Add test for mixed stability levels

Author: dianne

tests/ui/stability-attribute/auxiliary/mixed-levels.rs

@@ -0,0 +1,29 @@
+//! definitions for ../mixed-levels.rs
+
+#![stable(feature = "stable_feature", since = "1.0.0")]
+#![feature(staged_api)]
+#![crate_type = "lib"]
+
+#[stable(feature = "stable_a", since = "1.0.0")]
+#[stable(feature = "stable_b", since = "1.8.2")]
+#[macro_export]
+macro_rules! stable_mac {
+    () => ()
+}
+
+#[unstable(feature = "unstable_a", issue = "none")]
+#[stable(feature = "stable_a", since = "1.0.0")]
+#[macro_export]
+macro_rules! unstable_mac {
+    () => ()
+}
+
+#[stable(feature = "stable_feature", since = "1.0.0")]
+#[rustc_const_stable(feature = "stable_c", since = "1.8.2")]
+#[rustc_const_stable(feature = "stable_d", since = "1.0.0")]
+pub const fn const_stable_fn() {}
+
+#[stable(feature = "stable_feature", since = "1.0.0")]
+#[rustc_const_unstable(feature = "unstable_c", issue = "none")]
+#[rustc_const_stable(feature = "stable_c", since = "1.8.2")]
+pub const fn const_unstable_fn() {}

tests/ui/stability-attribute/mixed-levels.rs

@@ -0,0 +1,13 @@
+//! Test stability levels for items formerly dependent on multiple unstable features.
+//@ aux-build:mixed-levels.rs
+
+extern crate mixed_levels;
+
+const USE_STABLE: () = mixed_levels::const_stable_fn();
+const USE_UNSTABLE: () = mixed_levels::const_unstable_fn();
+//~^ ERROR `const_unstable_fn` is not yet stable as a const fn
+
+fn main() {
+    mixed_levels::stable_mac!();
+    mixed_levels::unstable_mac!(); //~ ERROR use of unstable library feature `unstable_a` [E0658]
+}

tests/ui/stability-attribute/mixed-levels.stderr

@@ -0,0 +1,22 @@
+error[E0658]: use of unstable library feature `unstable_a`
+  --> $DIR/mixed-levels.rs:12:5
+   |
+LL |     mixed_levels::unstable_mac!();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(unstable_a)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: `const_unstable_fn` is not yet stable as a const fn
+  --> $DIR/mixed-levels.rs:7:26
+   |
+LL | const USE_UNSTABLE: () = mixed_levels::const_unstable_fn();
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: use of unstable library feature `unstable_c`
+   = help: add `#![feature(unstable_c)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0658`.