Rollup merge of #49299 - SimonSapin:ubiquity, r=nikomatsakis

Stabilize the copy_closures and clone_closures features

In addition to the `Fn*` family of traits, closures now implement `Copy` (and similarly `Clone`) if all of the captures do.

Tracking issue: #44490

src/libcore/clone.rs

@@ -63,6 +63,11 @@
 /// This trait can be used with `#[derive]` if all fields are `Clone`. The `derive`d
 /// implementation of [`clone`] calls [`clone`] on each field.
 ///
+/// ## Closures
+///
+/// Closure types automatically implement `Clone` if they capture no value from the environment
+/// or if all such captured values implement `Clone` themselves.
+///
 /// ## How can I implement `Clone`?
 ///
 /// Types that are [`Copy`] should have a trivial implementation of `Clone`. More formally:

src/libcore/marker.rs

@@ -166,6 +166,11 @@ pub trait Unsize<T: ?Sized> {
 /// are allowed to access `x` after the assignment. Under the hood, both a copy and a move
 /// can result in bits being copied in memory, although this is sometimes optimized away.
 ///
+/// ## Closures
+///
+/// Closure types automatically implement `Copy` if they capture no value from the environment
+/// or if all such captured values implement `Copy` themselves.
+///
 /// ## How can I implement `Copy`?
 ///
 /// There are two ways to implement `Copy` on your type. The simplest is to use `derive`:

src/librustc/dep_graph/dep_node.rs

@@ -617,8 +617,6 @@ define_dep_nodes!( <'tcx>
     [input] MissingExternCrateItem(CrateNum),
     [input] UsedCrateSource(CrateNum),
     [input] PostorderCnums,
-    [] HasCloneClosures(CrateNum),
-    [] HasCopyClosures(CrateNum),
 
     // This query is not expected to have inputs -- as a result, it's
     // not a good candidate for "replay" because it's essentially a

src/librustc/lib.rs

@@ -45,7 +45,7 @@
 #![feature(box_syntax)]
 #![feature(conservative_impl_trait)]
 #![feature(const_fn)]
-#![feature(copy_closures, clone_closures)]
+#![cfg_attr(stage0, feature(copy_closures, clone_closures))]
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]
 #![feature(dyn_trait)]

src/librustc/traits/select.rs

@@ -2086,14 +2086,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::TyClosure(def_id, substs) => {
                 let trait_id = obligation.predicate.def_id();
-                let copy_closures =
-                    Some(trait_id) == self.tcx().lang_items().copy_trait() &&
-                    self.tcx().has_copy_closures(def_id.krate);
-                let clone_closures =
-                    Some(trait_id) == self.tcx().lang_items().clone_trait() &&
-                    self.tcx().has_clone_closures(def_id.krate);
-
-                if copy_closures || clone_closures {
+                let is_copy_trait = Some(trait_id) == self.tcx().lang_items().copy_trait();
+                let is_clone_trait = Some(trait_id) == self.tcx().lang_items().clone_trait();
+                if is_copy_trait || is_clone_trait {
                     Where(ty::Binder(substs.upvar_tys(def_id, self.tcx()).collect()))
                 } else {
                     Never

src/librustc/ty/context.rs

@@ -2562,14 +2562,6 @@ pub fn provide(providers: &mut ty::maps::Providers) {
         assert_eq!(cnum, LOCAL_CRATE);
         tcx.output_filenames.clone()
     };
-    providers.has_copy_closures = |tcx, cnum| {
-        assert_eq!(cnum, LOCAL_CRATE);
-        tcx.features().copy_closures
-    };
-    providers.has_clone_closures = |tcx, cnum| {
-        assert_eq!(cnum, LOCAL_CRATE);
-        tcx.features().clone_closures
-    };
     providers.features_query = |tcx, cnum| {
         assert_eq!(cnum, LOCAL_CRATE);
         Lrc::new(tcx.sess.features_untracked().clone())

src/librustc/ty/maps/config.rs

@@ -610,24 +610,12 @@ impl<'tcx> QueryDescription<'tcx> for queries::output_filenames<'tcx> {
     }
 }
 
