Test that Self properly works in filters

Author: mejrs

tests/ui/on-unimplemented/use_self_no_underscore.rs

@@ -0,0 +1,14 @@
+#![feature(rustc_attrs)]
+
+#[rustc_on_unimplemented(on(
+    all(A = "{integer}", any(Self = "[{integral}; _]",)),
+    message = "an array of type `{Self}` cannot be built directly from an iterator",
+))]
+pub trait FromIterator<A>: Sized {
+    fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> Self;
+}
+fn main() {
+    let iter = 0..42_8;
+    let x: [u8; 8] = FromIterator::from_iter(iter);
+    //~^ ERROR an array of type `[u8; 8]` cannot be built directly from an iterator
+}

tests/ui/on-unimplemented/use_self_no_underscore.stderr

@@ -0,0 +1,15 @@
+error[E0277]: an array of type `[u8; 8]` cannot be built directly from an iterator
+  --> $DIR/use_self_no_underscore.rs:12:22
+   |
+LL |     let x: [u8; 8] = FromIterator::from_iter(iter);
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `FromIterator<{integer}>` is not implemented for `[u8; 8]`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/use_self_no_underscore.rs:7:1
+   |
+LL | pub trait FromIterator<A>: Sized {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.