1 files changed, 34 insertions, 0 deletions
diff --git a/src/tools/clippy/src/docs/print_in_format_impl.txt b/src/tools/clippy/src/docs/print_in_format_impl.txt
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--- /dev/null
+++ b/src/tools/clippy/src/docs/print_in_format_impl.txt
@@ -0,0 +1,34 @@
+### What it does
+Checks for use of `println`, `print`, `eprintln` or `eprint` in an
+implementation of a formatting trait.
+
+### Why is this bad?
+Using a print macro is likely unintentional since formatting traits
+should write to the `Formatter`, not stdout/stderr.
+
+### Example
+```
+use std::fmt::{Display, Error, Formatter};
+
+struct S;
+impl Display for S {
+    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
+        println!("S");
+
+        Ok(())
+    }
+}
+```
+Use instead:
+```
+use std::fmt::{Display, Error, Formatter};
+
+struct S;
+impl Display for S {
+    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
+        writeln!(f, "S");
+
+        Ok(())
+    }
+}
+```
+\ No newline at end of file