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Auto merge of rust-lang#128550 - compiler-errors:shadowed-params-perf…
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…, r=petrochenkov

Only walk ribs to collect possibly shadowed params if we are adding params in our new rib

No need to collect params from parent ribs if we literally have no params to declare in this new rib.

Attempt to win back some of the perf in rust-lang#128357 (comment).

Please review with whitespace *off*, the diff should be like 2 lines.

r? petrochenkov
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@bors
bors committed Aug 8, 2024
2 parents 86e7875 + abada5f commit 0d65e5a
Showing 1 changed file with 105 additions and 96 deletions.
201 changes: 105 additions & 96 deletions compiler/rustc_resolve/src/late.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2668,119 +2668,128 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
let mut function_type_rib = Rib::new(kind);
let mut function_value_rib = Rib::new(kind);
let mut function_lifetime_rib = LifetimeRib::new(lifetime_kind);
let mut seen_bindings = FxHashMap::default();
// Store all seen lifetimes names from outer scopes.
let mut seen_lifetimes = FxHashSet::default();

// We also can't shadow bindings from associated parent items.
for ns in [ValueNS, TypeNS] {
for parent_rib in self.ribs[ns].iter().rev() {
seen_bindings.extend(parent_rib.bindings.keys().map(|ident| (*ident, ident.span)));

// Break at mod level, to account for nested items which are
// allowed to shadow generic param names.
if matches!(parent_rib.kind, RibKind::Module(..)) {
break;
}
}
}

// Forbid shadowing lifetime bindings
for rib in self.lifetime_ribs.iter().rev() {
seen_lifetimes.extend(rib.bindings.iter().map(|(ident, _)| *ident));
if let LifetimeRibKind::Item = rib.kind {
break;
// Only check for shadowed bindings if we're declaring new params.
if !params.is_empty() {
let mut seen_bindings = FxHashMap::default();
// Store all seen lifetimes names from outer scopes.
let mut seen_lifetimes = FxHashSet::default();

// We also can't shadow bindings from associated parent items.
for ns in [ValueNS, TypeNS] {
for parent_rib in self.ribs[ns].iter().rev() {
seen_bindings
.extend(parent_rib.bindings.keys().map(|ident| (*ident, ident.span)));

// Break at mod level, to account for nested items which are
// allowed to shadow generic param names.
if matches!(parent_rib.kind, RibKind::Module(..)) {
break;
}
}
}
}

for param in params {
let ident = param.ident.normalize_to_macros_2_0();
debug!("with_generic_param_rib: {}", param.id);

if let GenericParamKind::Lifetime = param.kind
&& let Some(&original) = seen_lifetimes.get(&ident)
{
diagnostics::signal_lifetime_shadowing(self.r.tcx.sess, original, param.ident);
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
// Forbid shadowing lifetime bindings
for rib in self.lifetime_ribs.iter().rev() {
seen_lifetimes.extend(rib.bindings.iter().map(|(ident, _)| *ident));
if let LifetimeRibKind::Item = rib.kind {
break;
}
}

match seen_bindings.entry(ident) {
Entry::Occupied(entry) => {
let span = *entry.get();
let err = ResolutionError::NameAlreadyUsedInParameterList(ident.name, span);
self.report_error(param.ident.span, err);
let rib = match param.kind {
GenericParamKind::Lifetime => {
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}
GenericParamKind::Type { .. } => &mut function_type_rib,
GenericParamKind::Const { .. } => &mut function_value_rib,
};
for param in params {
let ident = param.ident.normalize_to_macros_2_0();
debug!("with_generic_param_rib: {}", param.id);

