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borrowck/type_check: remove helper left-over from unsized locals #154036

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Merged
rust-bors merged 1 commit into from
Mar 19, 2026
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borrowck/type_check: remove helper left-over from unsized locals #154036

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17 changes: 7 additions & 10 deletions compiler/rustc_borrowck/src/type_check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -374,10 +374,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
self.body
}

fn unsized_feature_enabled(&self) -> bool {
self.tcx().features().unsized_fn_params()
}

/// Equate the inferred type and the annotated type for user type annotations
#[instrument(skip(self), level = "debug")]
fn check_user_type_annotations(&mut self) {
Expand Down Expand Up @@ -660,7 +656,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
);
}

if !self.unsized_feature_enabled() {
if !self.tcx().features().unsized_fn_params() {
let trait_ref = ty::TraitRef::new(
tcx,
tcx.require_lang_item(LangItem::Sized, self.last_span),
Expand Down Expand Up @@ -936,9 +932,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}

// When `unsized_fn_params` is enabled, only function calls
// and nullary ops are checked in `check_call_dest`.
if !self.unsized_feature_enabled() {
// When `unsized_fn_params` is enabled, this is checked in `check_call_dest`,
// and `hir_typeck` still forces all non-argument locals to be sized (i.e., we don't
// fully re-check what was already checked on HIR).
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@RalfJung RalfJung Mar 18, 2026 •
edited
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Nullary ops don't exist any more so the comment needed updating.

And from all I can tell, we do not fully re-check non-argument locals to be sized here. Not sure if that is a problem, being sized cannot depend on lifetimes after all. But then I don't know why we re-check any of the sized stuff here.^^

Cc @lqd @lcnr

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@lqd lqd Mar 19, 2026

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Yeah, weird. I don't know either...

if !self.tcx().features().unsized_fn_params() {
match self.body.local_kind(local) {
LocalKind::ReturnPointer | LocalKind::Arg => {
// return values of normal functions are required to be
Expand Down Expand Up @@ -1953,8 +1950,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
}

// When `unsized_fn_params` is not enabled,
// this check is done at `check_local`.
if self.unsized_feature_enabled() {
// this check is done at `visit_local_decl`.
if self.tcx().features().unsized_fn_params() {
let span = term.source_info.span;
self.ensure_place_sized(dest_ty, span);
}
Expand Down
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