diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index f25631e028eec..487f3b76fc75f 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -359,9 +359,12 @@ impl fmt::Display for AllocErr {
     }
 }
 
-/// The `CannotReallocInPlace` error is used when `grow_in_place` or
-/// `shrink_in_place` were unable to reuse the given memory block for
+/// The `CannotReallocInPlace` error is used when [`grow_in_place`] or
+/// [`shrink_in_place`] were unable to reuse the given memory block for
 /// a requested layout.
+///
+/// [`grow_in_place`]: ./trait.Alloc.html#method.grow_in_place
+/// [`shrink_in_place`]: ./trait.Alloc.html#method.shrink_in_place
 #[unstable(feature = "allocator_api", issue = "32838")]
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct CannotReallocInPlace;
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index beafddc5a1019..f74e945b3cc1b 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -290,7 +290,7 @@ impl<T:Copy> Clone for Cell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T:Default> Default for Cell<T> {
+impl<T: Default> Default for Cell<T> {
     /// Creates a `Cell<T>`, with the `Default` value for T.
     #[inline]
     fn default() -> Cell<T> {
@@ -299,7 +299,7 @@ impl<T:Default> Default for Cell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T:PartialEq + Copy> PartialEq for Cell<T> {
+impl<T: PartialEq + Copy> PartialEq for Cell<T> {
     #[inline]
     fn eq(&self, other: &Cell<T>) -> bool {
         self.get() == other.get()
@@ -307,10 +307,10 @@ impl<T:PartialEq + Copy> PartialEq for Cell<T> {
 }
 
 #[stable(feature = "cell_eq", since = "1.2.0")]
-impl<T:Eq + Copy> Eq for Cell<T> {}
+impl<T: Eq + Copy> Eq for Cell<T> {}
 
 #[stable(feature = "cell_ord", since = "1.10.0")]
-impl<T:PartialOrd + Copy> PartialOrd for Cell<T> {
+impl<T: PartialOrd + Copy> PartialOrd for Cell<T> {
     #[inline]
     fn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering> {
         self.get().partial_cmp(&other.get())
@@ -338,7 +338,7 @@ impl<T:PartialOrd + Copy> PartialOrd for Cell<T> {
 }
 
 #[stable(feature = "cell_ord", since = "1.10.0")]
-impl<T:Ord + Copy> Ord for Cell<T> {
+impl<T: Ord + Copy> Ord for Cell<T> {
     #[inline]
     fn cmp(&self, other: &Cell<T>) -> Ordering {
         self.get().cmp(&other.get())
@@ -1008,7 +1008,7 @@ impl<T: Clone> Clone for RefCell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T:Default> Default for RefCell<T> {
+impl<T: Default> Default for RefCell<T> {
     /// Creates a `RefCell<T>`, with the `Default` value for T.
     #[inline]
     fn default() -> RefCell<T> {
diff --git a/src/libcore/ffi.rs b/src/libcore/ffi.rs
index 4f87cc506efae..eda0e7c518c58 100644
--- a/src/libcore/ffi.rs
+++ b/src/libcore/ffi.rs
@@ -60,7 +60,10 @@ impl fmt::Debug for c_void {
 #[lang = "va_list"]
 pub struct VaListImpl<'f> {
     ptr: *mut c_void,
-    _marker: PhantomData<&'f c_void>,
+
+    // Invariant over `'f`, so each `VaListImpl<'f>` object is tied to
+    // the region of the function it's defined in
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
@@ -96,7 +99,7 @@ pub struct VaListImpl<'f> {
     vr_top: *mut c_void,
     gr_offs: i32,
     vr_offs: i32,
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 /// PowerPC ABI implementation of a `va_list`.
@@ -114,7 +117,7 @@ pub struct VaListImpl<'f> {
     reserved: u16,
     overflow_arg_area: *mut c_void,
     reg_save_area: *mut c_void,
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 /// x86_64 ABI implementation of a `va_list`.
@@ -131,7 +134,7 @@ pub struct VaListImpl<'f> {
     fp_offset: i32,
     overflow_arg_area: *mut c_void,
     reg_save_area: *mut c_void,
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 /// asm.js ABI implementation of a `va_list`.
@@ -148,7 +151,7 @@ pub struct VaListImpl<'f> {
 #[lang = "va_list"]
 pub struct VaListImpl<'f> {
     inner: [crate::mem::MaybeUninit<i32>; 4],
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 #[cfg(all(target_arch = "asmjs", not(windows)))]
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 193cdb15b548d..0b3ef41891b5f 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -291,6 +291,8 @@ impl<T> Option<T> {
 
