Consider for Not

JelteF · Aug 28, 2024 · 8e6bf52 · 8e6bf52
1 parent b300a0c
commit 8e6bf52
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Showing 3 changed files with 36 additions and 3 deletions.
diff --git a/impl/src/from.rs b/impl/src/from.rs
@@ -224,9 +224,10 @@ impl<'a> Expansion<'a> {
                 let generics = {
                     let mut generics = self.generics.clone();
                     for (ty, ident) in field_tys.iter().zip(&gen_idents) {
-                        generics.make_where_clause().predicates.push(
-                            parse_quote! { #ty: derive_more::From<#ident> },
-                        );
+                        generics
+                            .make_where_clause()
+                            .predicates
+                            .push(parse_quote! { #ty: derive_more::From<#ident> });
                         generics
                             .params
                             .push(syn::TypeParam::from(ident.clone()).into());

diff --git a/impl/src/not_like.rs b/impl/src/not_like.rs
@@ -35,6 +35,7 @@ pub fn expand(input: &DeriveInput, trait_name: &str) -> TokenStream {
     };
 
     quote! {
+        #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
         #[automatically_derived]
         impl #impl_generics derive_more::#trait_ident for #input_type #ty_generics #where_clause {
             type Output = #output_type;

diff --git a/tests/not.rs b/tests/not.rs
@@ -1,4 +1,5 @@
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(nightly, feature(never_type))]
 #![allow(dead_code)] // some code is tested for type checking only
 
 use derive_more::Not;
@@ -27,3 +28,33 @@ enum EnumWithUnit {
     SmallInt(i32),
     Unit,
 }
+
+#[cfg(nightly)]
+mod never {
+    use super::*;
+
+    #[derive(Not)]
+    struct Tuple(!);
+
+    #[derive(Not)]
+    struct Struct {
+        field: !,
+    }
+
+    #[derive(Not)]
+    struct TupleMulti(i32, !);
+
+    #[derive(Not)]
+    struct StructMulti {
+        field: !,
+        other: i32,
+    }
+
+    #[derive(Not)]
+    enum Enum {
+        Tuple(!),
+        Struct { field: ! },
+        TupleMulti(i32, !),
+        StructMulti { field: !, other: i32 },
+    }
+}