1b46b007d7
This fixes a soundness problem where `Fn` unboxed closures can mutate free variables in the environment.
The following presently builds:
```rust
#![feature(unboxed_closures, overloaded_calls)]
fn main() {
let mut x = 0u;
let _f = |&:| x = 42;
}
```
However, this is equivalent to writing the following, which borrowck rightly rejects:
```rust
struct F<'a> {
x: &'a mut uint
}
impl<'a> Fn<(),()> for F<'a> {
#[rust_call_abi_hack]
fn call(&self, _: ()) {
*self.x = 42; // error: cannot assign to data in a `&` reference
}
}
fn main() {
let mut x = 0u;
let _f = F { x: &mut x };
}
```
This problem is unique to unboxed closures; boxed closures cannot be invoked through an immutable reference and are not subject to it.
This change marks upvars of `Fn` unboxed closures as freely aliasable in mem_categorization, which causes borrowck to reject attempts to mutate or mutably borrow them.
@zwarich pointed out that even with this change, there are remaining soundness issues related to regionck (issue #17403). This region issue affects boxed closures as well.
Closes issue #17780
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|---|---|---|
| .. | ||
| borrowck | ||
| cfg | ||
| save | ||
| traits | ||
| trans | ||
| typeck | ||
| astencode.rs | ||
| check_const.rs | ||
| check_loop.rs | ||
| check_match.rs | ||
| check_rvalues.rs | ||
| check_static_recursion.rs | ||
| check_static.rs | ||
| const_eval.rs | ||
| dataflow.rs | ||
| dead.rs | ||
| def.rs | ||
| dependency_format.rs | ||
| effect.rs | ||
| entry.rs | ||
| expr_use_visitor.rs | ||
| graph.rs | ||
| intrinsicck.rs | ||
| lang_items.rs | ||
| liveness.rs | ||
| mem_categorization.rs | ||
| pat_util.rs | ||
| privacy.rs | ||
| reachable.rs | ||
| region.rs | ||
| resolve_lifetime.rs | ||
| resolve.rs | ||
| stability.rs | ||
| subst.rs | ||
| ty_fold.rs | ||
| ty.rs | ||
| weak_lang_items.rs | ||