Implement Copy/Clone for closures

src/librustc/traits/select.rs

@@ -1340,7 +1340,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             self.assemble_candidates_from_impls(obligation, &mut candidates)?;
 
             // For other types, we'll use the builtin rules.
-            let copy_conditions = self.copy_conditions(obligation);
+            let copy_conditions = self.copy_clone_conditions(obligation);
             self.assemble_builtin_bound_candidates(copy_conditions, &mut candidates)?;
         } else if lang_items.sized_trait() == Some(def_id) {
             // Sized is never implementable by end-users, it is
@@ -1355,7 +1355,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                  // Same builtin conditions as `Copy`, i.e. every type which has builtin support
                  // for `Copy` also has builtin support for `Clone`, + tuples and arrays of `Clone`
                  // types have builtin support for `Clone`.
-                 let clone_conditions = self.copy_conditions(obligation);
+                 let clone_conditions = self.copy_clone_conditions(obligation);
                  self.assemble_builtin_bound_candidates(clone_conditions, &mut candidates)?;
              }
 
@@ -2050,7 +2050,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         }
     }
 
-    fn copy_conditions(&mut self, obligation: &TraitObligation<'tcx>)
+    fn copy_clone_conditions(&mut self, obligation: &TraitObligation<'tcx>)
                      -> BuiltinImplConditions<'tcx>
     {
         // NOTE: binder moved to (*)
@@ -2068,8 +2068,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 Where(ty::Binder(Vec::new()))
             }
 
-            ty::TyDynamic(..) | ty::TyStr | ty::TySlice(..) |
-            ty::TyClosure(..) | ty::TyGenerator(..) |
+            ty::TyDynamic(..) | ty::TyStr | ty::TySlice(..) | ty::TyGenerator(..) |
             ty::TyRef(_, ty::TypeAndMut { ty: _, mutbl: hir::MutMutable }) => {
                 Never
             }
@@ -2084,6 +2083,22 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 Where(ty::Binder(tys.to_vec()))
             }
 
+            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().sess.features.borrow().copy_closures;
+                let clone_closures =
+                    Some(trait_id) == self.tcx().lang_items().clone_trait() &&
+                    self.tcx().sess.features.borrow().clone_closures;
+
+                if copy_closures || clone_closures {
+                    Where(ty::Binder(substs.upvar_tys(def_id, self.tcx()).collect()))
+                } else {
+                    Never
+                }
+            }
+
             ty::TyAdt(..) | ty::TyProjection(..) | ty::TyParam(..) | ty::TyAnon(..) => {
                 // Fallback to whatever user-defined impls exist in this case.
                 None
@@ -2370,10 +2385,10 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     self.sized_conditions(obligation)
                 }
                 _ if Some(trait_def) == lang_items.copy_trait() => {
-                    self.copy_conditions(obligation)
+                    self.copy_clone_conditions(obligation)
                 }
                 _ if Some(trait_def) == lang_items.clone_trait() => {
-                    self.copy_conditions(obligation)
+                    self.copy_clone_conditions(obligation)
                 }
                 _ => bug!("unexpected builtin trait {:?}", trait_def)
             };

src/librustc/ty/instance.rs

@@ -38,7 +38,7 @@ pub enum InstanceDef<'tcx> {
     /// drop_in_place::<T>; None for empty drop glue.
     DropGlue(DefId, Option<Ty<'tcx>>),
 
-    /// Builtin method implementation, e.g. `Clone::clone`.
+    ///`<T as Clone>::clone` shim.
     CloneShim(DefId, Ty<'tcx>),
 }
 

src/librustc_mir/shim.rs

@@ -296,9 +296,15 @@ fn build_clone_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             let len = len.val.to_const_int().unwrap().to_u64().unwrap();
             builder.array_shim(ty, len)
         }
-        ty::TyTuple(tys, _) => builder.tuple_shim(tys),
+        ty::TyClosure(def_id, substs) => {
+            builder.tuple_like_shim(
+                &substs.upvar_tys(def_id, tcx).collect::<Vec<_>>(),
+                AggregateKind::Closure(def_id, substs)
+            )
+        }
+        ty::TyTuple(tys, _) => builder.tuple_like_shim(&**tys, AggregateKind::Tuple),
         _ => {
-            bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty);
+            bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
         }
     };
 
@@ -613,7 +619,12 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
         self.block(vec![], TerminatorKind::Resume, true);
     }
 
-    fn tuple_shim(&mut self, tys: &ty::Slice<Ty<'tcx>>) {
+    fn tuple_like_shim(&mut self, tys: &[ty::Ty<'tcx>], kind: AggregateKind<'tcx>) {
+        match kind {
+            AggregateKind::Tuple | AggregateKind::Closure(..) => (),
+            _ => bug!("only tuples and closures are accepted"),
+        };
+
         let rcvr = Lvalue::Local(Local::new(1+0)).deref();
 
         let mut returns = Vec::new();
@@ -646,17 +657,17 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
             }
         }
 
