I found something odd with mutablity and pattern matching.
let file = File::open_mode(&Path::new("test"), Truncate, Write);
match file {
Some(f) => f.write_str( "hello" ),
None => fail!("not a file")
}
results in a "cannot borrow immutable local variable as mutable" error,
as expected. But,
let mut file = File::open_mode(&Path::new("test"), Truncate, Write);
match file {
Some(f) => f.write_str( "hello" ),
None => fail!("not a file")
}
also results in a "cannot borrow immutable local variable as mutable"
error, and
let file = File::open_mode(&Path::new("test"), Truncate, Write);
match file {
Some(mut f) => f.write_str( "hello" ),
None => fail!("not a file")
}
works, while
let mut file = File::open_mode(&Path::new("test"), Truncate, Write);
match file {
Some(mut f) => f.write_str( "hello" ),
None => fail!("not a file")
}
results in a "variable does not need to be mutable" warning.
Shouldn't the third option also fail (and possibly the second option
succeed)?
--
Tommy M. McGuire
[email protected]
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