Arrays containing references eagerly default to having an unnecessarily restrictive lifetime

[huonw]

fn foo(x: &str) {
    let _array = ["foo", "bar", "baz", x];
}
fn main() {}

<anon>:2:40: 2:41 error: mismatched types: expected `&'static str` but found `&str` (lifetime mismatch)
<anon>:2     let _array = ["foo", "bar", "baz", x];
                                                ^
<anon>:1:17: 3:2 note: the anonymous lifetime #1 defined on the block at 1:16...
<anon>:1 fn foo(x: &str) {
<anon>:2     let _array = ["foo", "bar", "baz", x];
<anon>:3 }
note: ...does not necessarily outlive the static lifetime

This papercut comes up a bit with process spawning, where one (relatively) often writes things like ["--some-arg", "x", user_input] to build the command invocation.

---

One workaround is:

fn foo<'a>(x: &'a str) {
    let hack: &'a str = "foo";
    let _array = [hack, "bar", "baz", x];
}

[alexcrichton]

This seems like a recent regression (I thought this worked before). cc @pnkfelix, @nick29581, @zwarich, do you guys know if one of your recent PRs affected this?

[steveklabnik]

This code sample now works.