diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index e25742a4a61eb..ec9b5eba56106 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -108,6 +108,7 @@
 #![cfg_attr(stage0, feature(repr_transparent))]
 #![feature(rustc_attrs)]
 #![feature(specialization)]
+#![feature(split_ascii_whitespace)]
 #![feature(staged_api)]
 #![feature(str_internals)]
 #![feature(trusted_len)]
diff --git a/src/liballoc/str.rs b/src/liballoc/str.rs
index 32ca8d1fa5eba..ec9c39c916c47 100644
--- a/src/liballoc/str.rs
+++ b/src/liballoc/str.rs
@@ -78,6 +78,8 @@ pub use core::str::SplitWhitespace;
 pub use core::str::pattern;
 #[stable(feature = "encode_utf16", since = "1.8.0")]
 pub use core::str::EncodeUtf16;
+#[unstable(feature = "split_ascii_whitespace", issue = "48656")]
+pub use core::str::SplitAsciiWhitespace;
 
 #[unstable(feature = "slice_concat_ext",
            reason = "trait should not have to exist",
diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index 0c074582281d6..91447e01ad4fa 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -67,6 +67,8 @@ impl Layout {
     /// or returns `LayoutErr` if either of the following conditions
     /// are not met:
     ///
+    /// * `align` must not be zero,
+    ///
     /// * `align` must be a power of two,
     ///
     /// * `size`, when rounded up to the nearest multiple of `align`,
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 42fb1bc238b8e..5ae2f6349e5b7 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -21,7 +21,7 @@ use char;
 use fmt;
 use iter::{Map, Cloned, FusedIterator, TrustedLen, Filter};
 use iter_private::TrustedRandomAccess;
-use slice::{self, SliceIndex};
+use slice::{self, SliceIndex, Split as SliceSplit};
 use mem;
 
 pub mod pattern;
@@ -2722,7 +2722,10 @@ impl str {
     /// the original string slice, separated by any amount of whitespace.
     ///
     /// 'Whitespace' is defined according to the terms of the Unicode Derived
-    /// Core Property `White_Space`.
+    /// Core Property `White_Space`. If you only want to split on ASCII whitespace
+    /// instead, use [`split_ascii_whitespace`].
+    ///
+    /// [`split_ascii_whitespace`]: #method.split_ascii_whitespace
     ///
     /// # Examples
     ///
@@ -2756,6 +2759,53 @@ impl str {
         SplitWhitespace { inner: self.split(IsWhitespace).filter(IsNotEmpty) }
     }
 
+    /// Split a string slice by ASCII whitespace.
+    ///
+    /// The iterator returned will return string slices that are sub-slices of
+    /// the original string slice, separated by any amount of ASCII whitespace.
+    ///
+    /// To split by Unicode `Whitespace` instead, use [`split_whitespace`].
+    ///
+    /// [`split_whitespace`]: #method.split_whitespace
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(split_ascii_whitespace)]
+    /// let mut iter = "A few words".split_ascii_whitespace();
+    ///
+    /// assert_eq!(Some("A"), iter.next());
+    /// assert_eq!(Some("few"), iter.next());
+    /// assert_eq!(Some("words"), iter.next());
+    ///
+    /// assert_eq!(None, iter.next());
+    /// ```
+    ///
+    /// All kinds of ASCII whitespace are considered:
+    ///
+    /// ```
+    /// let mut iter = " Mary   had\ta little  \n\t lamb".split_whitespace();
+    /// assert_eq!(Some("Mary"), iter.next());
+    /// assert_eq!(Some("had"), iter.next());
+    /// assert_eq!(Some("a"), iter.next());
+    /// assert_eq!(Some("little"), iter.next());
+    /// assert_eq!(Some("lamb"), iter.next());
+    ///
+    /// assert_eq!(None, iter.next());
+    /// ```
+    #[unstable(feature = "split_ascii_whitespace", issue = "48656")]
+    #[inline]
+    pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace {
+        let inner = self
+            .as_bytes()
+            .split(IsAsciiWhitespace)
+            .filter(IsNotEmpty)
+            .map(UnsafeBytesToStr);
+        SplitAsciiWhitespace { inner }
+    }
+
     /// An iterator over the lines of a string, as string slices.
     ///
     /// Lines are ended with either a newline (`\n`) or a carriage return with
@@ -3895,6 +3945,20 @@ pub struct SplitWhitespace<'a> {
     inner: Filter<Split<'a, IsWhitespace>, IsNotEmpty>,
 }
 
+/// An iterator over the non-ASCII-whitespace substrings of a string,
+/// separated by any amount of ASCII whitespace.
+///
+/// This struct is created by the [`split_ascii_whitespace`] method on [`str`].
+/// See its documentation for more.
+///
+/// [`split_ascii_whitespace`]: ../../std/primitive.str.html#method.split_ascii_whitespace
+/// [`str`]: ../../std/primitive.str.html
+#[unstable(feature = "split_ascii_whitespace", issue = "48656")]
+#[derive(Clone, Debug)]
+pub struct SplitAsciiWhitespace<'a> {
+    inner: Map<Filter<SliceSplit<'a, u8, IsAsciiWhitespace>, IsNotEmpty>, UnsafeBytesToStr>,
+}
+
 #[derive(Clone)]
 struct IsWhitespace;
 
