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Don't move ?Trait bounds to param bounds if they're in where clauses

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This commit is contained in:
jackh726
2021-08-15 00:53:40 -04:00
parent 2eaf9fe364
commit f1f1d56d93
12 changed files with 103 additions and 82 deletions
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46
compiler/rustc_ast_lowering/src/item.rs
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@@ -2,7 +2,6 @@ use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
use super::{ImplTraitContext, ImplTraitPosition};
use crate::Arena;
use rustc_ast::node_id::NodeMap;
use rustc_ast::ptr::P;
use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
use rustc_ast::*;
@@ -1351,8 +1350,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
generics: &Generics,
itctx: ImplTraitContext<'_, 'hir>,
) -> GenericsCtor<'hir> {
// Collect `?Trait` bounds in where clause and move them to parameter definitions.
let mut add_bounds: NodeMap<Vec<_>> = Default::default();
// Error if `?Trait` bounds in where clauses don't refer directly to type paramters.
// Note: we used to clone these bounds directly onto the type parameter (and avoid lowering
// these into hir when we lower thee where clauses), but this makes it quite difficult to
// keep track of the Span info. Now, `is_unsized` in `AstConv` checks both param bounds and
// where clauses for `?Sized`.
for pred in &generics.where_clause.predicates {
if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
'next_bound: for bound in &bound_pred.bounds {
@@ -1368,7 +1370,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
{
for param in &generics.params {
if def_id == self.resolver.local_def_id(param.id).to_def_id() {
add_bounds.entry(param.id).or_default().push(bound.clone());
continue 'next_bound;
}
}
@@ -1386,7 +1387,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}
GenericsCtor {
params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
params: self.lower_generic_params_mut(&generics.params, itctx).collect(),
where_clause: self.lower_where_clause(&generics.where_clause),
span: self.lower_span(generics.span),
}
@@ -1419,32 +1420,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
ref bounded_ty,
ref bounds,
span,
}) => {
self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
bound_generic_params: this.lower_generic_params(
bound_generic_params,
&NodeMap::default(),
ImplTraitContext::disallowed(),
),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: this.arena.alloc_from_iter(bounds.iter().map(
|bound| match bound {
// We used to ignore `?Trait` bounds, as they were copied into type
// parameters already, but we need to keep them around only for
// diagnostics when we suggest removal of `?Sized` bounds. See
// `suggest_constraining_type_param`. This will need to change if
// we ever allow something *other* than `?Sized`.
GenericBound::Trait(p, TraitBoundModifier::Maybe) => {
hir::GenericBound::Unsized(this.lower_span(p.span))
}
_ => this.lower_param_bound(bound, ImplTraitContext::disallowed()),
},
)),
span: this.lower_span(span),
})
}) => self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
bound_generic_params: this
.lower_generic_params(bound_generic_params, ImplTraitContext::disallowed()),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: this.arena.alloc_from_iter(bounds.iter().map(|bound| {
this.lower_param_bound(bound, ImplTraitContext::disallowed())
})),
span: this.lower_span(span),
})
}
}),
WherePredicate::RegionPredicate(WhereRegionPredicate {
ref lifetime,
ref bounds,