Add must_use to StrExt methods
diff --git a/src/lib.rs b/src/lib.rs
index 79a22b6..192f972 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -551,24 +551,28 @@
/// potentially without allocating.
///
/// See [`str::to_lowercase`].
+ #[must_use = "this returns a new SmolStr without modifying the original"]
fn to_lowercase_smolstr(&self) -> SmolStr;
/// Returns the uppercase equivalent of this string slice as a new [`SmolStr`],
/// potentially without allocating.
///
/// See [`str::to_uppercase`].
+ #[must_use = "this returns a new SmolStr without modifying the original"]
fn to_uppercase_smolstr(&self) -> SmolStr;
/// Returns the ASCII lowercase equivalent of this string slice as a new [`SmolStr`],
/// potentially without allocating.
///
/// See [`str::to_ascii_lowercase`].
+ #[must_use = "this returns a new SmolStr without modifying the original"]
fn to_ascii_lowercase_smolstr(&self) -> SmolStr;
/// Returns the ASCII uppercase equivalent of this string slice as a new [`SmolStr`],
/// potentially without allocating.
///
/// See [`str::to_ascii_uppercase`].
+ #[must_use = "this returns a new SmolStr without modifying the original"]
fn to_ascii_uppercase_smolstr(&self) -> SmolStr;
}
