From 9ab1d5c73a67e0936f71abe6eaccef8d0b4bd25e Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sat, 17 Aug 2019 10:20:18 +0200
Subject: [PATCH] multi-variant enums are tricky

---
 src/librustc_lint/builtin.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index f4f6bd37774c..74cff1bab0f8 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -1971,6 +1971,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
                                 })
                             })
                         }
+                        // Multi-variant enums are tricky: if all but one variant are
+                        // uninhabited, we might actually do layout like for a single-variant
+                        // enum, and then even leaving them uninitialized could be okay.
                         _ => None, // Conservative fallback for multi-variant enum.
                     }
                 }
@@ -1978,7 +1981,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
                     // Proceed recursively, check all fields.
                     ty.tuple_fields().find_map(|field| ty_find_init_error(tcx, field, init))
                 }
-                // FIXME: *Only for `mem::uninitialized`*, we could also warn for multivariant enum.
                 // Conservative fallback.
                 _ => None,
             }