librustc: Make references to functions not have static lifetime.

This breaks code like:

    struct A<'a> {
        func: &'a fn() -> Option<int>
    }

    fn foo() -> Option<int> { ... }

    fn create() -> A<'static> {
        A {
            func: &foo
        }
    }

Change this code to not take functions by reference. For example:

    struct A {
        func: extern "Rust" fn() -> Option<int>
    }

    fn foo() -> Option<int> { ... }

    fn create() -> A {
        A {
            func: foo
        }
    }

Closes #13595.

[breaking-change]

Author: pcwalton

src/librustc/middle/mem_categorization.rs

@@ -500,11 +500,11 @@ impl<'t,TYPER:Typer> MemCategorizationContext<'t,TYPER> {
                id, expr_ty.repr(self.tcx()), def);
 
         match def {
-          def::DefStruct(..) | def::DefVariant(..) => {
+          def::DefStruct(..) | def::DefVariant(..) | def::DefFn(..) |
+          def::DefStaticMethod(..) => {
                 Ok(self.cat_rvalue_node(id, span, expr_ty))
           }
-          def::DefFn(..) | def::DefStaticMethod(..) | def::DefMod(_) |
-          def::DefForeignMod(_) | def::DefStatic(_, false) |
+          def::DefMod(_) | def::DefForeignMod(_) | def::DefStatic(_, false) |
           def::DefUse(_) | def::DefTrait(_) | def::DefTy(_) | def::DefPrimTy(_) |
           def::DefTyParam(..) | def::DefTyParamBinder(..) | def::DefRegion(_) |
           def::DefLabel(_) | def::DefSelfTy(..) | def::DefMethod(..) => {

src/test/compile-fail/static-reference-to-fn-1.rs

@@ -0,0 +1,34 @@
+// Copyright 2014 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.
+
+struct A<'a> {
+    func: &'a fn() -> Option<int>
+}
+
+impl<'a> A<'a> {
+    fn call(&self) -> Option<int> {
+        (*self.func)()
+    }
+}
+
+fn foo() -> Option<int> {
+    None
+}
+
+fn create() -> A<'static> {
+    A {
+        func: &foo, //~ ERROR borrowed value does not live long enough
+    }
+}
+
+fn main() {
+    let a = create();
+    a.call();
+}

src/test/compile-fail/static-reference-to-fn-2.rs

@@ -0,0 +1,58 @@
+// Copyright 2014 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.
+
+struct StateMachineIter<'a> {
+    statefn: &'a fn(&mut StateMachineIter<'a>) -> Option<&'static str>
+}
+
+impl<'a> Iterator<&'static str> for StateMachineIter<'a> {
+    fn next(&mut self) -> Option<&'static str> {
+        return  (*self.statefn)(self);
+    }
+}
+
+fn state1(self_: &mut StateMachineIter) -> Option<&'static str> {
+    self_.statefn = &state2;
+    //~^ ERROR borrowed value does not live long enough
+    return Some("state1");
+}
+
+fn state2(self_: &mut StateMachineIter) -> Option<(&'static str)> {
+    self_.statefn = &state3;
+    //~^ ERROR borrowed value does not live long enough
+    return Some("state2");
+}
+
+fn state3(self_: &mut StateMachineIter) -> Option<(&'static str)> {
+    self_.statefn = &finished;
+    //~^ ERROR borrowed value does not live long enough
+    return Some("state3");
+}
+
+fn finished(_: &mut StateMachineIter) -> Option<(&'static str)> {
+    return None;
+}
+
+fn state_iter() -> StateMachineIter<'static> {
+    StateMachineIter {
+        statefn: &state1 //~ ERROR borrowed value does not live long enough
+    }
+}
+
+
+fn main() {
+    let mut it = state_iter();
+    println!("{}",it.next());
+    println!("{}",it.next());
+    println!("{}",it.next());
+    println!("{}",it.next());
+    println!("{}",it.next());
+}
+