Remove Thunk struct and Invoke trait; change Thunk to be an alias

for `Box<FnBox()>`. I found the alias was still handy because it is
shorter than the fully written type.

This is a [breaking-change]: convert code using `Invoke` to use `FnBox`,
which is usually pretty straight-forward. Code using thunk mostly works
if you change `Thunk::new => Box::new` and `foo.invoke(arg)` to
`foo(arg)`.

Author: nikomatsakis

src/compiletest/compiletest.rs

@@ -31,7 +31,6 @@ extern crate log;
 use std::env;
 use std::fs;
 use std::path::{Path, PathBuf};
-use std::thunk::Thunk;
 use getopts::{optopt, optflag, reqopt};
 use common::Config;
 use common::{Pretty, DebugInfoGdb, DebugInfoLldb, Codegen};
@@ -351,7 +350,7 @@ pub fn make_test_name(config: &Config, testfile: &Path) -> test::TestName {
 pub fn make_test_closure(config: &Config, testfile: &Path) -> test::TestFn {
     let config = (*config).clone();
     let testfile = testfile.to_path_buf();
-    test::DynTestFn(Thunk::new(move || {
+    test::DynTestFn(Box::new(move || {
         runtest::run(config, &testfile)
     }))
 }

src/liballoc/boxed.rs

@@ -393,37 +393,33 @@ impl<'a, 'b> From<&'b str> for Box<Error + Send + 'a> {
 ///     }
 /// }
 /// ```
-#[cfg(not(stage0))]
 #[rustc_paren_sugar]
 #[unstable(feature = "core", reason = "Newly introduced")]
 pub trait FnBox<A> {
     type Output;
 
-    extern "rust-call" fn call_box(self: Box<Self>, args: A) -> Self::Output;
+    fn call_box(self: Box<Self>, args: A) -> Self::Output;
 }
 
-#[cfg(not(stage0))]
 impl<A,F> FnBox<A> for F
     where F: FnOnce<A>
 {
     type Output = F::Output;
 
-    extern "rust-call" fn call_box(self: Box<F>, args: A) -> F::Output {
+    fn call_box(self: Box<F>, args: A) -> F::Output {
         self.call_once(args)
     }
 }
 
-#[cfg(not(stage0))]
-impl<A,R> FnOnce<A> for Box<FnBox<A,Output=R>> {
+impl<'a,A,R> FnOnce<A> for Box<FnBox<A,Output=R>+'a> {
     type Output = R;
 
     extern "rust-call" fn call_once(self, args: A) -> R {
         self.call_box(args)
     }
 }
 
-#[cfg(not(stage0))]
-impl<A,R> FnOnce<A> for Box<FnBox<A,Output=R>+Send> {
+impl<'a,A,R> FnOnce<A> for Box<FnBox<A,Output=R>+Send+'a> {
     type Output = R;
 
     extern "rust-call" fn call_once(self, args: A) -> R {

src/librustdoc/test.rs

@@ -19,7 +19,6 @@ use std::path::PathBuf;
 use std::process::Command;
 use std::str;
 use std::sync::{Arc, Mutex};
-use std::thunk::Thunk;
 
 use testing;
 use rustc_lint;
@@ -366,7 +365,7 @@ impl Collector {
                 ignore: should_ignore,
                 should_panic: testing::ShouldPanic::No, // compiler failures are test failures
             },
-            testfn: testing::DynTestFn(Thunk::new(move|| {
+            testfn: testing::DynTestFn(Box::new(move|| {
                 runtest(&test,
                         &cratename,
                         libs,

src/libstd/rt/at_exit_imp.rs

@@ -64,7 +64,7 @@ pub fn cleanup() {
             if queue as usize != 0 {
                 let queue: Box<Queue> = Box::from_raw(queue);
                 for to_run in *queue {
-                    to_run.invoke(());
+                    to_run();
                 }
             }
         }

src/libstd/rt/mod.rs

@@ -21,7 +21,6 @@
 
 use prelude::v1::*;
 use sys;
-use thunk::Thunk;
 use usize;
 
 // Reexport some of our utilities which are expected by other crates.
@@ -153,7 +152,7 @@ fn lang_start(main: *const u8, argc: isize, argv: *const *const u8) -> isize {
 /// that the closure could not be registered, meaning that it is not scheduled
 /// to be rune.
 pub fn at_exit<F: FnOnce() + Send + 'static>(f: F) -> Result<(), ()> {
-    if at_exit_imp::push(Thunk::new(f)) {Ok(())} else {Err(())}
+    if at_exit_imp::push(Box::new(f)) {Ok(())} else {Err(())}
 }
 
 /// One-time runtime cleanup.

src/libstd/sync/future.rs

@@ -36,6 +36,7 @@
 use core::prelude::*;
 use core::mem::replace;
 
+use boxed::Box;
 use self::FutureState::*;
 use sync::mpsc::{Receiver, channel};
 use thunk::Thunk;
@@ -84,7 +85,7 @@ impl<A> Future<A> {
                 match replace(&mut self.state, Evaluating) {
                     Forced(_) | Evaluating => panic!("Logic error."),
                     Pending(f) => {
-                        self.state = Forced(f.invoke(()));
+                        self.state = Forced(f());
                         self.get_ref()
                     }
                 }
@@ -114,7 +115,7 @@ impl<A> Future<A> {
          * function. It is not spawned into another task.
          */
 
