v1.0.100

• Provide serde::ser::StdError and serde::de::StdError which are either a re-export of std::error::Error (if Serde's "std" feature is enabled) or a new identical trait (otherwise).

  #[cfg(feature = "std")]
  pub use std::error::Error as StdError;
  
  #[cfg(not(feature = "std"))]
  pub trait StdError: Debug + Display {
      fn source(&self) -> Option<&(StdError + 'static)> { None }
  }

  Serde's error traits serde::ser::Error and serde::de::Error require std::error::Error as a supertrait, but only when Serde is built with "std" enabled. Data formats that don't care about no_std support should generally provide their error types with a std::error::Error impl directly:

  #[derive(Debug)]
  struct MySerError {...}
  
  impl serde::ser::Error for MySerError {...}
  
  impl std::fmt::Display for MySerError {...}
  
  // We don't support no_std!
  impl std::error::Error for MySerError {}

  Data formats that do support no_std may either have a "std" feature of their own as has been required in the past:

  [features]
  std = ["serde/std"]

  #[cfg(feature = "std")]
  impl std::error::Error for MySerError {}

  ... or else now may provide the std Error impl unconditionally via Serde's re-export:

  impl serde::ser::StdError for MySerError {}