Deprecate redundant lint `option_map_or_err_ok` and take `manual_ok_or` out of pedantic (#14027)

While extending the `option_map_or_err_ok` lint (warn by default,
"style") to recognize η-expanded forms of `Ok`, as in

```rust
    // Should suggest `opt.ok_or("foobar")`
   let _ = opt.map_or(Err("foobar"), |x| Ok(x));
```

I discovered that the `manual_ok_or` lint (allow by default, "pedantic")
already covered exactly the cases handled by `option_map_or_err_ok`,
including the one I was adding. Apparently, `option_map_or_err_ok` was
added without realizing that the lint already existed under the
`manual_ok_or` name. As a matter of fact, artifacts of this second lint
were even present in the first lint `stderr` file and went unnoticed for
more than a year.

This PR:
- deprecates `option_map_or_err_ok` with a message saying to use
`manual_ok_or`
- moves `manual_ok_or` from "pedantic" to "style" (the category in which
`option_map_or_err_ok` was)

In addition, I think that this lint, which is short, machine applicable,
and leads to shorter and clearer code with less arguments (`Ok`
disappears) and the removal of one level of call (`Err(x)` is replaced
by `x`), is a reason by itself to be in "style".

changelog: [`option_map_or_err_ok` and `manual_ok_or`]: move
`manual_ok_or` from "pedantic" to "style", and deprecate the redundant
style lint `option_map_or_err_ok`.

6 files changed, 9 insertions, 36 deletions

diff --git a/tests/ui/deprecated.rs b/tests/ui/deprecated.rs
index 5617db90a47..35646e1c239 100644
--- a/tests/ui/deprecated.rs
+++ b/tests/ui/deprecated.rs
@@ -15,5 +15,6 @@
 #![warn(clippy::regex_macro)] //~ ERROR: lint `clippy::regex_macro`
 #![warn(clippy::pub_enum_variant_names)] //~ ERROR: lint `clippy::pub_enum_variant_names`
 #![warn(clippy::wrong_pub_self_convention)] //~ ERROR: lint `clippy::wrong_pub_self_convention`
+#![warn(clippy::option_map_or_err_ok)] //~ ERROR: lint `clippy::option_map_or_err_ok`
 
 fn main() {}
diff --git a/tests/ui/deprecated.stderr b/tests/ui/deprecated.stderr
index b3e1646c804..d7be1e583b0 100644
--- a/tests/ui/deprecated.stderr
+++ b/tests/ui/deprecated.stderr
@@ -79,5 +79,11 @@ error: lint `clippy::wrong_pub_self_convention` has been removed: `clippy::wrong
 LL | #![warn(clippy::wrong_pub_self_convention)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 13 previous errors
+error: lint `clippy::option_map_or_err_ok` has been removed: `clippy::manual_ok_or` covers this case
+  --> tests/ui/deprecated.rs:18:9
+   |
+LL | #![warn(clippy::option_map_or_err_ok)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 14 previous errors
 
diff --git a/tests/ui/manual_ok_or.stderr b/tests/ui/manual_ok_or.stderr
index 2441a75b5c4..4722f53580f 100644
--- a/tests/ui/manual_ok_or.stderr
+++ b/tests/ui/manual_ok_or.stderr
@@ -13,15 +13,6 @@ error: this pattern reimplements `Option::ok_or`
 LL |     foo.map_or(Err("error"), Ok);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `foo.ok_or("error")`
 
-error: called `map_or(Err(_), Ok)` on an `Option` value
-  --> tests/ui/manual_ok_or.rs:14:5
-   |
-LL |     foo.map_or(Err("error"), Ok);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `ok_or`: `foo.ok_or("error")`
-   |
-   = note: `-D clippy::option-map-or-err-ok` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::option_map_or_err_ok)]`
-
 error: this pattern reimplements `Option::ok_or`
   --> tests/ui/manual_ok_or.rs:17:5
    |
@@ -47,5 +38,5 @@ LL +         "{}{}{}{}{}{}{}",
 LL ~         "Alice", "Bob", "Sarah", "Marc", "Sandra", "Eric", "Jenifer"));
    |
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/tests/ui/option_map_or_err_ok.fixed b/tests/ui/option_map_or_err_ok.fixed
deleted file mode 100644
index 131f4b2093e..00000000000
--- a/tests/ui/option_map_or_err_ok.fixed
+++ /dev/null
@@ -1,7 +0,0 @@
-#![warn(clippy::option_map_or_err_ok)]
-
-fn main() {
-    let x = Some("a");
-    let _ = x.ok_or("a");
-    //~^ ERROR: called `map_or(Err(_), Ok)` on an `Option` value
-}
diff --git a/tests/ui/option_map_or_err_ok.rs b/tests/ui/option_map_or_err_ok.rs
deleted file mode 100644
index 0f07a592ae5..00000000000
--- a/tests/ui/option_map_or_err_ok.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-#![warn(clippy::option_map_or_err_ok)]
-
-fn main() {
-    let x = Some("a");
-    let _ = x.map_or(Err("a"), Ok);
-    //~^ ERROR: called `map_or(Err(_), Ok)` on an `Option` value
-}
diff --git a/tests/ui/option_map_or_err_ok.stderr b/tests/ui/option_map_or_err_ok.stderr
deleted file mode 100644
index 1971af80aa8..00000000000
--- a/tests/ui/option_map_or_err_ok.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error: called `map_or(Err(_), Ok)` on an `Option` value
-  --> tests/ui/option_map_or_err_ok.rs:5:13
-   |
-LL |     let _ = x.map_or(Err("a"), Ok);
-   |             ^^^^^^^^^^^^^^^^^^^^^^ help: consider using `ok_or`: `x.ok_or("a")`
-   |
-   = note: `-D clippy::option-map-or-err-ok` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::option_map_or_err_ok)]`
-
-error: aborting due to 1 previous error
-