@@ -3914,6 +3978,25 @@ impl FnMut<(char, )> for IsWhitespace {
     }
 }
 
+#[derive(Clone)]
+struct IsAsciiWhitespace;
+
+impl<'a> FnOnce<(&'a u8, )> for IsAsciiWhitespace {
+    type Output = bool;
+
+    #[inline]
+    extern "rust-call" fn call_once(mut self, arg: (&u8, )) -> bool {
+        self.call_mut(arg)
+    }
+}
+
+impl<'a> FnMut<(&'a u8, )> for IsAsciiWhitespace {
+    #[inline]
+    extern "rust-call" fn call_mut(&mut self, arg: (&u8, )) -> bool {
+        arg.0.is_ascii_whitespace()
+    }
+}
+
 #[derive(Clone)]
 struct IsNotEmpty;
 
@@ -3921,30 +4004,72 @@ impl<'a, 'b> FnOnce<(&'a &'b str, )> for IsNotEmpty {
     type Output = bool;
 
     #[inline]
-    extern "rust-call" fn call_once(mut self, arg: (&&str, )) -> bool {
+    extern "rust-call" fn call_once(mut self, arg: (&'a &'b str, )) -> bool {
         self.call_mut(arg)
     }
 }
 
 impl<'a, 'b> FnMut<(&'a &'b str, )> for IsNotEmpty {
     #[inline]
-    extern "rust-call" fn call_mut(&mut self, arg: (&&str, )) -> bool {
+    extern "rust-call" fn call_mut(&mut self, arg: (&'a &'b str, )) -> bool {
+        !arg.0.is_empty()
+    }
+}
+
+impl<'a, 'b> FnOnce<(&'a &'b [u8], )> for IsNotEmpty {
+    type Output = bool;
+
+    #[inline]
+    extern "rust-call" fn call_once(mut self, arg: (&'a &'b [u8], )) -> bool {
+        self.call_mut(arg)
+    }
+}
+
+impl<'a, 'b> FnMut<(&'a &'b [u8], )> for IsNotEmpty {
+    #[inline]
+    extern "rust-call" fn call_mut(&mut self, arg: (&'a &'b [u8], )) -> bool {
         !arg.0.is_empty()
     }
 }
 
+#[derive(Clone)]
+struct UnsafeBytesToStr;
+
+impl<'a> FnOnce<(&'a [u8], )> for UnsafeBytesToStr {
+    type Output = &'a str;
+
+    #[inline]
+    extern "rust-call" fn call_once(mut self, arg: (&'a [u8], )) -> &'a str {
+        self.call_mut(arg)
+    }
+}
+
+impl<'a> FnMut<(&'a [u8], )> for UnsafeBytesToStr {
+    #[inline]
+    extern "rust-call" fn call_mut(&mut self, arg: (&'a [u8], )) -> &'a str {
+        unsafe { from_utf8_unchecked(arg.0) }
+    }
+}
+
 
 #[stable(feature = "split_whitespace", since = "1.1.0")]
 impl<'a> Iterator for SplitWhitespace<'a> {
     type Item = &'a str;
 
+    #[inline]
     fn next(&mut self) -> Option<&'a str> {
         self.inner.next()
     }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
 }
 
 #[stable(feature = "split_whitespace", since = "1.1.0")]
 impl<'a> DoubleEndedIterator for SplitWhitespace<'a> {
+    #[inline]
     fn next_back(&mut self) -> Option<&'a str> {
         self.inner.next_back()
     }
@@ -3953,6 +4078,32 @@ impl<'a> DoubleEndedIterator for SplitWhitespace<'a> {
 #[stable(feature = "fused", since = "1.26.0")]
 impl<'a> FusedIterator for SplitWhitespace<'a> {}
 
