reject SmartPointer constructions not serving the purpose

3 files changed, 121 insertions, 0 deletions

diff --git a/tests/ui/deriving/deriving-smart-pointer-neg.rs b/tests/ui/deriving/deriving-smart-pointer-neg.rs
new file mode 100644
index 00000000000..bfb4e86b396
--- /dev/null
+++ b/tests/ui/deriving/deriving-smart-pointer-neg.rs
@@ -0,0 +1,45 @@
+#![feature(derive_smart_pointer, arbitrary_self_types)]
+
+use std::marker::SmartPointer;
+
+#[derive(SmartPointer)]
+//~^ ERROR: `SmartPointer` can only be derived on `struct`s with `#[repr(transparent)]`
+enum NotStruct<'a, T: ?Sized> {
+    Variant(&'a T),
+}
+
+#[derive(SmartPointer)]
+//~^ ERROR: At least one generic type should be designated as `#[pointee]` in order to derive `SmartPointer` traits
+#[repr(transparent)]
+struct NoPointee<'a, T: ?Sized> {
+    ptr: &'a T,
+}
+
+#[derive(SmartPointer)]
+//~^ ERROR: `SmartPointer` can only be derived on `struct`s with at least one field
+#[repr(transparent)]
+struct NoField<'a, #[pointee] T: ?Sized> {}
+//~^ ERROR: lifetime parameter `'a` is never used
+//~| ERROR: type parameter `T` is never used
+
+#[derive(SmartPointer)]
+//~^ ERROR: `SmartPointer` can only be derived on `struct`s with at least one field
+#[repr(transparent)]
+struct NoFieldUnit<'a, #[pointee] T: ?Sized>();
+//~^ ERROR: lifetime parameter `'a` is never used
+//~| ERROR: type parameter `T` is never used
+
+#[derive(SmartPointer)]
+//~^ ERROR: `SmartPointer` can only be derived on `struct`s with `#[repr(transparent)]`
+struct NotTransparent<'a, #[pointee] T: ?Sized> {
+    ptr: &'a T,
+}
+
+// However, reordering attributes should work nevertheless.
+#[repr(transparent)]
+#[derive(SmartPointer)]
+struct ThisIsAPossibleSmartPointer<'a, #[pointee] T: ?Sized> {
+    ptr: &'a T,
+}
+
+fn main() {}
diff --git a/tests/ui/deriving/deriving-smart-pointer-neg.stderr b/tests/ui/deriving/deriving-smart-pointer-neg.stderr
new file mode 100644
index 00000000000..d994a6ee376
--- /dev/null
+++ b/tests/ui/deriving/deriving-smart-pointer-neg.stderr
@@ -0,0 +1,75 @@
+error: `SmartPointer` can only be derived on `struct`s with `#[repr(transparent)]`
+  --> $DIR/deriving-smart-pointer-neg.rs:5:10
+   |
+LL | #[derive(SmartPointer)]
+   |          ^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `SmartPointer` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: At least one generic type should be designated as `#[pointee]` in order to derive `SmartPointer` traits
+  --> $DIR/deriving-smart-pointer-neg.rs:11:10
+   |
+LL | #[derive(SmartPointer)]
+   |          ^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `SmartPointer` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `SmartPointer` can only be derived on `struct`s with at least one field
+  --> $DIR/deriving-smart-pointer-neg.rs:18:10
+   |
+LL | #[derive(SmartPointer)]
+   |          ^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `SmartPointer` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `SmartPointer` can only be derived on `struct`s with at least one field
+  --> $DIR/deriving-smart-pointer-neg.rs:25:10
+   |
+LL | #[derive(SmartPointer)]
+   |          ^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `SmartPointer` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `SmartPointer` can only be derived on `struct`s with `#[repr(transparent)]`
+  --> $DIR/deriving-smart-pointer-neg.rs:32:10
+   |
+LL | #[derive(SmartPointer)]
+   |          ^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `SmartPointer` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0392]: lifetime parameter `'a` is never used
+  --> $DIR/deriving-smart-pointer-neg.rs:21:16
+   |
+LL | struct NoField<'a, #[pointee] T: ?Sized> {}
+   |                ^^ unused lifetime parameter
+   |
+   = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`
+
+error[E0392]: type parameter `T` is never used
+  --> $DIR/deriving-smart-pointer-neg.rs:21:31
+   |
+LL | struct NoField<'a, #[pointee] T: ?Sized> {}
+   |                               ^ unused type parameter
+   |
+   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
+
+error[E0392]: lifetime parameter `'a` is never used
+  --> $DIR/deriving-smart-pointer-neg.rs:28:20
+   |
+LL | struct NoFieldUnit<'a, #[pointee] T: ?Sized>();
+   |                    ^^ unused lifetime parameter
+   |
+   = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`
+
+error[E0392]: type parameter `T` is never used
+  --> $DIR/deriving-smart-pointer-neg.rs:28:35
+   |
+LL | struct NoFieldUnit<'a, #[pointee] T: ?Sized>();
+   |                                   ^ unused type parameter
+   |
+   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
+
+error: aborting due to 9 previous errors
+
+For more information about this error, try `rustc --explain E0392`.
diff --git a/tests/ui/deriving/deriving-smart-pointer.rs b/tests/ui/deriving/deriving-smart-pointer.rs
index cfc3369850b..d34a502da68 100644
--- a/tests/ui/deriving/deriving-smart-pointer.rs
+++ b/tests/ui/deriving/deriving-smart-pointer.rs
@@ -4,6 +4,7 @@
 use std::marker::SmartPointer;
 
 #[derive(SmartPointer)]
+#[repr(transparent)]
 struct MyPointer<'a, #[pointee] T: ?Sized> {
     ptr: &'a T,
 }