Auto merge of #59550 - Centril:rollup, r=Centril

Rollup of 10 pull requests

Successful merges:

 - #59376 (RFC 2008: Enum Variants)
 - #59453 (Recover from parse error in tuple syntax)
 - #59455 (Account for short-hand field syntax when suggesting borrow)
 - #59499 (Fix broken download link in the armhf-gnu image)
 - #59512 (implement `AsRawFd` for stdio locks)
 - #59525 (Whitelist some rustc attrs)
 - #59528 (Improve the dbg! macro docs )
 - #59532 (In doc examples, don't ignore read/write results)
 - #59534 (rustdoc: collapse blanket impls in the same way as normal impls)
 - #59537 (Fix OnceWith docstring.)

Failed merges:

r? @ghost

src/ci/docker/armhf-gnu/Dockerfile

@@ -71,7 +71,8 @@ COPY scripts/qemu-bare-bones-addentropy.c /tmp/addentropy.c
 RUN arm-linux-gnueabihf-gcc addentropy.c -o rootfs/addentropy -static
 
 # TODO: What is this?!
-RUN curl -O http://ftp.nl.debian.org/debian/dists/jessie/main/installer-armhf/current/images/device-tree/vexpress-v2p-ca15-tc1.dtb
+# Source of the file: https://github.com/vfdev-5/qemu-rpi2-vexpress/raw/master/vexpress-v2p-ca15-tc1.dtb
+RUN curl -O https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/vexpress-v2p-ca15-tc1.dtb
 
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh

src/doc/unstable-book/src/language-features/non-exhaustive.md

@@ -7,10 +7,12 @@ The tracking issue for this feature is: [#44109]
 ------------------------
 
 The `non_exhaustive` gate allows you to use the `#[non_exhaustive]` attribute
-on structs and enums. When applied within a crate, users of the crate will need
-to use the `_` pattern when matching enums and use the `..` pattern when
-matching structs. Structs marked as `non_exhaustive` will not be able to be
-created normally outside of the defining crate. This is demonstrated below:
+on structs, enums and enum variants. When applied within a crate, users of the
+crate will need to use the `_` pattern when matching enums and use the `..`
+pattern when matching structs. Enum variants cannot be matched against.
+Structs and enum variants marked as `non_exhaustive` will not be able to
+be created normally outside of the defining crate. This is demonstrated
+below:
 
 ```rust,ignore (pseudo-Rust)
 use std::error::Error as StdError;
@@ -72,4 +74,3 @@ let config = Config { window_width: 640, window_height: 480 };
 // when marked non_exhaustive.
 let &Config { window_width, window_height, .. } = config;
 ```
-

src/libcore/iter/sources.rs

@@ -375,8 +375,8 @@ pub fn once<T>(value: T) -> Once<T> {
     Once { inner: Some(value).into_iter() }
 }
 
-/// An iterator that repeats elements of type `A` endlessly by
-/// applying the provided closure `F: FnMut() -> A`.
+/// An iterator that yields a single element of type `A` by
+/// applying the provided closure `F: FnOnce() -> A`.
 ///
 /// This `struct` is created by the [`once_with`] function.
 /// See its documentation for more.

src/librustc/ty/mod.rs

@@ -1869,6 +1869,11 @@ impl<'a, 'gcx, 'tcx> VariantDef {
         if adt_kind == AdtKind::Struct && tcx.has_attr(parent_did, "non_exhaustive") {
             debug!("found non-exhaustive field list for {:?}", parent_did);
             flags = flags | VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
+        } else if let Some(variant_did) = variant_did {
+            if tcx.has_attr(variant_did, "non_exhaustive") {
+                debug!("found non-exhaustive field list for {:?}", variant_did);
+                flags = flags | VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
+            }
         }
 
         VariantDef {
@@ -2146,6 +2151,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
             debug!("found non-exhaustive variant list for {:?}", did);
             flags = flags | AdtFlags::IS_VARIANT_LIST_NON_EXHAUSTIVE;
         }
+
         flags |= match kind {
             AdtKind::Enum => AdtFlags::IS_ENUM,
             AdtKind::Union => AdtFlags::IS_UNION,
@@ -2299,21 +2305,25 @@ impl<'a, 'gcx, 'tcx> AdtDef {
             self.variants.iter().all(|v| v.fields.is_empty())
     }
 
+    /// Return a `VariantDef` given a variant id.
     pub fn variant_with_id(&self, vid: DefId) -> &VariantDef {
         self.variants.iter().find(|v| v.def_id == vid)
             .expect("variant_with_id: unknown variant")
     }
 
