Make functional record update/struct update syntax works inside closures when feature capture_disjoint_fields is enabled

src/test/ui/closures/2229_closure_analysis/run_pass/fru_syntax.rs

@@ -0,0 +1,30 @@
+// run-pass
+
+// Test that functional record update/struct update syntax works inside
+// a closure when the feature `capture_disjoint_fields` is enabled.
+
+#![feature(capture_disjoint_fields)]
+//~^ WARNING: the feature `capture_disjoint_fields` is incomplete
+//~| NOTE: `#[warn(incomplete_features)]` on by default
+//~| NOTE: see issue #53488 <https://github.com/rust-lang/rust/issues/53488>
+
+struct S {
+    a: String,
+    b: String,
+}
+
+fn main() {
+    let a = String::new();
+    let b = String::new();
+    let s = S {a, b};
+
+    let c = || {
+        let s2 = S {
+            a: format!("New a"),
+            ..s
+        };
+        println!("{} {}", s2.a, s2.b);
+    };
+
+    c();
+}

src/test/ui/closures/2229_closure_analysis/run_pass/fru_syntax.stderr

@@ -0,0 +1,11 @@
+warning: the feature `capture_disjoint_fields` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/fru_syntax.rs:6:12
+   |
+LL | #![feature(capture_disjoint_fields)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #53488 <https://github.com/rust-lang/rust/issues/53488> for more information
+
+warning: 1 warning emitted
+