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diff --git a/tests/ui/nll/issue-21232-partial-init-and-use.rs b/tests/ui/nll/issue-21232-partial-init-and-use.rs
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+++ b/tests/ui/nll/issue-21232-partial-init-and-use.rs
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+// This test enumerates various cases of interest for partial
+// [re]initialization of ADTs and tuples.
+//
+// See rust-lang/rust#21232, rust-lang/rust#54986, and rust-lang/rust#54987.
+//
+// All of tests in this file are expected to change from being
+// rejected, at least under NLL (by rust-lang/rust#54986) to being
+// **accepted** when rust-lang/rust#54987 is implemented.
+// (That's why there are assertions in the code.)
+//
+// See issue-21232-partial-init-and-erroneous-use.rs for cases of
+// tests that are meant to continue failing to compile once
+// rust-lang/rust#54987 is implemented.
+
+struct S<Y> {
+    x: u32,
+
+    // Note that even though `y` may implement `Drop`, under #54987 we
+    // will still allow partial initialization of `S` itself.
+    y: Y,
+}
+
+enum Void { }
+
+type B = Box<u32>;
+
+impl S<B> { fn new() -> Self { S { x: 0, y: Box::new(0) } } }
+
+fn borrow_s(s: &S<B>) { assert_eq!(s.x, 10); assert_eq!(*s.y, 20); }
+fn move_s(s: S<B>) {  assert_eq!(s.x, 10); assert_eq!(*s.y, 20); }
+fn borrow_field(x: &u32) { assert_eq!(*x, 10); }
+
+type T = (u32, B);
+type Tvoid = (u32, Void);
+
+fn borrow_t(t: &T) { assert_eq!(t.0, 10); assert_eq!(*t.1, 20); }
+fn move_t(t: T) {  assert_eq!(t.0, 10); assert_eq!(*t.1, 20); }
+
+struct Q<F> {
+    v: u32,
+    r: R<F>,
+}
+
+struct R<F> {
+    w: u32,
+    f: F,
+}
+
+impl<F> Q<F> { fn new(f: F) -> Self { Q { v: 0, r: R::new(f) } } }
+impl<F> R<F> { fn new(f: F) -> Self { R { w: 0, f } } }
+
+// Axes to cover:
+// * local/field: Is the structure in a local or a field
+// * fully/partial/void: Are we fully initializing it before using any part?
+//                       Is whole type empty due to a void component?
+// * init/reinit: First initialization, or did we previously initialize and then move out?
+// * struct/tuple: Is this a struct or a (X, Y).
+//
+// As a shorthand for the cases above, adding a numeric summary to
+// each test's fn name to denote each point on each axis.
+//
+// e.g., 1000 = field fully init struct; 0211 = local void reinit tuple
+
+// It got pretty monotonous writing the same code over and over, and I
+// feared I would forget details. So I abstracted some desiderata into
+// macros. But I left the initialization code inline, because that's
+// where the errors for #54986 will be emitted.
