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Make bound_context more like neighboring functions

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This commit is contained in:
Dylan MacKenzie 2020-01-05 16:33:26 -08:00
parent 9950a1f3bd
commit 14730ed445
1 changed files with 18 additions and 21 deletions
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39
src/librustc_passes/ast_validation.rs
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@ -24,6 +24,7 @@ use syntax::walk_list;
use rustc_error_codes::*;
/// A syntactic context that disallows certain kinds of bounds (e.g., `?Trait` or `?const Trait`).
#[derive(Clone, Copy)]
enum BoundContext {
ImplTrait,
@ -50,10 +51,11 @@ struct AstValidator<'a> {
/// e.g., `impl Iterator<Item = impl Debug>`.
outer_impl_trait: Option<Span>,
/// Tracks the context in which a bound can appear.
/// Keeps track of the `BoundContext` as we recurse.
///
/// This is used to forbid `?const Trait` bounds in certain contexts.
bound_context_stack: Vec<Option<BoundContext>>,
/// This is used to forbid `?const Trait` bounds in, e.g.,
/// `impl Iterator<Item = Box<dyn ?const Trait>`.
bound_context: Option<BoundContext>,
/// Used to ban `impl Trait` in path projections like `<impl Iterator>::Item`
/// or `Foo::Bar<impl Trait>`
@ -80,21 +82,19 @@ impl<'a> AstValidator<'a> {
}
fn with_impl_trait(&mut self, outer: Option<Span>, f: impl FnOnce(&mut Self)) {
self.bound_context_stack.push(outer.map(|_| BoundContext::ImplTrait));
let old = mem::replace(&mut self.outer_impl_trait, outer);
f(self);
if outer.is_some() {
self.with_bound_context(BoundContext::ImplTrait, |this| f(this));
} else {
f(self)
}
self.outer_impl_trait = old;
self.bound_context_stack.pop();
}
fn with_bound_context(&mut self, ctx: Option<BoundContext>, f: impl FnOnce(&mut Self)) {
self.bound_context_stack.push(ctx);
fn with_bound_context(&mut self, ctx: BoundContext, f: impl FnOnce(&mut Self)) {
let old = self.bound_context.replace(ctx);
f(self);
self.bound_context_stack.pop();
}
fn innermost_bound_context(&mut self) -> Option<BoundContext> {
self.bound_context_stack.iter().rev().find(|x| x.is_some()).copied().flatten()
self.bound_context = old;
}
fn visit_assoc_ty_constraint_from_generic_args(&mut self, constraint: &'a AssocTyConstraint) {
@ -119,9 +119,7 @@ impl<'a> AstValidator<'a> {
self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t))
}
TyKind::TraitObject(..) => {
self.with_bound_context(Some(BoundContext::TraitObject), |this| {
visit::walk_ty(this, t)
});
self.with_bound_context(BoundContext::TraitObject, |this| visit::walk_ty(this, t));
}
TyKind::Path(ref qself, ref path) => {
// We allow these:
@ -231,8 +229,7 @@ impl<'a> AstValidator<'a> {
}
}
// FIXME(ecstaticmorse): Instead, use the `bound_context_stack` to check this in
// `visit_param_bound`.
// FIXME(ecstaticmorse): Instead, use `bound_context` to check this in `visit_param_bound`.
fn no_questions_in_bounds(&self, bounds: &GenericBounds, where_: &str, is_trait: bool) {
for bound in bounds {
if let GenericBound::Trait(ref poly, TraitBoundModifier::Maybe) = *bound {
@ -744,7 +741,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
self.visit_generics(generics);
self.with_bound_context(Some(BoundContext::TraitBounds), |this| {
self.with_bound_context(BoundContext::TraitBounds, |this| {
walk_list!(this, visit_param_bound, bounds);
});
walk_list!(self, visit_trait_item, trait_items);
@ -903,7 +900,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
.span_err(bound.span(), "`?const` and `?` are mutually exclusive");
}
if let Some(ctx) = self.innermost_bound_context() {
if let Some(ctx) = self.bound_context {
let msg = format!("`?const` is not permitted in {}", ctx.description());
self.err_handler().span_err(bound.span(), &msg);
}
@ -1025,7 +1022,7 @@ pub fn check_crate(session: &Session, krate: &Crate, lints: &mut lint::LintBuffe
session,
has_proc_macro_decls: false,
outer_impl_trait: None,
bound_context_stack: Vec::new(),
bound_context: None,
is_impl_trait_banned: false,
is_assoc_ty_bound_banned: false,
lint_buffer: lints,