Auto merge of #69226 - JohnTitor:rollup-syn03oj, r=JohnTitor

Rollup of 6 pull requests

Successful merges:

 - #68495 (Updating str.chars docs to mention crates.io.)
 - #68701 (Improve #Safety of various methods in core::ptr)
 - #69158 (Don't print block exit state in dataflow graphviz if unchanged)
 - #69179 (Rename `FunctionRetTy` to `FnRetTy`)
 - #69186 ([tiny] parser: `macro_rules` is a weak keyword)
 - #69188 (Clean up E0309 explanation)

Failed merges:

r? @ghost

Author: bors

src/libcore/ptr/mod.rs

@@ -119,10 +119,13 @@ mod mut_ptr;
 ///
 /// Behavior is undefined if any of the following conditions are violated:
 ///
-/// * `to_drop` must be [valid] for reads.
+/// * `to_drop` must be [valid] for both reads and writes.
 ///
 /// * `to_drop` must be properly aligned.
 ///
+/// * The value `to_drop` points to must be valid for dropping, which may mean it must uphold
+///   additional invariants - this is type-dependent.
+///
 /// Additionally, if `T` is not [`Copy`], using the pointed-to value after
 /// calling `drop_in_place` can cause undefined behavior. Note that `*to_drop =
 /// foo` counts as a use because it will cause the value to be dropped
@@ -289,7 +292,7 @@ pub const fn slice_from_raw_parts_mut<T>(data: *mut T, len: usize) -> *mut [T] {
 ///
 /// Behavior is undefined if any of the following conditions are violated:
 ///
-/// * Both `x` and `y` must be [valid] for reads and writes.
+/// * Both `x` and `y` must be [valid] for both reads and writes.
 ///
 /// * Both `x` and `y` must be properly aligned.
 ///
@@ -355,7 +358,7 @@ pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
 ///
 /// Behavior is undefined if any of the following conditions are violated:
 ///
-/// * Both `x` and `y` must be [valid] for reads and writes of `count *
+/// * Both `x` and `y` must be [valid] for both reads and writes of `count *
 ///   size_of::<T>()` bytes.
 ///
 /// * Both `x` and `y` must be properly aligned.
@@ -471,10 +474,12 @@ unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, len: usize) {
 ///
 /// Behavior is undefined if any of the following conditions are violated:
 ///
-/// * `dst` must be [valid] for writes.
+/// * `dst` must be [valid] for both reads and writes.
 ///
 /// * `dst` must be properly aligned.
 ///
+/// * `dst` must point to a properly initialized value of type `T`.
+///
 /// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
 ///
 /// [valid]: ../ptr/index.html#safety
@@ -514,6 +519,8 @@ pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
 /// * `src` must be properly aligned. Use [`read_unaligned`] if this is not the
 ///   case.
 ///
+/// * `src` must point to a properly initialized value of type `T`.
+///
 /// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
 ///
 /// # Examples
@@ -628,6 +635,8 @@ pub unsafe fn read<T>(src: *const T) -> T {
 ///
 /// * `src` must be [valid] for reads.
 ///
+/// * `src` must point to a properly initialized value of type `T`.
+///
 /// Like [`read`], `read_unaligned` creates a bitwise copy of `T`, regardless of
 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
 /// value and the value at `*src` can [violate memory safety][read-ownership].
@@ -922,6 +931,8 @@ pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
 ///
 /// * `src` must be properly aligned.
 ///
+/// * `src` must point to a properly initialized value of type `T`.
+///
 /// Like [`read`], `read_volatile` creates a bitwise copy of `T`, regardless of
 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
 /// value and the value at `*src` can [violate memory safety][read-ownership].

