wrapper: allow to skip From and InnerFrom implementation

Author: dr-orlovsky

Cargo.lock

@@ -750,12 +750,12 @@ pub fn derive_getters(input: TokenStream) -> TokenStream {
 /// assert_eq!(w.into_inner(), HashMap::<usize, Vec<u8>>::default());
 /// ```
 ///
-/// Wrappers for indexable types
+/// Wrappers for indexable types, which do not allow explicit construction using `From` converters:
 /// ```
 /// # #[macro_use] extern crate amplify_derive;
 ///
-/// #[derive(Wrapper, From)]
-/// #[wrapper(Index, RangeOps)]
+/// #[derive(Wrapper)]
+/// #[wrapper(NoFrom, Index, RangeOps)]
 /// struct VecNewtype(Vec<u8>);
 /// ```
 #[proc_macro_derive(Wrapper, attributes(wrap, wrapper, amplify_crate))]

src/lib.rs

@@ -27,6 +27,8 @@ const EXAMPLE: &str = r#"#[wrapper(LowerHex, Add)]"#;
 #[derive(Copy, Clone, PartialEq, Eq, Ord, PartialOrd, Debug)]
 enum Wrapper {
     NoRefs,
+    NoFrom,
+    From,
     // Formatting
     FromStr,
     Display,
@@ -126,7 +128,7 @@ impl FromPath for Wrapper {
     const DERIVE: &'static str = "Wrapper";
     const NO_REFS: Self = Self::NoRefs;
 
-    fn default_set() -> Vec<Self> { vec![Wrapper::AsRef, Wrapper::Borrow] }
+    fn default_set() -> Vec<Self> { vec![Wrapper::From, Wrapper::AsRef, Wrapper::Borrow] }
 
     fn is_not_ref(&self) -> bool { *self != Wrapper::AsRef && *self != Wrapper::Borrow }
 
@@ -135,6 +137,8 @@ impl FromPath for Wrapper {
             Err(attr_err!(path.span(), NAME, "must contain at least one identifier", EXAMPLE)),
             |segment| {
                 Ok(match segment.ident.to_string().as_str() {
+                    "From" => Some(Wrapper::From),
+                    "NoFrom" => Some(Wrapper::NoFrom),
                     "FromStr" => Some(Wrapper::FromStr),
                     "Display" => Some(Wrapper::Display),
                     "Debug" => Some(Wrapper::Debug),
@@ -243,6 +247,15 @@ impl Wrapper {
         let amplify_crate = get_amplify_crate(input);
 
         match self {
+            Wrapper::From => quote! {
+                #[automatically_derived]
+                impl #impl_generics #amplify_crate::FromInner for #ident_name #ty_generics #where_clause {
+                    #[inline]
+                    fn from_inner(inner: Self::Inner) -> Self {
+                        Self::from(inner)
+                    }
+                }
+            },
             Wrapper::FromStr => quote! {
                 #[automatically_derived]
                 impl #impl_generics ::core::str::FromStr for #ident_name #ty_generics #where_clause
@@ -637,6 +650,7 @@ impl Wrapper {
                 }
             },
             Wrapper::NoRefs |
+            Wrapper::NoFrom |
             Wrapper::Hex |
             Wrapper::Exp |
             Wrapper::NumberFmt |
@@ -998,7 +1012,13 @@ pub(crate) fn inner(input: DeriveInput) -> Result<TokenStream2> {
 
     let (field, from) = get_params(&input)?;
 
-    let wrappers = get_wrappers::<Wrapper>(&input)?;
+    let mut wrappers = get_wrappers::<Wrapper>(&input)?;
+    if wrappers.contains(&Wrapper::NoFrom) {
+        wrappers = wrappers
+            .into_iter()
+            .filter(|w| *w != Wrapper::From && *w != Wrapper::NoFrom)
+            .collect();
+    }
     let wrapper_derive = wrappers
         .iter()
         .map(|w| w.into_token_stream2(&input, &from, &field));
@@ -1019,14 +1039,6 @@ pub(crate) fn inner(input: DeriveInput) -> Result<TokenStream2> {
             }
         }
 
-        #[automatically_derived]
-        impl #impl_generics #amplify_crate::FromInner for #ident_name #ty_generics #where_clause {
-            #[inline]
-            fn from_inner(inner: Self::Inner) -> Self {
-                Self::from(inner)
-            }
-        }
-
         #[automatically_derived]
         impl #impl_generics ::core::convert::From<#ident_name #ty_generics> for #from #where_clause {
             #[inline]