Unable to compile on stable rust version

[TheAifam5]

Environment:
rustup 1.18.3 (2019-05-23)
rustc 1.37.0 (eae3437df 2019-08-13)

Log:

   Compiling slog-journald v2.0.0
error[E0053]: method `emit_unit` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:188:9
    |
188 |         fn $name(&mut self, key: &str) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
195 |     __emitter!(emit_unit = "");
    |     --------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_none` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:188:9
    |
188 |         fn $name(&mut self, key: &str) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
196 |     __emitter!(emit_none = "None");
    |     ------------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_bool` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
198 |     __emitter!(emit_bool: bool);
    |     ---------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, bool) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, bool) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_char` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
199 |     __emitter!(emit_char: char);
    |     ---------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, char) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, char) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_u8` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
200 |     __emitter!(emit_u8: u8);
    |     ------------------------ in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, u8) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, u8) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_i8` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
201 |     __emitter!(emit_i8: i8);
    |     ------------------------ in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, i8) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, i8) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_u16` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
202 |     __emitter!(emit_u16: u16);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, u16) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, u16) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_i16` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
203 |     __emitter!(emit_i16: i16);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, i16) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, i16) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_u32` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
204 |     __emitter!(emit_u32: u32);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, u32) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, u32) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_i32` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
205 |     __emitter!(emit_i32: i32);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, i32) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, i32) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_u64` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
206 |     __emitter!(emit_u64: u64);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, u64) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, u64) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_i64` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
207 |     __emitter!(emit_i64: i64);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, i64) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, i64) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_f32` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
208 |     __emitter!(emit_f32: f32);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, f32) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, f32) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_f64` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
209 |     __emitter!(emit_f64: f64);
    |     -------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, f64) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, f64) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_usize` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
210 |     __emitter!(emit_usize: usize);
    |     ------------------------------ in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, usize) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, usize) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_isize` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
211 |     __emitter!(emit_isize: isize);
    |     ------------------------------ in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, isize) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, isize) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_str` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
212 |     __emitter!(emit_str: &str);
    |     --------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, &str) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, &str) -> std::result::Result<(), slog::Error>`

error[E0053]: method `emit_arguments` has an incompatible type for trait
   --> /home/theaifam5/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-journald-2.0.0/src/lib.rs:183:9
    |
183 |         fn $name(&mut self, key: &str, val: $T) -> slog::Result {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `slog::Key`, found &str
...
213 |     __emitter!(emit_arguments: &std::fmt::Arguments);
    |     ------------------------------------------------- in this macro invocation
    |
    = note: expected type `fn(&mut Serializer, slog::Key, &std::fmt::Arguments<'_>) -> std::result::Result<(), slog::Error>`
               found type `fn(&mut Serializer, &str, &std::fmt::Arguments<'_>) -> std::result::Result<(), slog::Error>`

error: aborting due to 18 previous errors

For more information about this error, try `rustc --explain E0053`.
error: Could not compile `slog-journald`.
warning: build failed, waiting for other jobs to finish...
error: build failed

[tmccombs]

could you provide more information on how you built this. I haven't been able to reproduce.

[TheAifam5]

That issue is related to this: slog-rs/kvfilter#17
while compiling with dynamic-keys feature.