Rollup merge of #73613 - oli-obk:const_prop_miscompile, r=wesleywiser

The const propagator cannot trace references.

Thus we avoid propagation of a local the moment we encounter references to it.

fixes #73609

cc @RalfJung

r? @wesleywiser

src/test/ui/mir/mir_detects_invalid_ops.rs

@@ -19,6 +19,6 @@ fn mod_by_zero() {
 fn oob_error_for_slices() {
     let a: *const [_] = &[1, 2, 3];
     unsafe {
-        let _b = (*a)[3]; //~ ERROR this operation will panic at runtime [unconditional_panic]
+        let _b = (*a)[3];
     }
 }

src/test/ui/mir/mir_detects_invalid_ops.stderr

@@ -12,11 +12,5 @@ error: this operation will panic at runtime
 LL |     let _z = 1 % y;
    |              ^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: this operation will panic at runtime
-  --> $DIR/mir_detects_invalid_ops.rs:22:18
-   |
-LL |         let _b = (*a)[3];
-   |                  ^^^^^^^ index out of bounds: the len is 3 but the index is 3
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors