6 files changed, 60 insertions, 19 deletions
diff --git a/library/coretests/tests/fmt/builders.rs b/library/coretests/tests/fmt/builders.rs
index ba4801f5912..156eebb1e9d 100644
--- a/library/coretests/tests/fmt/builders.rs
+++ b/library/coretests/tests/fmt/builders.rs
@@ -173,6 +173,21 @@ mod debug_struct {
             format!("{Bar:#?}")
         );
     }
+
+    #[test]
+    fn test_field_with() {
+        struct Foo;
+        impl fmt::Debug for Foo {
+            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+                fmt.debug_struct("Foo")
+                    .field_with("bar", |f| f.write_str("true"))
+                    .field_with("baz", |f| f.write_str("false"))
+                    .finish()
+            }
+        }
+
+        assert_eq!("Foo {\n    bar: true,\n    baz: false,\n}", format!("{Foo:#?}"))
+    }
 }
 
 mod debug_tuple {
diff --git a/library/coretests/tests/fmt/mod.rs b/library/coretests/tests/fmt/mod.rs
index 16f116d2590..586e890befe 100644
--- a/library/coretests/tests/fmt/mod.rs
+++ b/library/coretests/tests/fmt/mod.rs
@@ -58,6 +58,36 @@ fn test_fmt_debug_of_raw_pointers() {
 }
 
 #[test]
+fn test_fmt_debug_of_mut_reference() {
+    let mut x: u32 = 0;
+
+    assert_eq!(format!("{:?}", &mut x), "0");
+}
+
+#[test]
+fn test_default_write_impls() {
+    use core::fmt::Write;
+
+    struct Buf(String);
+
+    impl Write for Buf {
+        fn write_str(&mut self, s: &str) -> core::fmt::Result {
+            self.0.write_str(s)
+        }
+    }
+
+    let mut buf = Buf(String::new());
+    buf.write_char('a').unwrap();
+
+    assert_eq!(buf.0, "a");
+
+    let mut buf = Buf(String::new());
+    buf.write_fmt(format_args!("a")).unwrap();
+
+    assert_eq!(buf.0, "a");
+}
+
+#[test]
 fn test_estimated_capacity() {
     assert_eq!(format_args!("").estimated_capacity(), 0);
     assert_eq!(format_args!("{}", { "" }).estimated_capacity(), 0);
diff --git a/library/coretests/tests/fmt/num.rs b/library/coretests/tests/fmt/num.rs
index 4c145b484dd..052b16db521 100644
--- a/library/coretests/tests/fmt/num.rs
+++ b/library/coretests/tests/fmt/num.rs
@@ -323,3 +323,9 @@ fn test_format_debug_hex() {
     assert_eq!(format!("{:02x?}", b"Foo\0"), "[46, 6f, 6f, 00]");
     assert_eq!(format!("{:02X?}", b"Foo\0"), "[46, 6F, 6F, 00]");
 }
+
+#[test]
+#[should_panic = "Formatting argument out of range"]
+fn test_rt_width_too_long() {
+    let _ = format!("Hello {:width$}!", "x", width = u16::MAX as usize + 1);
+}
diff --git a/library/coretests/tests/lib.rs b/library/coretests/tests/lib.rs
index a246c806140..5c519f3a499 100644
--- a/library/coretests/tests/lib.rs
+++ b/library/coretests/tests/lib.rs
@@ -33,6 +33,7 @@
 #![feature(core_private_bignum)]
 #![feature(core_private_diy_float)]
 #![feature(cstr_display)]
+#![feature(debug_closure_helpers)]
 #![feature(dec2flt)]
 #![feature(drop_guard)]
 #![feature(duration_constants)]
diff --git a/library/coretests/tests/num/bignum.rs b/library/coretests/tests/num/bignum.rs
index f213fd5366c..6dfa496e018 100644
--- a/library/coretests/tests/num/bignum.rs
+++ b/library/coretests/tests/num/bignum.rs
@@ -168,25 +168,6 @@ fn test_div_rem_small() {
 }
 
 #[test]
-fn test_div_rem() {
-    fn div_rem(n: u64, d: u64) -> (Big, Big) {
-        let mut q = Big::from_small(42);
-        let mut r = Big::from_small(42);
-        Big::from_u64(n).div_rem(&Big::from_u64(d), &mut q, &mut r);
-        (q, r)
-    }
-    assert_eq!(div_rem(1, 1), (Big::from_small(1), Big::from_small(0)));
-    assert_eq!(div_rem(4, 3), (Big::from_small(1), Big::from_small(1)));
-    assert_eq!(div_rem(1, 7), (Big::from_small(0), Big::from_small(1)));
-    assert_eq!(div_rem(45, 9), (Big::from_small(5), Big::from_small(0)));
-    assert_eq!(div_rem(103, 9), (Big::from_small(11), Big::from_small(4)));
-    assert_eq!(div_rem(123456, 77), (Big::from_u64(1603), Big::from_small(25)));
-    assert_eq!(div_rem(0xffff, 1), (Big::from_u64(0xffff), Big::from_small(0)));
-    assert_eq!(div_rem(0xeeee, 0xffff), (Big::from_small(0), Big::from_u64(0xeeee)));
-    assert_eq!(div_rem(2_000_000, 2), (Big::from_u64(1_000_000), Big::from_u64(0)));
-}
-
-#[test]
 fn test_is_zero() {
     assert!(Big::from_small(0).is_zero());
     assert!(!Big::from_small(3).is_zero());
diff --git a/library/coretests/tests/ptr.rs b/library/coretests/tests/ptr.rs
index f8774833d0a..4d5138d539b 100644
--- a/library/coretests/tests/ptr.rs
+++ b/library/coretests/tests/ptr.rs
@@ -490,6 +490,14 @@ fn is_aligned() {
 }
 
 #[test]
+#[should_panic = "is_aligned_to: align is not a power-of-two"]
+fn invalid_is_aligned() {
+    let data = 42;
+    let ptr: *const i32 = &data;
+    assert!(ptr.is_aligned_to(3));
+}
+
+#[test]
 fn offset_from() {
     let mut a = [0; 5];
     let ptr1: *mut i32 = &mut a[1];