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

28 files changed, 71 insertions, 12 deletions

diff --git a/src/librustdoc/lint.rs b/src/librustdoc/lint.rs
index bdfdeeabc5a..2afb9e549d9 100644
--- a/src/librustdoc/lint.rs
+++ b/src/librustdoc/lint.rs
@@ -31,9 +31,9 @@ where
     allowed_lints.extend(lint_opts.iter().map(|(lint, _)| lint).cloned());
 
     let lints = || {
-        lint::builtin::HardwiredLints::get_lints()
+        lint::builtin::HardwiredLints::lint_vec()
             .into_iter()
-            .chain(rustc_lint::SoftLints::get_lints())
+            .chain(rustc_lint::SoftLints::lint_vec())
     };
 
     let lint_opts = lints()
diff --git a/src/tools/clippy/clippy_lints/src/cognitive_complexity.rs b/src/tools/clippy/clippy_lints/src/cognitive_complexity.rs
index 495d8ce3fa7..477435236a5 100644
--- a/src/tools/clippy/clippy_lints/src/cognitive_complexity.rs
+++ b/src/tools/clippy/clippy_lints/src/cognitive_complexity.rs
@@ -31,6 +31,7 @@ declare_clippy_lint! {
     pub COGNITIVE_COMPLEXITY,
     nursery,
     "functions that should be split up into multiple functions"
+    @eval_always = true
 }
 
 pub struct CognitiveComplexity {
diff --git a/src/tools/clippy/clippy_lints/src/ctfe.rs b/src/tools/clippy/clippy_lints/src/ctfe.rs
new file mode 100644
index 00000000000..2fe37a64db6
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/ctfe.rs
@@ -0,0 +1,40 @@
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::intravisit::FnKind;
+use rustc_hir::{Body, FnDecl};
+use rustc_lint::Level::Deny;
+use rustc_lint::{LateContext, LateLintPass, Lint};
+use rustc_session::declare_lint_pass;
+use rustc_span::Span;
+
+/// Ensures that Constant-time Function Evaluation is being done (specifically, MIR lint passes).
+/// As Clippy deactivates codegen, this lint ensures that CTFE (used in hard errors) is still ran.
+pub static CLIPPY_CTFE: &Lint = &Lint {
+    name: &"clippy::CLIPPY_CTFE",
+    default_level: Deny,
+    desc: "Ensure CTFE is being made",
+    edition_lint_opts: None,
+    report_in_external_macro: true,
+    future_incompatible: None,
+    is_externally_loaded: true,
+    crate_level_only: false,
+    eval_always: true,
+    ..Lint::default_fields_for_macro()
+};
+
+// No static CLIPPY_CTFE_INFO because we want this lint to be invisible
+
+declare_lint_pass! { ClippyCtfe => [CLIPPY_CTFE] }
+
+impl<'tcx> LateLintPass<'tcx> for ClippyCtfe {
+    fn check_fn(
+        &mut self,
+        cx: &LateContext<'_>,
+        _: FnKind<'tcx>,
+        _: &'tcx FnDecl<'tcx>,
+        _: &'tcx Body<'tcx>,
+        _: Span,
+        defid: LocalDefId,
+    ) {
+        cx.tcx.ensure().mir_drops_elaborated_and_const_checked(defid); // Lint
+    }
+}
diff --git a/src/tools/clippy/clippy_lints/src/declare_clippy_lint.rs b/src/tools/clippy/clippy_lints/src/declare_clippy_lint.rs
index b1e39c70baa..a785a9d377c 100644
--- a/src/tools/clippy/clippy_lints/src/declare_clippy_lint.rs
+++ b/src/tools/clippy/clippy_lints/src/declare_clippy_lint.rs
@@ -9,6 +9,7 @@ macro_rules! declare_clippy_lint {
         $desc:literal,
         $version_expr:expr,
         $version_lit:literal
+        $(, $eval_always: literal)?
     ) => {
         rustc_session::declare_tool_lint! {
             $(#[doc = $lit])*
@@ -17,6 +18,7 @@ macro_rules! declare_clippy_lint {
             $category,
             $desc,
             report_in_external_macro:true
+            $(, @eval_always = $eval_always)?
         }
 
         pub(crate) static ${concat($lint_name, _INFO)}: &'static crate::LintInfo = &crate::LintInfo {
@@ -33,11 +35,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         restriction,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Allow, crate::LintCategory::Restriction, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -46,12 +49,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         style,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Warn, crate::LintCategory::Style, $desc,
-            Some($version), $version
-
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -60,11 +63,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         correctness,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Deny, crate::LintCategory::Correctness, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
 
