Stop using specialization in rustc_index and rustc_borrowck

compiler/rustc_borrowck/src/facts.rs

@@ -213,8 +213,32 @@ trait FactCell {
     fn to_string(&self, location_table: &LocationTable) -> String;
 }
 
-impl<A: Debug> FactCell for A {
-    default fn to_string(&self, _location_table: &LocationTable) -> String {
+impl FactCell for BorrowIndex {
+    fn to_string(&self, _location_table: &LocationTable) -> String {
+        format!("{self:?}")
+    }
+}
+
+impl FactCell for Local {
+    fn to_string(&self, _location_table: &LocationTable) -> String {
+        format!("{self:?}")
+    }
+}
+
+impl FactCell for MovePathIndex {
+    fn to_string(&self, _location_table: &LocationTable) -> String {
+        format!("{self:?}")
+    }
+}
+
+impl FactCell for PoloniusRegionVid {
+    fn to_string(&self, _location_table: &LocationTable) -> String {
+        format!("{self:?}")
+    }
+}
+
+impl FactCell for RegionVid {
+    fn to_string(&self, _location_table: &LocationTable) -> String {
         format!("{self:?}")
     }
 }

compiler/rustc_borrowck/src/lib.rs

@@ -7,7 +7,6 @@
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]

compiler/rustc_index/src/lib.rs

@@ -1,10 +1,7 @@
 // tidy-alphabetical-start
 #![cfg_attr(all(feature = "nightly", test), feature(stmt_expr_attributes))]
-#![cfg_attr(
-    feature = "nightly",
-    feature(extend_one, min_specialization, new_uninit, step_trait, test)
-)]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
+#![cfg_attr(feature = "nightly", feature(extend_one, new_uninit, step_trait, test))]
 // tidy-alphabetical-end
 
 pub mod bit_set;

compiler/rustc_index_macros/src/lib.rs

@@ -34,10 +34,7 @@ mod newtype;
 ///   optimizations. The default max value is 0xFFFF_FF00.
 /// - `#[gate_rustc_only]`: makes parts of the generated code nightly-only.
 #[proc_macro]
-#[cfg_attr(
-    feature = "nightly",
-    allow_internal_unstable(step_trait, rustc_attrs, trusted_step, min_specialization)
-)]
+#[cfg_attr(feature = "nightly", allow_internal_unstable(step_trait, rustc_attrs, trusted_step))]
 pub fn newtype_index(input: TokenStream) -> TokenStream {
     newtype::newtype(input)
 }

compiler/rustc_index_macros/src/newtype.rs

@@ -139,10 +139,6 @@ impl Parse for Newtype {
                         Self::index(start).checked_sub(u).map(Self::from_usize)
                     }
                 }
-
-                // Safety: The implementation of `Step` upholds all invariants.
-                #gate_rustc_only
-                unsafe impl ::std::iter::TrustedStep for #name {}
             }
         } else {
             quote! {}

compiler/rustc_type_ir/src/lib.rs

@@ -2,7 +2,7 @@
 #![allow(rustc::usage_of_ty_tykind)]
 #![cfg_attr(
     feature = "nightly",
-    feature(associated_type_defaults, min_specialization, never_type, rustc_attrs, negative_impls)
+    feature(associated_type_defaults, never_type, rustc_attrs, negative_impls)
 )]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
 // tidy-alphabetical-end