+#[unstable(feature = "split_ascii_whitespace", issue = "48656")]
+impl<'a> Iterator for SplitAsciiWhitespace<'a> {
+    type Item = &'a str;
+
+    #[inline]
+    fn next(&mut self) -> Option<&'a str> {
+        self.inner.next()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+}
+
+#[unstable(feature = "split_ascii_whitespace", issue = "48656")]
+impl<'a> DoubleEndedIterator for SplitAsciiWhitespace<'a> {
+    #[inline]
+    fn next_back(&mut self) -> Option<&'a str> {
+        self.inner.next_back()
+    }
+}
+
+#[unstable(feature = "split_ascii_whitespace", issue = "48656")]
+impl<'a> FusedIterator for SplitAsciiWhitespace<'a> {}
+
 /// An iterator of [`u16`] over the string encoded as UTF-16.
 ///
 /// [`u16`]: ../../std/primitive.u16.html
diff --git a/src/libcore/tests/num/mod.rs b/src/libcore/tests/num/mod.rs
index b5e6a019a228c..24fe96a2b8255 100644
--- a/src/libcore/tests/num/mod.rs
+++ b/src/libcore/tests/num/mod.rs
@@ -574,6 +574,25 @@ macro_rules! test_float {
             assert_eq!((-9.0 as $fty).max($nan), -9.0);
             assert!(($nan as $fty).max($nan).is_nan());
         }
+        #[test]
+        fn mod_euc() {
+            let a: $fty = 42.0;
+            assert!($inf.mod_euc(a).is_nan());
+            assert_eq!(a.mod_euc($inf), a);
+            assert!(a.mod_euc($nan).is_nan());
+            assert!($inf.mod_euc($inf).is_nan());
+            assert!($inf.mod_euc($nan).is_nan());
+            assert!($nan.mod_euc($inf).is_nan());
+        }
+        #[test]
+        fn div_euc() {
+            let a: $fty = 42.0;
+            assert_eq!(a.div_euc($inf), 0.0);
+            assert!(a.div_euc($nan).is_nan());
+            assert!($inf.div_euc($inf).is_nan());
+            assert!($inf.div_euc($nan).is_nan());
+            assert!($nan.div_euc($inf).is_nan());
+        }
     } }
 }
 
diff --git a/src/librustc/traits/query/normalize.rs b/src/librustc/traits/query/normalize.rs
index d0ae0bdac8c09..6d2df4c201813 100644
--- a/src/librustc/traits/query/normalize.rs
+++ b/src/librustc/traits/query/normalize.rs
@@ -124,10 +124,10 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for QueryNormalizer<'cx, 'gcx, 'tcx
                         let concrete_ty = generic_ty.subst(self.tcx(), substs);
                         self.anon_depth += 1;
                         if concrete_ty == ty {
-                            println!("generic_ty: {:#?}", generic_ty);
-                            println!("substs {:#?}", substs);
+                            bug!("infinite recursion generic_ty: {:#?}, substs: {:#?}, \
+                                  concrete_ty: {:#?}, ty: {:#?}", generic_ty, substs, concrete_ty,
+                                  ty);
                         }
-                        assert_ne!(concrete_ty, ty, "infinite recursion");
                         let folded_ty = self.fold_ty(concrete_ty);
                         self.anon_depth -= 1;
                         folded_ty
diff --git a/src/libstd/f32.rs b/src/libstd/f32.rs
index ae30321f46dfc..8e8340b3ed901 100644
--- a/src/libstd/f32.rs
+++ b/src/libstd/f32.rs
@@ -254,7 +254,14 @@ impl f32 {
 
     /// Calculates the Euclidean modulo (self mod rhs), which is never negative.
     ///
-    /// In particular, the result `n` satisfies `0 <= n < rhs.abs()`.
+    /// In particular, the return value `r` satisfies `0.0 <= r < rhs.abs()` in
+    /// most cases. However, due to a floating point round-off error it can
+    /// result in `r == rhs.abs()`, violating the mathematical definition, if
+    /// `self` is much smaller than `rhs.abs()` in magnitude and `self < 0.0`.
+    /// This result is not an element of the function's codomain, but it is the
+    /// closest floating point number in the real numbers and thus fulfills the
+    /// property `self == self.div_euc(rhs) * rhs + self.mod_euc(rhs)`
+    /// approximatively.
     ///
     /// # Examples
     ///
@@ -266,6 +273,8 @@ impl f32 {
     /// assert_eq!((-a).mod_euc(b), 1.0);
     /// assert_eq!(a.mod_euc(-b), 3.0);
     /// assert_eq!((-a).mod_euc(-b), 1.0);
+    /// // limitation due to round-off error
+    /// assert!((-std::f32::EPSILON).mod_euc(3.0) != 0.0);
     /// ```
     #[inline]
     #[unstable(feature = "euclidean_division", issue = "49048")]
diff --git a/src/libstd/f64.rs b/src/libstd/f64.rs
index 7950d434b77e6..6880294afcaaf 100644
--- a/src/libstd/f64.rs
+++ b/src/libstd/f64.rs
@@ -230,7 +230,14 @@ impl f64 {
 
