Show all Deref implementations recursively

src/librustdoc/html/render/context.rs

@@ -6,7 +6,7 @@ use std::rc::Rc;
 use std::sync::mpsc::{channel, Receiver};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_span::edition::Edition;
@@ -54,6 +54,9 @@ crate struct Context<'tcx> {
     /// real location of an item. This is used to allow external links to
     /// publicly reused items to redirect to the right location.
     pub(super) render_redirect_pages: bool,
+    /// Tracks section IDs for `Deref` targets so they match in both the main
+    /// body and the sidebar.
+    pub(super) deref_id_map: RefCell<FxHashMap<DefId, String>>,
     /// The map used to ensure all generated 'id=' attributes are unique.
     pub(super) id_map: RefCell<IdMap>,
     /// Shared mutable state.
@@ -70,7 +73,7 @@ crate struct Context<'tcx> {
 
 // `Context` is cloned a lot, so we don't want the size to grow unexpectedly.
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Context<'_>, 104);
+rustc_data_structures::static_assert_size!(Context<'_>, 144);
 
 /// Shared mutable state used in [`Context`] and elsewhere.
 crate struct SharedContext<'tcx> {
@@ -513,6 +516,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             dst,
             render_redirect_pages: false,
             id_map: RefCell::new(id_map),
+            deref_id_map: RefCell::new(FxHashMap::default()),
             shared: Rc::new(scx),
             include_sources,
         };
@@ -536,6 +540,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             current: self.current.clone(),
             dst: self.dst.clone(),
             render_redirect_pages: self.render_redirect_pages,
+            deref_id_map: RefCell::new(FxHashMap::default()),
             id_map: RefCell::new(IdMap::new()),
             shared: Rc::clone(&self.shared),
             include_sources: self.include_sources,

src/librustdoc/html/render/mod.rs

@@ -1053,6 +1053,19 @@ fn render_assoc_items(
     containing_item: &clean::Item,
     it: DefId,
     what: AssocItemRender<'_>,
+) {
+    let mut derefs = FxHashSet::default();
+    derefs.insert(it);
+    render_assoc_items_inner(w, cx, containing_item, it, what, &mut derefs)
+}
+
+fn render_assoc_items_inner(
+    w: &mut Buffer,
+    cx: &Context<'_>,
+    containing_item: &clean::Item,
+    it: DefId,
+    what: AssocItemRender<'_>,
+    derefs: &mut FxHashSet<DefId>,
 ) {
     info!("Documenting associated items of {:?}", containing_item.name);
     let cache = cx.cache();
@@ -1062,31 +1075,39 @@ fn render_assoc_items(
     };
     let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
     if !non_trait.is_empty() {
+        let mut tmp_buf = Buffer::empty_from(w);
         let render_mode = match what {
             AssocItemRender::All => {
-                w.write_str(
+                tmp_buf.write_str(
                     "<h2 id=\"implementations\" class=\"small-section-header\">\
                          Implementations<a href=\"#implementations\" class=\"anchor\"></a>\
                     </h2>",
                 );
                 RenderMode::Normal
             }
             AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
+                let id =
+                    cx.derive_id(small_url_encode(format!("deref-methods-{:#}", type_.print(cx))));
+                if let Some(def_id) = type_.def_id(cx.cache()) {
+                    cx.deref_id_map.borrow_mut().insert(def_id, id.clone());
+                }
                 write!(
-                    w,
-                    "<h2 id=\"deref-methods\" class=\"small-section-header\">\
+                    tmp_buf,
+                    "<h2 id=\"{id}\" class=\"small-section-header\">\
                          <span>Methods from {trait_}&lt;Target = {type_}&gt;</span>\
-                         <a href=\"#deref-methods\" class=\"anchor\"></a>\
+                         <a href=\"#{id}\" class=\"anchor\"></a>\
                      </h2>",
+                    id = id,
                     trait_ = trait_.print(cx),
                     type_ = type_.print(cx),
                 );
                 RenderMode::ForDeref { mut_: deref_mut_ }
             }
         };
+        let mut impls_buf = Buffer::empty_from(w);
         for i in &non_trait {
             render_impl(
-                w,
+                &mut impls_buf,
                 cx,
                 i,
                 containing_item,
@@ -1103,18 +1124,27 @@ fn render_assoc_items(
                 },
             );
         }
+        if !impls_buf.is_empty() {
+            w.push_buffer(tmp_buf);
+            w.push_buffer(impls_buf);
+        }
     }
-    if let AssocItemRender::DerefFor { .. } = what {
-        return;
-    }
+
     if !traits.is_empty() {
         let deref_impl =
             traits.iter().find(|t| t.trait_did() == cx.tcx().lang_items().deref_trait());
         if let Some(impl_) = deref_impl {
             let has_deref_mut =
                 traits.iter().any(|t| t.trait_did() == cx.tcx().lang_items().deref_mut_trait());
-            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut);
+            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut, derefs);
+        }
+
+        // If we were already one level into rendering deref methods, we don't want to render
+        // anything after recursing into any further deref methods above.
+        if let AssocItemRender::DerefFor { .. } = what {
+            return;
         }
+
         let (synthetic, concrete): (Vec<&&Impl>, Vec<&&Impl>) =
             traits.iter().partition(|t| t.inner_impl().synthetic);
         let (blanket_impl, concrete): (Vec<&&Impl>, _) =
@@ -1166,6 +1196,7 @@ fn render_deref_methods(
     impl_: &Impl,
     container_item: &clean::Item,
     deref_mut: bool,
+    derefs: &mut FxHashSet<DefId>,
 ) {
     let cache = cx.cache();
     let deref_type = impl_.inner_impl().trait_.as_ref().unwrap();
@@ -1187,16 +1218,16 @@ fn render_deref_methods(
     if let Some(did) = target.def_id(cache) {
         if let Some(type_did) = impl_.inner_impl().for_.def_id(cache) {
             // `impl Deref<Target = S> for S`
-            if did == type_did {
+            if did == type_did || !derefs.insert(did) {
                 // Avoid infinite cycles
                 return;
             }
         }
-        render_assoc_items(w, cx, container_item, did, what);
+        render_assoc_items_inner(w, cx, container_item, did, what, derefs);
     } else {
         if let Some(prim) = target.primitive_type() {
             if let Some(&did) = cache.primitive_locations.get(&prim) {
-                render_assoc_items(w, cx, container_item, did, what);
+                render_assoc_items_inner(w, cx, container_item, did, what, derefs);
             }
         }
     }
@@ -1986,7 +2017,9 @@ fn sidebar_assoc_items(cx: &Context<'_>, out: &mut Buffer, it: &clean::Item) {
             if let Some(impl_) =
                 v.iter().find(|i| i.trait_did() == cx.tcx().lang_items().deref_trait())
             {
-                sidebar_deref_methods(cx, out, impl_, v);
+                let mut derefs = FxHashSet::default();
+                derefs.insert(did);
+                sidebar_deref_methods(cx, out, impl_, v, &mut derefs);
             }
 
