Walk into nested bodies when suggesting unit for unit fallback

Author: compiler-errors

compiler/rustc_hir_typeck/src/fallback.rs

@@ -684,6 +684,12 @@ impl<'tcx> Visitor<'tcx> for AnnotateUnitFallbackVisitor<'_, 'tcx> {
     }
 
     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) -> Self::Result {
+        if let hir::ExprKind::Closure(&hir::Closure { body, .. })
+        | hir::ExprKind::ConstBlock(hir::ConstBlock { body, .. }) = expr.kind
+        {
+            self.visit_body(self.fcx.tcx.hir().body(body))?;
+        }
+
         // Try to suggest adding an explicit qself `()` to a trait method path.
         // i.e. changing `Default::default()` to `<() as Default>::default()`.
         if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind

tests/ui/never_type/dont-suggest-turbofish-from-expansion.stderr

@@ -17,6 +17,10 @@ note: the lint level is defined here
    |
 LL | #![deny(dependency_on_unit_never_type_fallback)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: use `()` annotations to avoid fallback changes
+   |
+LL |         let created: () = create_ok_default()?;
+   |                    ++++
 
 error: aborting due to 1 previous error