Auto merge of #125077 - spastorino:add-new-fnsafety-enum2, r=jackh726

Rename Unsafe to Safety

Alternative to #124455, which is to just have one Safety enum to use everywhere, this opens the posibility of adding `ast::Safety::Safe` that's useful for unsafe extern blocks.

This leaves us today with:

```rust
enum ast::Safety {
    Unsafe(Span),
    Default,
    // Safe (going to be added for unsafe extern blocks)
}

enum hir::Safety {
    Unsafe,
    Safe,
}
```

We would convert from `ast::Safety::Default` into the right Safety level according the context.

compiler/rustc_ast/src/ast.rs

@@ -2105,7 +2105,7 @@ impl Ty {
 
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct BareFnTy {
-    pub unsafety: Unsafe,
+    pub safety: Safety,
     pub ext: Extern,
     pub generic_params: ThinVec<GenericParam>,
     pub decl: P<FnDecl>,
@@ -2484,11 +2484,15 @@ pub enum IsAuto {
     No,
 }
 
+/// Safety of items.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable, Debug)]
 #[derive(HashStable_Generic)]
-pub enum Unsafe {
-    Yes(Span),
-    No,
+pub enum Safety {
+    /// `unsafe` an item is explicitly marked as `unsafe`.
+    Unsafe(Span),
+    /// Default means no value was provided, it will take a default value given the context in
+    /// which is used.
+    Default,
 }
 
 /// Describes what kind of coroutine markers, if any, a function has.
@@ -2692,7 +2696,7 @@ pub struct ModSpans {
 pub struct ForeignMod {
     /// `unsafe` keyword accepted syntactically for macro DSLs, but not
     /// semantically by Rust.
-    pub unsafety: Unsafe,
+    pub safety: Safety,
     pub abi: Option<StrLit>,
     pub items: ThinVec<P<ForeignItem>>,
 }
@@ -3011,8 +3015,8 @@ impl Extern {
 /// included in this struct (e.g., `async unsafe fn` or `const extern "C" fn`).
 #[derive(Clone, Copy, Encodable, Decodable, Debug)]
 pub struct FnHeader {
-    /// The `unsafe` keyword, if any
-    pub unsafety: Unsafe,
+    /// Whether this is `unsafe`, or has a default safety
+    pub safety: Safety,
     /// Whether this is `async`, `gen`, or nothing.
     pub coroutine_kind: Option<CoroutineKind>,
     /// The `const` keyword, if any
@@ -3024,8 +3028,8 @@ pub struct FnHeader {
 impl FnHeader {
     /// Does this function header have any qualifiers or is it empty?
     pub fn has_qualifiers(&self) -> bool {
-        let Self { unsafety, coroutine_kind, constness, ext } = self;
-        matches!(unsafety, Unsafe::Yes(_))
+        let Self { safety, coroutine_kind, constness, ext } = self;
+        matches!(safety, Safety::Unsafe(_))
             || coroutine_kind.is_some()
             || matches!(constness, Const::Yes(_))
             || !matches!(ext, Extern::None)
@@ -3035,7 +3039,7 @@ impl FnHeader {
 impl Default for FnHeader {
     fn default() -> FnHeader {
         FnHeader {
-            unsafety: Unsafe::No,
+            safety: Safety::Default,
             coroutine_kind: None,
             constness: Const::No,
             ext: Extern::None,
@@ -3045,7 +3049,7 @@ impl Default for FnHeader {
 
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct Trait {
-    pub unsafety: Unsafe,
+    pub safety: Safety,
     pub is_auto: IsAuto,
     pub generics: Generics,
     pub bounds: GenericBounds,
@@ -3101,7 +3105,7 @@ pub struct TyAlias {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct Impl {
     pub defaultness: Defaultness,
-    pub unsafety: Unsafe,
+    pub safety: Safety,
     pub generics: Generics,
     pub constness: Const,
     pub polarity: ImplPolarity,
@@ -3209,7 +3213,7 @@ pub enum ItemKind {
     /// E.g., `mod foo;` or `mod foo { .. }`.
     /// `unsafe` keyword on modules is accepted syntactically for macro DSLs, but not
     /// semantically by Rust.
-    Mod(Unsafe, ModKind),
+    Mod(Safety, ModKind),
     /// An external module (`extern`).
     ///
     /// E.g., `extern {}` or `extern "C" {}`.