+    /// Return a `VariantDef` given a constructor id.
     pub fn variant_with_ctor_id(&self, cid: DefId) -> &VariantDef {
         self.variants.iter().find(|v| v.ctor_def_id == Some(cid))
             .expect("variant_with_ctor_id: unknown variant")
     }
 
+    /// Return the index of `VariantDef` given a variant id.
     pub fn variant_index_with_id(&self, vid: DefId) -> VariantIdx {
         self.variants.iter_enumerated().find(|(_, v)| v.def_id == vid)
             .expect("variant_index_with_id: unknown variant").0
     }
 
+    /// Return the index of `VariantDef` given a constructor id.
     pub fn variant_index_with_ctor_id(&self, cid: DefId) -> VariantIdx {
         self.variants.iter_enumerated().find(|(_, v)| v.ctor_def_id == Some(cid))
             .expect("variant_index_with_ctor_id: unknown variant").0
@@ -2930,8 +2940,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    // Returns `ty::VariantDef` if `def` refers to a struct,
-    // or variant or their constructors, panics otherwise.
+    /// Returns `ty::VariantDef` if `def` refers to a struct,
+    /// or variant or their constructors, panics otherwise.
     pub fn expect_variant_def(self, def: Def) -> &'tcx VariantDef {
         match def {
             Def::Variant(did) => {

src/librustc_metadata/encoder.rs

@@ -643,13 +643,18 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
             }
         };
 
-        // Variant constructors have the same visibility as the parent enums.
+        // Variant constructors have the same visibility as the parent enums, unless marked as
+        // non-exhaustive, in which case they are lowered to `pub(crate)`.
         let enum_id = tcx.hir().as_local_hir_id(enum_did).unwrap();
         let enum_vis = &tcx.hir().expect_item_by_hir_id(enum_id).vis;
+        let mut ctor_vis = ty::Visibility::from_hir(enum_vis, enum_id, tcx);
+        if variant.is_field_list_non_exhaustive() && ctor_vis == ty::Visibility::Public {
+            ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
+        }
 
         Entry {
             kind: EntryKind::Variant(self.lazy(&data)),
-            visibility: self.lazy(&ty::Visibility::from_hir(enum_vis, enum_id, tcx)),
+            visibility: self.lazy(&ctor_vis),
             span: self.lazy(&tcx.def_span(def_id)),
             attributes: LazySeq::empty(),
             children: LazySeq::empty(),

src/librustc_passes/ast_validation.rs

@@ -192,14 +192,6 @@ impl<'a> AstValidator<'a> {
         }
     }
 
-    fn invalid_non_exhaustive_attribute(&self, variant: &Variant) {
-        let has_non_exhaustive = attr::contains_name(&variant.node.attrs, "non_exhaustive");
-        if has_non_exhaustive {
-            self.err_handler().span_err(variant.span,
-                                        "#[non_exhaustive] is not yet supported on variants");
-        }
-    }
-
     fn invalid_visibility(&self, vis: &Visibility, note: Option<&str>) {
         if let VisibilityKind::Inherited = vis.node {
             return
@@ -608,7 +600,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             }
             ItemKind::Enum(ref def, _) => {
                 for variant in &def.variants {
-                    self.invalid_non_exhaustive_attribute(variant);
                     for field in variant.node.data.fields() {
                         self.invalid_visibility(&field.vis, None);
                     }

src/librustc_privacy/lib.rs

@@ -244,7 +244,26 @@ fn def_id_visibility<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
                     match tcx.hir().get_by_hir_id(parent_hir_id) {
                         Node::Variant(..) => {
                             let parent_did = tcx.hir().local_def_id_from_hir_id(parent_hir_id);
-                            return def_id_visibility(tcx, parent_did);
+                            let (mut ctor_vis, mut span, mut descr) = def_id_visibility(
+                                tcx, parent_did,
+                            );
+
+                            let adt_def = tcx.adt_def(tcx.hir().get_parent_did_by_hir_id(hir_id));
+                            let ctor_did = tcx.hir().local_def_id_from_hir_id(
+                                vdata.ctor_hir_id().unwrap());
+                            let variant = adt_def.variant_with_ctor_id(ctor_did);
+
+                            if variant.is_field_list_non_exhaustive() &&
+                                ctor_vis == ty::Visibility::Public
+                            {
+                                ctor_vis = ty::Visibility::Restricted(
+                                    DefId::local(CRATE_DEF_INDEX));
+                                let attrs = tcx.get_attrs(variant.def_id);
+                                span = attr::find_by_name(&attrs, "non_exhaustive").unwrap().span;
+                                descr = "crate-visible";
+                            }
+
+                            return (ctor_vis, span, descr);
                         }
                         Node::Item(..) => {
                             let item = match tcx.hir().get_by_hir_id(parent_hir_id) {

src/librustc_resolve/build_reduced_graph.rs

@@ -588,6 +588,14 @@ impl<'a> Resolver<'a> {
         let def = Def::Variant(def_id);
         self.define(parent, ident, TypeNS, (def, vis, variant.span, expansion));
 
