checker: do not allow nil sum types init

vlib/builtin/linux_bare/array_bare.v

@@ -0,0 +1,53 @@
+module builtin
+
+pub struct array {
+pub:
+	data         voidptr
+	len          int
+	cap          int
+	element_size int
+}
+
+// for now off the stack
+fn new_array_from_c_array(len int, cap int, elm_size int, c_array voidptr) array {
+	arr := array{
+		len: len
+		cap: cap
+		element_size: elm_size
+		data: c_array
+	}
+	return arr
+}
+
+// Private function. Used to implement array[] operator
+fn (a array) get(i int) voidptr {
+	if i < 0 || i >= a.len {
+		panic('array.get: index out of range') // FIXME: (i == $i, a.len == $a.len)')
+	}
+	return a.data + i * a.element_size
+}
+
+// Private function. Used to implement assigment to the array element.
+fn (mut a array) set(i int, val voidptr) {
+	if i < 0 || i >= a.len {
+		panic('array.set: index out of range') // FIXME: (i == $i, a.len == $a.len)')
+	}
+	mem_copy(a.data + a.element_size * i, val, a.element_size)
+}
+
+// array.repeat returns new array with the given array elements
+// repeated `nr_repeat` times
+pub fn (a array) repeat(nr_repeats int) array {
+	assert nr_repeats >= 0
+
+	arr := array{
+		len: nr_repeats * a.len
+		cap: nr_repeats * a.len
+		element_size: a.element_size
+		data: malloc(nr_repeats * a.len * a.element_size)
+	}
+	for i in 0 .. nr_repeats {
+		mem_copy(arr.data + i * a.len * a.element_size, a.data, a.len * a.element_size)
+	}
+	return arr
+}