     /// Calculates the Euclidean modulo (self mod rhs), which is never negative.
     ///
-    /// In particular, the result `n` satisfies `0 <= n < rhs.abs()`.
+    /// In particular, the return value `r` satisfies `0.0 <= r < rhs.abs()` in
+    /// most cases.  However, due to a floating point round-off error it can
+    /// result in `r == rhs.abs()`, violating the mathematical definition, if
+    /// `self` is much smaller than `rhs.abs()` in magnitude and `self < 0.0`.
+    /// This result is not an element of the function's codomain, but it is the
+    /// closest floating point number in the real numbers and thus fulfills the
+    /// property `self == self.div_euc(rhs) * rhs + self.mod_euc(rhs)`
+    /// approximatively.
     ///
     /// # Examples
     ///
@@ -242,6 +249,8 @@ impl f64 {
     /// assert_eq!((-a).mod_euc(b), 1.0);
     /// assert_eq!(a.mod_euc(-b), 3.0);
     /// assert_eq!((-a).mod_euc(-b), 1.0);
+    /// // limitation due to round-off error
+    /// assert!((-std::f64::EPSILON).mod_euc(3.0) != 0.0);
     /// ```
     #[inline]
     #[unstable(feature = "euclidean_division", issue = "49048")]
diff --git a/src/libstd/thread/local.rs b/src/libstd/thread/local.rs
index 40d3280baa687..a170abb2628e5 100644
--- a/src/libstd/thread/local.rs
+++ b/src/libstd/thread/local.rs
@@ -276,7 +276,7 @@ impl<T: 'static> LocalKey<T> {
     ///
     /// This will lazily initialize the value if this thread has not referenced
     /// this key yet. If the key has been destroyed (which may happen if this is called
-    /// in a destructor), this function will return a `ThreadLocalError`.
+    /// in a destructor), this function will return an [`AccessError`](struct.AccessError.html).
     ///
     /// # Panics
     ///
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index c813ec1977b88..6d55b3de75d2e 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -1359,17 +1359,17 @@ pub const EXPLAIN_LITERAL_MATCHER: &'static str =
     ":literal fragment specifier is experimental and subject to change";
 
 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
-    "Unsized tuple coercion is not stable enough for use and is subject to change";
+    "unsized tuple coercion is not stable enough for use and is subject to change";
 
 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
-    "Using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
+    "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
 
 pub const EXPLAIN_MACROS_IN_EXTERN: &'static str =
-    "Macro invocations in `extern {}` blocks are experimental.";
+    "macro invocations in `extern {}` blocks are experimental.";
 
 // mention proc-macros when enabled
 pub const EXPLAIN_PROC_MACROS_IN_EXTERN: &'static str =
-    "Macro and proc-macro invocations in `extern {}` blocks are experimental.";
+    "macro and proc-macro invocations in `extern {}` blocks are experimental.";
 
 struct PostExpansionVisitor<'a> {
     context: &'a Context<'a>,
diff --git a/src/test/compile-fail-fulldeps/proc-macro/macros-in-extern.rs b/src/test/compile-fail-fulldeps/proc-macro/macros-in-extern.rs
index 4c88df332460b..75d5ac6495ae8 100644
--- a/src/test/compile-fail-fulldeps/proc-macro/macros-in-extern.rs
+++ b/src/test/compile-fail-fulldeps/proc-macro/macros-in-extern.rs
@@ -26,13 +26,13 @@ fn main() {
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     #[no_output]
-    //~^ ERROR Macro and proc-macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro and proc-macro invocations in `extern {}` blocks are experimental.
     fn some_definitely_unknown_symbol_which_should_be_removed();
 
     #[nop_attr]
-    //~^ ERROR Macro and proc-macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro and proc-macro invocations in `extern {}` blocks are experimental.
     fn rust_get_test_int() -> isize;
 
     emit_input!(fn rust_dbg_extern_identity_u32(arg: u32) -> u32;);
-    //~^ ERROR Macro and proc-macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro and proc-macro invocations in `extern {}` blocks are experimental.
 }
diff --git a/src/test/compile-fail/edition-raw-pointer-method-2015.rs b/src/test/compile-fail/edition-raw-pointer-method-2015.rs
index b304443f63145..4ba44fa54d8cd 100644
--- a/src/test/compile-fail/edition-raw-pointer-method-2015.rs
+++ b/src/test/compile-fail/edition-raw-pointer-method-2015.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // ignore-tidy-linelength
-// compile-flags: --edition=2015 -Zunstable-options
+// edition:2015
 
 // tests that editions work with the tyvar warning-turned-error
 
diff --git a/src/test/compile-fail/edition-raw-pointer-method-2018.rs b/src/test/compile-fail/edition-raw-pointer-method-2018.rs
index d0cf81d59cf37..c8548ed35b972 100644
--- a/src/test/compile-fail/edition-raw-pointer-method-2018.rs
+++ b/src/test/compile-fail/edition-raw-pointer-method-2018.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // ignore-tidy-linelength
-// compile-flags: --edition=2018 -Zunstable-options
+// edition:2018
 
 // tests that editions work with the tyvar warning-turned-error
 
diff --git a/src/test/compile-fail/macros-in-extern.rs b/src/test/compile-fail/macros-in-extern.rs
index 7d7f95cbbf5cb..b6e273881ccd6 100644
--- a/src/test/compile-fail/macros-in-extern.rs
+++ b/src/test/compile-fail/macros-in-extern.rs
@@ -34,9 +34,9 @@ fn main() {
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     returns_isize!(rust_get_test_int);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     emits_nothing!();
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
 }
diff --git a/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-1.rs b/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-1.rs
index fcf4714ba9695..e04bb27f43500 100644
--- a/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-1.rs
+++ b/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-1.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018 -Zunstable-options
+// edition:2018
 