 
     /// Converts from [`Pin`]`<&Option<T>>` to `Option<`[`Pin`]`<&T>>`.
+    ///
+    /// [`Pin`]: ../pin/struct.Pin.html
     #[inline]
     #[stable(feature = "pin", since = "1.33.0")]
     pub fn as_pin_ref<'a>(self: Pin<&'a Option<T>>) -> Option<Pin<&'a T>> {
@@ -300,6 +302,8 @@ impl<T> Option<T> {
     }
 
     /// Converts from [`Pin`]`<&mut Option<T>>` to `Option<`[`Pin`]`<&mut T>>`.
+    ///
+    /// [`Pin`]: ../pin/struct.Pin.html
     #[inline]
     #[stable(feature = "pin", since = "1.33.0")]
     pub fn as_pin_mut<'a>(self: Pin<&'a mut Option<T>>) -> Option<Pin<&'a mut T>> {
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index c7c5849a00fa0..54e1c876f4caa 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -32,7 +32,7 @@ use crate::sys_common::{AsInner, IntoInner, FromInner};
 /// in each pair are owned strings; the latter are borrowed
 /// references.
 ///
-/// Note, `OsString` and `OsStr` internally do not necessarily hold strings in
+/// Note, `OsString` and [`OsStr`] internally do not necessarily hold strings in
 /// the form native to the platform; While on Unix, strings are stored as a
 /// sequence of 8-bit values, on Windows, where strings are 16-bit value based
 /// as just discussed, strings are also actually stored as a sequence of 8-bit
@@ -667,10 +667,11 @@ impl From<&OsStr> for Box<OsStr> {
 
 #[stable(feature = "os_string_from_box", since = "1.18.0")]
 impl From<Box<OsStr>> for OsString {
-    /// Converts a `Box<OsStr>` into a `OsString` without copying or allocating.
+    /// Converts a [`Box`]`<`[`OsStr`]`>` into a `OsString` without copying or
+    /// allocating.
     ///
     /// [`Box`]: ../boxed/struct.Box.html
-    /// [`OsString`]: ../ffi/struct.OsString.html
+    /// [`OsStr`]: ../ffi/struct.OsStr.html
     fn from(boxed: Box<OsStr>) -> OsString {
         boxed.into_os_string()
     }
diff --git a/src/test/ui/c-variadic/variadic-ffi-4.rs b/src/test/ui/c-variadic/variadic-ffi-4.rs
index 07c32ecbfc2dc..4a50d352a5b20 100644
--- a/src/test/ui/c-variadic/variadic-ffi-4.rs
+++ b/src/test/ui/c-variadic/variadic-ffi-4.rs
@@ -18,6 +18,7 @@ pub unsafe extern "C" fn no_escape2(_: usize, ap: ...) {
 
 pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
     *ap0 = ap1; //~ ERROR: mismatched types
+    //~^ ERROR: mismatched types
 }
 
 pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
@@ -29,5 +30,6 @@ pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...
 }
 
 pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
-    *ap0 = ap1.clone(); //~ ERROR: cannot infer an appropriate lifetime
+    *ap0 = ap1.clone(); //~ ERROR: mismatched types
+    //~^ ERROR: mismatched types
 }
diff --git a/src/test/ui/c-variadic/variadic-ffi-4.stderr b/src/test/ui/c-variadic/variadic-ffi-4.stderr
index 72d4d8b63445a..7aa510e611304 100644
--- a/src/test/ui/c-variadic/variadic-ffi-4.stderr
+++ b/src/test/ui/c-variadic/variadic-ffi-4.stderr
@@ -52,6 +52,7 @@ note: the anonymous lifetime #3 defined on the function body at 19:1...
    |
 LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     *ap0 = ap1;
+LL | |
 LL | | }
    | |_^
 note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 19:1
@@ -59,17 +60,43 @@ note: ...does not necessarily outlive the anonymous lifetime #2 defined on the f
    |
 LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     *ap0 = ap1;
+LL | |
+LL | | }
+   | |_^
+
+error[E0308]: mismatched types
+  --> $DIR/variadic-ffi-4.rs:20:12
+   |
+LL |     *ap0 = ap1;
+   |            ^^^ lifetime mismatch
+   |
+   = note: expected type `core::ffi::VaListImpl<'_>`
+              found type `core::ffi::VaListImpl<'_>`
+note: the anonymous lifetime #2 defined on the function body at 19:1...
+  --> $DIR/variadic-ffi-4.rs:19:1
+   |
+LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+LL | |     *ap0 = ap1;
+LL | |
+LL | | }
+   | |_^
+note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 19:1
+  --> $DIR/variadic-ffi-4.rs:19:1
+   |
+LL | / pub unsafe extern "C" fn no_escape3(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+LL | |     *ap0 = ap1;
+LL | |
 LL | | }
    | |_^
 
 error[E0490]: a value of type `core::ffi::VaListImpl<'_>` is borrowed for too long
-  --> $DIR/variadic-ffi-4.rs:24:11
+  --> $DIR/variadic-ffi-4.rs:25:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
    |
-note: the type is valid for the anonymous lifetime #1 defined on the function body at 23:1
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: the type is valid for the anonymous lifetime #1 defined on the function body at 24:1
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -79,8 +106,8 @@ LL | |
 LL | |
 LL | | }
    | |_^
-note: but the borrow lasts for the anonymous lifetime #3 defined on the function body at 23:1
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: but the borrow lasts for the anonymous lifetime #3 defined on the function body at 24:1
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -92,15 +119,15 @@ LL | | }
    | |_^
 
 error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:24:11
+  --> $DIR/variadic-ffi-4.rs:25:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^ lifetime mismatch
    |
    = note: expected type `&mut core::ffi::VaListImpl<'_>`
               found type `&mut core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #3 defined on the function body at 23:1...
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: the anonymous lifetime #3 defined on the function body at 24:1...
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -110,8 +137,8 @@ LL | |
 LL | |
 LL | | }
    | |_^
-note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 23:1
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 24:1
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -123,15 +150,15 @@ LL | | }
    | |_^
 
 error[E0308]: mismatched types
-  --> $DIR/variadic-ffi-4.rs:24:11
+  --> $DIR/variadic-ffi-4.rs:25:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^ lifetime mismatch
    |
    = note: expected type `&mut core::ffi::VaListImpl<'_>`
               found type `&mut core::ffi::VaListImpl<'_>`
-note: the anonymous lifetime #2 defined on the function body at 23:1...
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: the anonymous lifetime #2 defined on the function body at 24:1...
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -141,8 +168,8 @@ LL | |
 LL | |
 LL | | }
    | |_^
-note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 23:1
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 24:1
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -154,13 +181,13 @@ LL | | }
    | |_^
 
