Type inference issue when destructuring a struct

[sfackler]

The program

extern mod extra;

use extra::url::Url;

fn main() {
    let Url { host, port, _ } = FromStr::from_str("localhost:1234").unwrap();
}

fails to compile with the following error message:

test.rs:6:5: 6:26 error: the type of this value must be known in this context
test.rs:6   let Url { host, port, _ } = FromStr::from_str("localhost:1234").unwrap();
                ^~~~~~~~~~~~~~~~~~~~~
test.rs:6:29: 6:46 error: failed to find an implementation of trait std::from_str::FromStr for [type error]
test.rs:6   let Url { host, port, _ } = FromStr::from_str("localhost:1234").unwrap();
                                        ^~~~~~~~~~~~~~~~~

even though the compiler should be able to infer that it's looking for the FromStr implementation for Url.

[metajack]

nominating feature complete

[nikomatsakis]

In general we require known types upon entering pattern matching, but you are correct it is stricter than necessary.

[catamorphism]

Just a bug

[Aatch]

Visiting for triage.

Wouldn't say it's a bug, per se, more a limitation in the current system.