compiler/rustc_ast/src/mut_visit.rs

@@ -499,8 +499,8 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
             vis.visit_mt(mt);
         }
         TyKind::BareFn(bft) => {
-            let BareFnTy { unsafety, ext: _, generic_params, decl, decl_span } = bft.deref_mut();
-            visit_unsafety(unsafety, vis);
+            let BareFnTy { safety, ext: _, generic_params, decl, decl_span } = bft.deref_mut();
+            visit_safety(safety, vis);
             generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
             vis.visit_fn_decl(decl);
             vis.visit_span(decl_span);
@@ -543,8 +543,8 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
 }
 
 fn noop_visit_foreign_mod<T: MutVisitor>(foreign_mod: &mut ForeignMod, vis: &mut T) {
-    let ForeignMod { unsafety, abi: _, items } = foreign_mod;
-    visit_unsafety(unsafety, vis);
+    let ForeignMod { safety, abi: _, items } = foreign_mod;
+    visit_safety(safety, vis);
     items.flat_map_in_place(|item| vis.flat_map_foreign_item(item));
 }
 
@@ -859,10 +859,10 @@ fn visit_defaultness<T: MutVisitor>(defaultness: &mut Defaultness, vis: &mut T)
 }
 
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
-fn visit_unsafety<T: MutVisitor>(unsafety: &mut Unsafe, vis: &mut T) {
-    match unsafety {
-        Unsafe::Yes(span) => vis.visit_span(span),
-        Unsafe::No => {}
+fn visit_safety<T: MutVisitor>(safety: &mut Safety, vis: &mut T) {
+    match safety {
+        Safety::Unsafe(span) => vis.visit_span(span),
+        Safety::Default => {}
     }
 }
 
@@ -1092,8 +1092,8 @@ impl NoopVisitItemKind for ItemKind {
                 vis.visit_generics(generics);
                 visit_opt(body, |body| vis.visit_block(body));
             }
-            ItemKind::Mod(unsafety, mod_kind) => {
-                visit_unsafety(unsafety, vis);
+            ItemKind::Mod(safety, mod_kind) => {
+                visit_safety(safety, vis);
                 match mod_kind {
                     ModKind::Loaded(items, _inline, ModSpans { inner_span, inject_use_span }) => {
                         vis.visit_span(inner_span);
@@ -1130,7 +1130,7 @@ impl NoopVisitItemKind for ItemKind {
             }
             ItemKind::Impl(box Impl {
                 defaultness,
-                unsafety,
+                safety,
                 generics,
                 constness,
                 polarity,
@@ -1139,16 +1139,16 @@ impl NoopVisitItemKind for ItemKind {
                 items,
             }) => {
                 visit_defaultness(defaultness, vis);
-                visit_unsafety(unsafety, vis);
+                visit_safety(safety, vis);
                 vis.visit_generics(generics);
                 visit_constness(constness, vis);
                 visit_polarity(polarity, vis);
                 visit_opt(of_trait, |trait_ref| vis.visit_trait_ref(trait_ref));
                 vis.visit_ty(self_ty);
                 items.flat_map_in_place(|item| vis.flat_map_impl_item(item));
             }
-            ItemKind::Trait(box Trait { unsafety, is_auto: _, generics, bounds, items }) => {
-                visit_unsafety(unsafety, vis);
+            ItemKind::Trait(box Trait { safety, is_auto: _, generics, bounds, items }) => {
+                visit_safety(safety, vis);
                 vis.visit_generics(generics);
                 visit_bounds(bounds, vis);
                 items.flat_map_in_place(|item| vis.flat_map_trait_item(item));
@@ -1254,10 +1254,10 @@ fn visit_const_item<T: MutVisitor>(
 }
 
 fn noop_visit_fn_header<T: MutVisitor>(header: &mut FnHeader, vis: &mut T) {
-    let FnHeader { unsafety, coroutine_kind, constness, ext: _ } = header;
+    let FnHeader { safety, coroutine_kind, constness, ext: _ } = header;
     visit_constness(constness, vis);
     coroutine_kind.as_mut().map(|coroutine_kind| vis.visit_coroutine_kind(coroutine_kind));
-    visit_unsafety(unsafety, vis);
+    visit_safety(safety, vis);
 }
 