-impl<'tcx> QueryDescription<'tcx> for queries::has_clone_closures<'tcx> {
-    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
-        format!("seeing if the crate has enabled `Clone` closures")
-    }
-}
-
 impl<'tcx> QueryDescription<'tcx> for queries::vtable_methods<'tcx> {
     fn describe(tcx: TyCtxt, key: ty::PolyTraitRef<'tcx> ) -> String {
         format!("finding all methods for trait {}", tcx.item_path_str(key.def_id()))
     }
 }
 
-impl<'tcx> QueryDescription<'tcx> for queries::has_copy_closures<'tcx> {
-    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
-        format!("seeing if the crate has enabled `Copy` closures")
-    }
-}
-
 impl<'tcx> QueryDescription<'tcx> for queries::features_query<'tcx> {
     fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
         format!("looking up enabled feature gates")

src/librustc/ty/maps/mod.rs

@@ -387,9 +387,6 @@ define_maps! { <'tcx>
     [] fn output_filenames: output_filenames_node(CrateNum)
         -> Arc<OutputFilenames>,
 
-    [] fn has_copy_closures: HasCopyClosures(CrateNum) -> bool,
-    [] fn has_clone_closures: HasCloneClosures(CrateNum) -> bool,
-
     // Erases regions from `ty` to yield a new type.
     // Normally you would just use `tcx.erase_regions(&value)`,
     // however, which uses this query as a kind of cache.

src/librustc/ty/maps/plumbing.rs

@@ -920,8 +920,6 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         }
         DepKind::UsedCrateSource => { force!(used_crate_source, krate!()); }
         DepKind::PostorderCnums => { force!(postorder_cnums, LOCAL_CRATE); }
-        DepKind::HasCloneClosures => { force!(has_clone_closures, krate!()); }
-        DepKind::HasCopyClosures => { force!(has_copy_closures, krate!()); }
 
         DepKind::Freevars => { force!(freevars, def_id!()); }
         DepKind::MaybeUnusedTraitImport => {

src/librustc_metadata/cstore.rs

@@ -226,16 +226,6 @@ impl CrateMetadata {
         attr::contains_name(&attrs, "no_builtins")
     }
 
-     pub fn has_copy_closures(&self, sess: &Session) -> bool {
-        let attrs = self.get_item_attrs(CRATE_DEF_INDEX, sess);
-        attr::contains_feature_attr(&attrs, "copy_closures")
-    }
-
-    pub fn has_clone_closures(&self, sess: &Session) -> bool {
-        let attrs = self.get_item_attrs(CRATE_DEF_INDEX, sess);
-        attr::contains_feature_attr(&attrs, "clone_closures")
-    }
-
     pub fn panic_strategy(&self) -> PanicStrategy {
         self.root.panic_strategy.clone()
     }

src/librustc_metadata/cstore_impl.rs

@@ -255,9 +255,6 @@ provide! { <'tcx> tcx, def_id, other, cdata,
 
     used_crate_source => { Lrc::new(cdata.source.clone()) }
 
-    has_copy_closures => { cdata.has_copy_closures(tcx.sess) }
-    has_clone_closures => { cdata.has_clone_closures(tcx.sess) }
-
     exported_symbols => {
         let cnum = cdata.cnum;
         assert!(cnum != LOCAL_CRATE);

src/librustc_typeck/lib.rs

@@ -76,7 +76,7 @@ This API is completely unstable and subject to change.
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(conservative_impl_trait)]
-#![feature(copy_closures, clone_closures)]
+#![cfg_attr(stage0, feature(copy_closures, clone_closures))]
 #![feature(crate_visibility_modifier)]
 #![feature(from_ref)]
 #![feature(match_default_bindings)]

src/libsyntax/feature_gate.rs

@@ -391,10 +391,6 @@ declare_features! (
     // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
     (active, non_exhaustive, "1.22.0", Some(44109), None),
 
-    // Copy/Clone closures (RFC 2132)
-    (active, clone_closures, "1.22.0", Some(44490), None),
-    (active, copy_closures, "1.22.0", Some(44490), None),
-
     // allow `'_` placeholder lifetimes
     (active, underscore_lifetimes, "1.22.0", Some(44524), None),
 
