Add test.

Author: cjgillot

tests/mir-opt/dead-store-elimination/place_mention.main.DeadStoreElimination.diff

@@ -0,0 +1,25 @@
+- // MIR for `main` before DeadStoreElimination
++ // MIR for `main` after DeadStoreElimination
+  
+  fn main() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/place_mention.rs:+0:11: +0:11
+      let mut _1: (&str, &str);            // in scope 0 at $DIR/place_mention.rs:+3:18: +3:36
+      scope 1 {
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/place_mention.rs:+3:18: +3:36
+-         _1 = (const "Hello", const "World"); // scope 0 at $DIR/place_mention.rs:+3:18: +3:36
+-                                          // mir::Constant
+-                                          // + span: $DIR/place_mention.rs:8:19: 8:26
+-                                          // + literal: Const { ty: &str, val: Value(Slice(..)) }
+-                                          // mir::Constant
+-                                          // + span: $DIR/place_mention.rs:8:28: 8:35
+-                                          // + literal: Const { ty: &str, val: Value(Slice(..)) }
+          PlaceMention(_1);                // scope 0 at $DIR/place_mention.rs:+3:18: +3:36
+          StorageDead(_1);                 // scope 0 at $DIR/place_mention.rs:+3:36: +3:37
+          _0 = const ();                   // scope 0 at $DIR/place_mention.rs:+0:11: +4:2
+          return;                          // scope 0 at $DIR/place_mention.rs:+4:2: +4:2
+      }
+  }
+  

tests/mir-opt/dead-store-elimination/place_mention.rs

@@ -0,0 +1,9 @@
+// unit-test: DeadStoreElimination
+// compile-flags: -Zmir-keep-place-mention
+
+// EMIT_MIR place_mention.main.DeadStoreElimination.diff
+fn main() {
+    // Verify that we account for the `PlaceMention` statement as a use of the tuple,
+    // and don't remove it as a dead store.
+    let (_, _) = ("Hello", "World");
+}