 #![feature(extern_absolute_paths)]
 
diff --git a/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-2.rs b/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-2.rs
index c256c5592c269..bebf0236bb4d0 100644
--- a/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-2.rs
+++ b/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-2.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018 -Zunstable-options
+// edition:2018
 
 #![feature(extern_absolute_paths)]
 
diff --git a/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-3.rs b/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-3.rs
index 837dc617b3ad0..5906a0719c842 100644
--- a/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-3.rs
+++ b/src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-3.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018 -Zunstable-options
+// edition:2018
 
 #![feature(extern_absolute_paths)]
 
diff --git a/src/test/compile-fail/rfc-2126-extern-absolute-paths/single-segment.rs b/src/test/compile-fail/rfc-2126-extern-absolute-paths/single-segment.rs
index 9b7baa0016344..7111176dbd9af 100644
--- a/src/test/compile-fail/rfc-2126-extern-absolute-paths/single-segment.rs
+++ b/src/test/compile-fail/rfc-2126-extern-absolute-paths/single-segment.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // aux-build:xcrate.rs
-// compile-flags: --edition=2018 -Zunstable-options
+// edition:2018
 
 #![feature(crate_in_paths)]
 #![feature(extern_absolute_paths)]
diff --git a/src/test/run-pass/async-await.rs b/src/test/run-pass/async-await.rs
index 817db4bb79ec3..8b649f6ef7bbd 100644
--- a/src/test/run-pass/async-await.rs
+++ b/src/test/run-pass/async-await.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 
 #![feature(arbitrary_self_types, async_await, await_macro, futures_api, pin)]
 
diff --git a/src/test/run-pass/auxiliary/edition-kw-macro-2015.rs b/src/test/run-pass/auxiliary/edition-kw-macro-2015.rs
index 9127c8e350a8c..69952e9f90af6 100644
--- a/src/test/run-pass/auxiliary/edition-kw-macro-2015.rs
+++ b/src/test/run-pass/auxiliary/edition-kw-macro-2015.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 
 #![feature(raw_identifiers)]
 
diff --git a/src/test/run-pass/auxiliary/edition-kw-macro-2018.rs b/src/test/run-pass/auxiliary/edition-kw-macro-2018.rs
index 4fef77d67ea71..415988586a066 100644
--- a/src/test/run-pass/auxiliary/edition-kw-macro-2018.rs
+++ b/src/test/run-pass/auxiliary/edition-kw-macro-2018.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 
 #![feature(raw_identifiers)]
 
diff --git a/src/test/run-pass/edition-keywords-2015-2015.rs b/src/test/run-pass/edition-keywords-2015-2015.rs
index 41480bb978ec2..73869e63de7c4 100644
--- a/src/test/run-pass/edition-keywords-2015-2015.rs
+++ b/src/test/run-pass/edition-keywords-2015-2015.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 // aux-build:edition-kw-macro-2015.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/run-pass/edition-keywords-2015-2018.rs b/src/test/run-pass/edition-keywords-2015-2018.rs
index 78835d510639f..0a1c6505854c9 100644
--- a/src/test/run-pass/edition-keywords-2015-2018.rs
+++ b/src/test/run-pass/edition-keywords-2015-2018.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 // aux-build:edition-kw-macro-2018.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/run-pass/edition-keywords-2018-2015.rs b/src/test/run-pass/edition-keywords-2018-2015.rs
index 46d5f222cbb31..4c22667d0bf43 100644
--- a/src/test/run-pass/edition-keywords-2018-2015.rs
+++ b/src/test/run-pass/edition-keywords-2018-2015.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 // aux-build:edition-kw-macro-2015.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/run-pass/edition-keywords-2018-2018.rs b/src/test/run-pass/edition-keywords-2018-2018.rs
index 06482988937b6..2a98b904da5db 100644
--- a/src/test/run-pass/edition-keywords-2018-2018.rs
+++ b/src/test/run-pass/edition-keywords-2018-2018.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 // aux-build:edition-kw-macro-2018.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/run-pass/rfc-2126-extern-absolute-paths/basic.rs b/src/test/run-pass/rfc-2126-extern-absolute-paths/basic.rs
index bbe066481a8b1..dfa583415f7b6 100644
--- a/src/test/run-pass/rfc-2126-extern-absolute-paths/basic.rs
+++ b/src/test/run-pass/rfc-2126-extern-absolute-paths/basic.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // aux-build:xcrate.rs
-// compile-flags: --edition=2018 -Zunstable-options
+// edition:2018
 
 #![feature(extern_absolute_paths)]
 
diff --git a/src/test/run-pass/rfc-2126-extern-absolute-paths/test.rs b/src/test/run-pass/rfc-2126-extern-absolute-paths/test.rs
index ead462cf0d2ca..6317dc17652cd 100644
--- a/src/test/run-pass/rfc-2126-extern-absolute-paths/test.rs
+++ b/src/test/run-pass/rfc-2126-extern-absolute-paths/test.rs
@@ -12,7 +12,8 @@
 //
 // Regression test for #47075.
 