-        // `return (returns[0], returns[1], ..., returns[tys.len() - 1]);`
+        // `return kind(returns[0], returns[1], ..., returns[tys.len() - 1]);`
         let ret_statement = self.make_statement(
             StatementKind::Assign(
                 Lvalue::Local(RETURN_POINTER),
                 Rvalue::Aggregate(
-                    box AggregateKind::Tuple,
+                    box kind,
                     returns.into_iter().map(Operand::Consume).collect()
                 )
             )
         );
-       self.block(vec![ret_statement], TerminatorKind::Return, false);
+        self.block(vec![ret_statement], TerminatorKind::Return, false);
     }
 }
 

src/libsyntax/feature_gate.rs

@@ -385,6 +385,10 @@ declare_features! (
 
     // allow '|' at beginning of match arms (RFC 1925)
     (active, match_beginning_vert, "1.21.0", Some(44101)),
+
+    // Copy/Clone closures (RFC 2132)
+    (active, clone_closures, "1.22.0", Some(44490)),
+    (active, copy_closures, "1.22.0", Some(44490)),
 );
 
 declare_features! (
@@ -1573,7 +1577,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute]) -> Features {
     let mut features = Features::new();
 
-    let mut feature_checker = MutexFeatureChecker::default();
+    let mut feature_checker = FeatureChecker::default();
 
     for attr in krate_attrs {
         if !attr.check_name("feature") {
@@ -1622,14 +1626,16 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute]) -> F
     features
 }
 
-// A collector for mutually-exclusive features and their flag spans
+/// A collector for mutually exclusive and interdependent features and their flag spans.
 #[derive(Default)]
-struct MutexFeatureChecker {
+struct FeatureChecker {
     proc_macro: Option<Span>,
     custom_attribute: Option<Span>,
+    copy_closures: Option<Span>,
+    clone_closures: Option<Span>,
 }
 
-impl MutexFeatureChecker {
+impl FeatureChecker {
     // If this method turns out to be a hotspot due to branching,
     // the branching can be eliminated by modifying `set!()` to set these spans
     // only for the features that need to be checked for mutual exclusion.
@@ -1642,6 +1648,14 @@ impl MutexFeatureChecker {
         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) {
@@ -1653,6 +1667,15 @@ impl MutexFeatureChecker {
 
             panic!(FatalError);
         }
+
+        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();
+
+            panic!(FatalError);
+        }
     }
 }
 

src/test/compile-fail/feature-gate-clone-closures.rs

@@ -0,0 +1,21 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[derive(Clone)]
+struct S(i32);
+
+fn main() {
+    let a = S(5);
+    let hello = move || {
+        println!("Hello {}", a.0);
+    };
+
+    let hello = hello.clone(); //~ ERROR no method named `clone` found for type
+}

src/test/compile-fail/feature-gate-copy-closures.rs

@@ -0,0 +1,19 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    let a = 5;
+    let hello = || {
+        println!("Hello {}", a);
+    };
+
+    let b = hello;
+    let c = hello; //~ ERROR use of moved value: `hello` [E0382]
+}

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

@@ -0,0 +1,24 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Check that closures do not implement `Clone` if their environment is not `Clone`.
+
+#![feature(clone_closures)]
+
+struct S(i32);
+
+fn main() {
+    let a = S(5);
+    let hello = move || {
+        println!("Hello {}", a.0);
+    };
+
+    let hello = hello.clone(); //~ ERROR the trait bound `S: std::clone::Clone` is not satisfied
+}

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

@@ -0,0 +1,24 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// 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 = || {
+        a += 1;
+    };
+
+    let b = hello;
+    let c = hello; //~ ERROR use of moved value: `hello` [E0382]
+}

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

@@ -0,0 +1,29 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Check that closures implement `Clone`.
+
+#![feature(clone_closures)]
+
+#[derive(Clone)]
+struct S(i32);
+
+fn main() {
+    let mut a = S(5);
+    let mut hello = move || {
+        a.0 += 1;
+        println!("Hello {}", a.0);
+        a.0
+    };
+
+    let mut hello2 = hello.clone();
+    assert_eq!(6, hello2());
+    assert_eq!(6, hello());
+}

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

@@ -0,0 +1,28 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Check that closures implement `Copy`.
+
+#![feature(copy_closures)]
+#![feature(clone_closures)]
+
+fn call<T, F: FnOnce() -> T>(f: F) -> T { f() }
+
+fn main() {
+    let a = 5;
+    let hello = || {
+        println!("Hello {}", a);
+        a
+    };
+
+    assert_eq!(5, call(hello.clone()));
+    assert_eq!(5, call(hello));
+    assert_eq!(5, call(hello));
+}