Rollup merge of rust-lang#68045 - Centril:liberate-lints, r=Mark-Simu…

…lacrum

Move more of `rustc::lint` into `rustc_lint`

Based on rust-lang#67806.

Here we try to consolidate more of the linting infra into `rustc::lint`. Some high-level notes:

- We now store an `Lrc<dyn Any + Send + Sync>` as opposed to `Lrc<LintStore>` in the `GlobalCtxt`. This enables us to avoid referring to the type, breaking a cyclic dependency, and so we can move things from `rustc::lint` to `rustc_lint`.

- `in_derive_expansion` is, and needs to, be moved as a method on `Span`.

- We reduce the number of ways on `tcx` to emit a lint so that the developer UX is more streamlined.

- `LintLevelsBuilder` is moved to `rustc_lint::levels`, leaving behind `LintLevelMap/Set` in a purified form due to current constraints (hopefully fixable in the future after rust-lang#68133).

- `struct_lint_level` is moved to `rustc::lint` due to current dependency constraints.

- `rustc::context` is moved to `rustc_lint::context`.

- The visitors in `rustc::lint` are moved to `rustc_lint::passes`.

Cargo.lock

@@ -3654,6 +3654,7 @@ dependencies = [
  "log",
  "rustc",
  "rustc_data_structures",
+ "rustc_error_codes",
  "rustc_errors",
  "rustc_feature",
  "rustc_hir",
@@ -3779,6 +3780,7 @@ dependencies = [
  "rustc_error_codes",
  "rustc_errors",
  "rustc_hir",
+ "rustc_lint",
  "rustc_metadata",
  "rustc_span",
  "syntax",

src/librustc/hir/check_attr.rs

@@ -5,7 +5,6 @@
 //! item.
 
 use crate::hir::map::Map;
-use crate::lint::builtin::UNUSED_ATTRIBUTES;
 use crate::ty::query::Providers;
 use crate::ty::TyCtxt;
 
@@ -16,6 +15,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc_hir::DUMMY_HIR_ID;
 use rustc_hir::{self, HirId, Item, ItemKind, TraitItem, TraitItemKind};
+use rustc_session::lint::builtin::UNUSED_ATTRIBUTES;
 use rustc_span::symbol::sym;
 use rustc_span::Span;
 use syntax::ast::Attribute;

src/librustc/lib.rs

@@ -71,8 +71,6 @@ extern crate rustc_data_structures;
 #[macro_use]
 extern crate log;
 #[macro_use]
-extern crate syntax;
-#[macro_use]
 extern crate smallvec;
 
 #[cfg(test)]