reflect: pass the right element type in verifyGCBitsSlice

Currently verifyGCBitsSlice creates a new array type to represent the
slice backing store, but passes the element type as the slice type in
this construction. This is incorrect, but the tests currently don't care
about it. They will in a follow-up CL, so fix it now.

Change-Id: I6ed8a9808ae78c624be316db1566376fa0e12758
Reviewed-on: https://go-review.googlesource.com/c/go/+/537981
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Michael Knyszek <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: mknyszek

src/reflect/all_test.go

@@ -7042,7 +7042,7 @@ func verifyGCBitsSlice(t *testing.T, typ Type, cap int, bits []byte) {
 	// repeat a bitmap for a small array or executing a repeat in
 	// a GC program.
 	val := MakeSlice(typ, 0, cap)
-	data := NewAt(ArrayOf(cap, typ), val.UnsafePointer())
+	data := NewAt(ArrayOf(cap, typ.Elem()), val.UnsafePointer())
 	heapBits := GCBits(data.Interface())
 	// Repeat the bitmap for the slice size, trimming scalars in
 	// the last element.