nightly feature doesn't compile

[messense]

error[E0599]: no variant or associated item named `Chars` found for enum `spec::UnknownArrayIter` in the current scope
    --> /Users/messense/.cargo/registry/src/index.crates.io-6f17d22bba15001f/jrsonnet-evaluator-0.5.0-pre9/src/arr/spec.rs:1004:10
     |
985  | /         pub enum $n<'t> {
986  | |             Bytes(<BytesArray as ArrayLike>::$v<'t>),
987  | |             Expr(<ExprArray as ArrayLike>::$v<'t>),
988  | |             Lazy(<LazyArray as ArrayLike>::$v<'t>),
...    |
995  | |             Repeated(Box<<RepeatedArray as ArrayLike>::$v<'t>>),
996  | |         }
     | |_________- variant or associated item `Chars` not found for this enum
...
1004 |               Self::Chars(e) => e.$m($($ident)*),
     |                     ^^^^^ variant or associated item not found in `UnknownArrayIter<'_>`
...
1087 |   impl_iter!(UnknownArrayIter => Result<Val>);
     |   ------------------------------------------- in this macro invocation
     |
     = note: this error originates in the macro `pass` which comes from the expansion of the macro `impl_iter` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no variant or associated item named `Chars` found for enum `spec::UnknownArrayIterLazy` in the current scope
    --> /Users/messense/.cargo/registry/src/index.crates.io-6f17d22bba15001f/jrsonnet-evaluator-0.5.0-pre9/src/arr/spec.rs:1004:10
     |
985  | /         pub enum $n<'t> {
986  | |             Bytes(<BytesArray as ArrayLike>::$v<'t>),
987  | |             Expr(<ExprArray as ArrayLike>::$v<'t>),
988  | |             Lazy(<LazyArray as ArrayLike>::$v<'t>),
...    |
995  | |             Repeated(Box<<RepeatedArray as ArrayLike>::$v<'t>>),
996  | |         }
     | |_________- variant or associated item `Chars` not found for this enum
...
1004 |               Self::Chars(e) => e.$m($($ident)*),
     |                     ^^^^^ variant or associated item not found in `UnknownArrayIterLazy<'_>`
...
1091 |   impl_iter!(UnknownArrayIterLazy => Thunk<Val>);
     |   ---------------------------------------------- in this macro invocation
     |
     = note: this error originates in the macro `pass` which comes from the expansion of the macro `impl_iter` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no variant or associated item named `Chars` found for enum `spec::UnknownArrayIterCheap` in the current scope
    --> /Users/messense/.cargo/registry/src/index.crates.io-6f17d22bba15001f/jrsonnet-evaluator-0.5.0-pre9/src/arr/spec.rs:1004:10
     |
985  | /         pub enum $n<'t> {
986  | |             Bytes(<BytesArray as ArrayLike>::$v<'t>),
987  | |             Expr(<ExprArray as ArrayLike>::$v<'t>),
988  | |             Lazy(<LazyArray as ArrayLike>::$v<'t>),
...    |
995  | |             Repeated(Box<<RepeatedArray as ArrayLike>::$v<'t>>),
996  | |         }
     | |_________- variant or associated item `Chars` not found for this enum
...
1004 |               Self::Chars(e) => e.$m($($ident)*),
     |                     ^^^^^ variant or associated item not found in `UnknownArrayIterCheap<'_>`
...
1095 |   impl_iter!(UnknownArrayIterCheap => Val);
     |   ---------------------------------------- in this macro invocation
     |
     = note: this error originates in the macro `pass` which comes from the expansion of the macro `impl_iter` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0599`.
error: could not compile `jrsonnet-evaluator` (lib) due to 15 previous errors