability: _,
expr,
define_opaque,
}) => {
vis.visit_ty(ty);
visit_opt(expr, |expr| vis.visit_expr(expr));
walk_define_opaques(vis, define_opaque);
}
ItemKind::Const(item) => {
visit_const_item(item, vis);
walk_const_item(vis, item);
}
ItemKind::Fn(func) => {
vis.visit_fn(FnKind::Fn(FnCtxt::Free, ident, visibility, &mut *func), span, id);
Expand Down Expand Up @@ -1382,7 +1386,7 @@ impl WalkItemKind for AssocItemKind {
) {
match self {
AssocItemKind::Const(item) => {
visit_const_item(item, visitor);
walk_const_item(visitor, item);
}
AssocItemKind::Fn(func) => {
visitor.visit_fn(
Expand Down Expand Up @@ -1442,14 +1446,13 @@ impl WalkItemKind for AssocItemKind {
}
}

fn visit_const_item<T: MutVisitor>(
ConstItem { defaultness, generics, ty, expr }: &mut ConstItem,
visitor: &mut T,
) {
visit_defaultness(visitor, defaultness);
visitor.visit_generics(generics);
visitor.visit_ty(ty);
visit_opt(expr, |expr| visitor.visit_expr(expr));
fn walk_const_item<T: MutVisitor>(vis: &mut T, item: &mut ConstItem) {
let ConstItem { defaultness, generics, ty, expr, define_opaque } = item;
visit_defaultness(vis, defaultness);
vis.visit_generics(generics);
vis.visit_ty(ty);
visit_opt(expr, |expr| vis.visit_expr(expr));
walk_define_opaques(vis, define_opaque);
}

fn walk_fn_header<T: MutVisitor>(vis: &mut T, header: &mut FnHeader) {
Expand Down Expand Up @@ -1526,9 +1529,16 @@ impl WalkItemKind for ForeignItemKind {
visitor: &mut impl MutVisitor,
) {
match self {
ForeignItemKind::Static(box StaticItem { ty, mutability: _, expr, safety: _ }) => {
ForeignItemKind::Static(box StaticItem {
ty,
mutability: _,
expr,
safety: _,
define_opaque,
}) => {
visitor.visit_ty(ty);
visit_opt(expr, |expr| visitor.visit_expr(expr));
walk_define_opaques(visitor, define_opaque);
}
ForeignItemKind::Fn(func) => {
visitor.visit_fn(
Expand Down Expand Up @@ -1929,6 +1939,18 @@ fn walk_capture_by<T: MutVisitor>(vis: &mut T, capture_by: &mut CaptureBy) {
}
}

fn walk_define_opaques<T: MutVisitor>(
vis: &mut T,
define_opaque: &mut Option<ThinVec<(NodeId, Path)>>,
) {
if let Some(define_opaque) = define_opaque {
for (id, path) in define_opaque {
vis.visit_id(id);
vis.visit_path(path)
}
}
}

/// Some value for the AST node that is valid but possibly meaningless. Similar
/// to `Default` but not intended for wide use. The value will never be used
/// meaningfully, it exists just to support unwinding in `visit_clobber` in the
Expand Down
53 changes: 46 additions & 7 deletions compiler/rustc_ast/src/visit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
pub use rustc_ast_ir::visit::VisitorResult;
pub use rustc_ast_ir::{try_visit, visit_opt, walk_list, walk_visitable_list};
use rustc_span::{Ident, Span};
use thin_vec::ThinVec;

