Test unstable Alloc param on Box

Author: Avi-D-coder

src/test/ui/stability-attribute/auxiliary/unstable_generic_param.rs

@@ -1,6 +1,5 @@
 #![crate_type = "lib"]
 #![feature(staged_api)]
-
 #![stable(feature = "stable_test_feature", since = "1.0.0")]
 
 #[stable(feature = "stable_test_feature", since = "1.0.0")]
@@ -75,3 +74,38 @@ pub const STRUCT4: Struct4 = Struct4 { field: 1 };
 
 #[stable(feature = "stable_test_feature", since = "1.0.0")]
 pub const STRUCT5: Struct5 = Struct5 { field: 1 };
+
+#[stable(feature = "stable_test_feature", since = "1.0.0")]
+pub trait Alloc {}
+
+#[stable(feature = "stable_test_feature", since = "1.0.0")]
+pub struct System {}
+
+#[stable(feature = "stable_test_feature", since = "1.0.0")]
+impl Alloc for System {}
+
+#[stable(feature = "stable_test_feature", since = "1.0.0")]
+pub struct Box1<T, #[unstable(feature = "box_alloc_param", issue = "none")] A: Alloc = System> {
+    ptr: *mut T,
+    alloc: A,
+}
+
+impl<T> Box1<T, System> {
+    #[stable(feature = "stable_test_feature", since = "1.0.0")]
+    pub fn new(mut t: T) -> Self {
+        unsafe { Self { ptr: &mut t, alloc: System {} } }
+    }
+}
+
+#[stable(feature = "stable_test_feature", since = "1.0.0")]
+pub struct Box2<T, A: Alloc = System> {
+    ptr: *mut T,
+    alloc: A,
+}
+
+impl<T> Box2<T, System> {
+    #[stable(feature = "stable_test_feature", since = "1.0.0")]
+    pub fn new(mut t: T) -> Self {
+        Self { ptr: &mut t, alloc: System {} }
+    }
+}

src/test/ui/stability-attribute/generics-default-stability.rs

@@ -109,4 +109,10 @@ fn main() {
 
     let _: Struct6<isize> = Struct6 { field: 1 }; // ok
     let _: Struct6<isize> = Struct6 { field: 0 }; // ok
+
+    let _: Box1<isize, System> = Box1::new(1); //~ ERROR use of unstable library feature 'box_alloc_param'
+    let _: Box1<isize> = Box1::new(1); // ok
+
+    let _: Box2<isize, System> = Box2::new(1); // ok
+    let _: Box2<isize> = Box2::new(1); // ok
 }

src/test/ui/stability-attribute/generics-default-stability.stderr

@@ -168,6 +168,14 @@ LL |     let _: Struct5<isize> = Struct5 { field: 0 };
    |
    = help: add `#![feature(unstable_default)]` to the crate attributes to enable
 
+error[E0658]: use of unstable library feature 'box_alloc_param'
+  --> $DIR/generics-default-stability.rs:113:24
+   |
+LL |     let _: Box1<isize, System> = Box1::new(1);
+   |                        ^^^^^^
+   |
+   = help: add `#![feature(box_alloc_param)]` to the crate attributes to enable
+
 warning: use of deprecated item 'unstable_generic_param::Struct4::field': test
   --> $DIR/generics-default-stability.rs:84:39
    |
@@ -192,6 +200,6 @@ warning: use of deprecated item 'unstable_generic_param::Struct5::field': test
 LL |     let _: Struct5<isize> = Struct5 { field: 0 };
    |                                       ^^^^^^^^
 
-error: aborting due to 12 previous errors; 16 warnings emitted
+error: aborting due to 13 previous errors; 16 warnings emitted
 
 For more information about this error, try `rustc --explain E0658`.