Auto merge of rust-lang#120614 - DianQK:simplify-switch-int, r=<try>

 Transforms match into an assignment statement

Fixes rust-lang#106459.

We should be able to do some similar transformations, like `enum` to `enum`.

r? mir-opt

compiler/rustc_middle/src/mir/terminator.rs

@@ -74,6 +74,12 @@ impl SwitchTargets {
     pub fn target_for_value(&self, value: u128) -> BasicBlock {
         self.iter().find_map(|(v, t)| (v == value).then_some(t)).unwrap_or_else(|| self.otherwise())
     }
+
+    /// Returns true if all targets (including the fallback target) are distinct.
+    #[inline]
+    pub fn is_distinct(&self) -> bool {
+        self.targets.iter().collect::<FxHashSet<_>>().len() == self.targets.len()
+    }
 }
 
 pub struct SwitchTargetsIter<'a> {