Rollup merge of #143544 - workingjubilee:rename-bare-fn, r=fmease

compiler: rename BareFn to FnPtr

At some point "BareFn" was the chosen name for a "bare" function, without the niceties of `~fn`, `&fn`, or a few other ways of writing a function type. However, at some point the syntax for a "bare function" and any other function diverged even more. We started calling them what they are: function pointers, denoted by their own syntax.

However, we never changed the *internal* name for these, as this divergence was very gradual. Personally, I have repeatedly searched for "FnPtr" and gotten confused until I find the name is BareFn, only to forget this until the next time, since I don't routinely interact with the higher-level AST and HIR. But even tools that interact with these internal types only touch on them in a few places, making a migration easy enough. Let's use a more intuitive and obvious name, as this 12+ year old name has little to do with current Rust.

Author: jhpratt

compiler/rustc_ast/src/ast.rs

@@ -2422,7 +2422,7 @@ impl Ty {
 }
 
 #[derive(Clone, Encodable, Decodable, Debug)]
-pub struct BareFnTy {
+pub struct FnPtrTy {
     pub safety: Safety,
     pub ext: Extern,
     pub generic_params: ThinVec<GenericParam>,
@@ -2455,8 +2455,8 @@ pub enum TyKind {
     ///
     /// Desugars into `Pin<&'a T>` or `Pin<&'a mut T>`.
     PinnedRef(Option<Lifetime>, MutTy),
-    /// A bare function (e.g., `fn(usize) -> bool`).
-    BareFn(P<BareFnTy>),
+    /// A function pointer type (e.g., `fn(usize) -> bool`).
+    FnPtr(P<FnPtrTy>),
     /// An unsafe existential lifetime binder (e.g., `unsafe<'a> &'a ()`).
     UnsafeBinder(P<UnsafeBinderTy>),
     /// The never type (`!`).

compiler/rustc_ast/src/util/classify.rs

@@ -265,7 +265,7 @@ fn type_trailing_braced_mac_call(mut ty: &ast::Ty) -> Option<&ast::MacCall> {
                 ty = &binder.inner_ty;
             }
 
-            ast::TyKind::BareFn(fn_ty) => match &fn_ty.decl.output {
+            ast::TyKind::FnPtr(fn_ty) => match &fn_ty.decl.output {
                 ast::FnRetTy::Default(_) => break None,
                 ast::FnRetTy::Ty(ret) => ty = ret,
             },

compiler/rustc_ast/src/visit.rs

@@ -1059,8 +1059,8 @@ macro_rules! common_visitor_and_walkers {
                 TyKind::Tup(tuple_element_types) => {
                     walk_list!(vis, visit_ty, tuple_element_types);
                 }
-                TyKind::BareFn(function_declaration) => {
-                    let BareFnTy { safety, ext: _, generic_params, decl, decl_span } =
+                TyKind::FnPtr(function_declaration) => {
+                    let FnPtrTy { safety, ext: _, generic_params, decl, decl_span } =
                         &$($mut)? **function_declaration;
                     try_visit!(visit_safety(vis, safety));
                     try_visit!(visit_generic_params(vis, generic_params));

compiler/rustc_ast_lowering/src/lib.rs

@@ -1269,9 +1269,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 let path = self.make_lang_item_qpath(LangItem::Pin, span, Some(args));
                 hir::TyKind::Path(path)
             }
-            TyKind::BareFn(f) => {
+            TyKind::FnPtr(f) => {
                 let generic_params = self.lower_lifetime_binder(t.id, &f.generic_params);
-                hir::TyKind::BareFn(self.arena.alloc(hir::BareFnTy {
+                hir::TyKind::FnPtr(self.arena.alloc(hir::FnPtrTy {
                     generic_params,
                     safety: self.lower_safety(f.safety, hir::Safety::Safe),
                     abi: self.lower_extern(f.ext),

compiler/rustc_ast_passes/messages.ftl

@@ -48,9 +48,6 @@ ast_passes_auto_super_lifetime = auto traits cannot have super traits or lifetim
 
 ast_passes_bad_c_variadic = only foreign, `unsafe extern "C"`, or `unsafe extern "C-unwind"` functions may have a C-variadic arg
 