-// compile-flags: --test --edition=2018 -Zunstable-options
+// edition:2018
+// compile-flags: --test
 
 #![feature(extern_absolute_paths)]
 
diff --git a/src/test/ui/async-fn-multiple-lifetimes.rs b/src/test/ui/async-fn-multiple-lifetimes.rs
index ce062ded7f73f..aab4974e2e7a1 100644
--- a/src/test/ui/async-fn-multiple-lifetimes.rs
+++ b/src/test/ui/async-fn-multiple-lifetimes.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 
 #![feature(arbitrary_self_types, async_await, await_macro, futures_api, pin)]
 
diff --git a/src/test/ui/auxiliary/edition-kw-macro-2015.rs b/src/test/ui/auxiliary/edition-kw-macro-2015.rs
index 9127c8e350a8c..69952e9f90af6 100644
--- a/src/test/ui/auxiliary/edition-kw-macro-2015.rs
+++ b/src/test/ui/auxiliary/edition-kw-macro-2015.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 
 #![feature(raw_identifiers)]
 
diff --git a/src/test/ui/auxiliary/edition-kw-macro-2018.rs b/src/test/ui/auxiliary/edition-kw-macro-2018.rs
index 4fef77d67ea71..415988586a066 100644
--- a/src/test/ui/auxiliary/edition-kw-macro-2018.rs
+++ b/src/test/ui/auxiliary/edition-kw-macro-2018.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 
 #![feature(raw_identifiers)]
 
diff --git a/src/test/ui/edition-keywords-2015-2015-expansion.rs b/src/test/ui/edition-keywords-2015-2015-expansion.rs
index b8a1994a10575..349ab3e27ad32 100644
--- a/src/test/ui/edition-keywords-2015-2015-expansion.rs
+++ b/src/test/ui/edition-keywords-2015-2015-expansion.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 // aux-build:edition-kw-macro-2015.rs
 // compile-pass
 
diff --git a/src/test/ui/edition-keywords-2015-2015-parsing.rs b/src/test/ui/edition-keywords-2015-2015-parsing.rs
index 1fb91ca006cc7..08cba2d2908a6 100644
--- a/src/test/ui/edition-keywords-2015-2015-parsing.rs
+++ b/src/test/ui/edition-keywords-2015-2015-parsing.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 // aux-build:edition-kw-macro-2015.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/ui/edition-keywords-2015-2018-expansion.rs b/src/test/ui/edition-keywords-2015-2018-expansion.rs
index bc14c104c49fc..082eb8d89f9f1 100644
--- a/src/test/ui/edition-keywords-2015-2018-expansion.rs
+++ b/src/test/ui/edition-keywords-2015-2018-expansion.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 // aux-build:edition-kw-macro-2018.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/ui/edition-keywords-2015-2018-parsing.rs b/src/test/ui/edition-keywords-2015-2018-parsing.rs
index 0b680eb16c7f4..337d6be6bbcd8 100644
--- a/src/test/ui/edition-keywords-2015-2018-parsing.rs
+++ b/src/test/ui/edition-keywords-2015-2018-parsing.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 // aux-build:edition-kw-macro-2018.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/ui/edition-keywords-2018-2015-expansion.rs b/src/test/ui/edition-keywords-2018-2015-expansion.rs
index 6f85f427eb054..6e2073e0e494a 100644
--- a/src/test/ui/edition-keywords-2018-2015-expansion.rs
+++ b/src/test/ui/edition-keywords-2018-2015-expansion.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 // aux-build:edition-kw-macro-2015.rs
 // compile-pass
 
diff --git a/src/test/ui/edition-keywords-2018-2015-parsing.rs b/src/test/ui/edition-keywords-2018-2015-parsing.rs
index 02dc8c8795675..713da57f7e2c7 100644
--- a/src/test/ui/edition-keywords-2018-2015-parsing.rs
+++ b/src/test/ui/edition-keywords-2018-2015-parsing.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 // aux-build:edition-kw-macro-2015.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/ui/edition-keywords-2018-2018-expansion.rs b/src/test/ui/edition-keywords-2018-2018-expansion.rs
index ef7f63e225ce1..50db4202e98d3 100644
--- a/src/test/ui/edition-keywords-2018-2018-expansion.rs
+++ b/src/test/ui/edition-keywords-2018-2018-expansion.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 // aux-build:edition-kw-macro-2018.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/ui/edition-keywords-2018-2018-parsing.rs b/src/test/ui/edition-keywords-2018-2018-parsing.rs
index f9b4d0e18c14b..263ec95caa7d6 100644
--- a/src/test/ui/edition-keywords-2018-2018-parsing.rs
+++ b/src/test/ui/edition-keywords-2018-2018-parsing.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 // aux-build:edition-kw-macro-2018.rs
 
