pin_init: allow nonstandard_style for generated identifiers

Allows `nonstandard_style` lint on locally generated identifiers in
`pin_init!`.

Since the same warning will be reported by the compiler on the struct
definition, having the extra warning emitted at the macro call site is
unnecessary and confusing.

Suggested-by: Gary Guo <gary@garyguo.net>
Link: #125
Signed-off-by: Mirko Adzic <adzicmirko97@gmail.com>

Author: Mirko-A

internal/src/pin_data.rs

@@ -164,7 +164,10 @@ fn generate_unpin_impl(
     quote! {
         // This struct will be used for the unpin analysis. It is needed, because only structurally
         // pinned fields are relevant whether the struct should implement `Unpin`.
-        #[allow(dead_code)] // The fields below are never used.
+        #[allow(
+            dead_code, // The fields below are never used.
+            nonstandard_style // The warning will be emitted on the struct definition.
+        )]
         struct __Unpin #generics_with_pin_lt
         #where_token
             #predicates
@@ -302,7 +305,9 @@ fn generate_projections(
     let docs = format!(" Pin-projections of [`{ident}`]");
     quote! {
         #[doc = #docs]
-        #[allow(dead_code)]
+        // Allow `nonstandard_style` since the same warning will be emitted on
+        // the struct definition.
+        #[allow(dead_code, nonstandard_style)]
         #[doc(hidden)]
         #vis struct #projection #generics_with_pin_lt {
             #(#fields_decl)*
@@ -395,6 +400,9 @@ fn generate_the_pin_data(
             ///   to deallocate.
             #pin_safety
             #(#attrs)*
+            // Allow `nonstandard_style` since the same warning will be emitted on
+            // the struct definition.
+            #[allow(nonstandard_style)]
             #vis unsafe fn #ident<E>(
                 self,
                 slot: *mut #ty,