-        Future {state: Pending(Thunk::new(f))}
+        Future {state: Pending(Box::new(f))}
     }
 }
 

src/libstd/sys/common/thread.rs

@@ -25,6 +25,7 @@ pub fn start_thread(main: *mut libc::c_void) {
     unsafe {
         stack::record_os_managed_stack_bounds(0, usize::MAX);
         let _handler = stack_overflow::Handler::new();
-        Box::from_raw(main as *mut Thunk).invoke(());
+        let main: Box<Thunk> = Box::from_raw(main as *mut Thunk);
+        main();
     }
 }

src/libstd/thread/mod.rs

@@ -257,7 +257,7 @@ impl Builder {
     pub fn spawn<F>(self, f: F) -> io::Result<JoinHandle> where
         F: FnOnce(), F: Send + 'static
     {
-        self.spawn_inner(Thunk::new(f)).map(|i| JoinHandle(i))
+        self.spawn_inner(Box::new(f)).map(|i| JoinHandle(i))
     }
 
     /// Spawn a new child thread that must be joined within a given
@@ -279,7 +279,7 @@ impl Builder {
     pub fn scoped<'a, T, F>(self, f: F) -> io::Result<JoinGuard<'a, T>> where
         T: Send + 'a, F: FnOnce() -> T, F: Send + 'a
     {
-        self.spawn_inner(Thunk::new(f)).map(|inner| {
+        self.spawn_inner(Box::new(f)).map(|inner| {
             JoinGuard { inner: inner, _marker: PhantomData }
         })
     }
@@ -315,7 +315,7 @@ impl Builder {
                 thread_info::set(imp::guard::current(), their_thread);
             }
 
-            let mut output = None;
+            let mut output: Option<T> = None;
             let try_result = {
                 let ptr = &mut output;
 
@@ -327,7 +327,11 @@ impl Builder {
                 // 'unwinding' flag in the thread itself. For these reasons,
                 // this unsafety should be ok.
                 unsafe {
-                    unwind::try(move || *ptr = Some(f.invoke(())))
+                    unwind::try(move || {
+                        let f: Thunk<(), T> = f;
+                        let v: T = f();
+                        *ptr = Some(v)
+                    })
                 }
             };
             unsafe {
@@ -340,7 +344,7 @@ impl Builder {
         };
 
         Ok(JoinInner {
-            native: try!(unsafe { imp::create(stack_size, Thunk::new(main)) }),
+            native: try!(unsafe { imp::create(stack_size, Box::new(main)) }),
             thread: my_thread,
             packet: my_packet,
             joined: false,
@@ -820,7 +824,7 @@ mod test {
         let x: Box<_> = box 1;
         let x_in_parent = (&*x) as *const i32 as usize;
 
-        spawnfn(Thunk::new(move|| {
+        spawnfn(Box::new(move|| {
             let x_in_child = (&*x) as *const i32 as usize;
             tx.send(x_in_child).unwrap();
         }));
@@ -832,15 +836,15 @@ mod test {
     #[test]
     fn test_avoid_copying_the_body_spawn() {
         avoid_copying_the_body(|v| {
-            thread::spawn(move || v.invoke(()));
+            thread::spawn(move || v());
         });
     }
 
     #[test]
     fn test_avoid_copying_the_body_thread_spawn() {
         avoid_copying_the_body(|f| {
             thread::spawn(move|| {
-                f.invoke(());
+                f();
             });
         })
     }
@@ -849,7 +853,7 @@ mod test {
     fn test_avoid_copying_the_body_join() {
         avoid_copying_the_body(|f| {
             let _ = thread::spawn(move|| {
-                f.invoke(())
+                f()
             }).join();
         })
     }
@@ -862,13 +866,13 @@ mod test {
         // valgrind-friendly. try this at home, instead..!)
         const GENERATIONS: u32 = 16;
         fn child_no(x: u32) -> Thunk<'static> {
-            return Thunk::new(move|| {
+            return Box::new(move|| {
                 if x < GENERATIONS {
-                    thread::spawn(move|| child_no(x+1).invoke(()));
+                    thread::spawn(move|| child_no(x+1)());
                 }
             });
         }
-        thread::spawn(|| child_no(0).invoke(()));
+        thread::spawn(|| child_no(0)());
     }
 
     #[test]

src/libstd/thunk.rs

@@ -12,45 +12,9 @@
 #![allow(missing_docs)]
 #![unstable(feature = "std_misc")]
 
-use alloc::boxed::Box;
+use alloc::boxed::{Box, FnBox};
 use core::marker::Send;
-use core::ops::FnOnce;
 
-pub struct Thunk<'a, A=(),R=()> {
-    invoke: Box<Invoke<A,R>+Send + 'a>,
-}
+pub type Thunk<'a, A=(), R=()> =
+    Box<FnBox<A,Output=R> + Send + 'a>;
 
-impl<'a, R> Thunk<'a,(),R> {
-    pub fn new<F>(func: F) -> Thunk<'a,(),R>
-        where F : FnOnce() -> R, F : Send + 'a
-    {
-        Thunk::with_arg(move|()| func())
-    }
-}
-
-impl<'a,A,R> Thunk<'a,A,R> {
-    pub fn with_arg<F>(func: F) -> Thunk<'a,A,R>
-        where F : FnOnce(A) -> R, F : Send + 'a
-    {
-        Thunk {
-            invoke: Box::<F>::new(func)
-        }
-    }
-
-    pub fn invoke(self, arg: A) -> R {
-        self.invoke.invoke(arg)
-    }
-}
-
-pub trait Invoke<A=(),R=()> {
-    fn invoke(self: Box<Self>, arg: A) -> R;
-}
-
-impl<A,R,F> Invoke<A,R> for F
-    where F : FnOnce(A) -> R
-{
-    fn invoke(self: Box<F>, arg: A) -> R {
-        let f = *self;
-        f(arg)
-    }
-}