[drop tracking] Use parent expression for scope

Previously we were just using the parent node as the scope for a
temporary value, but it turns out this is too narrow. For example, in
an expression like

    Foo {
        b: &42,
        a: async { 0 }.await,
    }

the scope for the &42 was set to the ExprField node for `b: &42`, when
we actually want to use the Foo struct expression.

We fix this by recursively searching through parent nodes until we find
a Node::Expr. It may be that we don't find one, and if so that's okay,
we will just fall back on the enclosing temporary scope which is always
sufficient.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/test/ui/async-await/issue-73137.rs b/src/test/ui/async-await/issue-73137.rs
index c43ce2cadba..dcbe7765a9e 100644
--- a/src/test/ui/async-await/issue-73137.rs
+++ b/src/test/ui/async-await/issue-73137.rs
@@ -2,6 +2,9 @@
 
 // run-pass
 // edition:2018
+// revisions: normal drop-tracking
+// [normal]compile-flags: -Zdrop-tracking=no
+// [drop-tracking]compile-flags: -Zdrop-tracking
 
 #![allow(dead_code)]
 use std::future::Future;