Add test for multiple unstable_feature_bound attr

Author: tiif

tests/ui/unstable-feature_bound/unstable_feature_bound_multi_attr.rs

@@ -0,0 +1,37 @@
+#![allow(internal_features)]
+#![feature(staged_api)]
+#![allow(dead_code)]
+#![unstable(feature = "feat_bar", issue = "none" )]
+
+
+/// Test the behaviour of multiple unstable_feature_bound attribute.
+
+trait Foo {
+    fn foo();
+}
+struct Bar;
+
+#[unstable_feature_bound(feat_bar, feat_koo)]
+#[unstable_feature_bound(feat_foo, feat_moo)]
+impl Foo for Bar {
+    fn foo(){}
+}
+
+#[unstable_feature_bound(feat_bar, feat_koo)]
+#[unstable_feature_bound(feat_foo, feat_moo)]
+fn moo() {
+    Bar::foo();
+}
+
+#[unstable_feature_bound(feat_bar, feat_koo, feat_foo, feat_moo)]
+fn koo() {
+    Bar::foo();
+}
+
+#[unstable_feature_bound(feat_koo, feat_foo, feat_moo)]
+fn boo() {
+    Bar::foo();
+    //~^ ERROR: type annotations needed: cannot satisfy `unstable feature: `feat_bar``
+}
+
+fn main() {}

tests/ui/unstable-feature_bound/unstable_feature_bound_multi_attr.stderr

@@ -0,0 +1,18 @@
+error[E0284]: type annotations needed: cannot satisfy `unstable feature: `feat_bar``
+  --> $DIR/unstable_feature_bound_multi_attr.rs:33:5
+   |
+LL |     Bar::foo();
+   |     ^^^ cannot satisfy `unstable feature: `feat_bar``
+   |
+note: required for `Bar` to implement `Foo`
+  --> $DIR/unstable_feature_bound_multi_attr.rs:16:6
+   |
+LL | #[unstable_feature_bound(feat_bar, feat_koo)]
+   | --------------------------------------------- unsatisfied trait bound introduced here
+LL | #[unstable_feature_bound(feat_foo, feat_moo)]
+LL | impl Foo for Bar {
+   |      ^^^     ^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0284`.