Simplify OptionalWrapper

- We never use `self`, so there is no need to pass it as a parameter...
- ... which then removes the need to instanciate the wrapper with `new`
- There is no reason to expect other type than `Option` so we can contrain
  the trait to the type directly instead of using the `IsOption` trait

miette-derive/src/help.rs

@@ -108,7 +108,7 @@ impl Help {
                         Some(quote! {
                             Self::#ident #display_pat => {
                                 use miette::macro_helpers::ToOption;
-                                miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&#help).as_ref().map(|#var| -> std::boxed::Box<dyn std::fmt::Display + '_> { std::boxed::Box::new(format!("{}", #var)) })
+                                miette::macro_helpers::OptionalWrapper::<#ty>::to_option(&#help).as_ref().map(|#var| -> std::boxed::Box<dyn std::fmt::Display + '_> { std::boxed::Box::new(format!("{}", #var)) })
                             },
                         })
                     }
@@ -137,7 +137,7 @@ impl Help {
                         #[allow(unused_variables, deprecated)]
                         let Self #display_pat = self;
                         use miette::macro_helpers::ToOption;
-                        miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&self.#member).as_ref().map(|#var| -> std::boxed::Box<dyn std::fmt::Display + '_> { std::boxed::Box::new(format!("{}", #var)) })
+                        miette::macro_helpers::OptionalWrapper::<#ty>::to_option(&self.#member).as_ref().map(|#var| -> std::boxed::Box<dyn std::fmt::Display + '_> { std::boxed::Box::new(format!("{}", #var)) })
                     }
                 })
             }

miette-derive/src/label.rs

@@ -186,7 +186,7 @@ impl Labels {
             };
 
             Some(quote! {
-                miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&self.#span)
+                miette::macro_helpers::OptionalWrapper::<#ty>::to_option(&self.#span)
                 .map(|#var| #ctor(
                     #display,
                     #var.clone(),
@@ -273,7 +273,7 @@ impl Labels {
                         };
 
                         Some(quote! {
-                            miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(#field)
+                            miette::macro_helpers::OptionalWrapper::<#ty>::to_option(#field)
                             .map(|#var| #ctor(
                                 #display,
                                 #var.clone(),

src/macro_helpers.rs

@@ -3,38 +3,25 @@ use crate::protocol::{LabeledSpan, SourceSpan};
 // Huge thanks to @jam1gamer for this hack:
 // https://twitter.com/jam1garner/status/1515887996444323840
 
-#[doc(hidden)]
-pub trait IsOption {}
-impl<T> IsOption for Option<T> {}
-
 #[doc(hidden)]
 #[derive(Debug, Default)]
 pub struct OptionalWrapper<T>(pub core::marker::PhantomData<T>);
 
-impl<T> OptionalWrapper<T> {
-    pub fn new() -> Self {
-        Self(core::marker::PhantomData)
-    }
-}
-
 #[doc(hidden)]
 pub trait ToOption {
     #[doc(hidden)]
-    fn to_option<T>(self, value: T) -> Option<T>;
+    fn to_option<T>(value: T) -> Option<T>;
 }
 
-impl<T> OptionalWrapper<T>
-where
-    T: IsOption,
-{
+impl<T> OptionalWrapper<Option<T>> {
     #[doc(hidden)]
-    pub fn to_option(self, value: &T) -> &T {
+    pub fn to_option(value: &Option<T>) -> &Option<T> {
         value
     }
 }
 
-impl<T> ToOption for &OptionalWrapper<T> {
-    fn to_option<U>(self, value: U) -> Option<U> {
+impl<T> ToOption for OptionalWrapper<T> {
+    fn to_option<U>(value: U) -> Option<U> {
         Some(value)
     }
 }