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Rollup merge of rust-lang#127818 - oli-obk:ast_validation_simplificat…
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…ions, r=petrochenkov

Various ast validation simplifications

Changes pulled out of rust-lang#127524

These are needed to make ast validation a mutable visitor, as we can't keep immutable references to the AST around in that case. But I think they are simplifying things in general and can stand on their own
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@matthiaskrgr
matthiaskrgr committed Jul 16, 2024
2 parents 862852f + d9f9592 commit ab4cc44
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Showing 2 changed files with 27 additions and 71 deletions.
96 changes: 26 additions & 70 deletions compiler/rustc_ast_passes/src/ast_validation.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -38,35 +38,20 @@ use std::mem;
use std::ops::{Deref, DerefMut};
use thin_vec::thin_vec;

use crate::errors;
use crate::errors::{self, TildeConstReason};

/// Is `self` allowed semantically as the first parameter in an `FnDecl`?
enum SelfSemantic {
Yes,
No,
}

/// What is the context that prevents using `~const`?
// FIXME(effects): Consider getting rid of this in favor of `errors::TildeConstReason`, they're
// almost identical. This gets rid of an abstraction layer which might be considered bad.
enum DisallowTildeConstContext<'a> {
TraitObject,
Fn(FnKind<'a>),
Trait(Span),
TraitImpl(Span),
Impl(Span),
TraitAssocTy(Span),
TraitImplAssocTy(Span),
InherentAssocTy(Span),
Item,
}

enum TraitOrTraitImpl<'a> {
enum TraitOrTraitImpl {
Trait { span: Span, constness: Option<Span> },
TraitImpl { constness: Const, polarity: ImplPolarity, trait_ref: &'a TraitRef },
TraitImpl { constness: Const, polarity: ImplPolarity, trait_ref: Span },
}

impl<'a> TraitOrTraitImpl<'a> {
impl TraitOrTraitImpl {
fn constness(&self) -> Option<Span> {
match self {
Self::Trait { constness: Some(span), .. }
Expand All @@ -81,9 +66,9 @@ struct AstValidator<'a> {
features: &'a Features,

/// The span of the `extern` in an `extern { ... }` block, if any.
extern_mod: Option<&'a Item>,
extern_mod: Option<Span>,

outer_trait_or_trait_impl: Option<TraitOrTraitImpl<'a>>,
outer_trait_or_trait_impl: Option<TraitOrTraitImpl>,

has_proc_macro_decls: bool,

Expand All @@ -92,7 +77,7 @@ struct AstValidator<'a> {
/// e.g., `impl Iterator<Item = impl Debug>`.
outer_impl_trait: Option<Span>,

disallow_tilde_const: Option<DisallowTildeConstContext<'a>>,
disallow_tilde_const: Option<TildeConstReason>,

/// Used to ban `impl Trait` in path projections like `<impl Iterator>::Item`
/// or `Foo::Bar<impl Trait>`
Expand All @@ -115,7 +100,7 @@ impl<'a> AstValidator<'a> {
trait_.map(|(constness, polarity, trait_ref)| TraitOrTraitImpl::TraitImpl {
constness,
polarity,
trait_ref,
trait_ref: trait_ref.path.span,
}),
);
f(self);
Expand Down Expand Up @@ -145,7 +130,7 @@ impl<'a> AstValidator<'a> {

fn with_tilde_const(
&mut self,
disallowed: Option<DisallowTildeConstContext<'a>>,
disallowed: Option<TildeConstReason>,
f: impl FnOnce(&mut Self),
) {
let old = mem::replace(&mut self.disallow_tilde_const, disallowed);
Expand Down Expand Up @@ -224,7 +209,7 @@ impl<'a> AstValidator<'a> {
}
}
TyKind::TraitObject(..) => self
.with_tilde_const(Some(DisallowTildeConstContext::TraitObject), |this| {
.with_tilde_const(Some(TildeConstReason::TraitObject), |this| {
visit::walk_ty(this, t)
}),
TyKind::Path(qself, path) => {
Expand Down Expand Up @@ -354,7 +339,7 @@ impl<'a> AstValidator<'a> {
}
}

fn check_trait_fn_not_const(&self, constness: Const, parent: &TraitOrTraitImpl<'a>) {
fn check_trait_fn_not_const(&self, constness: Const, parent: &TraitOrTraitImpl) {
let Const::Yes(span) = constness else {
return;
};
Expand All @@ -367,7 +352,7 @@ impl<'a> AstValidator<'a> {
..
} = parent
{
Some(trait_ref.path.span.shrink_to_lo())
Some(trait_ref.shrink_to_lo())
} else {
None
};
Expand Down Expand Up @@ -579,7 +564,7 @@ impl<'a> AstValidator<'a> {
}

fn current_extern_span(&self) -> Span {
self.session.source_map().guess_head_span(self.extern_mod.unwrap().span)
self.session.source_map().guess_head_span(self.extern_mod.unwrap())
}

