Fix indentation of error message

[sgrif]

So I just encountered this error for the first time. It's unclear what
it means, why I encountered it, or how to fix it. But worst of all, it
has a random newline and weird indentation! This commit fixes that last
bit.

[rust-highfive]

r? @nikomatsakis

(rust_highfive has picked a reviewer for you, use r? to override)

[alexcrichton]

@bors: r+

[bors]

📌 Commit ec648a1 has been approved by alexcrichton

[bors]

⌛ Testing commit ec648a1 with merge 1780ccb...

[bors]

💔 Test failed - status-travis

[alexcrichton]

@bors: retry * network error

…

On Sun, Feb 19, 2017 at 3:10 PM, bors ***@***.***> wrote: 💔 Test failed - status-travis <https://travis-ci.org/rust-lang/rust/builds/203243033> — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#39940 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD95HcxnoI-s57TKlELqNobHRVWcD70ks5reK-vgaJpZM4MFRC_> .

[nikomatsakis]

@sgrif example code? it probably means you've got a recursive enum somewhere.

[sgrif]

@nikomatsakis The type is an hlist, which is recursive but not represented as an enum. The code this impl (but for a 16 element hlist/tuple instead of 2):

impl<A, B, SqlA, SqlB, DB> Queryable<Cons<SqlA, Cons<SqlB, Nil>>, DB> for (A, B) where
    DB: Backend + HasSqlType<SqlA> + HasSqlType<SqlB>,
    DB: HasSqlType<Cons<SqlA, Cons<SqlB, Nil>>>,
    A: Queryable<SqlA, DB>,
    B: Queryable<SqlB, DB>,
    Cons<A, Cons<B, Nil>>: FromSqlRow<Cons<SqlA, Cons<SqlB, Nil>>, DB>,
{
    type Row = Cons<A, Cons<B, Nil>>;

    fn build(Cons(a, Cons(b, Nil)): Self::Row) -> Self {
        (a, b)
    }
}

We ended up dropping the max size we generate that impl for to 12, which resolved the issue. (We picked 12 arbitrarily because it's the largest tuple that libstd provides impls of things like PartialEq for. Any number smaller than 16 would have worked as well). Upping the recursion limit worked there as well.

[nikomatsakis]

@sgrif ah ok

[sgrif]

@nikomatsakis The error message should probably mention that #![recursion_limit="double"] is an option though. Not sure how to make this do that

[GuillaumeGomez]

@bors: rollup