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Auto merge of #119163 - fmease:refactor-ast-trait-bound-modifiers, r=compiler-errors

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Refactor AST trait bound modifiers

Instead of having two types to represent trait bound modifiers in the parser / the AST (`parser::ty::BoundModifiers` & `ast::TraitBoundModifier`), only to map one to the other later, just use `parser::ty::BoundModifiers` (moved & renamed to `ast::TraitBoundModifiers`).

The struct type is more extensible and easier to deal with (see [here](https://github.com/rust-lang/rust/pull/119099/files#r1430749981) and [here](https://github.com/rust-lang/rust/pull/119099/files#r1430752116) for context) since it more closely models what it represents: A compound of two kinds of modifiers, constness and polarity. Modeling this as an enum (the now removed `ast::TraitBoundModifier`) meant one had to add a new variant per *combination* of modifier kind, which simply isn't scalable and which lead to a lot of explicit non-DRY matches.

NB: `hir::TraitBoundModifier` being an enum is fine since HIR doesn't need to worry representing invalid modifier kind combinations as those get rejected during AST validation thereby immensely cutting down the number of possibilities.
This commit is contained in:
bors 2023-12-22 02:00:55 +00:00
commit aaef5fe497
16 changed files with 195 additions and 201 deletions
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4
compiler/rustc_ast_passes/messages.ftl
View file

@ -152,6 +152,8 @@ ast_passes_impl_trait_path = `impl Trait` is not allowed in path parameters
ast_passes_incompatible_features = `{$f1}` and `{$f2}` are incompatible, using them at the same time is not allowed
.help = remove one of these features
ast_passes_incompatible_trait_bound_modifiers = `{$left}` and `{$right}` are mutually exclusive
ast_passes_inherent_cannot_be = inherent impls cannot be {$annotation}
.because = {$annotation} because of this
.type = inherent impl for this type
@ -195,8 +197,6 @@ ast_passes_nomangle_ascii = `#[no_mangle]` requires ASCII identifier
ast_passes_obsolete_auto = `impl Trait for .. {"{}"}` is an obsolete syntax
.help = use `auto trait Trait {"{}"}` instead
ast_passes_optional_const_exclusive = `~const` and `{$modifier}` are mutually exclusive
ast_passes_optional_trait_object = `?Trait` is not permitted in trait object types
ast_passes_optional_trait_supertrait = `?Trait` is not permitted in supertraits

33
compiler/rustc_ast_passes/src/ast_validation.rs
View file

@ -1196,18 +1196,18 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
}
fn visit_param_bound(&mut self, bound: &'a GenericBound, ctxt: BoundKind) {
if let GenericBound::Trait(poly, modify) = bound {
match (ctxt, modify) {
(BoundKind::SuperTraits, TraitBoundModifier::Maybe) => {
if let GenericBound::Trait(poly, modifiers) = bound {
match (ctxt, modifiers.constness, modifiers.polarity) {
(BoundKind::SuperTraits, BoundConstness::Never, BoundPolarity::Maybe(_)) => {
self.dcx().emit_err(errors::OptionalTraitSupertrait {
span: poly.span,
path_str: pprust::path_to_string(&poly.trait_ref.path),
});
}
(BoundKind::TraitObject, TraitBoundModifier::Maybe) => {
(BoundKind::TraitObject, BoundConstness::Never, BoundPolarity::Maybe(_)) => {
self.dcx().emit_err(errors::OptionalTraitObject { span: poly.span });
}
(_, &TraitBoundModifier::MaybeConst(span))
(_, BoundConstness::Maybe(span), BoundPolarity::Positive)
if let Some(reason) = &self.disallow_tilde_const =>
{
let reason = match reason {
@ -1235,16 +1235,15 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
};
self.dcx().emit_err(errors::TildeConstDisallowed { span, reason });
}
(_, TraitBoundModifier::MaybeConstMaybe) => {
self.dcx().emit_err(errors::OptionalConstExclusive {
(
_,
BoundConstness::Maybe(_),
BoundPolarity::Maybe(_) | BoundPolarity::Negative(_),
) => {
self.dcx().emit_err(errors::IncompatibleTraitBoundModifiers {
span: bound.span(),
modifier: "?",
});
}
(_, TraitBoundModifier::MaybeConstNegative) => {
self.dcx().emit_err(errors::OptionalConstExclusive {
span: bound.span(),
modifier: "!",
left: modifiers.constness.as_str(),
right: modifiers.polarity.as_str(),
});
}
_ => {}
@ -1252,7 +1251,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
}
// Negative trait bounds are not allowed to have associated constraints
if let GenericBound::Trait(trait_ref, TraitBoundModifier::Negative) = bound
if let GenericBound::Trait(trait_ref, modifiers) = bound
&& let BoundPolarity::Negative(_) = modifiers.polarity
&& let Some(segment) = trait_ref.trait_ref.path.segments.last()
&& let Some(ast::GenericArgs::AngleBracketed(args)) = segment.args.as_deref()
{
@ -1494,7 +1494,8 @@ fn deny_equality_constraints(
for param in &generics.params {
if param.ident == potential_param.ident {
for bound in &param.bounds {
if let ast::GenericBound::Trait(trait_ref, TraitBoundModifier::None) = bound
if let ast::GenericBound::Trait(trait_ref, TraitBoundModifiers::NONE) =
bound
{
if let [trait_segment] = &trait_ref.trait_ref.path.segments[..] {
let assoc = pprust::path_to_string(&ast::Path::from_ident(

7
compiler/rustc_ast_passes/src/errors.rs
View file

@ -580,11 +580,12 @@ pub enum TildeConstReason {
}
#[derive(Diagnostic)]
#[diag(ast_passes_optional_const_exclusive)]
pub struct OptionalConstExclusive {
#[diag(ast_passes_incompatible_trait_bound_modifiers)]
pub struct IncompatibleTraitBoundModifiers {
#[primary_span]
pub span: Span,
pub modifier: &'static str,
pub left: &'static str,
pub right: &'static str,
}
#[derive(Diagnostic)]