cgen: fix multi_array index issue

vlib/builtin/array.v

@@ -43,6 +43,21 @@ fn __new_array_with_default(mylen int, cap int, elm_size int, val voidptr) array
 	return arr
 }
 
+fn __new_array_with_array_default(mylen int, cap int, elm_size int, val array) array {
+	cap_ := if cap < mylen { mylen } else { cap }
+	arr := array{
+		element_size: elm_size
+		data: vcalloc(cap_ * elm_size)
+		len: mylen
+		cap: cap_
+	}
+	for i in 0..arr.len {
+		val_clone := val.clone()
+		C.memcpy(charptr(arr.data) + i*elm_size, &val_clone, elm_size)
+	}
+	return arr
+}
+
 // Private function, used by V (`nums := [1, 2, 3]`)
 fn new_array_from_c_array(len, cap, elm_size int, c_array voidptr) array {
 	cap_ := if cap < len { len } else { cap }

vlib/builtin/array_test.v

@@ -816,3 +816,9 @@ fn test_array_with_cap() {
 	assert a5.len == 1
 	assert a5.cap == 10
 }
+
+fn test_mutli_array_index() {
+	mut a := [][]int{len:2, init: []int{len:3, init:0}}
+	a[0][0] = 1
+	assert '$a' == '[[1, 0, 0], [0, 0, 0]]'
+}

vlib/v/gen/cgen.v

@@ -4320,10 +4320,16 @@ fn (mut g Gen) array_init(it ast.ArrayInit) {
 		g.write('}')
 		return
 	}
-	// elem_sym := g.table.get_type_symbol(it.elem_type)
 	elem_type_str := g.typ(it.elem_type)
 	if it.exprs.len == 0 {
+		elem_sym := g.table.get_type_symbol(it.elem_type)
+		is_default_array := elem_sym.kind == .array && it.has_default
+
+		if is_default_array {
+			g.write('__new_array_with_array_default(')
+		} else {
 			g.write('__new_array_with_default(')
+		}
 		if it.has_len {
 			g.expr(it.len_expr)
 			g.write(', ')
@@ -4337,11 +4343,15 @@ fn (mut g Gen) array_init(it ast.ArrayInit) {
 			g.write('0, ')
 		}
 		g.write('sizeof($elem_type_str), ')
+		if is_default_array {
+			g.write('_val_$it.pos.pos)')
+		} else {
 			if it.has_default || (it.has_len && it.elem_type == table.string_type) {
 				g.write('&_val_$it.pos.pos)')
 			} else {
 				g.write('0)')
 			}
+		}
 		return
 	}
 	len := it.exprs.len