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)`.

2 files changed, 2 insertions, 3 deletions

diff --git a/src/libstd/rt/at_exit_imp.rs b/src/libstd/rt/at_exit_imp.rs
index 9079c0aaffb..beb2870807a 100644
--- a/src/libstd/rt/at_exit_imp.rs
+++ b/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();
                 }
             }
         }
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index 696c7960c3e..632d9647212 100644
--- a/src/libstd/rt/mod.rs
+++ b/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.