Rename CLIPPY_CTFE->CTFE and use declare_tool_lint to declare it

Author: flip1995

clippy_lints/src/ctfe.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
+    }
+}