Rollup merge of #141072 - Rynibami:stabilize-const-result-flatten, r=jhpratt

Stabilize feature `result_flattening`

Stabilizes the `Result::flatten` method

## Implementations

- [x] Implementation `Result::flatten`: https://github.com/rust-lang/rust/pull/70140
- [x] Implementation `const` `Result::flatten`: https://github.com/rust-lang/rust/pull/130692
- [x] Update stabilization attribute macros (this PR)

## Stabilization process

- [x] Created this PR [suggested](https://github.com/rust-lang/rust/issues/70142#issuecomment-2885044548) by ``@RalfJung``
- [x] FCP (haven't found any, is it applicable here?)
- [ ] Close issue rust-lang/rust#70142

4 files changed, 10 insertions, 12 deletions

diff --git a/tests/ui/map_flatten.rs b/tests/ui/map_flatten.rs
index d7e9c9d9900..0970da8039a 100644
--- a/tests/ui/map_flatten.rs
+++ b/tests/ui/map_flatten.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::map_flatten)]
-#![feature(result_flattening)]
+
 //@no-rustfix
 // issue #8506, multi-line
 #[rustfmt::skip]
diff --git a/tests/ui/map_flatten_fixable.fixed b/tests/ui/map_flatten_fixable.fixed
index f8379ed23c5..6d8a27d3018 100644
--- a/tests/ui/map_flatten_fixable.fixed
+++ b/tests/ui/map_flatten_fixable.fixed
@@ -1,4 +1,3 @@
-#![feature(result_flattening)]
 #![allow(
     clippy::let_underscore_untyped,
     clippy::missing_docs_in_private_items,
diff --git a/tests/ui/map_flatten_fixable.rs b/tests/ui/map_flatten_fixable.rs
index 040a9ca85f6..845e3a79ae2 100644
--- a/tests/ui/map_flatten_fixable.rs
+++ b/tests/ui/map_flatten_fixable.rs
@@ -1,4 +1,3 @@
-#![feature(result_flattening)]
 #![allow(
     clippy::let_underscore_untyped,
     clippy::missing_docs_in_private_items,
diff --git a/tests/ui/map_flatten_fixable.stderr b/tests/ui/map_flatten_fixable.stderr
index fe68eb7e4ab..05d4d9a6ad8 100644
--- a/tests/ui/map_flatten_fixable.stderr
+++ b/tests/ui/map_flatten_fixable.stderr
@@ -1,5 +1,5 @@
 error: called `map(..).flatten()` on `Iterator`
-  --> tests/ui/map_flatten_fixable.rs:17:47
+  --> tests/ui/map_flatten_fixable.rs:16:47
    |
 LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect();
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `filter_map` and remove the `.flatten()`: `filter_map(option_id)`
@@ -8,43 +8,43 @@ LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().coll
    = help: to override `-D warnings` add `#[allow(clippy::map_flatten)]`
 
 error: called `map(..).flatten()` on `Iterator`
-  --> tests/ui/map_flatten_fixable.rs:19:47
+  --> tests/ui/map_flatten_fixable.rs:18:47
    |
 LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect();
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `filter_map` and remove the `.flatten()`: `filter_map(option_id_ref)`
 
 error: called `map(..).flatten()` on `Iterator`
-  --> tests/ui/map_flatten_fixable.rs:21:47
+  --> tests/ui/map_flatten_fixable.rs:20:47
    |
 LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect();
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `filter_map` and remove the `.flatten()`: `filter_map(option_id_closure)`
 
 error: called `map(..).flatten()` on `Iterator`
-  --> tests/ui/map_flatten_fixable.rs:23:47
+  --> tests/ui/map_flatten_fixable.rs:22:47
    |
 LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect();
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `filter_map` and remove the `.flatten()`: `filter_map(|x| x.checked_add(1))`
 
 error: called `map(..).flatten()` on `Iterator`
-  --> tests/ui/map_flatten_fixable.rs:27:47
+  --> tests/ui/map_flatten_fixable.rs:26:47
    |
 LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect();
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `flat_map` and remove the `.flatten()`: `flat_map(|x| 0..x)`
 
 error: called `map(..).flatten()` on `Option`
-  --> tests/ui/map_flatten_fixable.rs:31:40
+  --> tests/ui/map_flatten_fixable.rs:30:40
    |
 LL |     let _: Option<_> = (Some(Some(1))).map(|x| x).flatten();
    |                                        ^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `and_then` and remove the `.flatten()`: `and_then(|x| x)`
 
 error: called `map(..).flatten()` on `Result`
-  --> tests/ui/map_flatten_fixable.rs:35:42
+  --> tests/ui/map_flatten_fixable.rs:34:42
    |
 LL |     let _: Result<_, &str> = (Ok(Ok(1))).map(|x| x).flatten();
    |                                          ^^^^^^^^^^^^^^^^^^^^ help: try replacing `map` with `and_then` and remove the `.flatten()`: `and_then(|x| x)`
 
 error: called `map(..).flatten()` on `Iterator`
-  --> tests/ui/map_flatten_fixable.rs:45:10
+  --> tests/ui/map_flatten_fixable.rs:44:10
    |
 LL |           .map(|n| match n {
    |  __________^
@@ -74,7 +74,7 @@ LL ~         });
    |
 
 error: called `map(..).flatten()` on `Option`
-  --> tests/ui/map_flatten_fixable.rs:66:10
+  --> tests/ui/map_flatten_fixable.rs:65:10
    |
 LL |           .map(|_| {
    |  __________^