 pub fn noop_visit_crate<T: MutVisitor>(krate: &mut Crate, vis: &mut T) {

compiler/rustc_ast/src/visit.rs

@@ -366,7 +366,7 @@ impl WalkItemKind for ItemKind {
             }
             ItemKind::Impl(box Impl {
                 defaultness: _,
-                unsafety: _,
+                safety: _,
                 generics,
                 constness: _,
                 polarity: _,
@@ -384,7 +384,7 @@ impl WalkItemKind for ItemKind {
                 try_visit!(visitor.visit_generics(generics));
                 try_visit!(visitor.visit_variant_data(struct_definition));
             }
-            ItemKind::Trait(box Trait { unsafety: _, is_auto: _, generics, bounds, items }) => {
+            ItemKind::Trait(box Trait { safety: _, is_auto: _, generics, bounds, items }) => {
                 try_visit!(visitor.visit_generics(generics));
                 walk_list!(visitor, visit_param_bound, bounds, BoundKind::SuperTraits);
                 walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Trait);

compiler/rustc_ast_lowering/src/delegation.rs

@@ -188,7 +188,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 Asyncness::No => hir::IsAsync::NotAsync,
             };
             hir::FnHeader {
-                unsafety: sig.unsafety,
+                safety: sig.safety,
                 constness: self.tcx.constness(sig_id),
                 asyncness,
                 abi: sig.abi,
@@ -341,7 +341,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn generate_header_error(&self) -> hir::FnHeader {
         hir::FnHeader {
-            unsafety: hir::Unsafety::Normal,
+            safety: hir::Safety::Safe,
             constness: hir::Constness::NotConst,
             asyncness: hir::IsAsync::NotAsync,
             abi: abi::Abi::Rust,

compiler/rustc_ast_lowering/src/item.rs

@@ -323,7 +323,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 hir::ItemKind::Union(vdata, generics)
             }
             ItemKind::Impl(box Impl {
-                unsafety,
+                safety,
                 polarity,
                 defaultness,
                 constness,
@@ -388,7 +388,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(*s)),
                 };
                 hir::ItemKind::Impl(self.arena.alloc(hir::Impl {
-                    unsafety: self.lower_unsafety(*unsafety),
+                    safety: self.lower_safety(*safety),
                     polarity,
                     defaultness,
                     defaultness_span,
@@ -398,14 +398,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     items: new_impl_items,
                 }))
             }
-            ItemKind::Trait(box Trait { is_auto, unsafety, generics, bounds, items }) => {
+            ItemKind::Trait(box Trait { is_auto, safety, generics, bounds, items }) => {
                 // FIXME(const_trait_impl, effects, fee1-dead) this should be simplified if possible
                 let constness = attrs
                     .unwrap_or(&[])
                     .iter()
                     .find(|x| x.has_name(sym::const_trait))
                     .map_or(Const::No, |x| Const::Yes(x.span));
-                let (generics, (unsafety, items, bounds)) = self.lower_generics(
+                let (generics, (safety, items, bounds)) = self.lower_generics(
                     generics,
                     constness,
                     id,
@@ -418,11 +418,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         let items = this.arena.alloc_from_iter(
                             items.iter().map(|item| this.lower_trait_item_ref(item)),
                         );
-                        let unsafety = this.lower_unsafety(*unsafety);
-                        (unsafety, items, bounds)
+                        let safety = this.lower_safety(*safety);
+                        (safety, items, bounds)
                     },
                 );
-                hir::ItemKind::Trait(*is_auto, unsafety, generics, bounds, items)
+                hir::ItemKind::Trait(*is_auto, safety, generics, bounds, items)
             }
             ItemKind::TraitAlias(generics, bounds) => {
                 let (generics, bounds) = self.lower_generics(
@@ -1360,7 +1360,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             hir::IsAsync::NotAsync
         };
         hir::FnHeader {
-            unsafety: self.lower_unsafety(h.unsafety),
+            safety: self.lower_safety(h.safety),
             asyncness: asyncness,
             constness: self.lower_constness(h.constness),
             abi: self.lower_extern(h.ext),
@@ -1410,10 +1410,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    pub(super) fn lower_unsafety(&mut self, u: Unsafe) -> hir::Unsafety {
-        match u {
-            Unsafe::Yes(_) => hir::Unsafety::Unsafe,
-            Unsafe::No => hir::Unsafety::Normal,
+    pub(super) fn lower_safety(&mut self, s: Safety) -> hir::Safety {
+        match s {
+            Safety::Unsafe(_) => hir::Safety::Unsafe,
+            Safety::Default => hir::Safety::Safe,
         }
     }
 

compiler/rustc_ast_lowering/src/lib.rs

@@ -1324,7 +1324,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 let generic_params = self.lower_lifetime_binder(t.id, &f.generic_params);
                 hir::TyKind::BareFn(self.arena.alloc(hir::BareFnTy {
                     generic_params,
-                    unsafety: self.lower_unsafety(f.unsafety),
+                    safety: self.lower_safety(f.safety),
                     abi: self.lower_extern(f.ext),
                     decl: self.lower_fn_decl(&f.decl, t.id, t.span, FnDeclKind::Pointer, None),
                     param_names: self.lower_fn_params_to_names(&f.decl),