 #![feature(raw_identifiers)]
diff --git a/src/test/ui/feature-gate-async-await-2015-edition.rs b/src/test/ui/feature-gate-async-await-2015-edition.rs
index b1dd6a77e976a..5b865e9c1c7cb 100644
--- a/src/test/ui/feature-gate-async-await-2015-edition.rs
+++ b/src/test/ui/feature-gate-async-await-2015-edition.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2015
+// edition:2015
 
 #![feature(futures_api)]
 
diff --git a/src/test/ui/feature-gate-async-await.rs b/src/test/ui/feature-gate-async-await.rs
index 971b75c6dd036..be34842dea3a6 100644
--- a/src/test/ui/feature-gate-async-await.rs
+++ b/src/test/ui/feature-gate-async-await.rs
@@ -8,7 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
+
 #![feature(futures_api)]
 
 async fn foo() {} //~ ERROR async fn is unstable
diff --git a/src/test/ui/feature-gate-async-await.stderr b/src/test/ui/feature-gate-async-await.stderr
index fdee6e205750b..79ed5c4d008b1 100644
--- a/src/test/ui/feature-gate-async-await.stderr
+++ b/src/test/ui/feature-gate-async-await.stderr
@@ -1,5 +1,5 @@
 error[E0658]: async fn is unstable (see issue #50547)
-  --> $DIR/feature-gate-async-await.rs:14:1
+  --> $DIR/feature-gate-async-await.rs:15:1
    |
 LL | async fn foo() {} //~ ERROR async fn is unstable
    | ^^^^^^^^^^^^^^^^^
@@ -7,7 +7,7 @@ LL | async fn foo() {} //~ ERROR async fn is unstable
    = help: add #![feature(async_await)] to the crate attributes to enable
 
 error[E0658]: async blocks are unstable (see issue #50547)
-  --> $DIR/feature-gate-async-await.rs:17:13
+  --> $DIR/feature-gate-async-await.rs:18:13
    |
 LL |     let _ = async {}; //~ ERROR async blocks are unstable
    |             ^^^^^^^^
@@ -15,7 +15,7 @@ LL |     let _ = async {}; //~ ERROR async blocks are unstable
    = help: add #![feature(async_await)] to the crate attributes to enable
 
 error[E0658]: async closures are unstable (see issue #50547)
-  --> $DIR/feature-gate-async-await.rs:18:13
+  --> $DIR/feature-gate-async-await.rs:19:13
    |
 LL |     let _ = async || {}; //~ ERROR async closures are unstable
    |             ^^^^^^^^^^^
diff --git a/src/test/ui/feature-gate-macro_at_most_once_rep.rs b/src/test/ui/feature-gate-macro_at_most_once_rep.rs
index 19f5aca5730e1..bdce1952a9a21 100644
--- a/src/test/ui/feature-gate-macro_at_most_once_rep.rs
+++ b/src/test/ui/feature-gate-macro_at_most_once_rep.rs
@@ -12,7 +12,7 @@
 // gate is not used.
 
 macro_rules! m { ($(a)?) => {} }
-//~^ ERROR Using the `?` macro Kleene operator for "at most one" repetition is unstable
+//~^ ERROR using the `?` macro Kleene operator for "at most one" repetition is unstable
 
 fn main() {
     m!();
diff --git a/src/test/ui/feature-gate-macro_at_most_once_rep.stderr b/src/test/ui/feature-gate-macro_at_most_once_rep.stderr
index 8eba07e6c088b..9ca71d937f859 100644
--- a/src/test/ui/feature-gate-macro_at_most_once_rep.stderr
+++ b/src/test/ui/feature-gate-macro_at_most_once_rep.stderr
@@ -1,4 +1,4 @@
-error[E0658]: Using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
+error[E0658]: using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
   --> $DIR/feature-gate-macro_at_most_once_rep.rs:14:20
    |
 LL | macro_rules! m { ($(a)?) => {} }
diff --git a/src/test/ui/feature-gate-macros_in_extern.rs b/src/test/ui/feature-gate-macros_in_extern.rs
index 9c758241ea1b8..5271f75b6328c 100644
--- a/src/test/ui/feature-gate-macros_in_extern.rs
+++ b/src/test/ui/feature-gate-macros_in_extern.rs
@@ -27,9 +27,9 @@ macro_rules! emits_nothing(
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     returns_isize!(rust_get_test_int);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
     emits_nothing!();
-    //~^ ERROR Macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
 }
diff --git a/src/test/ui/feature-gate-macros_in_extern.stderr b/src/test/ui/feature-gate-macros_in_extern.stderr
index 49aca0db2d46c..748adc390d8bb 100644
--- a/src/test/ui/feature-gate-macros_in_extern.stderr
+++ b/src/test/ui/feature-gate-macros_in_extern.stderr
@@ -1,4 +1,4 @@
-error[E0658]: Macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental. (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:29:5
    |
 LL |     returns_isize!(rust_get_test_int);
@@ -6,7 +6,7 @@ LL |     returns_isize!(rust_get_test_int);
    |
    = help: add #![feature(macros_in_extern)] to the crate attributes to enable
 
