add test for enum discriminants

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: Exclude enum_discriminant2.rs due to ICE
	* rust/compile/enum_discriminant2.rs: New test.
	* rust/compile/enum_discriminant3.rs: New test.

Signed-off-by: Ryutaro Okada <[email protected]>

Author: sakupan102

gcc/testsuite/rust/compile/enum_discriminant2.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let y = 3;
+    enum Foo {
+        Bar = y,
+        // { dg-error "cannot find value .y. in this scope" "" { target *-*-* } .-1 }
+    }
+}

gcc/testsuite/rust/compile/enum_discriminant3.rs

@@ -0,0 +1,8 @@
+const x: isize = 1;
+// { dg-warning "unused name" "" { target *-*-* } .-1 }
+
+fn main() {
+    enum Foo {
+        Bar = x,
+    }
+}

gcc/testsuite/rust/compile/nr2/exclude

@@ -28,4 +28,5 @@ torture/loop4.rs
 torture/loop8.rs
 torture/name_resolve1.rs
 issue-3568.rs
+enum_discriminant2.rs
 # please don't delete the trailing newline