rust-lang-ci
diff --git a/‎library/core/src/fmt/builders.rs
Copy file name to clipboardExpand all lines: library/core/src/fmt/builders.rs
+1Lines changed: 1 addition & 0 deletions b/‎library/core/src/fmt/builders.rs
Copy file name to clipboardExpand all lines: library/core/src/fmt/builders.rs
+1Lines changed: 1 addition & 0 deletions
@@ -1228,6 +1228,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {
 /// assert_eq!(format!("{:?}", wrapped), "'a'");
 /// ```
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
+#[must_use = "returns a type implementing Debug and Display, which do not have any effects unless they are used"]
 pub fn from_fn<F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result>(f: F) -> FromFn<F> {
     FromFn(f)
 }
Original file line number	Diff line number	Diff line change
`@@ -1228,6 +1228,7 @@ impl<'a, 'b: 'a> DebugMap<'a, 'b> {`
`1228`	`1228`	`/// assert_eq!(format!("{:?}", wrapped), "'a'");`
`1229`	`1229`	/// ```
`1230`	`1230`	`#[unstable(feature = "debug_closure_helpers", issue = "117729")]`
	`1231`	`+#[must_use = "returns a type implementing Debug and Display, which do not have any effects unless they are used"]`
`1231`	`1232`	`pub fn from_fn<F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result>(f: F) -> FromFn<F> {`
`1232`	`1233`	`FromFn(f)`
`1233`	`1234`	`}`