             let format_impls = |impls: Vec<&Impl>| {
@@ -2060,7 +2093,13 @@ fn sidebar_assoc_items(cx: &Context<'_>, out: &mut Buffer, it: &clean::Item) {
     }
 }
 
-fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &[Impl]) {
+fn sidebar_deref_methods(
+    cx: &Context<'_>,
+    out: &mut Buffer,
+    impl_: &Impl,
+    v: &[Impl],
+    derefs: &mut FxHashSet<DefId>,
+) {
     let c = cx.cache();
 
     debug!("found Deref: {:?}", impl_);
@@ -2077,7 +2116,7 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &[
         if let Some(did) = target.def_id(c) {
             if let Some(type_did) = impl_.inner_impl().for_.def_id(c) {
                 // `impl Deref<Target = S> for S`
-                if did == type_did {
+                if did == type_did || !derefs.insert(did) {
                     // Avoid infinite cycles
                     return;
                 }
@@ -2101,9 +2140,17 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &[
                 })
                 .collect::<Vec<_>>();
             if !ret.is_empty() {
+                let map;
+                let id = if let Some(target_def_id) = real_target.def_id(c) {
+                    map = cx.deref_id_map.borrow();
+                    map.get(&target_def_id).expect("Deref section without derived id")
+                } else {
+                    "deref-methods"
+                };
                 write!(
                     out,
-                    "<h3 class=\"sidebar-title\"><a href=\"#deref-methods\">Methods from {}&lt;Target={}&gt;</a></h3>",
+                    "<h3 class=\"sidebar-title\"><a href=\"#{}\">Methods from {}&lt;Target={}&gt;</a></h3>",
+                    id,
                     Escape(&format!("{:#}", impl_.inner_impl().trait_.as_ref().unwrap().print(cx))),
                     Escape(&format!("{:#}", real_target.print(cx))),
                 );
@@ -2116,6 +2163,21 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &[
                 out.push_str("</div>");
             }
         }
+
+        // Recurse into any further impls that might exist for `target`
+        if let Some(target_did) = target.def_id_no_primitives() {
+            if let Some(target_impls) = c.impls.get(&target_did) {
+                if let Some(target_deref_impl) = target_impls.iter().find(|i| {
+                    i.inner_impl()
+                        .trait_
+                        .as_ref()
+                        .map(|t| Some(t.def_id()) == cx.tcx().lang_items().deref_trait())
+                        .unwrap_or(false)
+                }) {
+                    sidebar_deref_methods(cx, out, target_deref_impl, target_impls, derefs);
+                }
+            }
+        }
     }
 }
 

src/librustdoc/passes/collect_trait_impls.rs

@@ -3,7 +3,8 @@ use crate::clean::*;
 use crate::core::DocContext;
 use crate::fold::DocFolder;
 
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::DefId;
 use rustc_middle::ty::DefIdTree;
 use rustc_span::symbol::sym;
 