src/libcore/str/mod.rs

@@ -2658,7 +2658,8 @@ impl str {
     ///
     /// It's important to remember that [`char`] represents a Unicode Scalar
     /// Value, and may not match your idea of what a 'character' is. Iteration
-    /// over grapheme clusters may be what you actually want.
+    /// over grapheme clusters may be what you actually want. This functionality
+    /// is not provided by Rust's standard library, check crates.io instead.
     ///
     /// # Examples
     ///

src/librustc_ast_lowering/expr.rs

@@ -480,8 +480,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
     ) -> hir::ExprKind<'hir> {
         let output = match ret_ty {
-            Some(ty) => FunctionRetTy::Ty(ty),
-            None => FunctionRetTy::Default(span),
+            Some(ty) => FnRetTy::Ty(ty),
+            None => FnRetTy::Default(span),
         };
         let ast_decl = FnDecl { inputs: vec![], output };
         let decl = self.lower_fn_decl(&ast_decl, None, /* impl trait allowed */ false, None);
@@ -721,7 +721,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         fn_decl_span: Span,
     ) -> hir::ExprKind<'hir> {
         let outer_decl =
-            FnDecl { inputs: decl.inputs.clone(), output: FunctionRetTy::Default(fn_decl_span) };
+            FnDecl { inputs: decl.inputs.clone(), output: FnRetTy::Default(fn_decl_span) };
         // We need to lower the declaration outside the new scope, because we
         // have to conserve the state of being inside a loop condition for the
         // closure argument types.
@@ -747,7 +747,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             // `|x: u8| future_from_generator(|| -> X { ... })`.
             let body_id = this.lower_fn_body(&outer_decl, |this| {
                 let async_ret_ty =
-                    if let FunctionRetTy::Ty(ty) = &decl.output { Some(ty.clone()) } else { None };
+                    if let FnRetTy::Ty(ty) = &decl.output { Some(ty.clone()) } else { None };
                 let async_body = this.make_async_expr(
                     capture_clause,
                     closure_id,

src/librustc_ast_lowering/lib.rs

@@ -1725,16 +1725,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             )
         } else {
             match decl.output {
-                FunctionRetTy::Ty(ref ty) => {
+                FnRetTy::Ty(ref ty) => {
                     let context = match in_band_ty_params {
                         Some((def_id, _)) if impl_trait_return_allow => {
                             ImplTraitContext::OpaqueTy(Some(def_id), hir::OpaqueTyOrigin::FnReturn)
                         }
                         _ => ImplTraitContext::disallowed(),
                     };
-                    hir::FunctionRetTy::Return(self.lower_ty(ty, context))
+                    hir::FnRetTy::Return(self.lower_ty(ty, context))
                 }
-                FunctionRetTy::Default(span) => hir::FunctionRetTy::DefaultReturn(span),
+                FnRetTy::Default(span) => hir::FnRetTy::DefaultReturn(span),
             }
         };
 
@@ -1781,10 +1781,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     // `elided_lt_replacement`: replacement for elided lifetimes in the return type
     fn lower_async_fn_ret_ty(
         &mut self,
-        output: &FunctionRetTy,
+        output: &FnRetTy,
         fn_def_id: DefId,
         opaque_ty_node_id: NodeId,
-    ) -> hir::FunctionRetTy<'hir> {
+    ) -> hir::FnRetTy<'hir> {
         debug!(
             "lower_async_fn_ret_ty(\
              output={:?}, \
@@ -1949,27 +1949,27 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // only the lifetime parameters that we must supply.
         let opaque_ty_ref = hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, generic_args);
         let opaque_ty = self.ty(opaque_ty_span, opaque_ty_ref);
-        hir::FunctionRetTy::Return(self.arena.alloc(opaque_ty))
+        hir::FnRetTy::Return(self.arena.alloc(opaque_ty))
     }
 
     /// Transforms `-> T` into `Future<Output = T>`
     fn lower_async_fn_output_type_to_future_bound(
         &mut self,
-        output: &FunctionRetTy,
+        output: &FnRetTy,
         fn_def_id: DefId,
         span: Span,
     ) -> hir::GenericBound<'hir> {
         // Compute the `T` in `Future<Output = T>` from the return type.
         let output_ty = match output {
-            FunctionRetTy::Ty(ty) => {
+            FnRetTy::Ty(ty) => {
                 // Not `OpaqueTyOrigin::AsyncFn`: that's only used for the
                 // `impl Future` opaque type that `async fn` implicitly
                 // generates.
                 let context =
                     ImplTraitContext::OpaqueTy(Some(fn_def_id), hir::OpaqueTyOrigin::FnReturn);
                 self.lower_ty(ty, context)
             }
-            FunctionRetTy::Default(ret_ty_span) => self.arena.alloc(self.ty_tup(*ret_ty_span, &[])),
+            FnRetTy::Default(ret_ty_span) => self.arena.alloc(self.ty_tup(*ret_ty_span, &[])),
         };
 
