add a canary test for complex repr(simd)

src/test/ui/simd/simd-array-trait.rs

@@ -0,0 +1,40 @@
+// Figuring out the size of a vector type that depends on traits doesn't ICE
+
+#![allow(dead_code)]
+
+// pretty-expanded FIXME #23616
+
+#![feature(repr_simd, platform_intrinsics, const_generics)]
+#![allow(non_camel_case_types, incomplete_features)]
+
+pub trait Simd {
+    type Lane: Clone + Copy;
+    const SIZE: usize;
+}
+
+pub struct i32x4;
+impl Simd for i32x4 {
+    type Lane = i32;
+    const SIZE: usize = 4;
+}
+
+#[repr(simd)]
+#[derive(Copy, Clone)]
+pub struct T<S: Simd>([S::Lane; S::SIZE]); //~ ERROR constant expression depends on a generic parameter
+
+extern "platform-intrinsic" {
+    fn simd_insert<T, E>(x: T, idx: u32, y: E) -> T;
+    fn simd_extract<T, E>(x: T, idx: u32) -> E;
+}
+
+pub fn main() {
+    let mut t = T::<i32x4>([0; 4]);
+    unsafe {
+        for i in 0_i32..4 {
+            t = simd_insert(t, i as u32, i);
+        }
+        for i in 0_i32..4 {
+            assert_eq!(i, simd_extract(t, i as u32));
+        }
+    }
+}