diff --git a/src/doc/unstable-book/src/library-features/proc-macro.md b/src/doc/unstable-book/src/library-features/proc-macro.md
deleted file mode 100644
index 19e7f663c7ac3..0000000000000
--- a/src/doc/unstable-book/src/library-features/proc-macro.md
+++ /dev/null
@@ -1,7 +0,0 @@
-# `proc_macro`
-
-The tracking issue for this feature is: [#38356]
-
-[#38356]: https://github.com/rust-lang/rust/issues/38356
-
-------------------------
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index 93d7e66b7b203..301e44632b823 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -715,7 +715,7 @@ impl<T> Vec<T> {
     ///
     /// # Panics
     ///
-    /// Panics if `index` is out of bounds.
+    /// Panics if `index > len`.
     ///
     /// # Examples
     ///
diff --git a/src/libcore/slice/memchr.rs b/src/libcore/slice/memchr.rs
index 00183be97e751..69c9cb37dcfd3 100644
--- a/src/libcore/slice/memchr.rs
+++ b/src/libcore/slice/memchr.rs
@@ -56,7 +56,7 @@ fn repeat_byte(b: u8) -> usize {
     rep
 }
 
-/// Return the first index matching the byte `a` in `text`.
+/// Return the first index matching the byte `x` in `text`.
 pub fn memchr(x: u8, text: &[u8]) -> Option<usize> {
     // Scan for a single byte value by reading two `usize` words at a time.
     //
@@ -101,7 +101,7 @@ pub fn memchr(x: u8, text: &[u8]) -> Option<usize> {
     text[offset..].iter().position(|elt| *elt == x).map(|i| offset + i)
 }
 
-/// Return the last index matching the byte `a` in `text`.
+/// Return the last index matching the byte `x` in `text`.
 pub fn memrchr(x: u8, text: &[u8]) -> Option<usize> {
     // Scan for a single byte value by reading two `usize` words at a time.
     //
diff --git a/src/librustc/mir/README.md b/src/librustc/mir/README.md
index fb0c7ce1df23d..cac86be0fcb75 100644
--- a/src/librustc/mir/README.md
+++ b/src/librustc/mir/README.md
@@ -59,7 +59,7 @@ ensure that, before the MIR at a particular phase in the processing
 pipeline is stolen, anyone who may want to read from it has already
 done so. Concretely, this means that if you have some query `foo(D)`
 that wants to access the result of `mir_const(D)` or
-`mir_validated(D)`, you need to have the successor pass either "force"
+`mir_validated(D)`, you need to have the successor pass "force"
 `foo(D)` using `ty::queries::foo::force(...)`. This will force a query
 to execute even though you don't directly require its result.
 
diff --git a/src/tools/tidy/src/unstable_book.rs b/src/tools/tidy/src/unstable_book.rs
index ff032b14ad1d5..a4a35a706fd91 100644
--- a/src/tools/tidy/src/unstable_book.rs
+++ b/src/tools/tidy/src/unstable_book.rs
@@ -87,7 +87,9 @@ pub fn check(path: &path::Path, bad: &mut bool) {
     // Library features
 
     let lang_features = collect_lang_features(path);
-    let lib_features = collect_lib_features(path);
+    let lib_features = collect_lib_features(path).into_iter().filter(|&(ref name, _)| {
+        !lang_features.contains_key(name)
+    }).collect();
 
     let unstable_lib_feature_names = collect_unstable_feature_names(&lib_features);
     let unstable_book_lib_features_section_file_names =
diff --git a/src/tools/unstable-book-gen/src/main.rs b/src/tools/unstable-book-gen/src/main.rs
index 5c2bd1e3e087d..f66a18547c3b5 100644
--- a/src/tools/unstable-book-gen/src/main.rs
+++ b/src/tools/unstable-book-gen/src/main.rs
@@ -129,7 +129,9 @@ fn main() {
     let dest_path = Path::new(&dest_path_str).join("src");
 
     let lang_features = collect_lang_features(src_path);
-    let lib_features = collect_lib_features(src_path);
+    let lib_features = collect_lib_features(src_path).into_iter().filter(|&(ref name, _)| {
+        !lang_features.contains_key(name)
+    }).collect();
 
     let doc_src_path = src_path.join(PATH_STR);