-ast_passes_bare_fn_invalid_safety = function pointers cannot be declared with `safe` safety qualifier
-    .suggestion = remove safe from this item
-
 ast_passes_body_in_extern = incorrect `{$kind}` inside `extern` block
     .cannot_have = cannot have a body
     .invalid = the invalid body
@@ -135,6 +132,9 @@ ast_passes_fn_param_forbidden_self =
 ast_passes_fn_param_too_many =
     function can not have more than {$max_num_args} arguments
 
+ast_passes_fn_ptr_invalid_safety = function pointers cannot be declared with `safe` safety qualifier
+    .suggestion = remove safe from this item
+
 ast_passes_fn_without_body =
     free function without a body
     .suggestion = provide a definition for the function

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -499,9 +499,9 @@ impl<'a> AstValidator<'a> {
         }
     }
 
-    fn check_bare_fn_safety(&self, span: Span, safety: Safety) {
+    fn check_fn_ptr_safety(&self, span: Span, safety: Safety) {
         if matches!(safety, Safety::Safe(_)) {
-            self.dcx().emit_err(errors::InvalidSafetyOnBareFn { span });
+            self.dcx().emit_err(errors::InvalidSafetyOnFnPtr { span });
         }
     }
 
@@ -785,8 +785,8 @@ impl<'a> AstValidator<'a> {
 
     fn visit_ty_common(&mut self, ty: &'a Ty) {
         match &ty.kind {
-            TyKind::BareFn(bfty) => {
-                self.check_bare_fn_safety(bfty.decl_span, bfty.safety);
+            TyKind::FnPtr(bfty) => {
+                self.check_fn_ptr_safety(bfty.decl_span, bfty.safety);
                 self.check_fn_decl(&bfty.decl, SelfSemantic::No);
                 Self::check_decl_no_pat(&bfty.decl, |span, _, _| {
                     self.dcx().emit_err(errors::PatternFnPointer { span });

compiler/rustc_ast_passes/src/errors.rs

@@ -225,8 +225,8 @@ pub(crate) struct InvalidSafetyOnItem {
 }
 
 #[derive(Diagnostic)]
-#[diag(ast_passes_bare_fn_invalid_safety)]
-pub(crate) struct InvalidSafetyOnBareFn {
+#[diag(ast_passes_fn_ptr_invalid_safety)]
+pub(crate) struct InvalidSafetyOnFnPtr {
     #[primary_span]
     pub span: Span,
 }

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -286,9 +286,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 
     fn visit_ty(&mut self, ty: &'a ast::Ty) {
         match &ty.kind {
-            ast::TyKind::BareFn(bare_fn_ty) => {
+            ast::TyKind::FnPtr(fn_ptr_ty) => {
                 // Function pointers cannot be `const`
-                self.check_late_bound_lifetime_defs(&bare_fn_ty.generic_params);
+                self.check_late_bound_lifetime_defs(&fn_ptr_ty.generic_params);
             }
             ast::TyKind::Never => {
                 gate!(&self, never_type, ty.span, "the `!` type is experimental");

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1285,7 +1285,7 @@ impl<'a> State<'a> {
                 self.print_type(typ);
                 self.pclose();
             }
-            ast::TyKind::BareFn(f) => {
+            ast::TyKind::FnPtr(f) => {
                 self.print_ty_fn(f.ext, f.safety, &f.decl, None, &f.generic_params);
             }
             ast::TyKind::UnsafeBinder(f) => {

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -414,12 +414,12 @@ fn find_type_parameters(
     impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
         fn visit_ty(&mut self, ty: &'a ast::Ty) {
             let stack_len = self.bound_generic_params_stack.len();
-            if let ast::TyKind::BareFn(bare_fn) = &ty.kind
-                && !bare_fn.generic_params.is_empty()
+            if let ast::TyKind::FnPtr(fn_ptr) = &ty.kind
+                && !fn_ptr.generic_params.is_empty()
             {
                 // Given a field `x: for<'a> fn(T::SomeType<'a>)`, we wan't to account for `'a` so
                 // that we generate `where for<'a> T::SomeType<'a>: ::core::clone::Clone`. #122622
-                self.bound_generic_params_stack.extend(bare_fn.generic_params.iter().cloned());
+                self.bound_generic_params_stack.extend(fn_ptr.generic_params.iter().cloned());
             }
 
             if let ast::TyKind::Path(_, path) = &ty.kind

compiler/rustc_hir/src/def.rs

@@ -831,7 +831,7 @@ pub enum LifetimeRes {
         /// Id of the introducing place. That can be:
         /// - an item's id, for the item's generic parameters;
         /// - a TraitRef's ref_id, identifying the `for<...>` binder;
-        /// - a BareFn type's id.
+        /// - a FnPtr type's id.
         ///
         /// This information is used for impl-trait lifetime captures, to know when to or not to
         /// capture any given lifetime.