use crate::ast::*;
use crate::ptr::P;
Expand Down Expand Up @@ -371,14 +372,28 @@ impl WalkItemKind for ItemKind {
match self {
ItemKind::ExternCrate(_rename) => {}
ItemKind::Use(use_tree) => try_visit!(visitor.visit_use_tree(use_tree, id, false)),
ItemKind::Static(box StaticItem { ty, safety: _, mutability: _, expr }) => {
ItemKind::Static(box StaticItem {
ty,
safety: _,
mutability: _,
expr,
define_opaque,
}) => {
try_visit!(visitor.visit_ty(ty));
visit_opt!(visitor, visit_expr, expr);
try_visit!(walk_define_opaques(visitor, define_opaque));
}
ItemKind::Const(box ConstItem { defaultness: _, generics, ty, expr }) => {
ItemKind::Const(box ConstItem {
defaultness: _,
generics,
ty,
expr,
define_opaque,
}) => {
try_visit!(visitor.visit_generics(generics));
try_visit!(visitor.visit_ty(ty));
visit_opt!(visitor, visit_expr, expr);
try_visit!(walk_define_opaques(visitor, define_opaque));
}
ItemKind::Fn(func) => {
let kind = FnKind::Fn(FnCtxt::Free, ident, vis, &*func);
Expand Down Expand Up @@ -729,9 +744,16 @@ impl WalkItemKind for ForeignItemKind {
visitor: &mut V,
) -> V::Result {
match self {
ForeignItemKind::Static(box StaticItem { ty, mutability: _, expr, safety: _ }) => {
ForeignItemKind::Static(box StaticItem {
ty,
mutability: _,
expr,
safety: _,
define_opaque,
}) => {
try_visit!(visitor.visit_ty(ty));
visit_opt!(visitor, visit_expr, expr);
try_visit!(walk_define_opaques(visitor, define_opaque));
}
ForeignItemKind::Fn(func) => {
let kind = FnKind::Fn(FnCtxt::Foreign, ident, vis, &*func);
Expand Down Expand Up @@ -907,9 +929,7 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>) -> V::Resu
try_visit!(visitor.visit_fn_decl(decl));
visit_opt!(visitor, visit_contract, contract);
visit_opt!(visitor, visit_block, body);
for (id, path) in define_opaque.iter().flatten() {
try_visit!(visitor.visit_path(path, *id))
}
try_visit!(walk_define_opaques(visitor, define_opaque));
}
FnKind::Closure(binder, coroutine_kind, decl, body) => {
try_visit!(visitor.visit_closure_binder(binder));
Expand All @@ -933,10 +953,17 @@ impl WalkItemKind for AssocItemKind {
visitor: &mut V,
) -> V::Result {
match self {
AssocItemKind::Const(box ConstItem { defaultness: _, generics, ty, expr }) => {
AssocItemKind::Const(box ConstItem {
defaultness: _,
generics,
ty,
expr,
define_opaque,
}) => {
try_visit!(visitor.visit_generics(generics));
try_visit!(visitor.visit_ty(ty));
visit_opt!(visitor, visit_expr, expr);
try_visit!(walk_define_opaques(visitor, define_opaque));
}
AssocItemKind::Fn(func) => {
let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, vis, &*func);
Expand Down Expand Up @@ -1337,3 +1364,15 @@ pub fn walk_attr_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a AttrArgs) -
}
V::Result::output()
}

fn walk_define_opaques<'a, V: Visitor<'a>>(
visitor: &mut V,
define_opaque: &'a Option<ThinVec<(NodeId, Path)>>,
) -> V::Result {
if let Some(define_opaque) = define_opaque {
for (id, path) in define_opaque {
try_visit!(visitor.visit_path(path, *id));
}
}
V::Result::output()
}
72 changes: 54 additions & 18 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -188,14 +188,21 @@ impl<'hir> LoweringContext<'_, 'hir> {

