Add const-types test

src/test/ui/const-generics/const-types.rs

@@ -0,0 +1,16 @@
+// run-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+#[allow(dead_code)]
+
+struct ConstArray<T, const LEN: usize> {
+    array: [T; LEN],
+}
+
+fn main() {
+    let arr = ConstArray::<i32, 8> {
+        array: [0; 8],
+    };
+}

src/test/ui/const-generics/const-types.stderr

@@ -0,0 +1,6 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/const-types.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+