compiler/rustc_hir/src/hir.rs

@@ -3526,7 +3526,7 @@ impl PrimTy {
 }
 
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
-pub struct BareFnTy<'hir> {
+pub struct FnPtrTy<'hir> {
     pub safety: Safety,
     pub abi: ExternAbi,
     pub generic_params: &'hir [GenericParam<'hir>],
@@ -3645,8 +3645,8 @@ pub enum TyKind<'hir, Unambig = ()> {
     Ptr(MutTy<'hir>),
     /// A reference (i.e., `&'a T` or `&'a mut T`).
     Ref(&'hir Lifetime, MutTy<'hir>),
-    /// A bare function (e.g., `fn(usize) -> bool`).
-    BareFn(&'hir BareFnTy<'hir>),
+    /// A function pointer (e.g., `fn(usize) -> bool`).
+    FnPtr(&'hir FnPtrTy<'hir>),
     /// An unsafe binder type (e.g. `unsafe<'a> Foo<'a>`).
     UnsafeBinder(&'hir UnsafeBinderTy<'hir>),
     /// The never type (`!`).
@@ -4498,7 +4498,7 @@ pub enum ForeignItemKind<'hir> {
     ///
     /// All argument idents are actually always present (i.e. `Some`), but
     /// `&[Option<Ident>]` is used because of code paths shared with `TraitFn`
-    /// and `BareFnTy`. The sharing is due to all of these cases not allowing
+    /// and `FnPtrTy`. The sharing is due to all of these cases not allowing
     /// arbitrary patterns for parameters.
     Fn(FnSig<'hir>, &'hir [Option<Ident>], &'hir Generics<'hir>),
     /// A foreign static item (`static ext: u8`).

compiler/rustc_hir/src/intravisit.rs

@@ -1001,7 +1001,7 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v, AmbigArg>) -
         TyKind::Tup(tuple_element_types) => {
             walk_list!(visitor, visit_ty_unambig, tuple_element_types);
         }
-        TyKind::BareFn(ref function_declaration) => {
+        TyKind::FnPtr(ref function_declaration) => {
             walk_list!(visitor, visit_generic_param, function_declaration.generic_params);
             try_visit!(visitor.visit_fn_decl(function_declaration.decl));
         }

compiler/rustc_hir_analysis/src/collect.rs

@@ -198,7 +198,7 @@ fn placeholder_type_error_diag<'cx, 'tcx>(
         let mut is_const_or_static = false;
 
         if let Some(hir_ty) = hir_ty
-            && let hir::TyKind::BareFn(_) = hir_ty.kind
+            && let hir::TyKind::FnPtr(_) = hir_ty.kind
         {
             is_fn = true;
 

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -454,7 +454,7 @@ fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<S
         type Result = ControlFlow<Span>;
         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx, AmbigArg>) -> ControlFlow<Span> {
             match ty.kind {
-                hir::TyKind::BareFn(..) => {
+                hir::TyKind::FnPtr(..) => {
                     self.outer_index.shift_in(1);
                     let res = intravisit::walk_ty(self, ty);
                     self.outer_index.shift_out(1);