@@ -567,6 +563,9 @@ declare_features! (
     (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
     // Termination trait in main (RFC 1937)
     (accepted, termination_trait, "1.26.0", Some(43301), None),
+    // Copy/Clone closures (RFC 2132)
+    (accepted, clone_closures, "1.26.0", Some(44490), None),
+    (accepted, copy_closures, "1.26.0", Some(44490), None),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must
@@ -1887,8 +1886,6 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
 struct FeatureChecker {
     proc_macro: Option<Span>,
     custom_attribute: Option<Span>,
-    copy_closures: Option<Span>,
-    clone_closures: Option<Span>,
 }
 
 impl FeatureChecker {
@@ -1904,14 +1901,6 @@ impl FeatureChecker {
         if features.custom_attribute {
             self.custom_attribute = self.custom_attribute.or(Some(span));
         }
-
-        if features.copy_closures {
-            self.copy_closures = self.copy_closures.or(Some(span));
-        }
-
-        if features.clone_closures {
-            self.clone_closures = self.clone_closures.or(Some(span));
-        }
     }
 
     fn check(self, handler: &Handler) {
@@ -1923,15 +1912,6 @@ impl FeatureChecker {
 
             FatalError.raise();
         }
-
-        if let (Some(span), None) = (self.copy_closures, self.clone_closures) {
-            handler.struct_span_err(span, "`#![feature(copy_closures)]` can only be used with \
-                                           `#![feature(clone_closures)]`")
-                  .span_note(span, "`#![feature(copy_closures)]` declared here")
-                  .emit();
-
-            FatalError.raise();
-        }
     }
 }
 

src/test/compile-fail/not-clone-closure.rs

@@ -10,8 +10,6 @@
 
 // Check that closures do not implement `Clone` if their environment is not `Clone`.
 
-#![feature(clone_closures)]
-
 struct S(i32);
 
 fn main() {

src/test/compile-fail/not-copy-closure.rs

@@ -10,9 +10,6 @@
 
 // Check that closures do not implement `Copy` if their environment is not `Copy`.
 
-#![feature(copy_closures)]
-#![feature(clone_closures)]
-
 fn main() {
     let mut a = 5;
     let hello = || {

src/test/run-pass/clone-closure.rs

@@ -10,8 +10,6 @@
 
 // Check that closures implement `Clone`.
 
-#![feature(clone_closures)]
-
 #[derive(Clone)]
 struct S(i32);
 

src/test/run-pass/copy-closure.rs

@@ -10,9 +10,6 @@
 
 // Check that closures implement `Copy`.
 
-#![feature(copy_closures)]
-#![feature(clone_closures)]
-
 fn call<T, F: FnOnce() -> T>(f: F) -> T { f() }
 
 fn main() {

src/test/ui/span/borrowck-call-is-borrow-issue-12224.rs

@@ -58,7 +58,10 @@ fn test6() {
 
 fn test7() {
     fn foo<F>(_: F) where F: FnMut(Box<FnMut(isize)>, isize) {}
-    let mut f = |g: Box<FnMut(isize)>, b: isize| {};
+    let s = String::new();  // Capture to make f !Copy
+    let mut f = move |g: Box<FnMut(isize)>, b: isize| {
+        let _ = s.len();
+    };
     f(Box::new(|a| {
         foo(f);
         //~^ ERROR cannot move `f` into closure because it is borrowed

src/test/ui/span/borrowck-call-is-borrow-issue-12224.stderr

@@ -28,19 +28,19 @@ LL |     f.f.call_mut(())
    |     ^^^ cannot borrow as mutable
 
 error[E0504]: cannot move `f` into closure because it is borrowed
-  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:63:13
+  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:66:13
    |
 LL |     f(Box::new(|a| {
    |     - borrow of `f` occurs here
 LL |         foo(f);
    |             ^ move into closure occurs here
 
 error[E0507]: cannot move out of captured outer variable in an `FnMut` closure
-  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:63:13
+  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:66:13
    |
-LL |     let mut f = |g: Box<FnMut(isize)>, b: isize| {};
+LL |     let mut f = move |g: Box<FnMut(isize)>, b: isize| {
    |         ----- captured outer variable
-LL |     f(Box::new(|a| {
+...
 LL |         foo(f);
    |             ^ cannot move out of captured outer variable in an `FnMut` closure