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-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_field.rs38
-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_variant.rs39
-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs46
-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.rs39
-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.stderr12
-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.rs40
-rw-r--r--src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.stderr15
-rw-r--r--src/test/ui/transmutability/visibility/should_accept_if_src_has_private_field.rs38
-rw-r--r--src/test/ui/transmutability/visibility/should_accept_if_src_has_private_variant.rs39
-rw-r--r--src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.rs38
-rw-r--r--src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.stderr12
-rw-r--r--src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.rs39
-rw-r--r--src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.stderr15
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.rs37
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.stderr19
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.rs38
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.stderr19
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_tricky_unreachable_field.rs52
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.rs39
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.stderr19
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.rs42
-rw-r--r--src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.stderr32
22 files changed, 707 insertions, 0 deletions
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_field.rs b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_field.rs
new file mode 100644
index 000000000..5a8c81049
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_field.rs
@@ -0,0 +1,38 @@
+// check-pass
+//! If visibility is assumed, a transmutation should be accepted even if the
+//! destination type contains a private field.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, true>
+ // visibility IS assumed -------------------------------------^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(self) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(self) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(self) field: Zst, // <- private field
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_variant.rs b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_variant.rs
new file mode 100644
index 000000000..77ab4fa6b
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_private_variant.rs
@@ -0,0 +1,39 @@
+// check-pass
+//! If visibility is assumed, a transmutation should be accepted even if the
+//! destination type contains a private variant.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, true>
+ // visibility IS assumed -------------------------------------^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(self) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(self) field: Zst,
+ }
+}
+
+mod dst {
+ #[derive(Copy, Clone)]
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) union Dst {
+ pub(self) field: Zst, // <- private variant
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs
new file mode 100644
index 000000000..2421b24cb
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs
@@ -0,0 +1,46 @@
+// check-pass
+//! Unless visibility is assumed, a transmutation should be rejected if the
+//! destination type contains an unreachable field (e.g., a public field with a
+//! private type). (This rule is distinct from type privacy, which still may
+//! forbid naming such types.)
+//!
+//! This test exercises a tricky-to-implement instance of this principle: the
+//! "pub-in-priv trick". In the below example, the type `dst::private::Zst` is
+//! unreachable from `Context`.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, true>
+ // visibility IS assumed -------------------------------------^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ mod private {
+ #[repr(C)] pub struct Zst; // <- unreachable type
+ }
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: private::Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.rs b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.rs
new file mode 100644
index 000000000..80b454fda
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.rs
@@ -0,0 +1,39 @@
+//! If visibility is assumed, a transmutation should be accepted even if the
+//! destination type contains an unreachable field (e.g., a public field with a
+//! private type). (This rule is distinct from type privacy, which still may
+//! forbid naming such types.)
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, true>
+ // visibility IS assumed -------------------------------------^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(self) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(self) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(self) struct Zst; // <- unreachable type
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: Zst, //~ ERROR private type
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.stderr b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.stderr
new file mode 100644
index 000000000..be83b7ce3
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_field.stderr
@@ -0,0 +1,12 @@
+error[E0446]: private type `dst::Zst` in public interface
+ --> $DIR/should_accept_if_dst_has_unreachable_field.rs:32:9
+ |
+LL | #[repr(C)] pub(self) struct Zst; // <- unreachable type
+ | -------------------- `dst::Zst` declared as private
+...
+LL | pub(in super) field: Zst,
+ | ^^^^^^^^^^^^^^^^^^^^^^^^ can't leak private type
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0446`.
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.rs b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.rs
new file mode 100644
index 000000000..7c53c91e4
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.rs
@@ -0,0 +1,40 @@
+//! If visibility is assumed, a transmutation should be accepted even if the
+//! destination type contains an unreachable field (e.g., a public field with a
+//! private type). (This rule is distinct from type privacy, which still may
+//! forbid naming such types.)
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, true>
+ // visibility IS assumed -------------------------------------^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(self) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(self) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ // unreachable type
+ #[repr(C)] pub(self) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>(); //~ ERROR `Dst` is private
+}
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.stderr b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.stderr
new file mode 100644
index 000000000..827df05de
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_unreachable_ty.stderr
@@ -0,0 +1,15 @@
+error[E0603]: struct `Dst` is private
+ --> $DIR/should_accept_if_dst_has_unreachable_ty.rs:39:46
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^ private struct
+ |
+note: the struct `Dst` is defined here
+ --> $DIR/should_accept_if_dst_has_unreachable_ty.rs:32:16
+ |
+LL | #[repr(C)] pub(self) struct Dst {
+ | ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0603`.
