Macro impl_trait 

macro_rules! impl_trait {
    (FromStr<$err:ty> for
    $( $(#[$impl_meta:meta])* $type:ident
       $([$($decl:tt)+][$($args:tt)+ ])? $(where $($bounded:ident),+ )?
    );+
    | $s:ident | $expr:expr) => { ... };
    (Hash for
     $( $(#[$impl_meta:meta])* $type:ident
        $([$($decl:tt)+][$($args:tt)+ ])? $(where $($bounded:ident),+ )?
     );+
     | $self:ident, $state:ident | $expr:expr) => { ... };
    (PartialEq for
     $( $(#[$impl_meta:meta])* $type:ident
         $([$($decl:tt)+][$($args:tt)+ ])? $(where $($bounded:ident),+ )?
     );+
     | $self:ident, $other:ident | $expr:expr) => { ... };
    (fmt::Display+Error for
        $( $(#[$impl_meta:meta])* $type:ident
           $([$($decl:tt)+][$($args:tt)+ ])? $(where $($bounded:ident),+ )? );+
        | $self:ident, $f:ident | $expr:expr) => { ... };
    (fmt::$trait:ident for
     $( $(#[$impl_meta:meta])* $type:ident
        $([$($decl:tt)+][$($args:tt)+ ])? $(where $($bounded:ident),+ )?
     );+
     | $self:ident, $f:ident | $expr:expr) => { ... };
}

⌗ 🏗️ A helper macro to concisely implement a few common utility traits.

---

^{📍 code/util}

---

Traits supported

• FromStr
• Hash
• PartialEq (where other == &Self)
• fmt:: Debug, Display…
• fmt::Display+Error (common combination)

Features:

• Allows multiple types in a single invocation, separated by semicolon
• Supports types with or without lifetimes and generics.
• Comma between lifetimes and generics is optional but recommended for clarity.
• Requires the same formatting trait (fmt::<trait>) to be implemented for all generics.

Examples

struct S0(usize);
struct S1<T> { v: T }
struct S2<'a, T> { v: &'a T }
struct S3<T: Copy, const N: usize>{ v: [T; N] }

impl_trait![Hash for S0 |self, state| self.0.hash(state)];

// Note: assumes other == &Self
impl_trait![PartialEq for S0 |self, other| self.0 == other.0];

impl_trait![fmt::Binary for S1[T][T] where T |self, f| self.v.fmt(f)];
impl_trait!{fmt::Debug for
    S1[T][T] where T;
    S2['a, T]['a, T] where T;
    S3[T: Copy, const N: usize][T, N] where T |self, f| {
    write!(f, "S? {{ v: {:?} }}", self.v)
}}