         }
     };
@@ -74,11 +78,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         perf,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Warn, crate::LintCategory::Perf, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -87,11 +92,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         complexity,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Warn, crate::LintCategory::Complexity, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -100,11 +106,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         suspicious,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Warn, crate::LintCategory::Suspicious, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -113,11 +120,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         nursery,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Allow, crate::LintCategory::Nursery, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -126,11 +134,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         pedantic,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Allow, crate::LintCategory::Pedantic, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
     (
@@ -139,11 +148,12 @@ macro_rules! declare_clippy_lint {
         pub $lint_name:ident,
         cargo,
         $desc:literal
+        $(@eval_always = $eval_always: literal)?
     ) => {
         declare_clippy_lint! {@
             $(#[doc = $lit])*
             pub $lint_name, Allow, crate::LintCategory::Cargo, $desc,
-            Some($version), $version
+            Some($version), $version $(, $eval_always)?
         }
     };
 
diff --git a/src/tools/clippy/clippy_lints/src/lib.rs b/src/tools/clippy/clippy_lints/src/lib.rs
index 6e29dde2211..14110539709 100644
--- a/src/tools/clippy/clippy_lints/src/lib.rs
+++ b/src/tools/clippy/clippy_lints/src/lib.rs
@@ -65,6 +65,7 @@ extern crate clippy_utils;
 #[cfg_attr(feature = "internal", allow(clippy::missing_clippy_version_attribute))]
 mod utils;
 
+pub mod ctfe; // Very important lint, do not remove (rust#125116)
 pub mod declared_lints;
 pub mod deprecated_lints;
 
@@ -605,6 +606,8 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
         });
     }
 
