rustdoc: Index inherent methods on primitives

The set of types which can have an inherent impl changed slightly and rustdoc
just needed to catch up to understand what it means to see a `impl str`!

Closes #23511

src/librustdoc/clean/mod.rs

@@ -1428,6 +1428,21 @@ pub enum TypeKind {
     TypeTypedef,
 }
 
+impl Type {
+    pub fn primitive_type(&self) -> Option<PrimitiveType> {
+        match *self {
+            Primitive(p) | BorrowedRef { type_: box Primitive(p), ..} => Some(p),
+            Vector(..) | BorrowedRef{ type_: box Vector(..), ..  } => Some(Slice),
+            FixedVector(..) | BorrowedRef { type_: box FixedVector(..), .. } => {
+                Some(Array)
+            }
+            Tuple(..) => Some(PrimitiveTuple),
+            RawPointer(..) => Some(PrimitiveRawPointer),
+            _ => None,
+        }
+    }
+}
+
 impl PrimitiveType {
     fn from_str(s: &str) -> Option<PrimitiveType> {
         match s {

src/librustdoc/html/render.rs

@@ -1025,7 +1025,16 @@ impl DocFolder for Cache {
                         self.parent_stack.push(did);
                         true
                     }
-                    _ => false
+                    ref t => {
+                        match t.primitive_type() {
+                            Some(prim) => {
+                                let did = ast_util::local_def(prim.to_node_id());
+                                self.parent_stack.push(did);
+                                true
+                            }
+                            _ => false,
+                        }
+                    }
                 }
             }
             _ => false
@@ -1037,11 +1046,6 @@ impl DocFolder for Cache {
             Some(item) => {
                 match item {
                     clean::Item{ attrs, inner: clean::ImplItem(i), .. } => {
-                        use clean::{Primitive, Vector, ResolvedPath, BorrowedRef};
-                        use clean::PrimitiveType::{Array, Slice, PrimitiveTuple};
-                        use clean::PrimitiveType::{PrimitiveRawPointer};
-                        use clean::{FixedVector, Tuple, RawPointer};
-
                         // extract relevant documentation for this impl
                         let dox = match attrs.into_iter().find(|a| {
                             match *a {
@@ -1059,47 +1063,18 @@ impl DocFolder for Cache {
                         // Figure out the id of this impl. This may map to a
                         // primitive rather than always to a struct/enum.
                         let did = match i.for_ {
-                            ResolvedPath { did, .. } |
-                            BorrowedRef {
-                                type_: box ResolvedPath { did, .. }, ..
+                            clean::ResolvedPath { did, .. } |
+                            clean::BorrowedRef {
+                                type_: box clean::ResolvedPath { did, .. }, ..
                             } => {
                                 Some(did)
                             }
 
-                            // References to primitives are picked up as well to
-                            // recognize implementations for &str, this may not
-                            // be necessary in a DST world.
-                            Primitive(p) |
-                                BorrowedRef { type_: box Primitive(p), ..} =>
-                            {
-                                Some(ast_util::local_def(p.to_node_id()))
+                            ref t => {
+                                t.primitive_type().map(|p| {
+                                    ast_util::local_def(p.to_node_id())
+                                })
                             }
-
-                            FixedVector(..) |
-                                BorrowedRef { type_: box FixedVector(..), .. } =>
-                            {
-                                Some(ast_util::local_def(Array.to_node_id()))
-                            }
-
-                            // In a DST world, we may only need Vector, but for
-                            // now we also pick up borrowed references
-                            Vector(..) |
-                                BorrowedRef{ type_: box Vector(..), ..  } =>
-                            {
-                                Some(ast_util::local_def(Slice.to_node_id()))
-                            }
-
-                            Tuple(..) => {
-                                let id = PrimitiveTuple.to_node_id();
-                                Some(ast_util::local_def(id))
-                            }
-
-                            RawPointer(..) => {
-                                let id = PrimitiveRawPointer.to_node_id();
-                                Some(ast_util::local_def(id))
-                            }
-
-                            _ => None,
                         };
 
                         if let Some(did) = did {

src/test/rustdoc/issue-23511.rs

@@ -0,0 +1,24 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(no_std, lang_items, core)]
+#![no_std]
+
+extern crate core;
+
+pub mod str {
+    #![doc(primitive = "str")]
+
+    #[lang = "str"]
+    impl str {
+        // @has search-index.js foo
+        pub fn foo(&self) {}
+    }
+}