Auto merge of rust-lang#128812 - nnethercote:shrink-TyKind-FnPtr, r=c…

…ompiler-errors

Shrink `TyKind::FnPtr`.

By splitting the `FnSig` within `TyKind::FnPtr` into `FnSigTys` and `FnHeader`, which can be packed more efficiently. This reduces the size of the hot `TyKind` type from 32 bytes to 24 bytes on 64-bit platforms. This reduces peak memory usage by a few percent on some benchmarks. It also reduces cache misses and page faults similarly, though this doesn't translate to clear cycles or wall-time improvements on CI.

r? `@compiler-errors`

clippy_lints/src/casts/fn_to_numeric_cast.rs

@@ -15,7 +15,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
  }
 
  match cast_from.kind() {
- ty::FnDef(..) | ty::FnPtr(_) => {
+ ty::FnDef(..) | ty::FnPtr(..) => {
  let mut applicability = Applicability::MaybeIncorrect;
  let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
  let to_nbits = utils::int_ty_to_nbits(cast_to, cx.tcx);

clippy_lints/src/casts/fn_to_numeric_cast_any.rs

@@ -14,7 +14,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
  _ => { /* continue to checks */ },
  }
 
- if let ty::FnDef(..) | ty::FnPtr(_) = cast_from.kind() {
+ if let ty::FnDef(..) | ty::FnPtr(..) = cast_from.kind() {
  let mut applicability = Applicability::MaybeIncorrect;
  let from_snippet = snippet_with_applicability(cx, cast_expr.span, "..", &mut applicability);
 

clippy_lints/src/casts/fn_to_numeric_cast_with_truncation.rs

@@ -14,7 +14,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
  _ => return,
  }
  match cast_from.kind() {
- ty::FnDef(..) | ty::FnPtr(_) => {
+ ty::FnDef(..) | ty::FnPtr(..) => {
  let mut applicability = Applicability::MaybeIncorrect;
  let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
 

clippy_lints/src/default_numeric_fallback.rs

@@ -236,7 +236,7 @@ fn fn_sig_opt<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Option<PolyFnSig<'
  // We can't use `Ty::fn_sig` because it automatically performs args, this may result in FNs.
  match node_ty.kind() {
  ty::FnDef(def_id, _) => Some(cx.tcx.fn_sig(*def_id).instantiate_identity()),
- ty::FnPtr(fn_sig) => Some(*fn_sig),
+ ty::FnPtr(sig_tys, hdr) => Some(sig_tys.with(*hdr)),
  _ => None,
  }
 }

clippy_lints/src/dereference.rs

@@ -872,7 +872,7 @@ impl TyCoercionStability {
  | ty::Pat(..)
  | ty::Float(_)
  | ty::RawPtr(..)
- | ty::FnPtr(_)
+ | ty::FnPtr(..)
  | ty::Str
  | ty::Slice(..)
  | ty::Adt(..)

clippy_lints/src/eta_reduction.rs

@@ -158,7 +158,7 @@ fn check_clousure<'tcx>(cx: &LateContext<'tcx>, outer_receiver: Option<&Expr<'tc
 
  cx.tcx.fn_sig(def).skip_binder().skip_binder()
  },
- ty::FnPtr(sig) => sig.skip_binder(),
+ ty::FnPtr(sig_tys, hdr) => sig_tys.with(*hdr).skip_binder(),
  ty::Closure(_, subs) => cx
  .tcx
  .signature_unclosure(subs.as_closure().sig(), Safety::Safe)

clippy_lints/src/methods/map_flatten.rs

@@ -58,7 +58,7 @@ fn try_get_caller_ty_name_and_method_name(
 fn is_map_to_option(cx: &LateContext<'_>, map_arg: &Expr<'_>) -> bool {
  let map_closure_ty = cx.typeck_results().expr_ty(map_arg);
  match map_closure_ty.kind() {
- ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
+ ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(..) => {
  let map_closure_sig = match map_closure_ty.kind() {
  ty::Closure(_, args) => args.as_closure().sig(),
  _ => map_closure_ty.fn_sig(cx.tcx),

clippy_lints/src/mixed_read_write_in_expression.rs

@@ -166,7 +166,7 @@ impl<'a, 'tcx> Visitor<'tcx> for DivergenceVisitor<'a, 'tcx> {
  ExprKind::Call(func, _) => {
  let typ = self.cx.typeck_results().expr_ty(func);
  match typ.kind() {
- ty::FnDef(..) | ty::FnPtr(_) => {
+ ty::FnDef(..) | ty::FnPtr(..) => {
  let sig = typ.fn_sig(self.cx.tcx);
  if self.cx.tcx.instantiate_bound_regions_with_erased(sig).output().kind() == &ty::Never {
  self.report_diverging_sub_expr(e);

clippy_lints/src/multiple_unsafe_ops_per_block.rs

@@ -130,7 +130,7 @@ fn collect_unsafe_exprs<'tcx>(
  ExprKind::Call(path_expr, _) => {
  let sig = match *cx.typeck_results().expr_ty(path_expr).kind() {
  ty::FnDef(id, _) => cx.tcx.fn_sig(id).skip_binder(),
- ty::FnPtr(sig) => sig,
+ ty::FnPtr(sig_tys, hdr) => sig_tys.with(hdr),
  _ => return Continue(Descend::Yes),
  };
  if sig.safety() == Safety::Unsafe {

clippy_lints/src/mut_reference.rs

@@ -79,7 +79,7 @@ fn check_arguments<'tcx>(
  fn_kind: &str,
 ) {
  match type_definition.kind() {
- ty::FnDef(..) | ty::FnPtr(_) => {
+ ty::FnDef(..) | ty::FnPtr(..) => {
  let parameters = type_definition.fn_sig(cx.tcx).skip_binder().inputs();
  for (argument, parameter) in iter::zip(arguments, parameters) {
  match parameter.kind() {

clippy_utils/src/ty.rs

@@ -541,7 +541,7 @@ pub fn peel_mid_ty_refs_is_mutable(ty: Ty<'_>) -> (Ty<'_>, usize, Mutability) {
 /// Returns `true` if the given type is an `unsafe` function.
 pub fn type_is_unsafe_function<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
  match ty.kind() {
- ty::FnDef(..) | ty::FnPtr(_) => ty.fn_sig(cx.tcx).safety() == Safety::Unsafe,
+ ty::FnDef(..) | ty::FnPtr(..) => ty.fn_sig(cx.tcx).safety() == Safety::Unsafe,
  _ => false,
  }
 }
@@ -721,7 +721,7 @@ pub fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'t
  cx.tcx.item_super_predicates(def_id).iter_instantiated(cx.tcx, args),
  cx.tcx.opt_parent(def_id),
  ),
- ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig, None)),
+ ty::FnPtr(sig_tys, hdr) => Some(ExprFnSig::Sig(sig_tys.with(hdr), None)),
  ty::Dynamic(bounds, _, _) => {
  let lang_items = cx.tcx.lang_items();
  match bounds.principal() {

clippy_utils/src/visitors.rs

@@ -441,7 +441,7 @@ pub fn is_expr_unsafe<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
  ty::FnDef(id, _) if self.cx.tcx.fn_sig(id).skip_binder().safety() == Safety::Unsafe => {
  self.is_unsafe = true;
  },
- ty::FnPtr(sig) if sig.safety() == Safety::Unsafe => self.is_unsafe = true,
+ ty::FnPtr(_, hdr) if hdr.safety == Safety::Unsafe => self.is_unsafe = true,
  _ => walk_expr(self, e),
  },
  ExprKind::Path(ref p)