Use `derive_default_enum` in the compiler

2 files changed, 3 insertions, 7 deletions

diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index b874947cc69..2fd01c2d595 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -95,9 +95,10 @@ pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable<
 /// This is used so that the region values inferred by HIR region solving are
 /// not exposed, and so that we can avoid doing work in HIR typeck that MIR
 /// typeck will also do.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, Default)]
 pub enum RegionckMode {
     /// The default mode: report region errors, don't erase regions.
+    #[default]
     Solve,
     /// Erase the results of region after solving.
     Erase {
@@ -108,12 +109,6 @@ pub enum RegionckMode {
     },
 }
 
-impl Default for RegionckMode {
-    fn default() -> Self {
-        RegionckMode::Solve
-    }
-}
-
 impl RegionckMode {
     /// Indicates that the MIR borrowck will repeat these region
     /// checks, so we should ignore errors if NLL is (unconditionally)
diff --git a/compiler/rustc_infer/src/lib.rs b/compiler/rustc_infer/src/lib.rs
index d0f1ff649d0..e4b407e7c11 100644
--- a/compiler/rustc_infer/src/lib.rs
+++ b/compiler/rustc_infer/src/lib.rs
@@ -15,6 +15,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
+#![feature(derive_default_enum)]
 #![feature(extend_one)]
 #![feature(iter_zip)]
 #![feature(let_else)]