Convert many impls of DocFolder to DocVisitor

Many of `DocFolder`'s impls didn't actually transform the syntax tree,
so they can be visitors instead.

src/librustdoc/passes/bare_urls.rs

@@ -1,8 +1,8 @@
 use super::Pass;
 use crate::clean::*;
 use crate::core::DocContext;
-use crate::fold::DocFolder;
 use crate::html::markdown::main_body_opts;
+use crate::visit::DocVisitor;
 use core::ops::Range;
 use pulldown_cmark::{Event, Parser, Tag};
 use regex::Regex;
@@ -53,16 +53,17 @@ impl<'a, 'tcx> BareUrlsLinter<'a, 'tcx> {
 }
 
 crate fn check_bare_urls(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
-    BareUrlsLinter { cx }.fold_crate(krate)
+    BareUrlsLinter { cx }.visit_crate(&krate);
+    krate
 }
 
-impl<'a, 'tcx> DocFolder for BareUrlsLinter<'a, 'tcx> {
-    fn fold_item(&mut self, item: Item) -> Option<Item> {
+impl<'a, 'tcx> DocVisitor for BareUrlsLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
         let hir_id = match DocContext::as_local_hir_id(self.cx.tcx, item.def_id) {
             Some(hir_id) => hir_id,
             None => {
                 // If non-local, no need to check anything.
-                return Some(self.fold_item_recur(item));
+                return;
             }
         };
         let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
@@ -106,6 +107,6 @@ impl<'a, 'tcx> DocFolder for BareUrlsLinter<'a, 'tcx> {
             }
         }
 
-        Some(self.fold_item_recur(item))
+        self.visit_item_recur(item)
     }
 }

src/librustdoc/passes/calculate_doc_coverage.rs

@@ -1,9 +1,9 @@
 use crate::clean;
 use crate::core::DocContext;
-use crate::fold::{self, DocFolder};
 use crate::html::markdown::{find_testable_code, ErrorCodes};
 use crate::passes::check_doc_test_visibility::{should_have_doc_example, Tests};
 use crate::passes::Pass;
+use crate::visit::DocVisitor;
 use rustc_hir as hir;
 use rustc_lint::builtin::MISSING_DOCS;
 use rustc_middle::lint::LintLevelSource;
@@ -23,7 +23,7 @@ crate const CALCULATE_DOC_COVERAGE: Pass = Pass {
 
 fn calculate_doc_coverage(krate: clean::Crate, ctx: &mut DocContext<'_>) -> clean::Crate {
     let mut calc = CoverageCalculator { items: Default::default(), ctx };
-    let krate = calc.fold_crate(krate);
+    calc.visit_crate(&krate);
 
     calc.print_results();
 
@@ -182,17 +182,18 @@ impl<'a, 'b> CoverageCalculator<'a, 'b> {
     }
 }
 
-impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
-    fn fold_item(&mut self, i: clean::Item) -> Option<clean::Item> {
+impl<'a, 'b> DocVisitor for CoverageCalculator<'a, 'b> {
+    fn visit_item(&mut self, i: &clean::Item) {
+        if !i.def_id.is_local() {
+            // non-local items are skipped because they can be out of the users control,
+            // especially in the case of trait impls, which rustdoc eagerly inlines
+            return;
+        }
+
         match *i.kind {
-            _ if !i.def_id.is_local() => {
-                // non-local items are skipped because they can be out of the users control,
-                // especially in the case of trait impls, which rustdoc eagerly inlines
-                return Some(i);
-            }
             clean::StrippedItem(..) => {
                 // don't count items in stripped modules
-                return Some(i);
+                return;
             }
             // docs on `use` and `extern crate` statements are not displayed, so they're not
             // worth counting
@@ -269,6 +270,6 @@ impl<'a, 'b> fold::DocFolder for CoverageCalculator<'a, 'b> {
             }
         }
 
