Missing trait bound on NaiveDateTime and print_sql!()

[anp]

Per discussion on gitter:

print_sql!(pullrequest.select(sql::<(Date, BigInt)>("created_at::date as d, COUNT(*)"))
                       .filter(created_at.ge(since).and(created_at.le(until)))
                       .group_by(d))

Gives a compiler error:

$ cargo run
   Compiling rust-dashboard v0.1.0 (file:///home/adam/rust-projects/rust-dashboard)
<diesel macros>:5:5: 5:60 error: the trait bound `chrono::NaiveDateTime: diesel::types::ToSql<diesel::types::Timestamp, diesel::backend::Debug>` is not satisfied [E0277]
<diesel macros>:5 ) ; QueryFragment:: < $ crate:: backend:: Debug > :: to_sql (
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<diesel macros>:1:46: 1:69 note: in this expansion of debug_sql! (defined in <diesel macros>)
<std macros>:2:25: 2:56 note: in this expansion of format_args!
<std macros>:3:1: 3:54 note: in this expansion of print! (defined in <std macros>)
<diesel macros>:1:25: 1:71 note: in this expansion of println! (defined in <std macros>)
src/reports/mod.rs:45:5: 47:37 note: in this expansion of print_sql! (defined in <diesel macros>)
<diesel macros>:5:5: 5:60 help: run `rustc --explain E0277` to see a detailed explanation
<diesel macros>:5:5: 5:60 help: the following implementations were found:
<diesel macros>:5:5: 5:60 help:   <chrono::NaiveDateTime as diesel::types::ToSql<diesel::types::Nullable<diesel::types::Timestamp>, DB>>
<diesel macros>:5:5: 5:60 help:   <chrono::NaiveDateTime as diesel::types::ToSql<diesel::types::Timestamp, diesel::pg::Pg>>
<diesel macros>:5:5: 5:60 note: required by `diesel::query_builder::QueryFragment::to_sql`
src/reports/mod.rs:45:5: 47:37 error: mismatched types:
 expected `std::result::Result<std::collections::BTreeMap<chrono::NaiveDate, i64>, error::DashError>`,
    found `()`
(expected enum `std::result::Result`,
    found ()) [E0308]
src/reports/mod.rs:45     print_sql!(pullrequest.select(sql::<(Date, BigInt)>("created_at::date as d, COUNT(*)"))
src/reports/mod.rs:46                        .filter(created_at.ge(since).and(created_at.le(until)))
src/reports/mod.rs:47                        .group_by(d))
src/reports/mod.rs:45:5: 47:37 note: in this expansion of print_sql! (defined in <diesel macros>)
src/reports/mod.rs:45:5: 47:37 help: run `rustc --explain E0308` to see a detailed explanation
error: aborting due to 2 previous errors
error: Could not compile `rust-dashboard`.

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