test: add method chain test

Author: FoseFx

tests/ui/or_then_unwrap.fixed

@@ -26,6 +26,10 @@ fn main() {
     let result: Result<&str, &str> = Err("Error");
     let _ = result.unwrap_or("fallback"); // should trigger lint
 
+    // as part of a method chain
+    let option: Option<&str> = None;
+    let _ = option.map(|v| v).unwrap_or("fallback").to_string().chars(); // should trigger lint
+
     // Not Option/Result
     let instance = SomeStruct {};
     let _ = instance.or(Some(SomeStruct {})).unwrap(); // should not trigger lint

tests/ui/or_then_unwrap.rs

@@ -26,6 +26,10 @@ fn main() {
     let result: Result<&str, &str> = Err("Error");
     let _ = result.or::<&str>(Ok("fallback")).unwrap(); // should trigger lint
 
+    // as part of a method chain
+    let option: Option<&str> = None;
+    let _ = option.map(|v| v).or(Some("fallback")).unwrap().to_string().chars(); // should trigger lint
+
     // Not Option/Result
     let instance = SomeStruct {};
     let _ = instance.or(Some(SomeStruct {})).unwrap(); // should not trigger lint

tests/ui/or_then_unwrap.stderr

@@ -12,5 +12,11 @@ error: .or(Ok(…)).unwrap() found
 LL |     let _ = result.or::<&str>(Ok("fallback")).unwrap(); // should trigger lint
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or("fallback")`
 
-error: aborting due to 2 previous errors
+error: .or(Some(…)).unwrap() found
+  --> $DIR/or_then_unwrap.rs:31:31
+   |
+LL |     let _ = option.map(|v| v).or(Some("fallback")).unwrap().to_string().chars(); // should trigger lint
+   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or("fallback")`
+
+error: aborting due to 3 previous errors