tests for #[repr(no_niche)].

src/test/ui/repr/feature-gate-no-niche.rs

@@ -0,0 +1,20 @@
+use std::num::NonZeroU8 as N8;
+use std::num::NonZeroU16 as N16;
+
+#[repr(no_niche)]
+pub struct Cloaked(N16);
+//~^^ ERROR the attribute `repr(no_niche)` is currently unstable [E0658]
+
+#[repr(transparent, no_niche)]
+pub struct Shadowy(N16);
+//~^^ ERROR the attribute `repr(no_niche)` is currently unstable [E0658]
+
+#[repr(no_niche)]
+pub enum Cloaked1 { _A(N16), }
+//~^^ ERROR the attribute `repr(no_niche)` is currently unstable [E0658]
+
+#[repr(no_niche)]
+pub enum Cloaked2 { _A(N16), _B(u8, N8) }
+//~^^ ERROR the attribute `repr(no_niche)` is currently unstable [E0658]
+
+fn main() { }

src/test/ui/repr/feature-gate-no-niche.stderr

@@ -0,0 +1,35 @@
+error[E0658]: the attribute `repr(no_niche)` is currently unstable
+  --> $DIR/feature-gate-no-niche.rs:4:8
+   |
+LL | #[repr(no_niche)]
+   |        ^^^^^^^^
+   |
+   = help: add `#![feature(no_niche)]` to the crate attributes to enable
+
+error[E0658]: the attribute `repr(no_niche)` is currently unstable
+  --> $DIR/feature-gate-no-niche.rs:8:21
+   |
+LL | #[repr(transparent, no_niche)]
+   |                     ^^^^^^^^
+   |
+   = help: add `#![feature(no_niche)]` to the crate attributes to enable
+
+error[E0658]: the attribute `repr(no_niche)` is currently unstable
+  --> $DIR/feature-gate-no-niche.rs:12:8
+   |
+LL | #[repr(no_niche)]
+   |        ^^^^^^^^
+   |
+   = help: add `#![feature(no_niche)]` to the crate attributes to enable
+
+error[E0658]: the attribute `repr(no_niche)` is currently unstable
+  --> $DIR/feature-gate-no-niche.rs:16:8
+   |
+LL | #[repr(no_niche)]
+   |        ^^^^^^^^
+   |
+   = help: add `#![feature(no_niche)]` to the crate attributes to enable
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0658`.

src/test/ui/repr/repr-no-niche-inapplicable-to-unions.rs

@@ -0,0 +1,14 @@
+#![feature(no_niche)]
+
+use std::num::NonZeroU8 as N8;
+use std::num::NonZeroU16 as N16;
+
+#[repr(no_niche)]
+pub union Cloaked1 { _A: N16 }
+//~^^ ERROR attribute should be applied to struct or enum [E0517]
+
+#[repr(no_niche)]
+pub union Cloaked2 { _A: N16, _B: (u8, N8) }
+//~^^ ERROR attribute should be applied to struct or enum [E0517]
+
+fn main() { }

src/test/ui/repr/repr-no-niche-inapplicable-to-unions.stderr

@@ -0,0 +1,19 @@
+error[E0517]: attribute should be applied to struct or enum
+  --> $DIR/repr-no-niche-inapplicable-to-unions.rs:6:8
+   |
+LL | #[repr(no_niche)]
+   |        ^^^^^^^^
+LL | pub union Cloaked1 { _A: N16 }
+   | ------------------------------ not a struct or enum
+
+error[E0517]: attribute should be applied to struct or enum
+  --> $DIR/repr-no-niche-inapplicable-to-unions.rs:10:8
+   |
+LL | #[repr(no_niche)]
+   |        ^^^^^^^^
+LL | pub union Cloaked2 { _A: N16, _B: (u8, N8) }
+   | -------------------------------------------- not a struct or enum
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0517`.