diff --git a/src/libcollectionstest/lib.rs b/src/libcollectionstest/lib.rs
index 9b50478472f..0e3f9d5aadd 100644
--- a/src/libcollectionstest/lib.rs
+++ b/src/libcollectionstest/lib.rs
@@ -14,6 +14,7 @@
 #![feature(collections)]
 #![feature(collections_drain)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(hash)]
 #![feature(rand)]
 #![feature(rustc_private)]
diff --git a/src/libcoretest/lib.rs b/src/libcoretest/lib.rs
index 3d14b3f3c81..6ec3f5b7869 100644
--- a/src/libcoretest/lib.rs
+++ b/src/libcoretest/lib.rs
@@ -14,6 +14,7 @@
 #![feature(box_syntax)]
 #![feature(unboxed_closures)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(test)]
 #![feature(rand)]
 #![feature(unicode)]
diff --git a/src/liblog/lib.rs b/src/liblog/lib.rs
index 4c92162b2d6..15767024ba8 100644
--- a/src/liblog/lib.rs
+++ b/src/liblog/lib.rs
@@ -173,6 +173,7 @@
 #![feature(staged_api)]
 #![feature(box_syntax)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(std_misc)]
 
 use std::boxed;
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index c92bb81c5fb..4a715ca621c 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -29,6 +29,7 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
+#![feature(const_fn)]
 #![feature(core)]
 #![feature(duration)]
 #![feature(duration_span)]
diff --git a/src/librustc_trans/lib.rs b/src/librustc_trans/lib.rs
index 8866e7ff19d..f25c6eb21a4 100644
--- a/src/librustc_trans/lib.rs
+++ b/src/librustc_trans/lib.rs
@@ -30,6 +30,7 @@
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]
+#![feature(const_fn)]
 #![feature(libc)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
diff --git a/src/test/auxiliary/issue-17718.rs b/src/test/auxiliary/issue-17718.rs
index b347e674f0a..373fc042175 100644
--- a/src/test/auxiliary/issue-17718.rs
+++ b/src/test/auxiliary/issue-17718.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(const_fn)]
+
 use std::sync::atomic;
 
 pub const C1: usize = 1;
diff --git a/src/test/compile-fail/dropck_arr_cycle_checked.rs b/src/test/compile-fail/dropck_arr_cycle_checked.rs
index c9713ebcebe..19f790ddc90 100644
--- a/src/test/compile-fail/dropck_arr_cycle_checked.rs
+++ b/src/test/compile-fail/dropck_arr_cycle_checked.rs
@@ -13,6 +13,8 @@
 //
 // (Compare against compile-fail/dropck_vec_cycle_checked.rs)
 
+#![feature(const_fn)]
+
 use std::cell::Cell;
 use id::Id;
 
diff --git a/src/test/compile-fail/dropck_tarena_cycle_checked.rs b/src/test/compile-fail/dropck_tarena_cycle_checked.rs
index 9309f5a243c..584e5eabf0c 100644
--- a/src/test/compile-fail/dropck_tarena_cycle_checked.rs
+++ b/src/test/compile-fail/dropck_tarena_cycle_checked.rs
@@ -17,6 +17,7 @@
 //  for the error message we see here.)
 
 #![allow(unstable)]
+#![feature(const_fn)]
 
 extern crate arena;
 
diff --git a/src/test/compile-fail/dropck_trait_cycle_checked.rs b/src/test/compile-fail/dropck_trait_cycle_checked.rs
index 1d8c7e9ac3e..6e0679da949 100644
--- a/src/test/compile-fail/dropck_trait_cycle_checked.rs
+++ b/src/test/compile-fail/dropck_trait_cycle_checked.rs
@@ -13,6 +13,8 @@
 //
 // (Compare against compile-fail/dropck_vec_cycle_checked.rs)
 
+#![feature(const_fn)]
+
 use std::cell::Cell;
 use id::Id;
 
diff --git a/src/test/compile-fail/dropck_vec_cycle_checked.rs b/src/test/compile-fail/dropck_vec_cycle_checked.rs
index 8722246bb4e..bc33ff8399a 100644
--- a/src/test/compile-fail/dropck_vec_cycle_checked.rs
+++ b/src/test/compile-fail/dropck_vec_cycle_checked.rs
@@ -12,6 +12,8 @@
 //
 // (Compare against compile-fail/dropck_arr_cycle_checked.rs)
 
+#![feature(const_fn)]
+
 use std::cell::Cell;
 use id::Id;
 
diff --git a/src/test/compile-fail/functional-struct-update-respects-privacy.rs b/src/test/compile-fail/functional-struct-update-respects-privacy.rs
index 3f41401eb69..d2df0d9ef27 100644
--- a/src/test/compile-fail/functional-struct-update-respects-privacy.rs
+++ b/src/test/compile-fail/functional-struct-update-respects-privacy.rs
@@ -10,6 +10,8 @@
 
 // RFC 736 (and Issue 21407): functional struct update should respect privacy.
 
