Updating from_sql_row

Author: msdrigg

diesel_derives/src/from_sql_row.rs

@@ -9,8 +9,13 @@ pub fn derive(mut item: syn::DeriveInput) -> Result<TokenStream, Diagnostic> {
         MetaItem::with_name(&item.attrs, "diesel").unwrap_or_else(|| MetaItem::empty("diesel"));
     let struct_ty = ty_for_foreign_derive(&item, &flags)?;
 
-    item.generics.params.push(parse_quote!(__ST));
-    item.generics.params.push(parse_quote!(__DB));
+    // To prevent double issue with mutable borrow below while creating where clause
+    let initial_item = item.clone();
+
+    let lifetimes = initial_item.generics.lifetimes().collect::<Vec<_>>();
+    let ty_params = initial_item.generics.type_params().collect::<Vec<_>>();
+    let const_params = initial_item.generics.const_params().collect::<Vec<_>>();
+
     {
         let where_clause = item
             .generics
@@ -26,12 +31,13 @@ pub fn derive(mut item: syn::DeriveInput) -> Result<TokenStream, Diagnostic> {
             .predicates
             .push(parse_quote!(Self: FromSql<__ST, __DB>));
     }
-    let (impl_generics, _, where_clause) = item.generics.split_for_impl();
+    let (_, _, where_clause) = item.generics.split_for_impl();
 
     Ok(wrap_in_dummy_mod(quote! {
         use diesel::deserialize::{self, FromSql, Queryable};
 
-        impl #impl_generics Queryable<__ST, __DB> for #struct_ty
+        // Need to put __ST and __DB after lifetimes but before const params
+        impl<#(#lifetimes,)* __ST, __DB, #(#ty_params,)* #(#const_params,)*> Queryable<__ST, __DB> for #struct_ty
         #where_clause
         {
             type Row = Self;