Add UI test

Author: Aaron1011

src/test/ui/privacy/pub-priv-dep/auxiliary/priv_dep.rs

@@ -0,0 +1 @@
+pub struct OtherType;

src/test/ui/privacy/pub-priv-dep/pub-priv1.rs

@@ -0,0 +1,31 @@
+ // aux-build:priv_dep.rs
+#![feature(public_private_dependencies)]
+#![deny(leaked_private_dependency)]
+
+// This crate is a private dependency
+extern crate priv_dep;
+
+use priv_dep::OtherType;
+
+// Type from private dependency used in private
+// type - this is fine
+struct PrivateType {
+    field: OtherType
+}
+
+pub struct PublicType {
+    pub field: OtherType,
+    //~^ ERROR type `priv_dep::OtherType` from private dependency 'priv_dep' in public interface [leaked_private_dependency]
+    //~| WARNING this was previously accepted
+    priv_field: OtherType,
+}
+
+impl PublicType {
+    pub fn pub_fn(param: OtherType) {}
+    //~^ ERROR type `priv_dep::OtherType` from private dependency 'priv_dep' in public interface [leaked_private_dependency]
+    //~| WARNING this was previously accepted
+
+    fn priv_fn(param: OtherType) {}
+}
+
+fn main() {}

src/test/ui/privacy/pub-priv-dep/pub-priv1.stderr

@@ -0,0 +1,25 @@
+error: type `priv_dep::OtherType` from private dependency 'priv_dep' in public interface
+  --> $DIR/pub-priv1.rs:17:5
+   |
+LL |     pub field: OtherType,
+   |     ^^^^^^^^^^^^^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/pub-priv1.rs:3:9
+   |
+LL | #![deny(leaked_private_dependency)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #44663 <https://github.com/rust-lang/rust/issues/44663>
+
+error: type `priv_dep::OtherType` from private dependency 'priv_dep' in public interface
+  --> $DIR/pub-priv1.rs:24:5
+   |
+LL |     pub fn pub_fn(param: OtherType) {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #44663 <https://github.com/rust-lang/rust/issues/44663>
+
+error: aborting due to 2 previous errors
+