+        // If the variant is marked as non_exhaustive then lower the visibility to within the
+        // crate.
+        let mut ctor_vis = vis;
+        let has_non_exhaustive = attr::contains_name(&variant.node.attrs, "non_exhaustive");
+        if has_non_exhaustive && vis == ty::Visibility::Public {
+            ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
+        }
+
         // Define a constructor name in the value namespace.
         // Braced variants, unlike structs, generate unusable names in
         // value namespace, they are reserved for possible future use.
@@ -597,7 +605,7 @@ impl<'a> Resolver<'a> {
         let ctor_def_id = self.definitions.local_def_id(ctor_node_id);
         let ctor_kind = CtorKind::from_ast(&variant.node.data);
         let ctor_def = Def::Ctor(ctor_def_id, CtorOf::Variant, ctor_kind);
-        self.define(parent, ident, ValueNS, (ctor_def, vis, variant.span, expansion));
+        self.define(parent, ident, ValueNS, (ctor_def, ctor_vis, variant.span, expansion));
     }
 
     /// Constructs the reduced graph for one foreign item.

src/librustc_typeck/check/demand.rs

@@ -270,6 +270,26 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         None
     }
 
+    fn is_hir_id_from_struct_pattern_shorthand_field(&self, hir_id: hir::HirId, sp: Span) -> bool {
+        let cm = self.sess().source_map();
+        let parent_id = self.tcx.hir().get_parent_node_by_hir_id(hir_id);
+        if let Some(parent) = self.tcx.hir().find_by_hir_id(parent_id) {
+            // Account for fields
+            if let Node::Expr(hir::Expr {
+                node: hir::ExprKind::Struct(_, fields, ..), ..
+            }) = parent {
+                if let Ok(src) = cm.span_to_snippet(sp) {
+                    for field in fields {
+                        if field.ident.as_str() == src.as_str() && field.is_shorthand {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+        false
+    }
+
     /// This function is used to determine potential "simple" improvements or users' errors and
     /// provide them useful help. For example:
     ///
@@ -299,6 +319,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             return None;
         }
 
+        let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
+            expr.hir_id,
+            sp,
+        );
+
         match (&expected.sty, &checked_ty.sty) {
             (&ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (&exp.sty, &check.sty) {
                 (&ty::Str, &ty::Array(arr, _)) |
@@ -337,12 +362,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 // bar(&x); // error, expected &mut
                 // ```
                 let ref_ty = match mutability {
-                    hir::Mutability::MutMutable => self.tcx.mk_mut_ref(
-                                                       self.tcx.mk_region(ty::ReStatic),
-                                                       checked_ty),
-                    hir::Mutability::MutImmutable => self.tcx.mk_imm_ref(
-                                                       self.tcx.mk_region(ty::ReStatic),
-                                                       checked_ty),
+                    hir::Mutability::MutMutable => {
+                        self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
+                    }
+                    hir::Mutability::MutImmutable => {
+                        self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
+                    }
                 };
                 if self.can_coerce(ref_ty, expected) {
                     if let Ok(src) = cm.span_to_snippet(sp) {
@@ -363,14 +388,22 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         if let Some(sugg) = self.can_use_as_ref(expr) {
                             return Some(sugg);
                         }
+                        let field_name = if is_struct_pat_shorthand_field {
+                            format!("{}: ", sugg_expr)
+                        } else {
+                            String::new()
+                        };
                         return Some(match mutability {
-                            hir::Mutability::MutMutable => {
-                                (sp, "consider mutably borrowing here", format!("&mut {}",
-                                                                                sugg_expr))
-                            }
-                            hir::Mutability::MutImmutable => {
-                                (sp, "consider borrowing here", format!("&{}", sugg_expr))
-                            }
+                            hir::Mutability::MutMutable => (
+                                sp,
+                                "consider mutably borrowing here",
+                                format!("{}&mut {}", field_name, sugg_expr),
+                            ),
+                            hir::Mutability::MutImmutable => (
+                                sp,
+                                "consider borrowing here",
+                                format!("{}&{}", field_name, sugg_expr),
+                            ),
                         });
                     }
                 }
@@ -411,12 +444,18 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                                                       checked,
                                                                       sp) {
                                 // do not suggest if the span comes from a macro (#52783)
-                                if let (Ok(code),
-                                        true) = (cm.span_to_snippet(sp), sp == expr.span) {
+                                if let (Ok(code), true) = (
+                                    cm.span_to_snippet(sp),
+                                    sp == expr.span,
+                                ) {
                                     return Some((
                                         sp,
                                         "consider dereferencing the borrow",
-                                        format!("*{}", code),
+                                        if is_struct_pat_shorthand_field {
+                                            format!("{}: *{}", code, code)
+                                        } else {
+                                            format!("*{}", code)
+                                        },
                                     ));
                                 }
                             }

