Rollup merge of #57302 - sinkuu:unused_assignments_fp, r=estebank

Fix unused_assignments false positive

Fixes #22630.

In liveness analysis, make `continue` jump to the loop condition's `LiveNode` (`cond` as in comment) instead of the loop's one (`expr`).

069b0c4108/src/librustc/middle/liveness.rs (L1358-L1370)

src/test/ui/liveness/liveness-dead.rs

@@ -27,4 +27,13 @@ fn f5(mut x: i32) {
     x = 4; //~ ERROR: value assigned to `x` is never read
 }
 
+// #22630
+fn f6() {
+    let mut done = false;
+    while !done {
+        done = true; // no error
+        continue;
+    }
+}
+
 fn main() {}