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diff --git a/src/tools/clippy/src/docs/map_flatten.txt b/src/tools/clippy/src/docs/map_flatten.txt
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+++ b/src/tools/clippy/src/docs/map_flatten.txt
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+### What it does
+Checks for usage of `_.map(_).flatten(_)` on `Iterator` and `Option`
+
+### Why is this bad?
+Readability, this can be written more concisely as
+`_.flat_map(_)` for `Iterator` or `_.and_then(_)` for `Option`
+
+### Example
+```
+let vec = vec![vec![1]];
+let opt = Some(5);
+
+vec.iter().map(|x| x.iter()).flatten();
+opt.map(|x| Some(x * 2)).flatten();
+```
+
+Use instead:
+```
+vec.iter().flat_map(|x| x.iter());
+opt.and_then(|x| Some(x * 2));
+```
+\ No newline at end of file