Auto merge of #120614 - DianQK:simplify-switch-int, r=cjgillot

 Transforms match into an assignment statement

Fixes #106459.

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

r? mir-opt

compiler/rustc_middle/src/mir/terminator.rs

@@ -85,6 +85,12 @@ impl SwitchTargets {
         self.values.push(value);
         self.targets.insert(self.targets.len() - 1, bb);
     }
+
+    /// 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> {