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -704,7 +704,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
     #[instrument(level = "debug", skip(self))]
     fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx, AmbigArg>) {
         match ty.kind {
-            hir::TyKind::BareFn(c) => {
+            hir::TyKind::FnPtr(c) => {
                 let (mut bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) = c
                     .generic_params
                     .iter()
@@ -728,8 +728,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     where_bound_origin: None,
                 };
                 self.with(scope, |this| {
-                    // a bare fn has no bounds, so everything
-                    // contained within is scoped within its binder.
+                    // a FnPtr has no bounds, so everything within is scoped within its binder
                     intravisit::walk_ty(this, ty);
                 });
             }
@@ -758,8 +757,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     where_bound_origin: None,
                 };
                 self.with(scope, |this| {
-                    // a bare fn has no bounds, so everything
-                    // contained within is scoped within its binder.
+                    // everything within is scoped within its binder
                     intravisit::walk_ty(this, ty);
                 });
             }
@@ -1419,7 +1417,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             hir::Node::OpaqueTy(_) => "higher-ranked lifetime from outer `impl Trait`",
             // Other items are fine.
             hir::Node::Item(_) | hir::Node::TraitItem(_) | hir::Node::ImplItem(_) => return Ok(()),
-            hir::Node::Ty(hir::Ty { kind: hir::TyKind::BareFn(_), .. }) => {
+            hir::Node::Ty(hir::Ty { kind: hir::TyKind::FnPtr(_), .. }) => {
                 "higher-ranked lifetime from function pointer"
             }
             hir::Node::Ty(hir::Ty { kind: hir::TyKind::TraitObject(..), .. }) => {

compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs

@@ -393,9 +393,9 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
             let params = if let Some(generics) = node.generics() {
                 generics.params
             } else if let hir::Node::Ty(ty) = node
-                && let hir::TyKind::BareFn(bare_fn) = ty.kind
+                && let hir::TyKind::FnPtr(fn_ptr) = ty.kind
             {
-                bare_fn.generic_params
+                fn_ptr.generic_params
             } else {
                 &[]
             };

compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs

@@ -21,8 +21,8 @@ pub(crate) fn validate_cmse_abi<'tcx>(
         ExternAbi::CmseNonSecureCall => {
             let hir_node = tcx.hir_node(hir_id);
             let hir::Node::Ty(hir::Ty {
-                span: bare_fn_span,
-                kind: hir::TyKind::BareFn(bare_fn_ty),
+                span: fn_ptr_span,
+                kind: hir::TyKind::FnPtr(fn_ptr_ty),
                 ..
             }) = hir_node
             else {
@@ -49,31 +49,31 @@ pub(crate) fn validate_cmse_abi<'tcx>(
                 Ok(Err(index)) => {
                     // fn(x: u32, u32, u32, u16, y: u16) -> u32,
                     //                           ^^^^^^
-                    let span = if let Some(ident) = bare_fn_ty.param_idents[index] {
-                        ident.span.to(bare_fn_ty.decl.inputs[index].span)
+                    let span = if let Some(ident) = fn_ptr_ty.param_idents[index] {
+                        ident.span.to(fn_ptr_ty.decl.inputs[index].span)
                     } else {
-                        bare_fn_ty.decl.inputs[index].span
+                        fn_ptr_ty.decl.inputs[index].span
                     }
-                    .to(bare_fn_ty.decl.inputs.last().unwrap().span);
-                    let plural = bare_fn_ty.param_idents.len() - index != 1;
+                    .to(fn_ptr_ty.decl.inputs.last().unwrap().span);
+                    let plural = fn_ptr_ty.param_idents.len() - index != 1;
                     dcx.emit_err(errors::CmseInputsStackSpill { span, plural, abi });
                 }
                 Err(layout_err) => {
                     if should_emit_generic_error(abi, layout_err) {
-                        dcx.emit_err(errors::CmseCallGeneric { span: *bare_fn_span });
+                        dcx.emit_err(errors::CmseCallGeneric { span: *fn_ptr_span });
                     }
                 }
             }
 
             match is_valid_cmse_output(tcx, fn_sig) {
                 Ok(true) => {}
                 Ok(false) => {
-                    let span = bare_fn_ty.decl.output.span();
+                    let span = fn_ptr_ty.decl.output.span();
                     dcx.emit_err(errors::CmseOutputStackSpill { span, abi });
                 }
                 Err(layout_err) => {
                     if should_emit_generic_error(abi, layout_err) {
-                        dcx.emit_err(errors::CmseCallGeneric { span: *bare_fn_span });
+                        dcx.emit_err(errors::CmseCallGeneric { span: *fn_ptr_span });
                     }
                 }
             };

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2402,7 +2402,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             hir::TyKind::Tup(fields) => {
                 Ty::new_tup_from_iter(tcx, fields.iter().map(|t| self.lower_ty(t)))
             }
-            hir::TyKind::BareFn(bf) => {
+            hir::TyKind::FnPtr(bf) => {
                 require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, hir_ty.span);
 
