From ca9988ec49debec4cd567d0aa719e2ee108c038b Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Tue, 25 Mar 2025 20:17:29 +1100
Subject: [PATCH 1/2] Remove `kw::Empty` uses from `rustc_middle`.

There are several places in `rustc_middle` that check for an empty
lifetime name. These checks appear to be totally unnecessary, because
empty lifetime names aren't produced here. (Empty lifetime names *are*
possible in `hir::Lifetime`. Perhaps there was some confusion between
it and the `rustc_middle` types?)

This commit removes the `kw::Empty` checks.
---
 compiler/rustc_middle/src/ty/generics.rs     |  4 +---
 compiler/rustc_middle/src/ty/mod.rs          |  2 +-
 compiler/rustc_middle/src/ty/print/pretty.rs | 10 ++++------
 compiler/rustc_middle/src/ty/region.rs       |  6 ++----
 4 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 85d9db7ee7473..d4cc562e70cc7 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -73,9 +73,7 @@ impl GenericParamDef {
 
     pub fn is_anonymous_lifetime(&self) -> bool {
         match self.kind {
-            GenericParamDefKind::Lifetime => {
-                self.name == kw::UnderscoreLifetime || self.name == kw::Empty
-            }
+            GenericParamDefKind::Lifetime => self.name == kw::UnderscoreLifetime,
             _ => false,
         }
     }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 6bdd0a0647d30..ac98cbc8d6cba 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -457,7 +457,7 @@ impl EarlyParamRegion {
     /// Does this early bound region have a name? Early bound regions normally
     /// always have names except when using anonymous lifetimes (`'_`).
     pub fn has_name(&self) -> bool {
-        self.name != kw::UnderscoreLifetime && self.name != kw::Empty
+        self.name != kw::UnderscoreLifetime
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 3ef8ecc59e402..3281cb4135a0a 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -2591,11 +2591,9 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         // to fit that into a short string. Hence the recommendation to use
         // `explain_region()` or `note_and_explain_region()`.
         match *region {
-            ty::ReEarlyParam(ref data) => {
-                if data.name != kw::Empty {
-                    p!(write("{}", data.name));
-                    return Ok(());
-                }
+            ty::ReEarlyParam(data) => {
+                p!(write("{}", data.name));
+                return Ok(());
             }
             ty::ReLateParam(ty::LateParamRegion { kind, .. }) => {
                 if let Some(name) = kind.get_name() {
@@ -2834,7 +2832,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
 
                         (name, ty::BoundRegionKind::Named(CRATE_DEF_ID.to_def_id(), name))
                     }
-                    ty::BoundRegionKind::Named(def_id, kw::UnderscoreLifetime | kw::Empty) => {
+                    ty::BoundRegionKind::Named(def_id, kw::UnderscoreLifetime) => {
                         let name = next_name(self);
 
                         if let Some(lt_idx) = lifetime_idx {
diff --git a/compiler/rustc_middle/src/ty/region.rs b/compiler/rustc_middle/src/ty/region.rs
index fb52cf96b0297..c78306f2ca379 100644
--- a/compiler/rustc_middle/src/ty/region.rs
+++ b/compiler/rustc_middle/src/ty/region.rs
@@ -400,9 +400,7 @@ impl LateParamRegionKind {
 
     pub fn is_named(&self) -> bool {
         match *self {
-            LateParamRegionKind::Named(_, name) => {
-                name != kw::UnderscoreLifetime && name != kw::Empty
-            }
+            LateParamRegionKind::Named(_, name) => name != kw::UnderscoreLifetime,
             _ => false,
         }
     }
@@ -475,7 +473,7 @@ impl core::fmt::Debug for BoundRegion {
 impl BoundRegionKind {
     pub fn is_named(&self) -> bool {
         match *self {
-            BoundRegionKind::Named(_, name) => name != kw::UnderscoreLifetime && name != kw::Empty,
+            BoundRegionKind::Named(_, name) => name != kw::UnderscoreLifetime,
             _ => false,
         }
     }

From 5a6ed74a6cae1b8bd994a9b2738896b425726c52 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Thu, 27 Mar 2025 19:10:14 +1100
Subject: [PATCH 2/2] Remove `kw::Empty` uses from `src/librustdoc`.

Much like the ones in the previous commit.
---
 src/librustdoc/clean/mod.rs | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index de6dc088176ff..f72acaae02f23 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1943,14 +1943,11 @@ fn clean_trait_object_lifetime_bound<'tcx>(
     // latter contrary to `clean_middle_region`.
     match *region {
         ty::ReStatic => Some(Lifetime::statik()),
-        ty::ReEarlyParam(region) if region.name != kw::Empty => Some(Lifetime(region.name)),
-        ty::ReBound(_, ty::BoundRegion { kind: ty::BoundRegionKind::Named(_, name), .. })
-            if name != kw::Empty =>
-        {
+        ty::ReEarlyParam(region) => Some(Lifetime(region.name)),
+        ty::ReBound(_, ty::BoundRegion { kind: ty::BoundRegionKind::Named(_, name), .. }) => {
             Some(Lifetime(name))
         }
-        ty::ReEarlyParam(_)
-        | ty::ReBound(..)
+        ty::ReBound(..)
         | ty::ReLateParam(_)
         | ty::ReVar(_)
         | ty::RePlaceholder(_)