Macro forward_lower_exp 

macro_rules! forward_lower_exp {
    (<$($generic:ident),+> in $this:ty => $field:tt $(,)?) => { ... };
    (<$($generic:ident),+> in $this:ty $(,)?) => { ... };
    ($this:ty => $field:tt $(,)?) => { ... };
    ($this:ty $(,)?) => { ... };
}

Implement LowerExp by forwarding to a field.

The formatter is passed through unchanged. Emitted code supports no_std. Omit the field for a tuple newtype. All type parameters receive a LowerExp bound.

Examples

With a newtype struct:

struct Value(u32);

impl_more::forward_lower_exp!(Value);

assert_eq!(
    format!("{:e}", Value(42)),
    "4.2e1",
);

With a generic newtype struct:

struct Value<T>(T);

impl_more::forward_lower_exp!(<T> in Value<T>);

let inner = 42u32;

assert_eq!(
    format!("{:e}", Value(inner)),
    "4.2e1",
);

Select a named field with => field:

struct Value {
    inner: u32,
}

impl_more::forward_lower_exp!(Value => inner);

let value = Value { inner: 42 };

assert_eq!(
    format!("{:e}", value),
    "4.2e1",
);