src/librustc_typeck/diagnostics.rs

@@ -4341,11 +4341,12 @@ foo.method(); // Ok!
 "##,
 
 E0638: r##"
-This error indicates that the struct or enum must be matched non-exhaustively
-as it has been marked as `non_exhaustive`.
+This error indicates that the struct, enum or enum variant must be matched
+non-exhaustively as it has been marked as `non_exhaustive`.
 
 When applied within a crate, downstream users of the crate will need to use the
 `_` pattern when matching enums and use the `..` pattern when matching structs.
+Downstream crates cannot match against non-exhaustive enum variants.
 
 For example, in the below example, since the enum is marked as
 `non_exhaustive`, it is required that downstream crates match non-exhaustively
@@ -4390,10 +4391,10 @@ Similarly, for structs, match with `..` to avoid this error.
 "##,
 
 E0639: r##"
-This error indicates that the struct or enum cannot be instantiated from
-outside of the defining crate as it has been marked as `non_exhaustive` and as
-such more fields/variants may be added in future that could cause adverse side
-effects for this code.
+This error indicates that the struct, enum or enum variant cannot be
+instantiated from outside of the defining crate as it has been marked
+as `non_exhaustive` and as such more fields/variants may be added in
+future that could cause adverse side effects for this code.
 
 It is recommended that you look for a `new` function or equivalent in the
 crate's documentation.

src/librustdoc/clean/mod.rs

@@ -421,6 +421,9 @@ impl Item {
     pub fn is_enum(&self) -> bool {
         self.type_() == ItemType::Enum
     }
+    pub fn is_variant(&self) -> bool {
+        self.type_() == ItemType::Variant
+    }
     pub fn is_associated_type(&self) -> bool {
         self.type_() == ItemType::AssociatedType
     }

src/librustdoc/html/render.rs

@@ -2604,7 +2604,15 @@ fn document_non_exhaustive_header(item: &clean::Item) -> &str {
 fn document_non_exhaustive(w: &mut fmt::Formatter<'_>, item: &clean::Item) -> fmt::Result {
     if item.is_non_exhaustive() {
         write!(w, "<div class='docblock non-exhaustive non-exhaustive-{}'>", {
-            if item.is_struct() { "struct" } else if item.is_enum() { "enum" } else { "type" }
+            if item.is_struct() {
+                "struct"
+            } else if item.is_enum() {
+                "enum"
+            } else if item.is_variant() {
+                "variant"
+            } else {
+                "type"
+            }
         })?;
 
         if item.is_struct() {
@@ -2617,6 +2625,10 @@ fn document_non_exhaustive(w: &mut fmt::Formatter<'_>, item: &clean::Item) -> fm
             write!(w, "Non-exhaustive enums could have additional variants added in future. \
                        Therefore, when matching against variants of non-exhaustive enums, an \
                        extra wildcard arm must be added to account for any future variants.")?;
+        } else if item.is_variant() {
+            write!(w, "Non-exhaustive enum variants could have additional fields added in future. \
+                       Therefore, non-exhaustive enum variants cannot be constructed in external \
+                       crates and cannot be matched against.")?;
         } else {
             write!(w, "This type will require a wildcard arm in any match statements or \
                        constructors.")?;
@@ -3679,6 +3691,7 @@ fn item_enum(w: &mut fmt::Formatter<'_>, cx: &Context, it: &clean::Item,
             }
             write!(w, "</code></span>")?;
             document(w, cx, variant)?;
+            document_non_exhaustive(w, variant)?;
 
             use crate::clean::{Variant, VariantKind};
             if let clean::VariantItem(Variant {