+
+macro_rules! use_fully {
+    (struct $s:expr) => { {
+        borrow_field(& $s.x );
+        borrow_s(& $s );
+        move_s( $s );
+    } };
+
+    (tuple $t:expr) => { {
+        borrow_field(& $t.0 );
+        borrow_t(& $t );
+        move_t( $t );
+    } }
+}
+
+macro_rules! use_part {
+    (struct $s:expr) => { {
+        borrow_field(& $s.x );
+        match $s { S { ref x, y: _ } => { borrow_field(x); } }
+    } };
+
+    (tuple $t:expr) => { {
+        borrow_field(& $t.0 );
+        match $t { (ref x, _) => { borrow_field(x); } }
+    } }
+}
+
+fn test_0000_local_fully_init_and_use_struct() {
+    let s: S<B>;
+    s.x = 10; s.y = Box::new(20); //~ ERROR E0381
+    use_fully!(struct s);
+}
+
+fn test_0001_local_fully_init_and_use_tuple() {
+    let t: T;
+    t.0 = 10; t.1 = Box::new(20); //~ ERROR E0381
+    use_fully!(tuple t);
+}
+
+fn test_0010_local_fully_reinit_and_use_struct() {
+    let mut s: S<B> = S::new(); drop(s);
+    s.x = 10; s.y = Box::new(20);
+    //~^ ERROR assign to part of moved value: `s` [E0382]
+    use_fully!(struct s);
+}
+
+fn test_0011_local_fully_reinit_and_use_tuple() {
+    let mut t: T = (0, Box::new(0)); drop(t);
+    t.0 = 10; t.1 = Box::new(20);
+    //~^ ERROR assign to part of moved value: `t` [E0382]
+    use_fully!(tuple t);
+}
+
+fn test_0100_local_partial_init_and_use_struct() {
+    let s: S<B>;
+    s.x = 10; //~ ERROR E0381
+    use_part!(struct s);
+}
+
+fn test_0101_local_partial_init_and_use_tuple() {
+    let t: T;
+    t.0 = 10; //~ ERROR E0381
+    use_part!(tuple t);
+}
+
+fn test_0110_local_partial_reinit_and_use_struct() {
+    let mut s: S<B> = S::new(); drop(s);
+    s.x = 10;
+    //~^ ERROR assign to part of moved value: `s` [E0382]
+    use_part!(struct s);
+}
+
+fn test_0111_local_partial_reinit_and_use_tuple() {
+    let mut t: T = (0, Box::new(0)); drop(t);
+    t.0 = 10;
+    //~^ ERROR assign to part of moved value: `t` [E0382]
+    use_part!(tuple t);
+}
+
+fn test_0200_local_void_init_and_use_struct() {
+    let s: S<Void>;
+    s.x = 10; //~ ERROR E0381
+    use_part!(struct s);
+}
+
+fn test_0201_local_void_init_and_use_tuple() {
+    let t: Tvoid;
+    t.0 = 10; //~ ERROR E0381
+    use_part!(tuple t);
+}
+
+// NOTE: uniform structure of tests here makes n21n (aka combining
+// Void with Reinit) an (even more) senseless case, as we cannot
+// safely create initial instance containing Void to move out of and
+// then reinitialize. While I was tempted to sidestep this via some
+// unsafe code (eek), lets just instead not encode such tests.
+
+// fn test_0210_local_void_reinit_and_use_struct() { unimplemented!() }
+// fn test_0211_local_void_reinit_and_use_tuple() { unimplemented!() }
+
+fn test_1000_field_fully_init_and_use_struct() {
+    let q: Q<S<B>>;
+    q.r.f.x = 10; q.r.f.y = Box::new(20); //~ ERROR E0381
+    use_fully!(struct q.r.f);
+}
+
+fn test_1001_field_fully_init_and_use_tuple() {
+    let q: Q<T>;
+    q.r.f.0 = 10; q.r.f.1 = Box::new(20); //~ ERROR E0381
+    use_fully!(tuple q.r.f);
+}
+
+fn test_1010_field_fully_reinit_and_use_struct() {
+    let mut q: Q<S<B>> = Q::new(S::new()); drop(q.r);
+    q.r.f.x = 10; q.r.f.y = Box::new(20);
+    //~^ ERROR assign to part of moved value: `q.r` [E0382]
+    use_fully!(struct q.r.f);
+}
+
+fn test_1011_field_fully_reinit_and_use_tuple() {
+    let mut q: Q<T> = Q::new((0, Box::new(0))); drop(q.r);
