feat: add unnecessary literal option lint

[born-in-autumn]

Fixes #17808

changelog: [`unnecessary_literal_option`]: add new lint

• Followed [lint naming conventions][lint_naming]
• Added passing UI tests (including committed .stderr file)
• cargo test passes locally
• Executed cargo dev update_lints
• Added lint documentation
• Run cargo dev fmt

LLM disclosure: new contrbutor, everything in this PR was written manually, without LLM assistance

changelog:
The main change is the addition of a new lint, which is based onunnecessary_literal_unwrap, It adds lint suggestions for several different Option cases where the result is already known. It passes the UI tests. For naming conventions and comments, I followed existing code patterns. No extra logic was added.

Thanks for your time!

[rustbot]

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[CommanderStorm]

 error: called `unwrap` on `x` after checking its variant with `is_some`
   --> tests/ui/checked_unwrap/simple_conditionals.rs:46:9
... 155 lines skipped ...
    |         ^^^^^^^^^^^^^^
 
+error: used `is_some()` on `Some` value
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:45:8
+   |
+LL |     if x.is_some() {
+   |        ^^^^^^^^^^^
+   |
+help: replace this with `true`
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:44:13
+   |
+LL |     let x = Some(());
+   |             ^^^^^^^^
+   = note: `-D clippy::unnecessary-literal-option` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::unnecessary_literal_option)]`

Please go through the dogfooding errors.
You may need to expect(..) this a few times.

View changes since this review

[born-in-autumn]

 error: called `unwrap` on `x` after checking its variant with `is_some`
   --> tests/ui/checked_unwrap/simple_conditionals.rs:46:9
... 155 lines skipped ...
    |         ^^^^^^^^^^^^^^
 
+error: used `is_some()` on `Some` value
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:45:8
+   |
+LL |     if x.is_some() {
+   |        ^^^^^^^^^^^
+   |
+help: replace this with `true`
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:44:13
+   |
+LL |     let x = Some(());
+   |             ^^^^^^^^
+   = note: `-D clippy::unnecessary-literal-option` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::unnecessary_literal_option)]`

Please go through the dogfooding errors. You may need to expect(..) this a few times.

View changes since this review

thanks for reminding me. I spent some time fixing these CI issues.