Merge pull request #3812 from weiznich/use_diagnostic_on_unimplemented

Use `#[diagnostic::on_unimplemented]`

.github/workflows/ci.yml

@@ -302,7 +302,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: nightly-2023-01-22
+          toolchain: nightly-2023-09-21
       - name: Cache cargo registry
         uses: actions/cache@v3
         with:
@@ -318,7 +318,7 @@ jobs:
 
       - name: Run compile tests
         shell: bash
-        run: cargo +nightly-2023-01-22  test --manifest-path diesel_compile_tests/Cargo.toml
+        run: cargo +nightly-2023-09-21  test --manifest-path diesel_compile_tests/Cargo.toml
 
   rustfmt_and_clippy:
     name: Check rustfmt style && run clippy

diesel/src/deserialize.rs

@@ -420,7 +420,7 @@ pub use diesel_derives::QueryableByName;
 /// ```
 #[cfg_attr(
     feature = "nightly-error-messages",
-    rustc_on_unimplemented(
+    diagnostic::on_unimplemented(
         message = "Cannot deserialize a value of the database type `{A}` as `{Self}`",
         note = "Double check your type mappings via the documentation of `{A}`"
     )
@@ -453,11 +453,10 @@ pub trait FromSql<A, DB: Backend>: Sized {
 ///    * [`QueryableByName`]
 #[cfg_attr(
     feature = "nightly-error-messages",
-    rustc_on_unimplemented(on(
-        ST = "diesel::sql_types::Untyped",
+    diagnostic::on_unimplemented(
         note = "`diesel::sql_query` requires the loading target to column names for loading values.\n\
                  You need to provide a type that explicitly derives `diesel::deserialize::QueryableByName`",
-    ))
+    )
 )]
 pub trait FromSqlRow<ST, DB: Backend>: Sized {
     /// See the trait documentation.

diesel/src/expression/mod.rs

@@ -313,7 +313,7 @@ where
 /// a left join, you must call `.nullable()` on it.
 #[cfg_attr(
     feature = "nightly-error-messages",
-    rustc_on_unimplemented(
+    diagnostic::on_unimplemented(
         message = "Cannot select `{Self}` from `{QS}`",
         note = "`{Self}` is no valid selection for `{QS}`"
     )

diesel/src/lib.rs

@@ -214,6 +214,7 @@
 //! various bugs in rustdoc. It can be used to check if you depend on any such hidden `#[deprecated]` item.
 //! - `nightly-error-messages`: This feature enables the generation of improved compiler error messages for
 //! common mistakes using diesel. This feature requires a nightly rust compiler and is considered to be unstable.
+//! It requires adding `#![feature(diagnostic_namespace)]` to your crate.
 //! We might remove it in future diesel versions without replacement or deprecation.
 //!
 //!
@@ -222,7 +223,7 @@
 //! - `with-deprecated`
 //! - `32-column-tables`
 
-#![cfg_attr(feature = "nightly-error-messages", feature(rustc_attrs))]
+#![cfg_attr(feature = "nightly-error-messages", feature(diagnostic_namespace))]
 #![cfg_attr(feature = "unstable", feature(trait_alias))]
 #![cfg_attr(doc_cfg, feature(doc_cfg, doc_auto_cfg))]
 #![cfg_attr(feature = "128-column-tables", recursion_limit = "256")]

diesel/src/query_dsl/load_dsl.rs

@@ -179,6 +179,14 @@ mod private {
         doc_cfg,
         doc(cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"))
     )]
+    #[cfg_attr(
+        feature = "nightly-error-messages",
+        diagnostic::on_unimplemented(
+            note = "This is a mismatch between what your query returns and what your type expects the query to return\n\
+                Consider using `#[derive(Selectable)]` + `#[diesel(check_for_backend({DB}))]` on your struct `{U}` and \n\
+                in your query `.select({U}::as_select())` to get a better error message",
+        )
+    )]
     pub trait CompatibleType<U, DB> {
         type SqlType;
     }

diesel_compile_tests/rust-toolchain

@@ -1 +1 @@
-nightly-2023-01-22
+nightly-2023-09-21

diesel_compile_tests/tests/fail/aggregate_expression_requires_column_from_same_table.rs

@@ -1,3 +1,4 @@
+#![feature(diagnostic_namespace)]
 extern crate diesel;
 
 use diesel::*;

diesel_compile_tests/tests/fail/any_is_only_selectable_if_inner_expr_is_selectable.stderr

@@ -10,7 +10,7 @@ error[E0271]: type mismatch resolving `<table as AppearsInFromClause<table>>::Co
   --> tests/fail/any_is_only_selectable_if_inner_expr_is_selectable.rs:31:15
    |
 31 |         .load(&mut conn);
-   |          ---- ^^^^^^^^^ expected struct `Once`, found struct `Never`
+   |          ---- ^^^^^^^^^ expected `Once`, found `Never`
    |          |
    |          required by a bound introduced by this call
    |
@@ -27,6 +27,9 @@ note: required for `more_stuff::columns::names` to implement `AppearsOnTable<stu
 note: required by a bound in `diesel::RunQueryDsl::load`
   --> $DIESEL/src/query_dsl/mod.rs
    |
+   |     fn load<'query, U>(self, conn: &mut Conn) -> QueryResult<Vec<U>>
+   |        ---- required by a bound in this associated function
+   |     where
    |         Self: LoadQuery<'query, Conn, U>,
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `RunQueryDsl::load`
 
@@ -59,5 +62,8 @@ note: required for `more_stuff::columns::names` to implement `AppearsOnTable<stu
 note: required by a bound in `diesel::RunQueryDsl::load`
   --> $DIESEL/src/query_dsl/mod.rs
    |
+   |     fn load<'query, U>(self, conn: &mut Conn) -> QueryResult<Vec<U>>
+   |        ---- required by a bound in this associated function
+   |     where
    |         Self: LoadQuery<'query, Conn, U>,
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `RunQueryDsl::load`

diesel_compile_tests/tests/fail/array_expressions_must_be_correct_type.rs

@@ -1,3 +1,4 @@
+#![feature(diagnostic_namespace)]
 extern crate diesel;
 
 use diesel::dsl::*;