                 Ty::new_fn_ptr(
@@ -2660,28 +2660,28 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         debug!(?output_ty);
 
         let fn_ty = tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, safety, abi);
-        let bare_fn_ty = ty::Binder::bind_with_vars(fn_ty, bound_vars);
+        let fn_ptr_ty = ty::Binder::bind_with_vars(fn_ty, bound_vars);
 
-        if let hir::Node::Ty(hir::Ty { kind: hir::TyKind::BareFn(bare_fn_ty), span, .. }) =
+        if let hir::Node::Ty(hir::Ty { kind: hir::TyKind::FnPtr(fn_ptr_ty), span, .. }) =
             tcx.hir_node(hir_id)
         {
-            check_abi(tcx, hir_id, *span, bare_fn_ty.abi);
+            check_abi(tcx, hir_id, *span, fn_ptr_ty.abi);
         }
 
         // reject function types that violate cmse ABI requirements
-        cmse::validate_cmse_abi(self.tcx(), self.dcx(), hir_id, abi, bare_fn_ty);
+        cmse::validate_cmse_abi(self.tcx(), self.dcx(), hir_id, abi, fn_ptr_ty);
 
-        if !bare_fn_ty.references_error() {
+        if !fn_ptr_ty.references_error() {
             // Find any late-bound regions declared in return type that do
             // not appear in the arguments. These are not well-formed.
             //
             // Example:
             //     for<'a> fn() -> &'a str <-- 'a is bad
             //     for<'a> fn(&'a String) -> &'a str <-- 'a is ok
-            let inputs = bare_fn_ty.inputs();
+            let inputs = fn_ptr_ty.inputs();
             let late_bound_in_args =
                 tcx.collect_constrained_late_bound_regions(inputs.map_bound(|i| i.to_owned()));
-            let output = bare_fn_ty.output();
+            let output = fn_ptr_ty.output();
             let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(output);
 
             self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| {
@@ -2695,7 +2695,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             });
         }
 
-        bare_fn_ty
+        fn_ptr_ty
     }
 
     /// Given a fn_hir_id for a impl function, suggest the type that is found on the

compiler/rustc_hir_pretty/src/lib.rs

@@ -405,7 +405,7 @@ impl<'a> State<'a> {
                 }
                 self.pclose();
             }
-            hir::TyKind::BareFn(f) => {
+            hir::TyKind::FnPtr(f) => {
                 self.print_ty_fn(f.abi, f.safety, f.decl, None, f.generic_params, f.param_idents);
             }
             hir::TyKind::UnsafeBinder(unsafe_binder) => {

compiler/rustc_hir_typeck/src/callee.rs

@@ -203,7 +203,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let adjusted_ty =
             self.structurally_resolve_type(autoderef.span(), autoderef.final_ty(false));
 
-        // If the callee is a bare function or a closure, then we're all set.
+        // If the callee is a function pointer or a closure, then we're all set.
         match *adjusted_ty.kind() {
             ty::FnDef(..) | ty::FnPtr(..) => {
                 let adjustments = self.adjust_steps(autoderef);

compiler/rustc_lint/src/nonstandard_style.rs

@@ -431,7 +431,7 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
     }
 
     fn check_ty(&mut self, cx: &LateContext<'_>, ty: &hir::Ty<'_, hir::AmbigArg>) {
-        if let hir::TyKind::BareFn(hir::BareFnTy { param_idents, .. }) = &ty.kind {
+        if let hir::TyKind::FnPtr(hir::FnPtrTy { param_idents, .. }) = &ty.kind {
             for param_ident in *param_idents {
                 if let Some(param_ident) = param_ident {
                     self.check_snake_case(cx, "variable", param_ident);

compiler/rustc_lint/src/types.rs

@@ -1577,7 +1577,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         impl<'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'tcx> {
             fn visit_ty(&mut self, ty: &'_ hir::Ty<'_, AmbigArg>) {
                 debug!(?ty);
-                if let hir::TyKind::BareFn(hir::BareFnTy { abi, .. }) = ty.kind
+                if let hir::TyKind::FnPtr(hir::FnPtrTy { abi, .. }) = ty.kind
                     && !abi.is_rustic_abi()
                 {
                     self.spans.push(ty.span);