Rename HIR `TypeBinding` to `AssocItemConstraint` and related cleanup
Rename `hir::TypeBinding` and `ast::AssocConstraint` to `AssocItemConstraint` and update all items and locals using the old terminology.
Motivation: The terminology *type binding* is extremely outdated. "Type bindings" not only include constraints on associated *types* but also on associated *constants* (feature `associated_const_equality`) and on RPITITs of associated *functions* (feature `return_type_notation`). Hence the word *item* in the new name. Furthermore, the word *binding* commonly refers to a mapping from a binder/identifier to a "value" for some definition of "value". Its use in "type binding" made sense when equality constraints (e.g., `AssocTy = Ty`) were the only kind of associated item constraint. Nowadays however, we also have *associated type bounds* (e.g., `AssocTy: Bound`) for which the term *binding* doesn't make sense.
---
Old terminology (HIR, rustdoc):
```
`TypeBinding`: (associated) type binding
├── `Constraint`: associated type bound
└── `Equality`: (associated) equality constraint (?)
├── `Ty`: (associated) type binding
└── `Const`: associated const equality (constraint)
```
Old terminology (AST, abbrev.):
```
`AssocConstraint`
├── `Bound`
└── `Equality`
├── `Ty`
└── `Const`
```
New terminology (AST, HIR, rustdoc):
```
`AssocItemConstraint`: associated item constraint
├── `Bound`: associated type bound
└── `Equality`: associated item equality constraint OR associated item binding (for short)
├── `Ty`: associated type equality constraint OR associated type binding (for short)
└── `Const`: associated const equality constraint OR associated const binding (for short)
```
r? compiler-errors
When these `Box<Generics>` types were introduced,
`Generics` was made with `Vec` and much larger.
Now that it's made with `ThinVec`, `Type` is bigger
and should be boxed instead.
rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI
Fixes#90435.
This hides `#[repr(transparent)]` when the non-1-ZST field the struct is "transparent" over is private.
CC `@RalfJung`
Tentatively nominating it for the release notes, feel free to remove the nomination.
`@rustbot` label needs-fcp relnotes A-rustdoc-ui
[rustdoc] Show enum discrimant if it is a C-like variant
Fixes https://github.com/rust-lang/rust/issues/101337.
We currently display values for associated constant items in traits:
And we also display constant values like [here](file:///home/imperio/rust/rust/build/x86_64-unknown-linux-gnu/doc/std/f32/consts/constant.E.html).
I think that for coherency, we should display values of C-like enum variants.
With this change, it looks like this:
As for the display of the constant value itself, I used what we already have to keep coherency.
We display the C-like variants value in the following scenario:
1. It is a C-like variant with a value set => all the time
2. It is a C-like variant without a value set: All other variants are C-like variants and at least one them has its value set.
Here is the result in code:
```rust
// Ax and Bx value will be displayed.
enum A {
Ax = 12,
Bx,
}
// Ax and Bx value will not be displayed
enum B {
Ax,
Bx,
}
// Bx value will not be displayed
enum C {
Ax(u32),
Bx,
}
// Bx value will not be displayed, Cx value will be displayed.
#[repr(u32)]
enum D {
Ax(u32),
Bx,
Cx = 12,
}
```
r? `@notriddle`