 error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements
-  --> $DIR/variadic-ffi-4.rs:24:11
+  --> $DIR/variadic-ffi-4.rs:25:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
    |
-note: first, the lifetime cannot outlive the anonymous lifetime #3 defined on the function body at 23:1...
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: first, the lifetime cannot outlive the anonymous lifetime #3 defined on the function body at 24:1...
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -171,12 +198,12 @@ LL | |
 LL | | }
    | |_^
 note: ...so that the type `core::ffi::VaListImpl<'_>` is not borrowed for too long
-  --> $DIR/variadic-ffi-4.rs:24:11
+  --> $DIR/variadic-ffi-4.rs:25:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
-note: but, the lifetime must be valid for the anonymous lifetime #1 defined on the function body at 23:1...
-  --> $DIR/variadic-ffi-4.rs:23:1
+note: but, the lifetime must be valid for the anonymous lifetime #1 defined on the function body at 24:1...
+  --> $DIR/variadic-ffi-4.rs:24:1
    |
 LL | / pub unsafe extern "C" fn no_escape4(_: usize, ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     ap0 = &mut ap1;
@@ -187,39 +214,62 @@ LL | |
 LL | | }
    | |_^
 note: ...so that reference does not outlive borrowed content
-  --> $DIR/variadic-ffi-4.rs:24:11
+  --> $DIR/variadic-ffi-4.rs:25:11
    |
 LL |     ap0 = &mut ap1;
    |           ^^^^^^^^
 
-error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
-  --> $DIR/variadic-ffi-4.rs:32:16
+error[E0308]: mismatched types
+  --> $DIR/variadic-ffi-4.rs:33:12
    |
 LL |     *ap0 = ap1.clone();
-   |                ^^^^^
+   |            ^^^^^^^^^^^ lifetime mismatch
    |
-note: first, the lifetime cannot outlive the anonymous lifetime #3 defined on the function body at 31:1...
-  --> $DIR/variadic-ffi-4.rs:31:1
+   = note: expected type `core::ffi::VaListImpl<'_>`
+              found type `core::ffi::VaListImpl<'_>`
+note: the anonymous lifetime #3 defined on the function body at 32:1...
+  --> $DIR/variadic-ffi-4.rs:32:1
    |
 LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     *ap0 = ap1.clone();
+LL | |
 LL | | }
    | |_^
-   = note: ...so that the types are compatible:
-           expected &core::ffi::VaListImpl<'_>
-              found &core::ffi::VaListImpl<'_>
-note: but, the lifetime must be valid for the anonymous lifetime #2 defined on the function body at 31:1...
-  --> $DIR/variadic-ffi-4.rs:31:1
+note: ...does not necessarily outlive the anonymous lifetime #2 defined on the function body at 32:1
+  --> $DIR/variadic-ffi-4.rs:32:1
    |
 LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
 LL | |     *ap0 = ap1.clone();
+LL | |
+LL | | }
+   | |_^
+
+error[E0308]: mismatched types
+  --> $DIR/variadic-ffi-4.rs:33:12
+   |
+LL |     *ap0 = ap1.clone();
+   |            ^^^^^^^^^^^ lifetime mismatch
+   |
+   = note: expected type `core::ffi::VaListImpl<'_>`
+              found type `core::ffi::VaListImpl<'_>`
+note: the anonymous lifetime #2 defined on the function body at 32:1...
+  --> $DIR/variadic-ffi-4.rs:32:1
+   |
+LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+LL | |     *ap0 = ap1.clone();
+LL | |
+LL | | }
+   | |_^
+note: ...does not necessarily outlive the anonymous lifetime #3 defined on the function body at 32:1
+  --> $DIR/variadic-ffi-4.rs:32:1
+   |
+LL | / pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
+LL | |     *ap0 = ap1.clone();
+LL | |
 LL | | }
    | |_^
-   = note: ...so that the expression is assignable:
-           expected core::ffi::VaListImpl<'_>
-              found core::ffi::VaListImpl<'_>
 
-error: aborting due to 9 previous errors
+error: aborting due to 11 previous errors
 
 Some errors have detailed explanations: E0308, E0621.
 For more information about an error, try `rustc --explain E0308`.