@@ -53,12 +54,35 @@ crate fn collect_trait_impls(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
     }
 
     let mut cleaner = BadImplStripper { prims, items: crate_items };
+    let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
+
+    // Follow all `Deref` targets of included items and recursively add them as valid
+    fn add_deref_target(
+        map: &FxHashMap<DefId, &Type>,
+        cleaner: &mut BadImplStripper,
+        type_did: DefId,
+    ) {
+        if let Some(target) = map.get(&type_did) {
+            debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
+            if let Some(target_prim) = target.primitive_type() {
+                cleaner.prims.insert(target_prim);
+            } else if let Some(target_did) = target.def_id_no_primitives() {
+                // `impl Deref<Target = S> for S`
+                if target_did == type_did {
+                    // Avoid infinite cycles
+                    return;
+                }
+                cleaner.items.insert(target_did.into());
+                add_deref_target(map, cleaner, target_did);
+            }
+        }
+    }
 
     // scan through included items ahead of time to splice in Deref targets to the "valid" sets
     for it in &new_items {
         if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
-            if cleaner.keep_impl(for_)
-                && trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
+            if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
+                && cleaner.keep_impl(for_, true)
             {
                 let target = items
                     .iter()
@@ -73,16 +97,26 @@ crate fn collect_trait_impls(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
                 } else if let Some(did) = target.def_id(&cx.cache) {
                     cleaner.items.insert(did.into());
                 }
+                if let Some(for_did) = for_.def_id_no_primitives() {
+                    if type_did_to_deref_target.insert(for_did, target).is_none() {
+                        // Since only the `DefId` portion of the `Type` instances is known to be same for both the
+                        // `Deref` target type and the impl for type positions, this map of types is keyed by
+                        // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
+                        if cleaner.keep_impl_with_def_id(for_did.into()) {
+                            add_deref_target(&type_did_to_deref_target, &mut cleaner, for_did);
+                        }
+                    }
+                }
             }
         }
     }
 
     new_items.retain(|it| {
         if let ImplItem(Impl { ref for_, ref trait_, ref blanket_impl, .. }) = *it.kind {
-            cleaner.keep_impl(for_)
-                || trait_
-                    .as_ref()
-                    .map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
+            cleaner.keep_impl(
+                for_,
+                trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
+            ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
                 || blanket_impl.is_some()
         } else {
             true
@@ -181,14 +215,14 @@ struct BadImplStripper {
 }
 
 impl BadImplStripper {
-    fn keep_impl(&self, ty: &Type) -> bool {
+    fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
         if let Generic(_) = ty {
             // keep impls made on generics
             true
         } else if let Some(prim) = ty.primitive_type() {
             self.prims.contains(&prim)
         } else if let Some(did) = ty.def_id_no_primitives() {
-            self.keep_impl_with_def_id(did.into())
+            is_deref || self.keep_impl_with_def_id(did.into())
         } else {
             false
         }

src/test/rustdoc-ui/recursive-deref-ice.rs

@@ -0,0 +1,19 @@
+// check-pass
+
+// ICE found in https://github.com/rust-lang/rust/issues/83123
+
+pub struct Attribute;
+
+pub struct Map<'hir> {}
+impl<'hir> Map<'hir> {
+    pub fn attrs(&self) -> &'hir [Attribute] { &[] }
+}
+
+pub struct List<T>(T);
+
+impl<T> std::ops::Deref for List<T> {
+    type Target = [T];
+    fn deref(&self) -> &[T] {
+        &[]
+    }
+}

src/test/rustdoc/deref-recursive-pathbuf.rs

@@ -0,0 +1,25 @@
+// #26207: Show all methods reachable via Deref impls, recursing through multiple dereferencing
+// levels and across multiple crates.
+// For `Deref` on non-foreign types, look at `deref-recursive.rs`.
+
+// @has 'foo/struct.Foo.html'
+// @has '-' '//*[@id="deref-methods-PathBuf"]' 'Methods from Deref<Target = PathBuf>'
+// @has '-' '//*[@class="impl-items"]//*[@id="method.as_path"]' 'pub fn as_path(&self)'
+// @has '-' '//*[@id="deref-methods-Path"]' 'Methods from Deref<Target = Path>'
+// @has '-' '//*[@class="impl-items"]//*[@id="method.exists"]' 'pub fn exists(&self)'
+// @has '-' '//*[@class="sidebar-title"]/a[@href="#deref-methods-PathBuf"]' 'Methods from Deref<Target=PathBuf>'
+// @has '-' '//*[@class="sidebar-links"]/a[@href="#method.as_path"]' 'as_path'
+// @has '-' '//*[@class="sidebar-title"]/a[@href="#deref-methods-Path"]' 'Methods from Deref<Target=Path>'
+// @has '-' '//*[@class="sidebar-links"]/a[@href="#method.exists"]' 'exists'
+
+#![crate_name = "foo"]
+
+use std::ops::Deref;
+use std::path::PathBuf;
+
+pub struct Foo(PathBuf);
+
+impl Deref for Foo {
+    type Target = PathBuf;
+    fn deref(&self) -> &PathBuf { &self.0 }
+}