Example of generic From

dummy/src/main.rs

@@ -1,10 +1,7 @@
 use nutype::nutype;
 
-#[nutype(
-    validate(predicate = |v| v),
-    derive(Default),
-    default = true
-)]
-pub struct TestData(bool);
+#[nutype(derive(Into, From))]
+pub struct Amount(i32);
 
-fn main() {}
+fn main() {
+}

nutype_macros/src/common/gen/traits.rs

@@ -65,6 +65,16 @@ pub fn gen_impl_trait_into(type_name: &TypeName, inner_type: impl Into<InnerType
                 value.into_inner()
             }
         }
+
+        // Alt implementation for Into without From.
+        // That works, but it breaks the symmetry between Into and From.
+        //
+        // impl ::core::convert::Into<#inner_type> for #type_name {
+        //     #[inline]
+        //     fn into(self) -> #inner_type {
+        //         self.0
+        //     }
+        // }
     }
 }
 
@@ -123,11 +133,17 @@ pub fn gen_impl_trait_borrow(type_name: &TypeName, borrowed_type: impl ToTokens)
 }
 
 pub fn gen_impl_trait_from(type_name: &TypeName, inner_type: impl ToTokens) -> TokenStream {
+    dbg!(quote!(#inner_type).to_string());
+
     quote! {
-        impl ::core::convert::From<#inner_type> for #type_name {
+        impl<T> ::core::convert::From<T> for #type_name
+        where
+            #inner_type: ::core::convert::From<T>
+        {
             #[inline]
-            fn from(raw_value: #inner_type) -> Self {
-                Self::new(raw_value)
+            fn from(raw_value: T) -> Self {
+                let inner_value = #inner_type::from(raw_value);
+                Self::new(inner_value)
             }
         }
     }

nutype_macros/src/string/gen/traits.rs

@@ -234,11 +234,11 @@ fn gen_impl_from_str(
 
 fn gen_impl_from_str_and_string(type_name: &TypeName) -> TokenStream {
     let impl_from_string = gen_impl_trait_from(type_name, quote!(String));
-    let impl_from_str = gen_impl_trait_from(type_name, quote!(&str));
+    // let impl_from_str = gen_impl_trait_from(type_name, quote!(&str));
 
     quote! {
         #impl_from_string
-        #impl_from_str
+        //#impl_from_str
     }
 }
 

test_suite/tests/integer.rs

@@ -460,8 +460,14 @@ mod types {
         )]
         struct Amount(isize);
 
-        assert_eq!(Amount::new(999), Err(AmountError::GreaterOrEqualViolated));
-        assert_eq!(Amount::new(2001), Err(AmountError::LessOrEqualViolated));
+        assert_eq!(
+            Amount::new(999isize),
+            Err(AmountError::GreaterOrEqualViolated)
+        );
+        assert_eq!(
+            Amount::new(2001isize),
+            Err(AmountError::LessOrEqualViolated)
+        );
         assert!(Amount::new(1000).is_ok());
         assert!(Amount::new(2000).is_ok());
     }
@@ -532,7 +538,7 @@ mod traits {
         #[nutype(derive(From))]
         pub struct Amount(u32);
 
-        let amount = Amount::from(350);
+        let amount = Amount::from(350u32);
         assert_eq!(amount.into_inner(), 350);
     }