Auto merge of #5694 - wangtheo:issue-5626, r=matthiaskrgr

#5626: lint iterator.map(|x| x)

changelog: adds a new lint for iterator.map(|x| x) (see https://github.com/rust-lang/rust-clippy/issues/5626)

The code also lints for result.map(|x| x) and option.map(|x| x). Also, I'm not sure if I'm checking for type adjustments correctly and I can't think of an example where .map(|x| x) would apply type adjustments.

src/lintlist/mod.rs

@@ -1144,6 +1144,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
         deprecation: None,
         module: "methods",
     },
+    Lint {
+        name: "map_identity",
+        group: "complexity",
+        desc: "using iterator.map(|x| x)",
+        deprecation: None,
+        module: "map_identity",
+    },
     Lint {
         name: "map_unwrap_or",
         group: "pedantic",