+    store.register_late_pass(|_| Box::new(ctfe::ClippyCtfe));
+
     store.register_late_pass(move |_| Box::new(operators::arithmetic_side_effects::ArithmeticSideEffects::new(conf)));
     store.register_late_pass(|_| Box::new(utils::dump_hir::DumpHir));
     store.register_late_pass(|_| Box::new(utils::author::Author));
diff --git a/src/tools/clippy/tests/ui/author.rs b/src/tools/clippy/tests/ui-internal/author.rs
index 0a1be356896..eb1f3e3f870 100644
--- a/src/tools/clippy/tests/ui/author.rs
+++ b/src/tools/clippy/tests/ui-internal/author.rs
@@ -1,3 +1,5 @@
+#![warn(clippy::author)]
+
 fn main() {
     #[clippy::author]
     let x: char = 0x45 as char;
diff --git a/src/tools/clippy/tests/ui/author.stdout b/src/tools/clippy/tests/ui-internal/author.stdout
index eed704e82fe..eed704e82fe 100644
--- a/src/tools/clippy/tests/ui/author.stdout
+++ b/src/tools/clippy/tests/ui-internal/author.stdout
diff --git a/src/tools/clippy/tests/ui/author/blocks.rs b/src/tools/clippy/tests/ui-internal/author/blocks.rs
index 164f7d0d9d6..164f7d0d9d6 100644
--- a/src/tools/clippy/tests/ui/author/blocks.rs
+++ b/src/tools/clippy/tests/ui-internal/author/blocks.rs
diff --git a/src/tools/clippy/tests/ui/author/blocks.stdout b/src/tools/clippy/tests/ui-internal/author/blocks.stdout
index 6bf48d5ba4e..6bf48d5ba4e 100644
--- a/src/tools/clippy/tests/ui/author/blocks.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/blocks.stdout
diff --git a/src/tools/clippy/tests/ui/author/call.rs b/src/tools/clippy/tests/ui-internal/author/call.rs
index e99c3c41dc4..e99c3c41dc4 100644
--- a/src/tools/clippy/tests/ui/author/call.rs
+++ b/src/tools/clippy/tests/ui-internal/author/call.rs
diff --git a/src/tools/clippy/tests/ui/author/call.stdout b/src/tools/clippy/tests/ui-internal/author/call.stdout
index 59d4da490fe..59d4da490fe 100644
--- a/src/tools/clippy/tests/ui/author/call.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/call.stdout
diff --git a/src/tools/clippy/tests/ui/author/if.rs b/src/tools/clippy/tests/ui-internal/author/if.rs
index 946088ab346..946088ab346 100644
--- a/src/tools/clippy/tests/ui/author/if.rs
+++ b/src/tools/clippy/tests/ui-internal/author/if.rs
diff --git a/src/tools/clippy/tests/ui/author/if.stdout b/src/tools/clippy/tests/ui-internal/author/if.stdout
index a85dcddd331..a85dcddd331 100644
--- a/src/tools/clippy/tests/ui/author/if.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/if.stdout
diff --git a/src/tools/clippy/tests/ui/author/issue_3849.rs b/src/tools/clippy/tests/ui-internal/author/issue_3849.rs
index 5f65746d71f..5f65746d71f 100644
--- a/src/tools/clippy/tests/ui/author/issue_3849.rs
+++ b/src/tools/clippy/tests/ui-internal/author/issue_3849.rs
diff --git a/src/tools/clippy/tests/ui/author/issue_3849.stdout b/src/tools/clippy/tests/ui-internal/author/issue_3849.stdout
index a5a8c0304ee..a5a8c0304ee 100644
--- a/src/tools/clippy/tests/ui/author/issue_3849.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/issue_3849.stdout
diff --git a/src/tools/clippy/tests/ui/author/loop.rs b/src/tools/clippy/tests/ui-internal/author/loop.rs
index ff5b6100117..ff5b6100117 100644
--- a/src/tools/clippy/tests/ui/author/loop.rs
+++ b/src/tools/clippy/tests/ui-internal/author/loop.rs
diff --git a/src/tools/clippy/tests/ui/author/loop.stdout b/src/tools/clippy/tests/ui-internal/author/loop.stdout
index 609d2491061..609d2491061 100644
--- a/src/tools/clippy/tests/ui/author/loop.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/loop.stdout
diff --git a/src/tools/clippy/tests/ui/author/macro_in_closure.rs b/src/tools/clippy/tests/ui-internal/author/macro_in_closure.rs
index 444e6a12165..444e6a12165 100644
--- a/src/tools/clippy/tests/ui/author/macro_in_closure.rs
+++ b/src/tools/clippy/tests/ui-internal/author/macro_in_closure.rs
diff --git a/src/tools/clippy/tests/ui/author/macro_in_closure.stdout b/src/tools/clippy/tests/ui-internal/author/macro_in_closure.stdout
index 66caf382d89..66caf382d89 100644
--- a/src/tools/clippy/tests/ui/author/macro_in_closure.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/macro_in_closure.stdout
diff --git a/src/tools/clippy/tests/ui/author/macro_in_loop.rs b/src/tools/clippy/tests/ui-internal/author/macro_in_loop.rs
index 8a520501f8d..8a520501f8d 100644
--- a/src/tools/clippy/tests/ui/author/macro_in_loop.rs
+++ b/src/tools/clippy/tests/ui-internal/author/macro_in_loop.rs
diff --git a/src/tools/clippy/tests/ui/author/macro_in_loop.stdout b/src/tools/clippy/tests/ui-internal/author/macro_in_loop.stdout
index 3f9be297c33..3f9be297c33 100644
--- a/src/tools/clippy/tests/ui/author/macro_in_loop.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/macro_in_loop.stdout
diff --git a/src/tools/clippy/tests/ui/author/matches.rs b/src/tools/clippy/tests/ui-internal/author/matches.rs
index 674e07ec2d3..674e07ec2d3 100644
--- a/src/tools/clippy/tests/ui/author/matches.rs
+++ b/src/tools/clippy/tests/ui-internal/author/matches.rs
diff --git a/src/tools/clippy/tests/ui/author/matches.stdout b/src/tools/clippy/tests/ui-internal/author/matches.stdout
index 91b3b6f6877..91b3b6f6877 100644
--- a/src/tools/clippy/tests/ui/author/matches.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/matches.stdout
diff --git a/src/tools/clippy/tests/ui/author/repeat.rs b/src/tools/clippy/tests/ui-internal/author/repeat.rs
index d8e9d589e68..d8e9d589e68 100644
--- a/src/tools/clippy/tests/ui/author/repeat.rs
+++ b/src/tools/clippy/tests/ui-internal/author/repeat.rs
diff --git a/src/tools/clippy/tests/ui/author/repeat.stdout b/src/tools/clippy/tests/ui-internal/author/repeat.stdout
index d9e3f864f12..d9e3f864f12 100644
--- a/src/tools/clippy/tests/ui/author/repeat.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/repeat.stdout
diff --git a/src/tools/clippy/tests/ui/author/struct.rs b/src/tools/clippy/tests/ui-internal/author/struct.rs
index a99bdfc1313..a99bdfc1313 100644
--- a/src/tools/clippy/tests/ui/author/struct.rs
+++ b/src/tools/clippy/tests/ui-internal/author/struct.rs
diff --git a/src/tools/clippy/tests/ui/author/struct.stdout b/src/tools/clippy/tests/ui-internal/author/struct.stdout
index 0b332d5e7d0..0b332d5e7d0 100644
--- a/src/tools/clippy/tests/ui/author/struct.stdout
+++ b/src/tools/clippy/tests/ui-internal/author/struct.stdout
diff --git a/src/tools/clippy/tests/ui/no_lints.rs b/src/tools/clippy/tests/ui/no_lints.rs
new file mode 100644
index 00000000000..a8467bb6ef7
--- /dev/null
+++ b/src/tools/clippy/tests/ui/no_lints.rs
@@ -0,0 +1,3 @@
+#![deny(clippy::all)]
+
+fn main() {}
\ No newline at end of file