Implement Clean<Crate> on hir::Crate directly

Author: Mark-Simulacrum

src/librustdoc/clean/mod.rs

@@ -137,13 +137,15 @@ pub struct Crate {
     pub masked_crates: FxHashSet<CrateNum>,
 }
 
-// The `()` here is rather ugly and would be great to remove. Unfortunately, we
-// already have a different Clean impl for `doctree::Module` which makes this
-// the only way to easily disambiguate.
-impl<'tcx> Clean<Crate> for ((), doctree::Module<'tcx>) {
+impl Clean<Crate> for hir::Crate {
+    // note that self here is ignored in favor of `cx.tcx.hir().krate()` since
+    // that gets around tying self's lifetime to the '_ in cx.
     fn clean(&self, cx: &DocContext<'_>) -> Crate {
         use crate::visit_lib::LibEmbargoVisitor;
 
+        let v = crate::visit_ast::RustdocVisitor::new(&cx);
+        let module = v.visit(cx.tcx.hir().krate());
+
         {
             let mut r = cx.renderinfo.borrow_mut();
             r.deref_trait_did = cx.tcx.lang_items().deref_trait();
@@ -161,7 +163,7 @@ impl<'tcx> Clean<Crate> for ((), doctree::Module<'tcx>) {
 
         // Clean the crate, translating the entire libsyntax AST to one that is
         // understood by rustdoc.
-        let mut module = self.1.clean(cx);
+        let mut module = module.clean(cx);
         let mut masked_crates = FxHashSet::default();
 
         match module.inner {

src/librustdoc/core.rs

@@ -30,7 +30,6 @@ use rustc_data_structures::sync::{self, Lrc};
 use std::sync::Arc;
 use std::rc::Rc;
 
-use crate::visit_ast::RustdocVisitor;
 use crate::config::{Options as RustdocOptions, RenderOptions};
 use crate::clean;
 use crate::clean::{Clean, MAX_DEF_ID, AttributesExt};
@@ -392,11 +391,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
             };
             debug!("crate: {:?}", tcx.hir().krate());
 
-            let mut krate = {
-                let v = RustdocVisitor::new(&ctxt);
-                let module = v.visit(tcx.hir().krate());
-                ((), module).clean(&ctxt)
-            };
+            let mut krate = tcx.hir().krate().clean(&ctxt);
 
             fn report_deprecated_attr(name: &str, diag: &errors::Handler) {
                 let mut msg = diag.struct_warn(&format!("the `#![doc({})]` attribute is \