From dbc6f5836c798ceea7518696a1cb72b8f602df76 Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Fri, 8 Aug 2025 23:11:08 +0800
Subject: [PATCH] rustc_metadata: remove unused private trait impls

---
 .../src/rmeta/decoder/cstore_impl.rs          | 18 ------
 .../rustc_metadata/src/rmeta/parameterized.rs |  7 +--
 compiler/rustc_metadata/src/rmeta/table.rs    | 63 -------------------
 3 files changed, 1 insertion(+), 87 deletions(-)

diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 0f3896fd9be8a..df95ed602cd36 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -74,24 +74,6 @@ impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>> ProcessQueryValue<'
     }
 }
 
-impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>>
-    ProcessQueryValue<'tcx, ty::EarlyBinder<'tcx, &'tcx [T]>>
-    for Option<DecodeIterator<'a, 'tcx, T>>
-{
-    #[inline(always)]
-    fn process_decoded(
-        self,
-        tcx: TyCtxt<'tcx>,
-        err: impl Fn() -> !,
-    ) -> ty::EarlyBinder<'tcx, &'tcx [T]> {
-        ty::EarlyBinder::bind(if let Some(iter) = self {
-            tcx.arena.alloc_from_iter(iter)
-        } else {
-            err()
-        })
-    }
-}
-
 impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>>
     ProcessQueryValue<'tcx, Option<&'tcx [T]>> for Option<DecodeIterator<'a, 'tcx, T>>
 {
diff --git a/compiler/rustc_metadata/src/rmeta/parameterized.rs b/compiler/rustc_metadata/src/rmeta/parameterized.rs
index d632e65104a7a..34180001f8044 100644
--- a/compiler/rustc_metadata/src/rmeta/parameterized.rs
+++ b/compiler/rustc_metadata/src/rmeta/parameterized.rs
@@ -6,7 +6,7 @@ use rustc_index::{Idx, IndexVec};
 use rustc_middle::ty::{Binder, EarlyBinder};
 use rustc_span::Symbol;
 
-use crate::rmeta::{LazyArray, LazyTable, LazyValue};
+use crate::rmeta::{LazyArray, LazyValue};
 
 pub(crate) trait ParameterizedOverTcx: 'static {
     type Value<'tcx>;
@@ -48,10 +48,6 @@ impl<T: ParameterizedOverTcx> ParameterizedOverTcx for LazyArray<T> {
     type Value<'tcx> = LazyArray<T::Value<'tcx>>;
 }
 
-impl<I: 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for LazyTable<I, T> {
-    type Value<'tcx> = LazyTable<I, T::Value<'tcx>>;
-}
-
 macro_rules! trivially_parameterized_over_tcx {
     ($($ty:ty),+ $(,)?) => {
         $(
@@ -154,7 +150,6 @@ parameterized_over_tcx! {
     rustc_middle::mir::CoroutineLayout,
     rustc_middle::mir::interpret::ConstAllocation,
     rustc_middle::ty::Clause,
-    rustc_middle::ty::ClauseKind,
     rustc_middle::ty::Const,
     rustc_middle::ty::ConstConditions,
     rustc_middle::ty::FnSig,
diff --git a/compiler/rustc_metadata/src/rmeta/table.rs b/compiler/rustc_metadata/src/rmeta/table.rs
index 28f406fbc9629..0671aa203993a 100644
--- a/compiler/rustc_metadata/src/rmeta/table.rs
+++ b/compiler/rustc_metadata/src/rmeta/table.rs
@@ -66,22 +66,6 @@ pub(super) trait FixedSizeEncoding: IsDefault {
     fn write_to_bytes(self, b: &mut Self::ByteArray);
 }
 
-/// This implementation is not used generically, but for reading/writing
-/// concrete `u32` fields in `Lazy*` structures, which may be zero.
-impl FixedSizeEncoding for u32 {
-    type ByteArray = [u8; 4];
-
-    #[inline]
-    fn from_bytes(b: &[u8; 4]) -> Self {
-        Self::from_le_bytes(*b)
-    }
-
-    #[inline]
-    fn write_to_bytes(self, b: &mut [u8; 4]) {
-        *b = self.to_le_bytes();
-    }
-}
-
 impl FixedSizeEncoding for u64 {
     type ByteArray = [u8; 8];
 
@@ -174,14 +158,6 @@ fixed_size_enum! {
     }
 }
 
-fixed_size_enum! {
-    ty::ImplPolarity {
-        ( Positive    )
-        ( Negative    )
-        ( Reservation )
-    }
-}
-
 fixed_size_enum! {
     hir::Constness {
         ( NotConst )
@@ -306,45 +282,6 @@ impl FixedSizeEncoding for bool {
     }
 }
 
-impl FixedSizeEncoding for Option<bool> {
-    type ByteArray = [u8; 1];
-
-    #[inline]
-    fn from_bytes(b: &[u8; 1]) -> Self {
-        match b[0] {
-            0 => Some(false),
-            1 => Some(true),
-            2 => None,
-            _ => unreachable!(),
-        }
-    }
-
-    #[inline]
-    fn write_to_bytes(self, b: &mut [u8; 1]) {
-        debug_assert!(!self.is_default());
-        b[0] = match self {
-            Some(false) => 0,
-            Some(true) => 1,
-            None => 2,
-        };
-    }
-}
-
-impl FixedSizeEncoding for UnusedGenericParams {
-    type ByteArray = [u8; 4];
-
-    #[inline]
-    fn from_bytes(b: &[u8; 4]) -> Self {
-        let x: u32 = u32::from_bytes(b);
-        UnusedGenericParams::from_bits(x)
-    }
-
-    #[inline]
-    fn write_to_bytes(self, b: &mut [u8; 4]) {
-        self.bits().write_to_bytes(b);
-    }
-}
-
 // NOTE(eddyb) there could be an impl for `usize`, which would enable a more
 // generic `LazyValue<T>` impl, but in the general case we might not need / want
 // to fit every `usize` in `u32`.