diff --git a/src/test/ui/transmutability/visibility/should_accept_if_src_has_private_field.rs b/src/test/ui/transmutability/visibility/should_accept_if_src_has_private_field.rs
new file mode 100644
index 000000000..c3f298f01
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_accept_if_src_has_private_field.rs
@@ -0,0 +1,38 @@
+// check-pass
+//! The presence of a private field in the source type does not affect
+//! transmutability.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(self) field: Zst, // <- private field
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/should_accept_if_src_has_private_variant.rs b/src/test/ui/transmutability/visibility/should_accept_if_src_has_private_variant.rs
new file mode 100644
index 000000000..73f6aece5
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_accept_if_src_has_private_variant.rs
@@ -0,0 +1,39 @@
+// check-pass
+//! The presence of a private variant in the source type does not affect
+//! transmutability.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[derive(Copy, Clone)]
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) union Src {
+ pub(self) field: Zst, // <- private variant
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.rs b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.rs
new file mode 100644
index 000000000..6d602601e
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.rs
@@ -0,0 +1,38 @@
+//! The presence of an unreachable field in the source type (e.g., a public
+//! field with a private type does not affect transmutability. (This rule is
+//! distinct from type privacy, which still may forbid naming such types.)
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(self) struct Zst; // <- unreachable type
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst, //~ ERROR private type
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.stderr b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.stderr
new file mode 100644
index 000000000..3f7d08d0a
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_field.stderr
@@ -0,0 +1,12 @@
+error[E0446]: private type `src::Zst` in public interface
+ --> $DIR/should_accept_if_src_has_unreachable_field.rs:23:9
+ |
+LL | #[repr(C)] pub(self) struct Zst; // <- unreachable type
+ | -------------------- `src::Zst` declared as private
+...
+LL | pub(in super) field: Zst,
+ | ^^^^^^^^^^^^^^^^^^^^^^^^ can't leak private type
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0446`.
diff --git a/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.rs b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.rs
new file mode 100644
index 000000000..1943fb871
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.rs
@@ -0,0 +1,39 @@
+//! The presence of an unreachable source type (i.e., the source type is
+//! private) does not affect transmutability. (This rule is distinct from type
+//! privacy, which still may forbid naming such types.)
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ // unreachable type
+ #[repr(C)] pub(self) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>(); //~ ERROR `Src` is private
+}
diff --git a/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.stderr b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.stderr
new file mode 100644
index 000000000..e961984e1
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_accept_if_src_has_unreachable_ty.stderr
@@ -0,0 +1,15 @@
+error[E0603]: struct `Src` is private
+ --> $DIR/should_accept_if_src_has_unreachable_ty.rs:38:36
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^ private struct
+ |
+note: the struct `Src` is defined here
+ --> $DIR/should_accept_if_src_has_unreachable_ty.rs:23:16
+ |
+LL | #[repr(C)] pub(self) struct Src {
+ | ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0603`.
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.rs b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.rs
new file mode 100644
index 000000000..fcf3f3a52
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.rs
@@ -0,0 +1,37 @@
+//! Unless visibility is assumed, a transmutation should be rejected if the
+//! destination type contains a private field.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(self) field: Zst, // <- private field
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>(); //~ ERROR cannot be safely transmuted
+}
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.stderr b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.stderr
new file mode 100644
index 000000000..85124019e
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_field.stderr
@@ -0,0 +1,19 @@
+error[E0277]: `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ --> $DIR/should_reject_if_dst_has_private_field.rs:36:41
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^^^^^^ `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ |
+ = help: the trait `BikeshedIntrinsicFrom<Src, test::Context, false, false, false, false>` is not implemented for `Dst`
+note: required by a bound in `is_transmutable`
+ --> $DIR/should_reject_if_dst_has_private_field.rs:13:14
+ |
+LL | pub fn is_transmutable<Src, Dst, Context>()
+ | --------------- required by a bound in this
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_transmutable`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.rs b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.rs
new file mode 100644
index 000000000..566b56467
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.rs
@@ -0,0 +1,38 @@
+//! Unless visibility is assumed, a transmutation should be rejected if the
+//! destination type contains a private variant.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ #[derive(Copy, Clone)]
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) union Dst {
+ pub(self) field: Zst, // <- private variant
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>(); //~ ERROR cannot be safely transmuted
+}
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.stderr b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.stderr
new file mode 100644
index 000000000..0be564d93
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.stderr
@@ -0,0 +1,19 @@
+error[E0277]: `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ --> $DIR/should_reject_if_dst_has_private_variant.rs:37:41
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^^^^^^ `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ |
+ = help: the trait `BikeshedIntrinsicFrom<Src, test::Context, false, false, false, false>` is not implemented for `Dst`
+note: required by a bound in `is_transmutable`
+ --> $DIR/should_reject_if_dst_has_private_variant.rs:13:14
+ |
+LL | pub fn is_transmutable<Src, Dst, Context>()
+ | --------------- required by a bound in this
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_transmutable`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_tricky_unreachable_field.rs b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_tricky_unreachable_field.rs
new file mode 100644
index 000000000..35fff5966
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_tricky_unreachable_field.rs
@@ -0,0 +1,52 @@
+// check-pass
+//! NOTE: This test documents a known-bug in the implementation of the
+//! transmutability trait. Once fixed, the above "check-pass" header should be
+//! removed, and an "ERROR cannot be safely transmuted" annotation should be added at the end
+//! of the line starting with `assert::is_transmutable`.