// Taint the resolution in case of errors to prevent follow up errors in typeck
self.r.record_partial_res(param.id, PartialRes::new(Res::Err));
rib.bindings.insert(ident, Res::Err);
if let GenericParamKind::Lifetime = param.kind
&& let Some(&original) = seen_lifetimes.get(&ident)
{
diagnostics::signal_lifetime_shadowing(self.r.tcx.sess, original, param.ident);
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}
Entry::Vacant(entry) => {
entry.insert(param.ident.span);
}
}

if param.ident.name == kw::UnderscoreLifetime {
self.r
.dcx()
.emit_err(errors::UnderscoreLifetimeIsReserved { span: param.ident.span });
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}
match seen_bindings.entry(ident) {
Entry::Occupied(entry) => {
let span = *entry.get();
let err = ResolutionError::NameAlreadyUsedInParameterList(ident.name, span);
self.report_error(param.ident.span, err);
let rib = match param.kind {
GenericParamKind::Lifetime => {
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}
GenericParamKind::Type { .. } => &mut function_type_rib,
GenericParamKind::Const { .. } => &mut function_value_rib,
};

if param.ident.name == kw::StaticLifetime {
self.r.dcx().emit_err(errors::StaticLifetimeIsReserved {
span: param.ident.span,
lifetime: param.ident,
});
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}
// Taint the resolution in case of errors to prevent follow up errors in typeck
self.r.record_partial_res(param.id, PartialRes::new(Res::Err));
rib.bindings.insert(ident, Res::Err);
continue;
}
Entry::Vacant(entry) => {
entry.insert(param.ident.span);
}
}

let def_id = self.r.local_def_id(param.id);
if param.ident.name == kw::UnderscoreLifetime {
self.r
.dcx()
.emit_err(errors::UnderscoreLifetimeIsReserved { span: param.ident.span });
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}

// Plain insert (no renaming).
let (rib, def_kind) = match param.kind {
GenericParamKind::Type { .. } => (&mut function_type_rib, DefKind::TyParam),
GenericParamKind::Const { .. } => (&mut function_value_rib, DefKind::ConstParam),
GenericParamKind::Lifetime => {
let res = LifetimeRes::Param { param: def_id, binder };
self.record_lifetime_param(param.id, res);
function_lifetime_rib.bindings.insert(ident, (param.id, res));
if param.ident.name == kw::StaticLifetime {
self.r.dcx().emit_err(errors::StaticLifetimeIsReserved {
span: param.ident.span,
lifetime: param.ident,
});
// Record lifetime res, so lowering knows there is something fishy.
self.record_lifetime_param(param.id, LifetimeRes::Error);
continue;
}
};

let res = match kind {
RibKind::Item(..) | RibKind::AssocItem => Res::Def(def_kind, def_id.to_def_id()),
RibKind::Normal => {
// FIXME(non_lifetime_binders): Stop special-casing
// const params to error out here.
if self.r.tcx.features().non_lifetime_binders
&& matches!(param.kind, GenericParamKind::Type { .. })
{
let def_id = self.r.local_def_id(param.id);

// Plain insert (no renaming).
let (rib, def_kind) = match param.kind {
GenericParamKind::Type { .. } => (&mut function_type_rib, DefKind::TyParam),
GenericParamKind::Const { .. } => {
(&mut function_value_rib, DefKind::ConstParam)
}
GenericParamKind::Lifetime => {
let res = LifetimeRes::Param { param: def_id, binder };
self.record_lifetime_param(param.id, res);
function_lifetime_rib.bindings.insert(ident, (param.id, res));
continue;
}
};

let res = match kind {
RibKind::Item(..) | RibKind::AssocItem => {
Res::Def(def_kind, def_id.to_def_id())
} else {
Res::Err
}
}
_ => span_bug!(param.ident.span, "Unexpected rib kind {:?}", kind),
};
self.r.record_partial_res(param.id, PartialRes::new(res));
rib.bindings.insert(ident, res);
RibKind::Normal => {
// FIXME(non_lifetime_binders): Stop special-casing
// const params to error out here.
if self.r.tcx.features().non_lifetime_binders
&& matches!(param.kind, GenericParamKind::Type { .. })
{
Res::Def(def_kind, def_id.to_def_id())
} else {
Res::Err
}
}
_ => span_bug!(param.ident.span, "Unexpected rib kind {:?}", kind),
};
self.r.record_partial_res(param.id, PartialRes::new(res));
rib.bindings.insert(ident, res);
}
}

self.lifetime_ribs.push(function_lifetime_rib);
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