Merge pull request #396 from dtolnay/deprecatedfrom

Suppress deprecation warning on generated From impls

Author: dtolnay

impl/src/expand.rs

@@ -170,10 +170,9 @@ fn impl_struct(input: Struct) -> TokenStream {
         let source_var = Ident::new("source", span);
         let body = from_initializer(from_field, backtrace_field, &source_var);
         quote_spanned! {span=>
-            #[allow(unused_qualifications, clippy::needless_lifetimes)]
+            #[allow(deprecated, unused_qualifications, clippy::needless_lifetimes)]
             #[automatically_derived]
             impl #impl_generics ::core::convert::From<#from> for #ty #ty_generics #where_clause {
-                #[allow(deprecated)]
                 fn from(#source_var: #from) -> Self {
                     #ty #body
                 }
@@ -435,10 +434,9 @@ fn impl_enum(input: Enum) -> TokenStream {
         let source_var = Ident::new("source", span);
         let body = from_initializer(from_field, backtrace_field, &source_var);
         Some(quote_spanned! {span=>
-            #[allow(unused_qualifications, clippy::needless_lifetimes)]
+            #[allow(deprecated, unused_qualifications, clippy::needless_lifetimes)]
             #[automatically_derived]
             impl #impl_generics ::core::convert::From<#from> for #ty #ty_generics #where_clause {
-                #[allow(deprecated)]
                 fn from(#source_var: #from) -> Self {
                     #ty::#variant #body
                 }

tests/test_lints.rs

@@ -64,6 +64,16 @@ fn test_deprecated() {
         Variant,
     }
 
+    #[derive(Error, Debug)]
+    pub enum DeprecatedFrom {
+        #[error(transparent)]
+        Variant(
+            #[from]
+            #[allow(deprecated)]
+            DeprecatedStruct,
+        ),
+    }
+
     #[allow(deprecated)]
     let _: DeprecatedStruct;
     #[allow(deprecated)]