This is indeed the case where flow-sensitivity is truly needed
(https://github.com/mozilla/rust/issues/4903). I don't think there's a
good workaround for such cases. I am in the process of just implement
flow sensitivity as part of some other changes.
Niko
John Clements wrote:
Here's the code I want to run:
pub enum EnumTwo {
A(uint),
B(uint)
}
fn get_map(env:</mut EnumTwo) -> </mut uint {
match *env {
A (ref mut map_a) => map_a,
B (ref mut map_b) => map_b
}
}
This fails with this error:
jclements-09740:/tmp clements> rustc --test ./zap.rs
Running /usr/local/bin/rustc:
./zap.rs:13:11: 13:25 error: loan of enum content as mutable conflicts with
prior loan
./zap.rs:13 B (ref mut map_b) => map_b
^~~~~~~~~~~~~~
./zap.rs:12:11: 12:25 note: prior loan as mutable granted here
./zap.rs:12 A (ref mut map_a) => map_a,
^~~~~~~~~~~~~~
error: aborting due to previous error
Patrick and I brainstormed on various moderately disgusting workarounds, but I
couldn't find one that worked and returned a mutable borrowed pointer. I think
I can see how to work around it by completely dismantling the abstraction that
returns the mutable pointer. Am I missing anything ?
John
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