diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 5b708cf4e1a..55a934c48a8 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -2132,7 +2132,7 @@ pub enum TyKind {
/// The `NodeId` exists to prevent lowering from having to
/// generate `NodeId`s on the fly, which would complicate
/// the generation of opaque `type Foo = impl Trait` items significantly.
- ImplTrait(NodeId, GenericBounds),
+ ImplTrait(NodeId, GenericBounds, Option
>),
/// No-op; kept solely so that we can pretty-print faithfully.
Paren(P),
/// Unused for now.
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index da57def263d..b8a5eeebf3a 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -518,9 +518,12 @@ pub fn noop_visit_ty(ty: &mut P, vis: &mut T) {
TyKind::TraitObject(bounds, _syntax) => {
visit_vec(bounds, |bound| vis.visit_param_bound(bound))
}
- TyKind::ImplTrait(id, bounds) => {
+ TyKind::ImplTrait(id, bounds, precise_capturing) => {
vis.visit_id(id);
visit_vec(bounds, |bound| vis.visit_param_bound(bound));
+ visit_opt(precise_capturing, |precise_capturing| {
+ vis.visit_generic_args(precise_capturing);
+ });
}
TyKind::MacCall(mac) => vis.visit_mac_call(mac),
TyKind::AnonStruct(id, fields) | TyKind::AnonUnion(id, fields) => {
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 9e9ae52962d..91740021727 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -457,8 +457,9 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
TyKind::TraitObject(bounds, ..) => {
walk_list!(visitor, visit_param_bound, bounds, BoundKind::TraitObject);
}
- TyKind::ImplTrait(_, bounds) => {
+ TyKind::ImplTrait(_, bounds, precise_capturing) => {
walk_list!(visitor, visit_param_bound, bounds, BoundKind::Impl);
+ visit_opt!(visitor, visit_generic_args, precise_capturing);
}
TyKind::Typeof(expression) => try_visit!(visitor.visit_anon_const(expression)),
TyKind::Infer | TyKind::ImplicitSelf | TyKind::Dummy | TyKind::Err(_) => {}
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 5005c22d4cc..a4470622972 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1398,7 +1398,8 @@ fn lower_ty_direct(&mut self, t: &Ty, itctx: ImplTraitContext) -> hir::Ty<'hir>
});
hir::TyKind::TraitObject(bounds, lifetime_bound, *kind)
}
- TyKind::ImplTrait(def_node_id, bounds) => {
+ TyKind::ImplTrait(def_node_id, bounds, precise_capturing) => {
+ assert!(precise_capturing.is_none(), "precise captures not supported yet!");
let span = t.span;
match itctx {
ImplTraitContext::OpaqueTy { origin, fn_kind } => self.lower_opaque_impl_trait(
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index cb4dcf3ae75..495e90e967b 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -737,7 +737,7 @@ fn visit_ty_common(&mut self, ty: &'a Ty) {
}
}
}
- TyKind::ImplTrait(_, bounds) => {
+ TyKind::ImplTrait(_, bounds, _) => {
if self.is_impl_trait_banned {
self.dcx().emit_err(errors::ImplTraitPath { span: ty.span });
}
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index d7cd3efe408..70a3ccb0f44 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -569,6 +569,7 @@ macro_rules! gate_all {
gate_all!(fn_delegation, "functions delegation is not yet fully implemented");
gate_all!(postfix_match, "postfix match is experimental");
gate_all!(mut_ref, "mutable by-reference bindings are experimental");
+ gate_all!(precise_capturing, "precise captures on `impl Trait` are experimental");
if !visitor.features.never_patterns {
if let Some(spans) = spans.get(&sym::never_patterns) {
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 51ccfe89fbd..6553ed72532 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1150,7 +1150,8 @@ pub fn print_type(&mut self, ty: &ast::Ty) {
}
self.print_type_bounds(bounds);
}
- ast::TyKind::ImplTrait(_, bounds) => {
+ ast::TyKind::ImplTrait(_, bounds, _precise_capturing) => {
+ // TODO(precise_capturing):
self.word_nbsp("impl");
self.print_type_bounds(bounds);
}
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index e6b19817de3..792cc1066f5 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -535,6 +535,8 @@ pub fn internal(&self, feature: Symbol) -> bool {
(unstable, must_not_suspend, "1.57.0", Some(83310)),
/// Allows `mut ref` and `mut ref mut` identifier patterns.
(incomplete, mut_ref, "CURRENT_RUSTC_VERSION", Some(123076)),
+ /// Allows `use<'a, 'b, A, B>` in `impl use<...> Trait` for precise capture of generic args.
+ (incomplete, precise_capturing, "CURRENT_RUSTC_VERSION", Some(123432)),
/// Allows using `#[naked]` on functions.
(unstable, naked_functions, "1.9.0", Some(90957)),
/// Allows specifying the as-needed link modifier
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 503caa35358..3fe1f21d56a 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -1235,7 +1235,7 @@ fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
ast::TyKind::TraitObject(..) => {}
ast::TyKind::BareFn(b)
if self.with_self_ty_parens && b.generic_params.len() > 0 => {}
- ast::TyKind::ImplTrait(_, bounds) if bounds.len() > 1 => {}
+ ast::TyKind::ImplTrait(_, bounds, _) if bounds.len() > 1 => {}
_ => {
let spans = if !ty.span.from_expansion() {
r.span
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index fde16ac957d..93a15c938ec 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -62,7 +62,7 @@ fn parse_ty_param(&mut self, preceding_attrs: AttrVec) -> PResult<'a, GenericPar
let snapshot = self.create_snapshot_for_diagnostic();
match self.parse_ty() {
Ok(p) => {
- if let TyKind::ImplTrait(_, bounds) = &p.kind {
+ if let TyKind::ImplTrait(_, bounds, None) = &p.kind {
let span = impl_span.to(self.token.span.shrink_to_lo());
let mut err = self.dcx().struct_span_err(
span,
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index d54eb8dc4c9..fd72dca6e21 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -625,7 +625,7 @@ fn parse_item_impl(
// This notably includes paths passed through `ty` macro fragments (#46438).
TyKind::Path(None, path) => path,
other => {
- if let TyKind::ImplTrait(_, bounds) = other
+ if let TyKind::ImplTrait(_, bounds, None) = other
&& let [bound] = bounds.as_slice()
{
// Suggest removing extra `impl` keyword:
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 1cea32cb90f..5d6c4f39ae1 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -316,7 +316,7 @@ fn parse_ty_common(
TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
}
(TyKind::TraitObject(bounds, _), kw::Impl) => {
- TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
+ TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds, None)
}
_ => return Err(err),
};
@@ -655,7 +655,6 @@ fn recover_fn_ptr_with_generics(
/// Parses an `impl B0 + ... + Bn` type.
fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
- // Always parse bounds greedily for better error recovery.
if self.token.is_lifetime() {
self.look_ahead(1, |t| {
if let token::Ident(sym, _) = t.kind {
@@ -669,9 +668,26 @@ fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
}
})
}
+
+ // parse precise captures, if any.
+ let precise_capturing = if self.eat_keyword(kw::Use) {
+ self.expect_lt()?;
+ let use_span = self.prev_token.span;
+ self.psess.gated_spans.gate(sym::precise_capturing, use_span);
+ let lo = self.token.span;
+ let args = self.parse_angle_args(None)?;
+ self.expect_gt()?;
+ Some(ast::AngleBracketedArgs { args, span: lo.to(self.prev_token.span) }.into())
+ } else {
+ None
+ };
+
+ // Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds()?;
+
*impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus);
- Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
+
+ Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds, precise_capturing))
}
/// Is a `dyn B0 + ... + Bn` type allowed here?
@@ -957,7 +973,7 @@ fn parse_generic_ty_bound(
Applicability::MaybeIncorrect,
)
}
- TyKind::ImplTrait(_, bounds)
+ TyKind::ImplTrait(_, bounds, None)
if let [GenericBound::Trait(tr, ..), ..] = bounds.as_slice() =>
{
(
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 33c9c7fcc62..9e881532311 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -793,7 +793,7 @@ fn visit_ty(&mut self, ty: &'ast Ty) {
self.r.record_partial_res(ty.id, PartialRes::new(res));
visit::walk_ty(self, ty)
}
- TyKind::ImplTrait(node_id, _) => {
+ TyKind::ImplTrait(node_id, _, _) => {
let candidates = self.lifetime_elision_candidates.take();
visit::walk_ty(self, ty);
self.record_lifetime_params_for_impl_trait(*node_id);
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index bb4294fbcfb..d79c638fa07 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -3121,7 +3121,7 @@ fn add_missing_lifetime_specifiers_label(
.inputs
.iter()
.filter_map(|param| match ¶m.ty.kind {
- TyKind::ImplTrait(_, bounds) => Some(bounds),
+ TyKind::ImplTrait(_, bounds, _) => Some(bounds),
_ => None,
})
.flat_map(|bounds| bounds.into_iter())
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index bfd0f77c237..19c3fc58943 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1375,6 +1375,7 @@
powif32,
powif64,
pre_dash_lto: "pre-lto",
+ precise_capturing,
precise_pointer_size_matching,
pref_align_of,
prefetch_read_data,