/// An `fn` in `extern { ... }` cannot have qualifiers, e.g. `async fn`.
Expand Down Expand Up @@ -980,7 +965,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
this.visit_vis(&item.vis);
this.visit_ident(item.ident);
let disallowed = matches!(constness, Const::No)
.then(|| DisallowTildeConstContext::TraitImpl(item.span));
.then(|| TildeConstReason::TraitImpl { span: item.span });
this.with_tilde_const(disallowed, |this| this.visit_generics(generics));
this.visit_trait_ref(t);
this.visit_ty(self_ty);
Expand Down Expand Up @@ -1035,7 +1020,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
this.visit_vis(&item.vis);
this.visit_ident(item.ident);
this.with_tilde_const(
Some(DisallowTildeConstContext::Impl(item.span)),
Some(TildeConstReason::Impl { span: item.span }),
|this| this.visit_generics(generics),
);
this.visit_ty(self_ty);
Expand Down Expand Up @@ -1080,7 +1065,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
}
ItemKind::ForeignMod(ForeignMod { abi, safety, .. }) => {
self.with_in_extern_mod(*safety, |this| {
let old_item = mem::replace(&mut this.extern_mod, Some(item));
let old_item = mem::replace(&mut this.extern_mod, Some(item.span));
this.visibility_not_permitted(
&item.vis,
errors::VisibilityNotPermittedNote::IndividualForeignItems,
Expand Down Expand Up @@ -1154,7 +1139,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
this.visit_ident(item.ident);
let disallowed = is_const_trait
.is_none()
.then(|| DisallowTildeConstContext::Trait(item.span));
.then(|| TildeConstReason::Trait { span: item.span });
this.with_tilde_const(disallowed, |this| {
this.visit_generics(generics);
walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits)
Expand Down Expand Up @@ -1399,40 +1384,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.dcx().emit_err(errors::ConstBoundTraitObject { span: trait_ref.span });
}
(_, BoundConstness::Maybe(span), BoundPolarity::Positive)
if let Some(reason) = &self.disallow_tilde_const =>
if let Some(reason) = self.disallow_tilde_const =>
{
let reason = match reason {
DisallowTildeConstContext::Fn(FnKind::Closure(..)) => {
errors::TildeConstReason::Closure
}
DisallowTildeConstContext::Fn(FnKind::Fn(_, ident, ..)) => {
errors::TildeConstReason::Function { ident: ident.span }
}
&DisallowTildeConstContext::Trait(span) => {
errors::TildeConstReason::Trait { span }
}
&DisallowTildeConstContext::TraitImpl(span) => {
errors::TildeConstReason::TraitImpl { span }
}
&DisallowTildeConstContext::Impl(span) => {
// FIXME(effects): Consider providing a help message or even a structured
// suggestion for moving such bounds to the assoc const fns if available.
errors::TildeConstReason::Impl { span }
}
&DisallowTildeConstContext::TraitAssocTy(span) => {
errors::TildeConstReason::TraitAssocTy { span }
}
&DisallowTildeConstContext::TraitImplAssocTy(span) => {
errors::TildeConstReason::TraitImplAssocTy { span }
}
&DisallowTildeConstContext::InherentAssocTy(span) => {
errors::TildeConstReason::InherentAssocTy { span }
}
DisallowTildeConstContext::TraitObject => {
errors::TildeConstReason::TraitObject
}
DisallowTildeConstContext::Item => errors::TildeConstReason::Item,
};
self.dcx().emit_err(errors::TildeConstDisallowed { span, reason });
}
(
Expand Down Expand Up @@ -1569,7 +1522,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
.and_then(TraitOrTraitImpl::constness)
.is_some();

let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
let disallowed = (!tilde_const_allowed).then(|| match fk {
FnKind::Fn(_, ident, _, _, _, _) => TildeConstReason::Function { ident: ident.span },
FnKind::Closure(_, _, _) => TildeConstReason::Closure,
});
self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
}

Expand Down Expand Up @@ -1664,12 +1620,12 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
AssocItemKind::Type(_) => {
let disallowed = (!parent_is_const).then(|| match self.outer_trait_or_trait_impl {
Some(TraitOrTraitImpl::Trait { .. }) => {
DisallowTildeConstContext::TraitAssocTy(item.span)
TildeConstReason::TraitAssocTy { span: item.span }
}
Some(TraitOrTraitImpl::TraitImpl { .. }) => {
DisallowTildeConstContext::TraitImplAssocTy(item.span)
TildeConstReason::TraitImplAssocTy { span: item.span }
}
None => DisallowTildeConstContext::InherentAssocTy(item.span),
None => TildeConstReason::InherentAssocTy { span: item.span },
});
self.with_tilde_const(disallowed, |this| {
this.with_in_trait_impl(None, |this| visit::walk_assoc_item(this, item, ctxt))
Expand Down Expand Up @@ -1852,7 +1808,7 @@ pub fn check_crate(
outer_trait_or_trait_impl: None,
has_proc_macro_decls: false,
outer_impl_trait: None,
disallow_tilde_const: Some(DisallowTildeConstContext::Item),
disallow_tilde_const: Some(TildeConstReason::Item),
is_impl_trait_banned: false,
extern_mod_safety: None,
lint_buffer: lints,
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_ast_passes/src/errors.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -612,7 +612,7 @@ pub struct TildeConstDisallowed {
pub reason: TildeConstReason,
}

#[derive(Subdiagnostic)]
#[derive(Subdiagnostic, Copy, Clone)]
pub enum TildeConstReason {
#[note(ast_passes_closure)]
Closure,
Expand Down

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