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -521,17 +521,17 @@ impl<'a> AstValidator<'a> {
     fn check_foreign_fn_headerless(
         &self,
         // Deconstruct to ensure exhaustiveness
-        FnHeader { unsafety, coroutine_kind, constness, ext }: FnHeader,
+        FnHeader { safety, coroutine_kind, constness, ext }: FnHeader,
     ) {
         let report_err = |span| {
             self.dcx().emit_err(errors::FnQualifierInExtern {
                 span: span,
                 block: self.current_extern_span(),
             });
         };
-        match unsafety {
-            Unsafe::Yes(span) => report_err(span),
-            Unsafe::No => (),
+        match safety {
+            Safety::Unsafe(span) => report_err(span),
+            Safety::Default => (),
         }
         match coroutine_kind {
             Some(knd) => report_err(knd.span()),
@@ -592,7 +592,7 @@ impl<'a> AstValidator<'a> {
             (Some(FnCtxt::Free), Some(header)) => match header.ext {
                 Extern::Explicit(StrLit { symbol_unescaped: sym::C, .. }, _)
                 | Extern::Implicit(_)
-                    if matches!(header.unsafety, Unsafe::Yes(_)) =>
+                    if matches!(header.safety, Safety::Unsafe(_)) =>
                 {
                     return;
                 }
@@ -891,7 +891,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
         match &item.kind {
             ItemKind::Impl(box Impl {
-                unsafety,
+                safety,
                 polarity,
                 defaultness: _,
                 constness,
@@ -910,7 +910,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         // which isn't allowed. Not a problem for this obscure, obsolete syntax.
                         this.dcx().emit_fatal(errors::ObsoleteAuto { span: item.span });
                     }
-                    if let (&Unsafe::Yes(span), &ImplPolarity::Negative(sp)) = (unsafety, polarity)
+                    if let (&Safety::Unsafe(span), &ImplPolarity::Negative(sp)) = (safety, polarity)
                     {
                         this.dcx().emit_err(errors::UnsafeNegativeImpl {
                             span: sp.to(t.path.span),
@@ -933,7 +933,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 return; // Avoid visiting again.
             }
             ItemKind::Impl(box Impl {
-                unsafety,
+                safety,
                 polarity,
                 defaultness,
                 constness,
@@ -956,7 +956,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         &item.vis,
                         errors::VisibilityNotPermittedNote::IndividualImplItems,
                     );
-                    if let &Unsafe::Yes(span) = unsafety {
+                    if let &Safety::Unsafe(span) = safety {
                         this.dcx().emit_err(errors::InherentImplCannotUnsafe {
                             span: self_ty.span,
                             annotation_span: span,
@@ -1020,13 +1020,13 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }
-            ItemKind::ForeignMod(ForeignMod { abi, unsafety, .. }) => {
+            ItemKind::ForeignMod(ForeignMod { abi, safety, .. }) => {
                 let old_item = mem::replace(&mut self.extern_mod, Some(item));
                 self.visibility_not_permitted(
                     &item.vis,
                     errors::VisibilityNotPermittedNote::IndividualForeignItems,
                 );
-                if let &Unsafe::Yes(span) = unsafety {
+                if let &Safety::Unsafe(span) = safety {
                     self.dcx().emit_err(errors::UnsafeItem { span, kind: "extern block" });
                 }
                 if abi.is_none() {
@@ -1078,8 +1078,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again
             }
-            ItemKind::Mod(unsafety, mod_kind) => {
-                if let &Unsafe::Yes(span) = unsafety {
+            ItemKind::Mod(safety, mod_kind) => {
+                if let &Safety::Unsafe(span) = safety {
                     self.dcx().emit_err(errors::UnsafeItem { span, kind: "module" });
                 }
                 // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584).