Fix unsafetyck disabling for custom MIR

compiler/rustc_middle/src/mir/mod.rs

@@ -533,6 +533,11 @@ impl<'tcx> Body<'tcx> {
         };
         injection_phase > self.phase
     }
+
+    #[inline]
+    pub fn is_custom_mir(&self) -> bool {
+        self.injection_phase.is_some()
+    }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)]

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -500,7 +500,7 @@ fn unsafety_check_result<'tcx>(
     // `mir_built` force this.
     let body = &tcx.mir_built(def).borrow();
 
-    if body.should_skip() {
+    if body.is_custom_mir() {
         return tcx.arena.alloc(UnsafetyCheckResult {
             violations: Vec::new(),
             used_unsafe_blocks: FxHashSet::default(),