Add unit assignment to MIR for asm!()

src/test/ui/asm/issue-89305.rs

@@ -0,0 +1,14 @@
+// Regression test for #89305, where a variable was erroneously reported
+// as both unused and possibly-uninitialized.
+
+// check-pass
+
+#![feature(asm)]
+#![warn(unused)]
+
+fn main() {
+    unsafe {
+        let x: () = asm!("nop");
+        //~^ WARNING: unused variable: `x`
+    }
+}

src/test/ui/asm/issue-89305.stderr

@@ -0,0 +1,15 @@
+warning: unused variable: `x`
+  --> $DIR/issue-89305.rs:11:13
+   |
+LL |         let x: () = asm!("nop");
+   |             ^ help: if this is intentional, prefix it with an underscore: `_x`
+   |
+note: the lint level is defined here
+  --> $DIR/issue-89305.rs:7:9
+   |
+LL | #![warn(unused)]
+   |         ^^^^^^
+   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
+
+warning: 1 warning emitted
+