reword documentation and lint message

Author: y21

clippy_lints/src/methods/mod.rs

@@ -3657,24 +3657,22 @@ declare_clippy_lint! {
 }
 
 declare_clippy_lint! {
-    /// Looks for one of two kinds of expressions:
-    /// - Calling `<T as TryInto<U>>::try_into` where `T` also implements `Into<U>`
-    /// - Calling `<T as TryFrom<U>>::try_from` where `T` also implements `From<U>`
+    /// ### What it does
+    /// Checks for calls to `TryInto::try_into` and `TryFrom::try_from` when their infallible counterparts
+    /// could be used.
     ///
     /// ### Why is this bad?
-    /// In those cases, the `TryInto` and `TryFrom` trait implementation is a blanket impl which forwards
+    /// In those cases, the `TryInto` and `TryFrom` trait implementation is a blanket impl that forwards
     /// to `Into` or `From`, which always succeeds.
-    /// Indeed, its associated `Error` type is the empty enum `Infallible`,
-    /// which is impossible to construct by nature, so the error handling that is then imposed by
-    /// the `Result<_, Infallible>` is unnecessary and can be avoided simply by calling `.into()` or `::from`
-    /// directly in the first place.
+    /// The returned `Result<_, Infallible>` requires error handling to get the contained value
+    /// even though the conversion can never fail.
     ///
     /// ### Example
     /// ```rust
     /// let _: Result<i64, _> = 1i32.try_into();
     /// let _: Result<i64, _> = <_>::try_from(1i32);
     /// ```
-    /// Use instead:
+    /// Use `from`/`into` instead:
     /// ```rust
     /// let _: i64 = 1i32.into();
     /// let _: i64 = <_>::from(1i32);

clippy_lints/src/methods/unnecessary_fallible_conversions.rs

@@ -74,11 +74,7 @@ fn check<'tcx>(
             cx,
             UNNECESSARY_FALLIBLE_CONVERSIONS,
             span,
-            match kind {
-                FunctionKind::TryFromFunction => "calling `TryFrom::try_from` when `From` could be used",
-                FunctionKind::TryIntoMethod
-                | FunctionKind::TryIntoFunction => "calling `TryInto::try_into` when `Into` could be used",
-            },
+            "use of a fallible conversion when an infallible one could be used",
             "use",
             sugg.into(),
             applicability