+//!
+//! Unless visibility is assumed, a transmutation should be rejected if the
+//! destination type contains an unreachable field (e.g., a public field with a
+//! private type). (This rule is distinct from type privacy, which still may
+//! forbid naming such types.)
+//!
+//! This test exercises a tricky-to-implement instance of this principle: the
+//! "pub-in-priv trick". In the below example, the type `dst::private::Zst` is
+//! unreachable from `Context`. Consequently, the transmute from `Src` to `Dst`
+//! SHOULD be rejected.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ mod private {
+ #[repr(C)] pub struct Zst; // <- unreachable type
+ }
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: private::Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+}
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.rs b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.rs
new file mode 100644
index 000000000..42799d803
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.rs
@@ -0,0 +1,39 @@
+//! Unless visibility is assumed, a transmutation should be rejected if the
+//! destination type contains an unreachable field (e.g., a public field with a
+//! private type). (This rule is distinct from type privacy, which still may
+//! forbid naming such types.)
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(self) struct Zst; // <- unreachable type
+
+ #[repr(C)] pub(in super) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>(); //~ ERROR cannot be safely transmuted
+}
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.stderr b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.stderr
new file mode 100644
index 000000000..95c68d452
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_field.stderr
@@ -0,0 +1,19 @@
+error[E0277]: `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ --> $DIR/should_reject_if_dst_has_unreachable_field.rs:38:41
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^^^^^^ `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ |
+ = help: the trait `BikeshedIntrinsicFrom<Src, test::Context, false, false, false, false>` is not implemented for `Dst`
+note: required by a bound in `is_transmutable`
+ --> $DIR/should_reject_if_dst_has_unreachable_field.rs:15:14
+ |
+LL | pub fn is_transmutable<Src, Dst, Context>()
+ | --------------- required by a bound in this
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_transmutable`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.rs b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.rs
new file mode 100644
index 000000000..e13b32b30
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.rs
@@ -0,0 +1,42 @@
+//! Unless visibility is assumed, a transmutation should be rejected if the
+//! destination type contains an unreachable field (e.g., a public field with a
+//! private type). (This rule is distinct from type privacy, which still may
+//! forbid naming such types.)
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+ use std::mem::BikeshedIntrinsicFrom;
+
+ pub fn is_transmutable<Src, Dst, Context>()
+ where
+ Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ // visibility is NOT assumed ---------------------------------^^^^^
+ {}
+}
+
+mod src {
+ #[repr(C)] pub(in super) struct Zst;
+
+ #[repr(C)] pub(in super) struct Src {
+ pub(in super) field: Zst,
+ }
+}
+
+mod dst {
+ #[repr(C)] pub(in super) struct Zst;
+
+ // unreachable type
+ #[repr(C)] pub(self) struct Dst {
+ pub(in super) field: Zst,
+ }
+}
+
+fn test() {
+ struct Context;
+ assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ //~^ ERROR `Dst` is private
+ //~| ERROR cannot be safely transmuted
+}
diff --git a/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.stderr b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.stderr
new file mode 100644
index 000000000..3391839e3
--- /dev/null
+++ b/src/test/ui/transmutability/visibility/should_reject_if_dst_has_unreachable_ty.stderr
@@ -0,0 +1,32 @@
+error[E0603]: struct `Dst` is private
+ --> $DIR/should_reject_if_dst_has_unreachable_ty.rs:39:46
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^ private struct
+ |
+note: the struct `Dst` is defined here
+ --> $DIR/should_reject_if_dst_has_unreachable_ty.rs:32:16
+ |
+LL | #[repr(C)] pub(self) struct Dst {
+ | ^^^^^^^^^^^^^^^^^^^^
+
+error[E0277]: `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ --> $DIR/should_reject_if_dst_has_unreachable_ty.rs:39:41
+ |
+LL | assert::is_transmutable::<src::Src, dst::Dst, Context>();
+ | ^^^^^^^^ `Src` cannot be safely transmuted into `Dst` in the defining scope of `test::Context`.
+ |
+ = help: the trait `BikeshedIntrinsicFrom<Src, test::Context, false, false, false, false>` is not implemented for `Dst`
+note: required by a bound in `is_transmutable`
+ --> $DIR/should_reject_if_dst_has_unreachable_ty.rs:15:14
+ |
+LL | pub fn is_transmutable<Src, Dst, Context>()
+ | --------------- required by a bound in this
+LL | where
+LL | Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_transmutable`
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0277, E0603.
+For more information about an error, try `rustc --explain E0277`.