Invoke a query only when it doesn't return immediately anyway

Author: oli-obk

compiler/rustc_interface/src/passes.rs

@@ -996,10 +996,9 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
 
     sess.time("MIR_borrow_checking", || {
         tcx.par_hir_body_owners(|def_id| {
-            // Run unsafety check because it's responsible for stealing and
-            // deallocating THIR.
-            tcx.ensure_ok().check_unsafety(def_id);
             if !tcx.is_typeck_child(def_id.to_def_id()) {
+                // Child unsafety and borrowck happens together with the parent
+                tcx.ensure_ok().check_unsafety(def_id);
                 tcx.ensure_ok().mir_borrowck(def_id)
             }
         });

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -1148,8 +1148,9 @@ impl UnsafeOpKind {
 
 pub(crate) fn check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
     // Closures and inline consts are handled by their owner, if it has a body
+    assert!(!tcx.is_typeck_child(def.to_def_id()));
     // Also, don't safety check custom MIR
-    if tcx.is_typeck_child(def.to_def_id()) || tcx.has_attr(def, sym::custom_mir) {
+    if tcx.has_attr(def, sym::custom_mir) {
         return;
     }