launchbadge#2934 solution using autoref trick instead of blanket impl…

…ementation for Option<T>
jonnyso · Jan 8, 2025 · 4d9f292 · 4d9f292
1 parent 5ad8a4e
commit 4d9f292
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Showing 2 changed files with 8 additions and 6 deletions.
diff --git a/sqlx-core/src/from_row.rs b/sqlx-core/src/from_row.rs
@@ -1,3 +1,5 @@
+use std::marker::PhantomData;
+
 use crate::{
     error::{Error, UnexpectedNullError},
     row::Row,
@@ -491,13 +493,13 @@ impl_from_row_for_tuple!(
     (15) -> T16;
 );
 
-pub struct Wrapper;
+pub struct Wrapper<T>(pub PhantomData<T>);
 
 pub trait FromOptRow<'r, R, T> {
     fn __from_row(&self, row: &'r R) -> Result<T, Error>;
 }
 
-impl<'r, R, T> FromOptRow<'r, R, Option<T>> for &Wrapper
+impl<'r, R, T> FromOptRow<'r, R, Option<T>> for Wrapper<Option<T>>
 where
     R: Row,
     T: FromRow<'r, R>,
@@ -513,7 +515,7 @@ where
     }
 }
 
-impl<'r, R, T> FromOptRow<'r, R, T> for Wrapper
+impl<'r, R, T> FromOptRow<'r, R, T> for &Wrapper<T>
 where
     R: Row,
     T: FromRow<'r, R>,
@@ -527,8 +529,10 @@ where
 #[macro_export]
 macro_rules! __from_opt_row {
     ($t:ty, $row:expr) => {{
+        use std::marker::PhantomData;
         use $crate::from_row::{FromOptRow, Wrapper};
-        let value: Result<$t, sqlx::Error> = Wrapper.__from_row($row);
+        let wrapper = Wrapper(PhantomData::<$t>);
+        let value = (&wrapper).__from_row($row);
         value
     }};
 }
diff --git a/sqlx-macros-core/src/derives/row.rs b/sqlx-macros-core/src/derives/row.rs
@@ -108,8 +108,6 @@ fn expand_derive_from_row_struct(
                 }
                 // Flatten
                 (true, None, false) => {
-                    predicates.push(parse_quote!(#ty: ::sqlx::FromRow<#lifetime, R>));
-                    //parse_quote!(<#ty as ::sqlx::FromRow<#lifetime, R>>::from_row(__row))
                     parse_quote!(::sqlx::__from_opt_row!(#ty, __row))
                 }
                 // Flatten + Try from