+#![feature(const_fn)]
+
 // The `foo` module attempts to maintains an invariant that each `S`
 // has a unique `u64` id.
 use self::foo::S;
diff --git a/src/test/compile-fail/issue-17718-const-borrow.rs b/src/test/compile-fail/issue-17718-const-borrow.rs
index 12a9a274631..ec6d1141c1a 100644
--- a/src/test/compile-fail/issue-17718-const-borrow.rs
+++ b/src/test/compile-fail/issue-17718-const-borrow.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(const_fn)]
+
 use std::cell::UnsafeCell;
 
 const A: UnsafeCell<usize> = UnsafeCell::new(1);
diff --git a/src/test/compile-fail/issue-7364.rs b/src/test/compile-fail/issue-7364.rs
index 999e5f9db2d..7d0a9007829 100644
--- a/src/test/compile-fail/issue-7364.rs
+++ b/src/test/compile-fail/issue-7364.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![feature(box_syntax)]
+#![feature(const_fn)]
 
 use std::cell::RefCell;
 
diff --git a/src/test/compile-fail/vec-must-not-hide-type-from-dropck.rs b/src/test/compile-fail/vec-must-not-hide-type-from-dropck.rs
index 0b2112edf72..37528959684 100644
--- a/src/test/compile-fail/vec-must-not-hide-type-from-dropck.rs
+++ b/src/test/compile-fail/vec-must-not-hide-type-from-dropck.rs
@@ -23,6 +23,8 @@
 // conditions above to be satisfied, meaning that if the dropck is
 // sound, it should reject this code.
 
+#![feature(const_fn)]
+
 use std::cell::Cell;
 use id::Id;
 
diff --git a/src/test/debuginfo/constant-debug-locs.rs b/src/test/debuginfo/constant-debug-locs.rs
index 72448ca2e00..8032b53e9dd 100644
--- a/src/test/debuginfo/constant-debug-locs.rs
+++ b/src/test/debuginfo/constant-debug-locs.rs
@@ -15,6 +15,7 @@
 #![allow(dead_code, unused_variables)]
 #![omit_gdb_pretty_printer_section]
 #![feature(std_misc, core)]
+#![feature(const_fn)]
 
 // This test makes sure that the compiler doesn't crash when trying to assign
 // debug locations to const-expressions.
diff --git a/src/test/run-pass-valgrind/cast-enum-with-dtor.rs b/src/test/run-pass-valgrind/cast-enum-with-dtor.rs
index 2c3d7ef39e4..b13e34256d2 100644
--- a/src/test/run-pass-valgrind/cast-enum-with-dtor.rs
+++ b/src/test/run-pass-valgrind/cast-enum-with-dtor.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![allow(dead_code)]
+#![feature(const_fn)]
 
 // check dtor calling order when casting enums.
 
diff --git a/src/test/run-pass/associated-types-project-from-type-param-via-bound-in-where-clause.rs b/src/test/run-pass/associated-types-project-from-type-param-via-bound-in-where-clause.rs
index 5ceb1013ad8..8dc7d79ec2a 100644
--- a/src/test/run-pass/associated-types-project-from-type-param-via-bound-in-where-clause.rs
+++ b/src/test/run-pass/associated-types-project-from-type-param-via-bound-in-where-clause.rs
@@ -12,6 +12,8 @@
 // `Item` originates in a where-clause, not the declaration of
 // `T`. Issue #20300.
 
+#![feature(const_fn)]
+
 use std::marker::{PhantomData};
 use std::sync::atomic::{AtomicUsize};
 use std::sync::atomic::Ordering::SeqCst;
diff --git a/src/test/run-pass/box-of-array-of-drop-1.rs b/src/test/run-pass/box-of-array-of-drop-1.rs
index 1c7359a0fad..e889d74c7cc 100644
--- a/src/test/run-pass/box-of-array-of-drop-1.rs
+++ b/src/test/run-pass/box-of-array-of-drop-1.rs
@@ -11,6 +11,8 @@
 // Test that we cleanup a fixed size Box<[D; k]> properly when D has a
 // destructor.
 