         // "<Output = T>"

src/librustc_ast_lowering/path.rs

@@ -397,8 +397,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 inputs.iter().map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed())),
             );
             let output_ty = match output {
-                FunctionRetTy::Ty(ty) => this.lower_ty(&ty, ImplTraitContext::disallowed()),
-                FunctionRetTy::Default(_) => this.arena.alloc(this.ty_tup(span, &[])),
+                FnRetTy::Ty(ty) => this.lower_ty(&ty, ImplTraitContext::disallowed()),
+                FnRetTy::Default(_) => this.arena.alloc(this.ty_tup(span, &[])),
             };
             let args = smallvec![GenericArg::Type(this.ty_tup(span, inputs))];
             let binding = this.output_ty_binding(output_ty.span, output_ty);

src/librustc_ast_passes/ast_validation.rs

@@ -954,7 +954,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             }
             GenericArgs::Parenthesized(ref data) => {
                 walk_list!(self, visit_ty, &data.inputs);
-                if let FunctionRetTy::Ty(ty) = &data.output {
+                if let FnRetTy::Ty(ty) = &data.output {
                     // `-> Foo` syntax is essentially an associated type binding,
                     // so it is also allowed to contain nested `impl Trait`.
                     self.with_impl_trait(None, |this| this.visit_ty(ty));

src/librustc_ast_passes/feature_gate.rs

@@ -419,8 +419,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         visit::walk_ty(self, ty)
     }
 
-    fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
-        if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
+    fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
+        if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
             if let ast::TyKind::Never = output_ty.kind {
                 // Do nothing.
             } else {

src/librustc_ast_pretty/pprust.rs

@@ -2673,8 +2673,8 @@ impl<'a> State<'a> {
         self.end();
     }
 
-    crate fn print_fn_ret_ty(&mut self, fn_ret_ty: &ast::FunctionRetTy) {
-        if let ast::FunctionRetTy::Ty(ty) = fn_ret_ty {
+    crate fn print_fn_ret_ty(&mut self, fn_ret_ty: &ast::FnRetTy) {
+        if let ast::FnRetTy::Ty(ty) = fn_ret_ty {
             self.space_if_not_bol();
             self.ibox(INDENT_UNIT);
             self.word_space("->");

src/librustc_ast_pretty/pprust/tests.rs

@@ -34,10 +34,8 @@ fn test_fun_to_string() {
     with_default_globals(|| {
         let abba_ident = ast::Ident::from_str("abba");
 
-        let decl = ast::FnDecl {
-            inputs: Vec::new(),
-            output: ast::FunctionRetTy::Default(rustc_span::DUMMY_SP),
-        };
+        let decl =
+            ast::FnDecl { inputs: Vec::new(), output: ast::FnRetTy::Default(rustc_span::DUMMY_SP) };
         let generics = ast::Generics::default();
         assert_eq!(
             fun_to_string(&decl, ast::FnHeader::default(), abba_ident, &generics),

src/librustc_builtin_macros/deriving/generic/mod.rs

@@ -957,7 +957,7 @@ impl<'a> MethodDef<'a> {
         let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
 
         let method_ident = cx.ident_of(self.name, trait_.span);
-        let fn_decl = cx.fn_decl(args, ast::FunctionRetTy::Ty(ret_type));
+        let fn_decl = cx.fn_decl(args, ast::FnRetTy::Ty(ret_type));
         let body_block = cx.block_expr(body);
 
         let unsafety = if self.is_unsafe { ast::Unsafe::Yes(trait_.span) } else { ast::Unsafe::No };