-error[E0658]: Macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental. (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:31:5
    |
 LL |     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
@@ -14,7 +14,7 @@ LL |     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
    |
    = help: add #![feature(macros_in_extern)] to the crate attributes to enable
 
-error[E0658]: Macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental. (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:33:5
    |
 LL |     emits_nothing!();
diff --git a/src/test/ui/feature-gate-unsized_tuple_coercion.rs b/src/test/ui/feature-gate-unsized_tuple_coercion.rs
index 4ddde01126363..8a43e75494d81 100644
--- a/src/test/ui/feature-gate-unsized_tuple_coercion.rs
+++ b/src/test/ui/feature-gate-unsized_tuple_coercion.rs
@@ -10,5 +10,5 @@
 
 fn main() {
     let _ : &(Send,) = &((),);
-    //~^ ERROR Unsized tuple coercion is not stable enough
+    //~^ ERROR unsized tuple coercion is not stable enough
 }
diff --git a/src/test/ui/feature-gate-unsized_tuple_coercion.stderr b/src/test/ui/feature-gate-unsized_tuple_coercion.stderr
index bf790a3b00390..08c15855a6a42 100644
--- a/src/test/ui/feature-gate-unsized_tuple_coercion.stderr
+++ b/src/test/ui/feature-gate-unsized_tuple_coercion.stderr
@@ -1,4 +1,4 @@
-error[E0658]: Unsized tuple coercion is not stable enough for use and is subject to change (see issue #42877)
+error[E0658]: unsized tuple coercion is not stable enough for use and is subject to change (see issue #42877)
   --> $DIR/feature-gate-unsized_tuple_coercion.rs:12:24
    |
 LL |     let _ : &(Send,) = &((),);
diff --git a/src/test/ui/lint-anon-param-edition.fixed b/src/test/ui/lint-anon-param-edition.fixed
index de223d9ccf7b6..c4379b496f8d4 100644
--- a/src/test/ui/lint-anon-param-edition.fixed
+++ b/src/test/ui/lint-anon-param-edition.fixed
@@ -11,7 +11,7 @@
 // tests that the anonymous_parameters lint is warn-by-default on the 2018 edition
 
 // compile-pass
-// compile-flags: --edition=2018
+// edition:2018
 // run-rustfix
 
 trait Foo {
diff --git a/src/test/ui/lint-anon-param-edition.rs b/src/test/ui/lint-anon-param-edition.rs
index 35406806df99c..13eb5dfd816ab 100644
--- a/src/test/ui/lint-anon-param-edition.rs
+++ b/src/test/ui/lint-anon-param-edition.rs
@@ -11,7 +11,7 @@
 // tests that the anonymous_parameters lint is warn-by-default on the 2018 edition
 
 // compile-pass
-// compile-flags: --edition=2018
+// edition:2018
 // run-rustfix
 
 trait Foo {
diff --git a/src/test/ui/no-args-non-move-async-closure.rs b/src/test/ui/no-args-non-move-async-closure.rs
index f2ecc44771883..9cb754167cfe5 100644
--- a/src/test/ui/no-args-non-move-async-closure.rs
+++ b/src/test/ui/no-args-non-move-async-closure.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --edition=2018
+// edition:2018
 
 #![feature(arbitrary_self_types, async_await, await_macro, futures_api, pin)]
 
diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index f66f5c5b70e7e..1dd7fe7f0cb39 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -298,6 +298,10 @@ impl TestProps {
                     .extend(flags.split_whitespace().map(|s| s.to_owned()));
             }
 
+            if let Some(edition) = config.parse_edition(ln) {
+                self.compile_flags.push(format!("--edition={}", edition));
+            }
+
             if let Some(r) = config.parse_revisions(ln) {
                 self.revisions.extend(r);
             }
@@ -371,9 +375,9 @@ impl TestProps {
                 self.compile_pass = config.parse_compile_pass(ln) || self.run_pass;
             }
 
-                        if !self.skip_codegen {
-                            self.skip_codegen = config.parse_skip_codegen(ln);
-                        }
+            if !self.skip_codegen {
+                self.skip_codegen = config.parse_skip_codegen(ln);
+            }
 
             if !self.disable_ui_testing_normalization {
                 self.disable_ui_testing_normalization =
@@ -647,6 +651,10 @@ impl Config {
     fn parse_run_rustfix(&self, line: &str) -> bool {
         self.parse_name_directive(line, "run-rustfix")
     }
+
+    fn parse_edition(&self, line: &str) -> Option<String> {
+        self.parse_name_value_directive(line, "edition")
+    }
 }
 
 pub fn lldb_version_to_int(version_string: &str) -> isize {
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index caf73f4f68b03..408eda5ba5bb5 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -1368,6 +1368,7 @@ impl<'test> TestCx<'test> {
             .arg(out_dir)
             .arg(&self.testpaths.file)
             .args(&self.props.compile_flags);
+
         if let Some(ref linker) = self.config.linker {
             rustdoc
                 .arg("--linker")