+#![feature(const_fn)]
+
 use std::thread;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
diff --git a/src/test/run-pass/box-of-array-of-drop-2.rs b/src/test/run-pass/box-of-array-of-drop-2.rs
index ad781f00356..f108ef4f5d2 100644
--- a/src/test/run-pass/box-of-array-of-drop-2.rs
+++ b/src/test/run-pass/box-of-array-of-drop-2.rs
@@ -11,6 +11,8 @@
 // Test that we cleanup dynamic sized Box<[D]> properly when D has a
 // destructor.
 
+#![feature(const_fn)]
+
 use std::thread;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
diff --git a/src/test/run-pass/const-fn-method.rs b/src/test/run-pass/const-fn-method.rs
index dc02758fe50..42c7a47c59d 100644
--- a/src/test/run-pass/const-fn-method.rs
+++ b/src/test/run-pass/const-fn-method.rs
@@ -10,7 +10,7 @@
 
 #![feature(const_fn)]
 
-struct Foo { val: u32 }
+struct Foo { value: u32 }
 
 impl Foo {
     const fn new() -> Foo {
diff --git a/src/test/run-pass/issue-17718-static-unsafe-interior.rs b/src/test/run-pass/issue-17718-static-unsafe-interior.rs
index c18d51e84d8..993e5e1c1e6 100644
--- a/src/test/run-pass/issue-17718-static-unsafe-interior.rs
+++ b/src/test/run-pass/issue-17718-static-unsafe-interior.rs
@@ -11,6 +11,8 @@
 // pretty-expanded FIXME #23616
 
 #![feature(core)]
+#![feature(const_fn)]
+
 
 use std::marker;
 use std::cell::UnsafeCell;
diff --git a/src/test/run-pass/issue-17718.rs b/src/test/run-pass/issue-17718.rs
index 457bbb23e18..2bb69d105ff 100644
--- a/src/test/run-pass/issue-17718.rs
+++ b/src/test/run-pass/issue-17718.rs
@@ -12,6 +12,7 @@
 
 
 #![feature(core)]
+#![feature(const_fn)]
 
 extern crate issue_17718 as other;
 
diff --git a/src/test/run-pass/issue-21486.rs b/src/test/run-pass/issue-21486.rs
index c20237f1f86..699189a4e6a 100644
--- a/src/test/run-pass/issue-21486.rs
+++ b/src/test/run-pass/issue-21486.rs
@@ -12,6 +12,7 @@
 // created via FRU and control-flow breaks in the middle of
 // construction.
 
+#![feature(const_fn)]
 
 use std::sync::atomic::{Ordering, AtomicUsize};
 
diff --git a/src/test/run-pass/nested-vec-3.rs b/src/test/run-pass/nested-vec-3.rs
index e59900caf07..89ac6261583 100644
--- a/src/test/run-pass/nested-vec-3.rs
+++ b/src/test/run-pass/nested-vec-3.rs
@@ -12,6 +12,7 @@
 // the contents implement Drop and we hit a panic in the middle of
 // construction.
 
+#![feature(const_fn)]
 
 use std::thread;
 use std::sync::atomic::{AtomicUsize, Ordering};
diff --git a/src/test/run-pass/struct-order-of-eval-3.rs b/src/test/run-pass/struct-order-of-eval-3.rs
index c0ed4ea3ce8..b67eb205396 100644
--- a/src/test/run-pass/struct-order-of-eval-3.rs
+++ b/src/test/run-pass/struct-order-of-eval-3.rs
@@ -11,6 +11,7 @@
 // Checks that functional-record-update order-of-eval is as expected
 // even when no Drop-implementations are involved.
 
+#![feature(const_fn)]
 
 use std::sync::atomic::{Ordering, AtomicUsize};
 
diff --git a/src/test/run-pass/struct-order-of-eval-4.rs b/src/test/run-pass/struct-order-of-eval-4.rs
index 83ea0e3ab74..20d27d8b309 100644
--- a/src/test/run-pass/struct-order-of-eval-4.rs
+++ b/src/test/run-pass/struct-order-of-eval-4.rs
@@ -11,6 +11,7 @@
 // Checks that struct-literal expression order-of-eval is as expected
 // even when no Drop-implementations are involved.
 
+#![feature(const_fn)]
 
 use std::sync::atomic::{Ordering, AtomicUsize};
 
diff --git a/src/test/run-pass/vector-sort-panic-safe.rs b/src/test/run-pass/vector-sort-panic-safe.rs
index f3c4ecb035e..209fe22207f 100644
--- a/src/test/run-pass/vector-sort-panic-safe.rs
+++ b/src/test/run-pass/vector-sort-panic-safe.rs
@@ -10,6 +10,7 @@
 
 
 #![feature(rand, core)]
+#![feature(const_fn)]
 
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::__rand::{thread_rng, Rng};