Rename rustc_serialize::opaque::Encoder as MemEncoder.

This avoids the name clash with `rustc_serialize::Encoder` (a trait),
and allows lots qualifiers to be removed and imports to be simplified
(e.g. fewer `as` imports).

(This was previously merged as commit 5 in #94732 and then was reverted
in #97905 because of a perf regression caused by commit 4 in #94732.)

compiler/rustc_middle/src/mir/graph_cyclic_cache.rs

@@ -3,7 +3,7 @@ use rustc_data_structures::graph::{
 };
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::OnceCell;
-use rustc_serialize as serialize;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 
 /// Helper type to cache the result of `graph::is_cyclic`.
 #[derive(Clone, Debug)]
@@ -36,17 +36,17 @@ impl GraphIsCyclicCache {
     }
 }
 
-impl<S: serialize::Encoder> serialize::Encodable<S> for GraphIsCyclicCache {
+impl<S: Encoder> Encodable<S> for GraphIsCyclicCache {
     #[inline]
     fn encode(&self, s: &mut S) {
-        serialize::Encodable::encode(&(), s);
+        Encodable::encode(&(), s);
     }
 }
 
-impl<D: serialize::Decoder> serialize::Decodable<D> for GraphIsCyclicCache {
+impl<D: Decoder> Decodable<D> for GraphIsCyclicCache {
     #[inline]
     fn decode(d: &mut D) -> Self {
-        let () = serialize::Decodable::decode(d);
+        let () = Decodable::decode(d);
         Self::new()
     }
 }

compiler/rustc_middle/src/mir/predecessors.rs

@@ -3,7 +3,7 @@
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::OnceCell;
 use rustc_index::vec::IndexVec;
-use rustc_serialize as serialize;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use smallvec::SmallVec;
 
 use crate::mir::{BasicBlock, BasicBlockData};
@@ -54,12 +54,12 @@ impl PredecessorCache {
     }
 }
 
-impl<S: serialize::Encoder> serialize::Encodable<S> for PredecessorCache {
+impl<S: Encoder> Encodable<S> for PredecessorCache {
     #[inline]
     fn encode(&self, _s: &mut S) {}
 }
 
-impl<D: serialize::Decoder> serialize::Decodable<D> for PredecessorCache {
+impl<D: Decoder> Decodable<D> for PredecessorCache {
     #[inline]
     fn decode(_: &mut D) -> Self {
         Self::new()

compiler/rustc_middle/src/mir/switch_sources.rs

@@ -5,7 +5,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::stable_map::FxHashMap;
 use rustc_data_structures::sync::OnceCell;
 use rustc_index::vec::IndexVec;
-use rustc_serialize as serialize;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use smallvec::SmallVec;
 
 use crate::mir::{BasicBlock, BasicBlockData, Terminator, TerminatorKind};
@@ -54,12 +54,12 @@ impl SwitchSourceCache {
     }
 }
 
-impl<S: serialize::Encoder> serialize::Encodable<S> for SwitchSourceCache {
+impl<S: Encoder> Encodable<S> for SwitchSourceCache {
     #[inline]
     fn encode(&self, _s: &mut S) {}
 }
 
-impl<D: serialize::Decoder> serialize::Decodable<D> for SwitchSourceCache {
+impl<D: Decoder> Decodable<D> for SwitchSourceCache {
     #[inline]
     fn decode(_: &mut D) -> Self {
         Self::new()

compiler/rustc_middle/src/mir/traversal.rs

@@ -1,7 +1,7 @@
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::OnceCell;
 use rustc_index::bit_set::BitSet;
-use rustc_serialize as serialize;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 
 use super::*;
 
@@ -365,12 +365,12 @@ impl PostorderCache {
     }
 }
 
-impl<S: serialize::Encoder> serialize::Encodable<S> for PostorderCache {
+impl<S: Encoder> Encodable<S> for PostorderCache {
     #[inline]
     fn encode(&self, _s: &mut S) {}
 }
 
-impl<D: serialize::Decoder> serialize::Decodable<D> for PostorderCache {
+impl<D: Decoder> Decodable<D> for PostorderCache {
     #[inline]
     fn decode(_: &mut D) -> Self {
         Self::new()