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diff --git a/src/tools/clippy/src/docs/inefficient_to_string.txt b/src/tools/clippy/src/docs/inefficient_to_string.txt
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+### What it does
+Checks for usage of `.to_string()` on an `&&T` where
+`T` implements `ToString` directly (like `&&str` or `&&String`).
+
+### Why is this bad?
+This bypasses the specialized implementation of
+`ToString` and instead goes through the more expensive string formatting
+facilities.
+
+### Example
+```
+// Generic implementation for `T: Display` is used (slow)
+["foo", "bar"].iter().map(|s| s.to_string());
+
+// OK, the specialized impl is used
+["foo", "bar"].iter().map(|&s| s.to_string());
+```
+\ No newline at end of file