When we normalize the types in a function signature, we may end up
resolving a projection to an opaque type (e.g. `Self::MyType` when
we have `type MyType = impl SomeTrait`). When the projection is
resolved, we will instantiate the generic parameters into fresh
inference variables.

While we do want to normalize projections to opaque types, we don't want
to replace the explicit generic parameters (e.g. `T` in `impl
MyTrait<T>`) with inference variables. We want the opaque type in the
function signature to be eligible to be a defining use of that opaque
type - adding inference variables prevents this, since the opaque type
substs now appears to refer to some specific type, rather than a generic
type.

To resolve this issue, we inspect the opaque types in the function
signature after normalization. Any inference variables in the substs are
replaced with the corresponding generic parameter in the identity substs
(e.g. `T` in `impl MyTrait<T>`). Note that normalization is the only way
that we can end up with inference variables in opaque substs in a
function signature - users have no way of getting inference variables
into a function signature.

Note that all of this refers to the opaque type (ty::Opaque) and its
subst - *not* to the underlying type.

Fixes #59342

Rework raw ident suggestions

Use heuristics to determine whethersuggesting raw identifiers is
appropriate.

Account for raw identifiers when printing a path in a `use` suggestion.

Fix #66126.

introduce benchmarks of HashSet operations

To avoid goofs such as corrected by #66280, I added benchmarks of binary HashSet operations.

Due to the fact x.py keeps recompiling the whole shebang (or at least a big part of it) whenever you touch the test code, and because piling up all tests in one file does not strike me as future proof, I tried moving the hash benches to the separate place they are for liballoc/collections/btree. But it turns out that, in a cleaned checkout, x.py still recompiles the whole shebang whenever you touch the test code (PS or when you add or delete any irrelevant file). So I'm not going to add more tests, and I doubt others will, and these tests have proven their point already, so this PR is kind of pointless

Stabilize Result::map_or_else

Stabilized this API:
```rust
impl<T, E> Result<T, E> {
    pub fn map_or_else<U, D: FnOnce(E) -> U, F: FnOnce(T) -> U>(self, default: D, f: F) -> U {
        match self {
            Ok(t) => f(t),
            Err(e) => default(e),
        }
    }
}
```

Closes #53268
r? @SimonSapin

Rollup of 5 pull requests

Successful merges:

 - #64856 (Scope format! temporaries)
 - #66411 (mem::forget docs: mention ManuallyDrop)
 - #66594 (Fix cycle when debug-printing opaque types)
 - #66641 (parser: recover on nested ADTs as enum variants)
 - #66659 (make `./x.py bench` again)

Failed merges:

r? @ghost

make `./x.py bench` again

Fixes #54016

parser: recover on nested ADTs as enum variants

Closes: https://github.com/rust-lang/rust/issues/66127

Fix cycle when debug-printing opaque types

Fixes #61577

When printing an opaque type in non-verbose mode, we use the
`tcx.predicates_of` query to retrieve the opaque type's bounds for
pretty-printing. However, the pervasiveness of logging within librustc
means that we may already be executing `tcx.predicates_of` for the
opaque type we're trying to print, leading to a cycle error.

This commit adds a new 'no queries' thread-local flag to the pretty
printer. This flag is enabled during the computation of `predicates_of`
for opaque types, and causes us to print the opaque type in 'verbose'
mode (which does not require computing any additinal queries). This
should only affect debug logging for highly nested log messages, not any
user-visible output.

mem::forget docs: mention ManuallyDrop

Cc @SimonSapin @Centril

Scope format! temporaries

This places the temporaries that `format!` generates to refer to its arguments (through `&dyn Trait`) in a short-lived scope surrounding just the invocation of `format!`. This enables `format!` to be used in generators without the temporaries preventing the generator from being `Send` (due to `dyn Trait` not being `Sync`).

See rust-lang/rust#64477 for details.

Use heuristics to determine whethersuggesting raw identifiers is
appropriate.

Account for raw identifiers when printing a path in a `use` suggestion.

Rollup of 5 pull requests

Successful merges:

 - #61351 (Stabilize cfg(doc))
 - #66539 (Point at type in `let` assignment on type errors)
 - #66655 (rustdoc: Mark `--extern-private` as unstable)
 - #66657 (rustdoc: Don't panic when failing to write .lock file)
 - #66673 (Move def collector from `rustc` to `rustc_resolve`)

Failed merges:

r? @ghost

Move def collector from `rustc` to `rustc_resolve`

It's used only from `rustc_resolve`, so we can move it there, thus reducing the size of `rustc` (https://github.com/rust-lang/rust/issues/65031).

It's quite possible that we can merge the def collector pass into the "build reduced graph" pass (they are always run together and do similar things), but it's some larger work.

r? @EddyB

rustdoc: Don't panic when failing to write .lock file

It can be treated like any other unexpected IO error.

I couldn't think of a good way to add a test for this unfortunately.

r? @GuillaumeGomez

rustdoc: Mark `--extern-private` as unstable

It's not even stable in rustc so it shouldn't be stable in rustdoc.

r? @kinnison

Point at type in `let` assignment on type errors

Fix #61067.

Stabilize cfg(doc)

cc #43781.

Update Clippy

r? @Manishearth @oli-obk

docs: fix lint name for `unused_variables`

debuginfo:  Support for std::collections::Hash* in windows debuggers.