-        Some(self.fold_item_recur(i))
+        self.visit_item_recur(i)
     }
 }

src/librustdoc/passes/check_code_block_syntax.rs

@@ -8,9 +8,9 @@ use rustc_span::{hygiene::AstPass, ExpnData, ExpnKind, FileName, InnerSpan, DUMM
 
 use crate::clean;
 use crate::core::DocContext;
-use crate::fold::DocFolder;
 use crate::html::markdown::{self, RustCodeBlock};
 use crate::passes::Pass;
+use crate::visit::DocVisitor;
 
 crate const CHECK_CODE_BLOCK_SYNTAX: Pass = Pass {
     name: "check-code-block-syntax",
@@ -19,7 +19,8 @@ crate const CHECK_CODE_BLOCK_SYNTAX: Pass = Pass {
 };
 
 crate fn check_code_block_syntax(krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
-    SyntaxChecker { cx }.fold_crate(krate)
+    SyntaxChecker { cx }.visit_crate(&krate);
+    krate
 }
 
 struct SyntaxChecker<'a, 'tcx> {
@@ -141,8 +142,8 @@ impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> DocFolder for SyntaxChecker<'a, 'tcx> {
-    fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
+impl<'a, 'tcx> DocVisitor for SyntaxChecker<'a, 'tcx> {
+    fn visit_item(&mut self, item: &clean::Item) {
         if let Some(dox) = &item.attrs.collapsed_doc_value() {
             let sp = item.attr_span(self.cx.tcx);
             let extra = crate::html::markdown::ExtraInfo::new_did(
@@ -155,7 +156,7 @@ impl<'a, 'tcx> DocFolder for SyntaxChecker<'a, 'tcx> {
             }
         }
 
-        Some(self.fold_item_recur(item))
+        self.visit_item_recur(item)
     }
 }
 

src/librustdoc/passes/check_doc_test_visibility.rs

@@ -7,8 +7,8 @@ use super::Pass;
 use crate::clean;
 use crate::clean::*;
 use crate::core::DocContext;
-use crate::fold::DocFolder;
 use crate::html::markdown::{find_testable_code, ErrorCodes, Ignore, LangString};
+use crate::visit::DocVisitor;
 use crate::visit_ast::inherits_doc_hidden;
 use rustc_hir as hir;
 use rustc_middle::lint::LintLevelSource;
@@ -27,17 +27,17 @@ struct DocTestVisibilityLinter<'a, 'tcx> {
 
 crate fn check_doc_test_visibility(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
     let mut coll = DocTestVisibilityLinter { cx };
-
-    coll.fold_crate(krate)
+    coll.visit_crate(&krate);
+    krate
 }
 
-impl<'a, 'tcx> DocFolder for DocTestVisibilityLinter<'a, 'tcx> {
-    fn fold_item(&mut self, item: Item) -> Option<Item> {
+impl<'a, 'tcx> DocVisitor for DocTestVisibilityLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
         let dox = item.attrs.collapsed_doc_value().unwrap_or_else(String::new);
 
         look_for_tests(self.cx, &dox, &item);
 
-        Some(self.fold_item_recur(item))
+        self.visit_item_recur(item)
     }
 }
 

src/librustdoc/passes/html_tags.rs

@@ -1,8 +1,8 @@
 use super::Pass;
 use crate::clean::*;
 use crate::core::DocContext;
-use crate::fold::DocFolder;
 use crate::html::markdown::main_body_opts;
+use crate::visit::DocVisitor;
 use core::ops::Range;
 use pulldown_cmark::{Event, Parser, Tag};
 use std::iter::Peekable;
@@ -19,13 +19,11 @@ struct InvalidHtmlTagsLinter<'a, 'tcx> {
 }
 
 crate fn check_invalid_html_tags(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
-    if !cx.tcx.sess.is_nightly_build() {
-        krate
-    } else {
+    if cx.tcx.sess.is_nightly_build() {
         let mut coll = InvalidHtmlTagsLinter { cx };
-
-        coll.fold_crate(krate)
+        coll.visit_crate(&krate);
     }
+    krate
 }
 
 const ALLOWED_UNCLOSED: &[&str] = &[
@@ -165,14 +163,14 @@ fn extract_tags(
     }
 }
 
-impl<'a, 'tcx> DocFolder for InvalidHtmlTagsLinter<'a, 'tcx> {
-    fn fold_item(&mut self, item: Item) -> Option<Item> {
+impl<'a, 'tcx> DocVisitor for InvalidHtmlTagsLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
         let tcx = self.cx.tcx;
         let hir_id = match DocContext::as_local_hir_id(tcx, item.def_id) {
             Some(hir_id) => hir_id,
             None => {
                 // If non-local, no need to check anything.
-                return Some(self.fold_item_recur(item));
+                return;
             }
         };
         let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
@@ -217,6 +215,6 @@ impl<'a, 'tcx> DocFolder for InvalidHtmlTagsLinter<'a, 'tcx> {
             }
         }
 
-        Some(self.fold_item_recur(item))
+        self.visit_item_recur(item)
     }
 }