Rollup merge of #138926 - nnethercote:less-kw-Empty-rustc_middle, r=lcnr

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.

r? `@lcnr`

Author: jhpratt

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,
         }
     }

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
     }
 }
 

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 {

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,
         }
     }

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(_)