self.lower_use_tree(use_tree, &prefix, id, vis_span, attrs)
}
ItemKind::Static(box ast::StaticItem { ty: t, safety: _, mutability: m, expr: e }) => {
ItemKind::Static(box ast::StaticItem {
ty: t,
safety: _,
mutability: m,
expr: e,
define_opaque,
}) => {
debug_assert_ne!(ident.name, kw::Empty);
let ident = self.lower_ident(ident);
let (ty, body_id) =
self.lower_const_item(t, span, e.as_deref(), ImplTraitPosition::StaticTy);
self.lower_define_opaque(hir_id, define_opaque);
hir::ItemKind::Static(ident, ty, *m, body_id)
}
ItemKind::Const(box ast::ConstItem { generics, ty, expr, .. }) => {
ItemKind::Const(box ast::ConstItem { generics, ty, expr, define_opaque, .. }) => {
debug_assert_ne!(ident.name, kw::Empty);
let ident = self.lower_ident(ident);
let (generics, (ty, body_id)) = self.lower_generics(
Expand All @@ -206,6 +213,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
this.lower_const_item(ty, span, expr.as_deref(), ImplTraitPosition::ConstTy)
},
);
self.lower_define_opaque(hir_id, &define_opaque);
hir::ItemKind::Const(ident, ty, generics, body_id)
}
ItemKind::Fn(box Fn {
Expand Down Expand Up @@ -243,7 +251,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
header: this.lower_fn_header(*header, hir::Safety::Safe, attrs),
span: this.lower_span(*fn_sig_span),
};
this.lower_define_opaque(hir_id, &define_opaque);
this.lower_define_opaque(hir_id, define_opaque);
let ident = this.lower_ident(ident);
hir::ItemKind::Fn {
ident,
Expand Down Expand Up @@ -662,7 +670,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
owner_id,
ident: self.lower_ident(i.ident),
kind: match &i.kind {
ForeignItemKind::Fn(box Fn { sig, generics, .. }) => {
ForeignItemKind::Fn(box Fn { sig, generics, define_opaque, .. }) => {
let fdec = &sig.decl;
let itctx = ImplTraitContext::Universal;
let (generics, (decl, fn_args)) =
Expand All @@ -683,17 +691,31 @@ impl<'hir> LoweringContext<'_, 'hir> {
// Unmarked safety in unsafe block defaults to unsafe.
let header = self.lower_fn_header(sig.header, hir::Safety::Unsafe, attrs);

if define_opaque.is_some() {
self.dcx().span_err(i.span, "foreign functions cannot define opaque types");
}

hir::ForeignItemKind::Fn(
hir::FnSig { header, decl, span: self.lower_span(sig.span) },
fn_args,
generics,
)
}
ForeignItemKind::Static(box StaticItem { ty, mutability, expr: _, safety }) => {
ForeignItemKind::Static(box StaticItem {
ty,
mutability,
expr: _,
safety,
define_opaque,
}) => {
let ty = self
.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::StaticTy));
let safety = self.lower_safety(*safety, hir::Safety::Unsafe);

if define_opaque.is_some() {
self.dcx().span_err(i.span, "foreign statics cannot define opaque types");
}

hir::ForeignItemKind::Static(ty, *mutability, safety)
}
ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
Expand Down Expand Up @@ -801,7 +823,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let trait_item_def_id = hir_id.expect_owner();

let (generics, kind, has_default) = match &i.kind {
AssocItemKind::Const(box ConstItem { generics, ty, expr, .. }) => {
AssocItemKind::Const(box ConstItem { generics, ty, expr, define_opaque, .. }) => {
let (generics, kind) = self.lower_generics(
generics,
i.id,
Expand All @@ -814,6 +836,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
hir::TraitItemKind::Const(ty, body)
},
);

if define_opaque.is_some() {
if expr.is_some() {
self.lower_define_opaque(hir_id, &define_opaque);
} else {
self.dcx().span_err(
i.span,
"only trait consts with default bodies can define opaque types",
);
}
}

(generics, kind, expr.is_some())
}
AssocItemKind::Fn(box Fn { sig, generics, body: None, define_opaque, .. }) => {
Expand Down Expand Up @@ -951,18 +985,20 @@ impl<'hir> LoweringContext<'_, 'hir> {
let attrs = self.lower_attrs(hir_id, &i.attrs, i.span);

let (generics, kind) = match &i.kind {
AssocItemKind::Const(box ConstItem { generics, ty, expr, .. }) => self.lower_generics(
generics,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let ty =
this.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy));
let body = this.lower_const_body(i.span, expr.as_deref());

hir::ImplItemKind::Const(ty, body)
},
),
AssocItemKind::Const(box ConstItem { generics, ty, expr, define_opaque, .. }) => self
.lower_generics(
generics,
i.id,
ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
|this| {
let ty = this
.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy));
let body = this.lower_const_body(i.span, expr.as_deref());
this.lower_define_opaque(hir_id, &define_opaque);

hir::ImplItemKind::Const(ty, body)
},
),
AssocItemKind::Fn(box Fn { sig, generics, body, contract, define_opaque, .. }) => {
let body_id = self.lower_maybe_coroutine_body(
sig.span,
Expand Down
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