Okay, I finally needed to debug code involving a HashMap!  Added support for HashSet s as well.

r? @michaelwoerister

### Local Testing

Verified these are passing locally:
```cmd
:: cmd.exe
python x.py test --stage 1 --build x86_64-pc-windows-msvc src/test/debuginfo
python x.py test --stage 1 --build i686-pc-windows-msvc src/test/debuginfo
python x.py test --stage 1 src/tools/tidy

:: MinGW MSYS2
./x.py test --stage 1 --build x86_64-pc-windows-gnu src/test/debuginfo
```

### Related Issues

* https://github.com/rust-lang/rust/issues/36503
* https://github.com/rust-lang/rust/issues/40460
* https://github.com/rust-gamedev/wg/issues/20

Rollup of 4 pull requests

Successful merges:

 - #65961 (add fn type_name_of_val)
 - #66574 (Update tidy check for error codes testing)
 - #66576 (made gdb pretty-printing more robust when printing uninitialized vec)
 - #66583 (Clarify Step Documentation)

Failed merges:

r? @ghost

It can be treated like any other unexpected IO error.

Clarify Step Documentation

While the redesign is in progress (#62886), clarify the purpose of replace_zero and replace_one.

First, "returning itself" is technically impossible due to the function signature of &mut self -> Self. A clone or copy operation must be used. So this is now explicitly stated in the documentation.

Second, the added docs give some guidance about the actual contract around implementation of replace_zero and replace one. Specifically, the only usage is to create a range with no more steps, by setting start to replace_one and end to replace_zero. So the only property that is actually used is `replace_one > replace_zero`. See https://github.com/rust-lang/rust/issues/42168#issuecomment-489554232

The new documentation does not say that is the *only* contract, and so it should not be considered an api change. It just highlights the most important detail for implementors.

The redesign doesn't seem to be landing any time soon, so this is a stopgap measure to reduce confusion in the meantime.

made gdb pretty-printing more robust when printing uninitialized vec

made gdb pretty-printing more robust when printing uninitialized vec

I based this solution on my reading of:

https://rethinkdb.com/blog/make-debugging-easier-with-custom-pretty-printers#what-is-still-to-be-done

That post claims that there is no clean way to check for garbage pointers, and
so this PR adopts the same solution of tentatively attempting to convert a
dererence to a string, which throws a clean exception on garbage that we can
catch and recover from.

I only made the change to vec and not the other pretty printers because I wanted
to focus my effort on the simplest thing that would resolve issue #64343. In
particular, I *considered* generalizing this fix to work on the other datatypes
in the pretty-printing support library, but I don't want to invest effort in
that until after we resolve our overall debugging support strategy; see also
issues #60826 and #65564.

Fix #64343

Update tidy check for error codes testing

Now that all the error codes have been grouped into one file, we moved the long error explanations into markdown files, which means that we need to read those markdown file to also count their code blocks as well.

So 2 "big" things happened here:
* No more need to keep the current error code when reading the `error_codes.rs` file since it's been put into the equivalent markdown file.
* Need to instead read the markdown file (but it's simpler since I can just look for code blocks directly).

add fn type_name_of_val

This function is often useful during testing and mirrors `align_of_val` and `size_of_val`.

# Example

Showing the default type of integers.

```rust
let x = 7;
println!("per default, integers have the type: {}", std::any::type_name_of_val(&x));
```

To my knowledge this can currently not be done without defining a function similar to `type_name_of_val`.

Enable `if` and `match` in constants behind a feature flag

This PR is an initial implementation of #49146. It introduces a `const_if_match` feature flag and does the following if it is enabled:
- Allows `Downcast` projections, `SwitchInt` terminators and `FakeRead`s for matched places through the MIR const-checker.
- Allows `if` and `match` expressions through the HIR const-checker.
- Stops converting `&&` to `&` and `||` to `|` in `const` and `static` items.

As a result, the following operations are now allowed in a const context behind the feature flag:
- `if` and `match`
- short circuiting logic operators (`&&` and `||`)
- the `assert` and `debug_assert` macros (if the `const_panic` feature flag is also enabled)

However, the following operations remain forbidden:
- `while`, `loop` and `for` (see #52000)
- the `?` operator (calls `From::from` on its error variant)
- the `assert_eq` and `assert_ne` macros, along with their `debug` variants (calls `fmt::Debug`)

This PR is possible now that we use dataflow for const qualification (see #64470 and #66385).

r? @oli-obk
cc @rust-lang/wg-const-eval @EddyB

It's not even stable in rustc so it shouldn't be stable in rustdoc.

Rollup of 8 pull requests

Successful merges:

 - #66183 (*Syntactically* permit visibilities on trait items & enum variants)
 - #66566 (Document pitfall with `impl PartialEq<B> for A`)
 - #66575 (Remove pretty printing of specific nodes in AST)
 - #66587 (Handle statics in MIR as const pointers)
 - #66619 (follow the convention in this file to use third-person singular verbs)
 - #66633 (Error code's long explanation cleanup)
 - #66637 (fix reoccuring typo: dereferencable -> dereferenceable)
 - #66639 (resolve: more declarative `fresh_binding`)

Failed merges:

r? @ghost

resolve: more declarative `fresh_binding`

Following up on https://github.com/rust-lang/rust/pull/64111, this PR redefines `fresh_binding` wrt. `already_bound_and` and `already_bound_or` in a more declarative and simplified fashion.

cc #54883

r? @petrochenkov