Rename CLIPPY_CTFE->CTFE and use declare_tool_lint to declare it

Author: flip1995

clippy_lints/src/ctfe.rs

@@ -65,7 +65,6 @@ 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;
 
@@ -607,7 +606,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
         store.register_late_pass(|_| Box::new(utils::internal_lints::slow_symbol_comparisons::SlowSymbolComparisons));
     }
 
-    store.register_late_pass(|_| Box::new(ctfe::ClippyCtfe));
+    store.register_late_pass(|_| Box::new(utils::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));

clippy_lints/src/lib.rs

@@ -0,0 +1,34 @@
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::intravisit::FnKind;
+use rustc_hir::{Body, FnDecl};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::Span;
+
+// Not using `declare_clippy_lint`, so that no static CLIPPY_CTFE_INFO is created, so this lint
+// doesn't show up in the documentation.
+declare_tool_lint! {
+    /// 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 clippy::CTFE,
+    Allow,
+    "Ensure CTFE is being made",
+    report_in_external_macro: true,
+    @eval_always = true
+}
+
+declare_lint_pass! { ClippyCtfe => [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
+    }
+}

clippy_lints/src/utils/ctfe.rs

@@ -1,4 +1,5 @@
 pub mod author;
+pub mod ctfe;
 pub mod dump_hir;
 pub mod format_args_collector;
 #[cfg(feature = "internal")]