Auto merge of #138464 - compiler-errors:less-type-ir, r=lcnr

Use `rustc_type_ir` directly less in the codebase

cc https://github.com/rust-lang/rust/issues/138449

This is a somewhat opinionated bundle of changes that will make working on https://github.com/rust-lang/rust/issues/138449 more easy, since it cuts out the bulk of the changes that would be necessitated by the lint. Namely:

1. Fold `rustc_middle::ty::fold` and `rustc_middle::ty::visit` into `rustc_middle::ty`. This is because we already reexport some parts of these modules into `rustc_middle::ty`, and there's really no benefit from namespacing away the rest of these modules's functionality given how important folding and visiting is to the type layer.
2. Rename `{Decodable,Encodable}_Generic` to `{Decodable,Encodable}_NoContext`[^why], change it to be "perfect derive" (`synstructure::AddBounds::Fields`), use it throughout `rustc_type_ir` instead of `TyEncodable`/`TyDecodable`.
3. Make `TyEncodable` and `TyDecodable` derives use `::rustc_middle::ty::codec::TyEncoder` (etc) for its generated paths, and move the `rustc_type_ir::codec` module back to `rustc_middle::ty::codec` :tada:.
4. Stop using `rustc_type_ir` in crates that aren't "fundamental" to the type system, namely middle/infer/trait-selection. This amounted mostly to changing imports from `use rustc_type_ir::...` to `use rustc_middle::ty::...`, but also this means that we can't glob import `TyKind::*` since the reexport into `rustc_middle::ty::TyKind` is a type alias. Instead, use the prefixed variants like `ty::Str` everywhere -- IMO this is a good change, since it makes it more regularized with most of the rest of the compiler.

[^why]: `_NoContext` is the name for derive macros with no additional generic bounds and which do "perfect derive" by generating bounds based on field types. See `HashStable_NoContext`.

I'm happy to cut out some of these changes into separate PRs to make landing it a bit easier, though I don't expect to have much trouble with bitrot.

r? lcnr

1 files changed, 7 insertions, 7 deletions

diff --git a/compiler/rustc_serialize/tests/opaque.rs b/compiler/rustc_serialize/tests/opaque.rs
index 0543e176ae5..5aeedbdcd4e 100644
--- a/compiler/rustc_serialize/tests/opaque.rs
+++ b/compiler/rustc_serialize/tests/opaque.rs
@@ -3,11 +3,11 @@
 use std::fmt::Debug;
 use std::fs;
 
-use rustc_macros::{Decodable_Generic, Encodable_Generic};
+use rustc_macros::{Decodable_NoContext, Encodable_NoContext};
 use rustc_serialize::opaque::{FileEncoder, MemDecoder};
 use rustc_serialize::{Decodable, Encodable};
 
-#[derive(PartialEq, Clone, Debug, Encodable_Generic, Decodable_Generic)]
+#[derive(PartialEq, Clone, Debug, Encodable_NoContext, Decodable_NoContext)]
 struct Struct {
     a: (),
     b: u8,
@@ -210,7 +210,7 @@ fn test_struct() {
     }]);
 }
 
-#[derive(PartialEq, Clone, Debug, Encodable_Generic, Decodable_Generic)]
+#[derive(PartialEq, Clone, Debug, Encodable_NoContext, Decodable_NoContext)]
 enum Enum {
     Variant1,
     Variant2(usize, u32),
@@ -259,7 +259,7 @@ fn test_tuples() {
 
 #[test]
 fn test_unit_like_struct() {
-    #[derive(Encodable_Generic, Decodable_Generic, PartialEq, Debug)]
+    #[derive(Encodable_NoContext, Decodable_NoContext, PartialEq, Debug)]
     struct UnitLikeStruct;
 
     check_round_trip(vec![UnitLikeStruct]);
@@ -267,7 +267,7 @@ fn test_unit_like_struct() {
 
 #[test]
 fn test_box() {
-    #[derive(Encodable_Generic, Decodable_Generic, PartialEq, Debug)]
+    #[derive(Encodable_NoContext, Decodable_NoContext, PartialEq, Debug)]
     struct A {
         foo: Box<[bool]>,
     }
@@ -280,12 +280,12 @@ fn test_box() {
 fn test_cell() {
     use std::cell::{Cell, RefCell};
 
-    #[derive(Encodable_Generic, Decodable_Generic, PartialEq, Debug)]
+    #[derive(Encodable_NoContext, Decodable_NoContext, PartialEq, Debug)]
     struct A {
         baz: isize,
     }
 
-    #[derive(Encodable_Generic, Decodable_Generic, PartialEq, Debug)]
+    #[derive(Encodable_NoContext, Decodable_NoContext, PartialEq, Debug)]
     struct B {
         foo: Cell<bool>,
         bar: RefCell<A>,