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

Use `rustc_type_ir` directly less in the codebase

cc #138449

This is a somewhat opinionated bundle of changes that will make working on #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

Author: bors

Cargo.lock

@@ -3440,7 +3440,6 @@ dependencies = [
  "rustc_symbol_mangling",
  "rustc_target",
  "rustc_trait_selection",
- "rustc_type_ir",
  "serde_json",
  "smallvec",
  "tempfile",
@@ -3473,7 +3472,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_trait_selection",
- "rustc_type_ir",
  "tracing",
 ]
 
@@ -3736,7 +3734,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_trait_selection",
- "rustc_type_ir",
  "smallvec",
  "tracing",
 ]
@@ -3775,7 +3772,6 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_trait_selection",
- "rustc_type_ir",
  "smallvec",
  "tracing",
 ]
@@ -3922,7 +3918,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_trait_selection",
- "rustc_type_ir",
  "smallvec",
  "tracing",
  "unicode-security",
@@ -3998,7 +3993,6 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_target",
- "rustc_type_ir",
  "tempfile",
  "tracing",
 ]
@@ -4114,7 +4108,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_trait_selection",
- "rustc_type_ir",
  "smallvec",
  "tracing",
 ]
@@ -4538,7 +4531,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_trait_selection",
- "rustc_type_ir",
  "tracing",
 ]
 

compiler/rustc_abi/src/lib.rs

@@ -52,7 +52,7 @@ use rustc_data_structures::stable_hasher::StableOrd;
 use rustc_hashes::Hash64;
 use rustc_index::{Idx, IndexSlice, IndexVec};
 #[cfg(feature = "nightly")]
-use rustc_macros::{Decodable_Generic, Encodable_Generic, HashStable_Generic};
+use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_Generic};
 
 mod callconv;
 mod layout;
@@ -74,7 +74,10 @@ pub use layout::{LayoutCalculator, LayoutCalculatorError};
 pub trait HashStableContext {}
 
 #[derive(Clone, Copy, PartialEq, Eq, Default)]
-#[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_Generic)
+)]
 pub struct ReprFlags(u8);
 
 bitflags! {
@@ -106,7 +109,10 @@ impl std::fmt::Debug for ReprFlags {
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
-#[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_Generic)
+)]
 pub enum IntegerType {
     /// Pointer-sized integer type, i.e. `isize` and `usize`. The field shows signedness, e.g.
     /// `Pointer(true)` means `isize`.
@@ -127,7 +133,10 @@ impl IntegerType {
 
 /// Represents the repr options provided by the user.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
-#[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_Generic)
+)]
 pub struct ReprOptions {
     pub int: Option<IntegerType>,
     pub align: Option<Align>,
@@ -487,7 +496,10 @@ impl FromStr for Endian {
 
 /// Size of a type in bytes.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_Generic)
+)]
 pub struct Size {
     raw: u64,
 }
@@ -713,7 +725,10 @@ impl Step for Size {
 
 /// Alignment of a type in bytes (always a power of two).
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_Generic)
+)]
 pub struct Align {
     pow2: u8,
 }
@@ -872,7 +887,10 @@ impl AbiAndPrefAlign {
 
 /// Integers, also used for enum discriminants.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
-#[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_Generic)
+)]
 pub enum Integer {
     I8,
     I16,