Auto merge of #125116 - blyxyas:ignore-allowed-lints-final, r=cjgillot

(Big performance change) Do not run lints that cannot emit

Before this change, adding a lint was a difficult matter because it always had some overhead involved. This was because all lints would run, no matter their default level, or if the user had `#![allow]`ed them. This PR changes that. This change would improve both the Rust lint infrastructure and Clippy, but Clippy will see the most benefit, as it has about 900 registered lints (and growing!)

So yeah, with this little patch we filter all lints pre-linting, and remove any lint that is either:
- Manually `#![allow]`ed in the whole crate,
- Allowed in the command line, or
- Not manually enabled with `#[warn]` or similar, and its default level is `Allow`

As some lints **need** to run, this PR also adds **loadbearing lints**. On a lint declaration, you can use the ``@eval_always` = true` marker to label it as loadbearing. A loadbearing lint will never be filtered (it will always run)

Fixes #106983

1 files changed, 6 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 94bdb913528..d7a60a843b7 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -29,6 +29,7 @@ use rustc_hir::def_id::{
 use rustc_hir::lang_items::{LangItem, LanguageItems};
 use rustc_hir::{Crate, ItemLocalId, ItemLocalMap, TraitCandidate};
 use rustc_index::IndexVec;
+use rustc_lint_defs::LintId;
 use rustc_macros::rustc_queries;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_query_system::query::{QueryCache, QueryMode, QueryState, try_get_cached};
@@ -422,6 +423,11 @@ rustc_queries! {
         desc { "computing `#[expect]`ed lints in this crate" }
     }
 
+    query lints_that_dont_need_to_run(_: ()) -> &'tcx FxIndexSet<LintId> {
+        arena_cache
+        desc { "Computing all lints that are explicitly enabled or with a default level greater than Allow" }
+    }
+
     query expn_that_defined(key: DefId) -> rustc_span::ExpnId {
         desc { |tcx| "getting the expansion that defined `{}`", tcx.def_path_str(key) }
         separate_provide_extern