Diagnose liveness on MIR.

Author: cjgillot

tests/ui/needless_match.fixed

@@ -1,7 +1,7 @@
 #![warn(clippy::needless_match)]
 #![allow(clippy::manual_map)]
 #![allow(dead_code)]
-
+#![allow(unused)]
 #[derive(Clone, Copy)]
 enum Simple {
     A,

tests/ui/needless_match.rs

@@ -1,7 +1,7 @@
 #![warn(clippy::needless_match)]
 #![allow(clippy::manual_map)]
 #![allow(dead_code)]
-
+#![allow(unused)]
 #[derive(Clone, Copy)]
 enum Simple {
     A,

tests/ui/useless_conversion.fixed

@@ -1,5 +1,5 @@
 #![deny(clippy::useless_conversion)]
-#![allow(clippy::needless_if, clippy::unnecessary_wraps)]
+#![allow(clippy::needless_if, clippy::unnecessary_wraps, unused)]
 // FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
 #![allow(static_mut_refs)]
 

tests/ui/useless_conversion.rs

@@ -1,5 +1,5 @@
 #![deny(clippy::useless_conversion)]
-#![allow(clippy::needless_if, clippy::unnecessary_wraps)]
+#![allow(clippy::needless_if, clippy::unnecessary_wraps, unused)]
 // FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
 #![allow(static_mut_refs)]