+    q.r.f.0 = 10; q.r.f.1 = Box::new(20);
+    //~^ ERROR assign to part of moved value: `q.r` [E0382]
+    use_fully!(tuple q.r.f);
+}
+
+fn test_1100_field_partial_init_and_use_struct() {
+    let q: Q<S<B>>;
+    q.r.f.x = 10; //~ ERROR E0381
+    use_part!(struct q.r.f);
+}
+
+fn test_1101_field_partial_init_and_use_tuple() {
+    let q: Q<T>;
+    q.r.f.0 = 10; //~ ERROR E0381
+    use_part!(tuple q.r.f);
+}
+
+fn test_1110_field_partial_reinit_and_use_struct() {
+    let mut q: Q<S<B>> = Q::new(S::new()); drop(q.r);
+    q.r.f.x = 10;
+    //~^ ERROR assign to part of moved value: `q.r` [E0382]
+    use_part!(struct q.r.f);
+}
+
+fn test_1111_field_partial_reinit_and_use_tuple() {
+    let mut q: Q<T> = Q::new((0, Box::new(0))); drop(q.r);
+    q.r.f.0 = 10;
+    //~^ ERROR assign to part of moved value: `q.r` [E0382]
+    use_part!(tuple q.r.f);
+}
+
+fn test_1200_field_void_init_and_use_struct() {
+    let mut q: Q<S<Void>>;
+    q.r.f.x = 10; //~ ERROR E0381
+    use_part!(struct q.r.f);
+}
+
+fn test_1201_field_void_init_and_use_tuple() {
+    let mut q: Q<Tvoid>;
+    q.r.f.0 = 10; //~ ERROR E0381
+    use_part!(tuple q.r.f);
+}
+
+// See NOTE abve.
+
+// fn test_1210_field_void_reinit_and_use_struct() { unimplemented!() }
+// fn test_1211_field_void_reinit_and_use_tuple() { unimplemented!() }
+
+// The below are some additional cases of interest that have been
+// transcribed from other bugs based on old erroneous codegen when we
+// encountered partial writes.
+
+fn issue_26996() {
+    let mut c = (1, "".to_owned());
+    match c {
+        c2 => {
+            c.0 = 2; //~ ERROR assign to part of moved value
+            assert_eq!(c2.0, 1);
+        }
+    }
+}
+
+fn issue_27021() {
+    let mut c = (1, (1, "".to_owned()));
+    match c {
+        c2 => {
+            (c.1).0 = 2; //~ ERROR assign to part of moved value
+            assert_eq!((c2.1).0, 1);
+        }
+    }
+
+    let mut c = (1, (1, (1, "".to_owned())));
+    match c.1 {
+        c2 => {
+            ((c.1).1).0 = 3; //~ ERROR assign to part of moved value
+            assert_eq!((c2.1).0, 1);
+        }
+    }
+}
+
+fn main() {
+    test_0000_local_fully_init_and_use_struct();
+    test_0001_local_fully_init_and_use_tuple();
+    test_0010_local_fully_reinit_and_use_struct();
+    test_0011_local_fully_reinit_and_use_tuple();
+    test_0100_local_partial_init_and_use_struct();
+    test_0101_local_partial_init_and_use_tuple();
+    test_0110_local_partial_reinit_and_use_struct();
+    test_0111_local_partial_reinit_and_use_tuple();
+    test_0200_local_void_init_and_use_struct();
+    test_0201_local_void_init_and_use_tuple();
+    // test_0210_local_void_reinit_and_use_struct();
+    // test_0211_local_void_reinit_and_use_tuple();
+    test_1000_field_fully_init_and_use_struct();
+    test_1001_field_fully_init_and_use_tuple();
+    test_1010_field_fully_reinit_and_use_struct();
+    test_1011_field_fully_reinit_and_use_tuple();
+    test_1100_field_partial_init_and_use_struct();
+    test_1101_field_partial_init_and_use_tuple();
+    test_1110_field_partial_reinit_and_use_struct();
+    test_1111_field_partial_reinit_and_use_tuple();
+    test_1200_field_void_init_and_use_struct();
+    test_1201_field_void_init_and_use_tuple();
+    // test_1210_field_void_reinit_and_use_struct();
+    // test_1211_field_void_reinit_and_use_tuple();
+
+    issue_26996();
+    issue_27021();
+}