From 2bef1c2a61bc49656666c698ca36035f6a415b8b Mon Sep 17 00:00:00 2001
From: Georg Semmler <github@weiznich.de>
Date: Mon, 31 Jul 2023 12:31:27 +0200
Subject: [PATCH] Fix #3719
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Add support for `#[diesel(deserialize_as = …)]` to
`#[diesel(check_for_backend())]` by using the correct deserialization type.
---
 diesel_derives/src/selectable.rs   |  2 +-
 diesel_derives/tests/helpers.rs    |  3 +++
 diesel_derives/tests/selectable.rs | 27 +++++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/diesel_derives/src/selectable.rs b/diesel_derives/src/selectable.rs
index 5edc93138c10..4d0b92b4c637 100644
--- a/diesel_derives/src/selectable.rs
+++ b/diesel_derives/src/selectable.rs
@@ -50,7 +50,7 @@ pub fn derive(item: DeriveInput) -> Result<TokenStream> {
             .filter(|(f, _)| !f.embed())
             .flat_map(|(f, ty)| {
                 backends.iter().map(move |b| {
-                    let field_ty = to_field_ty_bound(&f.ty);
+                    let field_ty = to_field_ty_bound(f.ty_for_deserialize());
                     let span = field_ty.span();
                     quote::quote_spanned! {span =>
                         #field_ty: diesel::deserialize::FromSqlRow<diesel::dsl::SqlTypeOf<#ty>, #b>
diff --git a/diesel_derives/tests/helpers.rs b/diesel_derives/tests/helpers.rs
index 361f68d09ca8..79715735f8c7 100644
--- a/diesel_derives/tests/helpers.rs
+++ b/diesel_derives/tests/helpers.rs
@@ -1,6 +1,9 @@
 use diesel::prelude::*;
 use diesel::sql_query;
 
+#[allow(dead_code)] // that's used in one of the compile tests
+pub type TestBackend = <TestConnection as diesel::Connection>::Backend;
+
 cfg_if! {
     if #[cfg(feature = "sqlite")] {
         pub type TestConnection = SqliteConnection;
diff --git a/diesel_derives/tests/selectable.rs b/diesel_derives/tests/selectable.rs
index a4aba7b49863..af1c73e4591c 100644
--- a/diesel_derives/tests/selectable.rs
+++ b/diesel_derives/tests/selectable.rs
@@ -145,3 +145,30 @@ fn manually_specified_expression() {
     let data = my_structs::table.select(A::as_select()).get_result(conn);
     assert!(data.is_err());
 }
+
+#[allow(dead_code)] // that's essentially a compile test
+#[test]
+fn check_for_backend_with_deserialize_as() {
+    table! {
+        tests {
+            id -> Integer,
+            name -> Text,
+        }
+    }
+
+    struct MyString(String);
+
+    impl From<String> for MyString {
+        fn from(s: String) -> Self {
+            Self(s)
+        }
+    }
+
+    #[derive(Queryable, Selectable)]
+    #[diesel(check_for_backend(crate::helpers::TestBackend))]
+    struct Test {
+        id: i32,
+        #[diesel(deserialize_as = String)]
+        name: MyString,
+    }
+}