Add failing test

Author: In-line

src/test/ui/suggestions/dont-suggest-doc-hidden-variant-for-enum/auxiliary/hidden-child.rs

@@ -0,0 +1,8 @@
+#![crate_type = "lib"]
+
+extern crate core;
+
+pub mod __private {
+    #[doc(hidden)]
+    pub use core::option::Option::{self, None, Some};
+}

src/test/ui/suggestions/dont-suggest-doc-hidden-variant-for-enum/auxiliary/hidden-parent.rs

@@ -0,0 +1,8 @@
+#![crate_type = "lib"]
+
+extern crate core;
+
+#[doc(hidden)]
+pub mod __private {
+    pub use core::option::Option::{self, None, Some};
+}

src/test/ui/suggestions/dont-suggest-doc-hidden-variant-for-enum/hidden-child.rs

@@ -0,0 +1,10 @@
+// aux-build:hidden-child.rs
+
+// FIXME(compiler-errors): This currently suggests the wrong thing.
+// UI test exists to track the problem.
+
+extern crate hidden_child;
+
+fn main() {
+    let x: Option<i32> = 1i32; //~ ERROR mismatched types
+}

src/test/ui/suggestions/dont-suggest-doc-hidden-variant-for-enum/hidden-child.stderr

@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> $DIR/hidden-child.rs:9:26
+   |
+LL |     let x: Option<i32> = 1i32;
+   |            -----------   ^^^^ expected enum `Option`, found `i32`
+   |            |
+   |            expected due to this
+   |
+   = note: expected enum `Option<i32>`
+              found type `i32`
+help: try wrapping the expression in `hidden_child::__private::Some`
+   |
+LL |     let x: Option<i32> = hidden_child::__private::Some(1i32);
+   |                          ++++++++++++++++++++++++++++++    +
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/suggestions/dont-suggest-doc-hidden-variant-for-enum/hidden-parent.rs

@@ -0,0 +1,7 @@
+// aux-build:hidden-parent.rs
+
+extern crate hidden_parent;
+
+fn main() {
+    let x: Option<i32> = 1i32; //~ ERROR mismatched types
+}

src/test/ui/suggestions/dont-suggest-doc-hidden-variant-for-enum/hidden-parent.stderr

@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> $DIR/hidden-parent.rs:6:26
+   |
+LL |     let x: Option<i32> = 1i32;
+   |            -----------   ^^^^ expected enum `Option`, found `i32`
+   |            |
+   |            expected due to this
+   |
+   = note: expected enum `Option<i32>`
+              found type `i32`
+help: try wrapping the expression in `hidden_parent::__private::Some`
+   |
+LL |     let x: Option<i32> = hidden_parent::__private::Some(1i32);
+   |                          +++++++++++++++++++++++++++++++    +
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.