No warning for unused struct member if explicitly ignored

The compiler gives no warning for an unused struct member if explicitly ignored.

This code:

struct MyStruct { foo: i32, bar: i32 }

fn main() {
    let my_struct = MyStruct { foo: 2, bar: 3 };
    match my_struct {
        MyStruct { foo, .. } => println!("foo is {}", foo)
    }
}

yields a warning:

<anon>:1:29: 1:37 warning: struct field is never used: `bar`, #[warn(dead_code)] on by default
<anon>:1 struct MyStruct { foo: i32, bar: i32 }
                                     ^~~~~~~~

While this code does not:

struct MyStruct { foo: i32, bar: i32 }

fn main() {
    let my_struct = MyStruct { foo: 2, bar: 3 };
    match my_struct {
        MyStruct { foo, bar: _ } => println!("foo is {}", foo)
    }
}

Meta

rustc --version --verbose:
rustc 1.0.0 (a59de37 2015-05-13) (built 2015-05-14)
binary: rustc
commit-hash: a59de37
commit-date: 2015-05-13
build-date: 2015-05-14
host: x86_64-unknown-linux-gnu
release: 1.0.0

[nagisa]

I think current behaviour is correct.

[abonander]

@nagisa On first impression I would have agreed with you but after some thought I think this case should trip the lint. Even though the field has been acknowledged by the programmer, which might explain why it doesn't trip the lint, it's still dead code and so should be marked by the lint.

Right. My sentiment is that it's not about the author of that specific match expression being aware of all the fields, but rather that there is an unnecessary field in the struct.