checker: disallow `x := [13]SumType{}` too

vlib/v/checker/checker.v

@@ -2943,6 +2943,13 @@ fn (mut c Checker) check_array_init_para_type(para string, expr ast.Expr, pos to
 	}
 }
 
+pub fn (mut c Checker) ensure_sumtype_array_has_default_value(array_init ast.ArrayInit) {
+	sym := c.table.get_type_symbol(array_init.elem_type)
+	if sym.kind == .sum_type && !array_init.has_default {
+		c.error('cannot initialize sum type array without default value', array_init.pos)
+	}
+}
+
 pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 	// println('checker: array init $array_init.pos.line_nr $c.file.path')
 	mut elem_type := table.void_type
@@ -2956,21 +2963,22 @@ pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 				c.check_array_init_para_type('len', array_init.len_expr, array_init.pos)
 			}
 		}
-		sym := c.table.get_type_symbol(array_init.elem_type)
 		if array_init.has_default {
 			default_typ := c.expr(array_init.default_expr)
 			c.check_expected(default_typ, array_init.elem_type) or {
 				c.error(err.msg, array_init.default_expr.position())
 			}
 		}
-		if sym.kind == .sum_type {
-			if array_init.has_len && !array_init.has_default {
-				c.error('cannot initalize sum type array without default value', array_init.elem_type_pos)
-			}
+		if array_init.has_len {
+			c.ensure_sumtype_array_has_default_value(array_init)
 		}
 		c.ensure_type_exists(array_init.elem_type, array_init.elem_type_pos) or {}
 		return array_init.typ
 	}
+	if array_init.is_fixed {
+		c.ensure_sumtype_array_has_default_value(array_init)
+		c.ensure_type_exists(array_init.elem_type, array_init.elem_type_pos) or {}
+	}
 	// a = []
 	if array_init.exprs.len == 0 {
 		// a := fn_returing_opt_array() or { [] }

vlib/v/checker/tests/array_init_sum_type_without_init_value_and_len_err.out

@@ -1,7 +1,14 @@
-vlib/v/checker/tests/array_init_sum_type_without_init_value_and_len_err.vv:4:9: error: cannot initalize sum type array without default value
+vlib/v/checker/tests/array_init_sum_type_without_init_value_and_len_err.vv:4:7: error: cannot initialize sum type array without default value
     2 | 
     3 | fn main() {
     4 |     a := []Foo{len: 10}
-      |            ~~~
+      |          ~~~~~~
     5 |     println(a)
     6 |
+vlib/v/checker/tests/array_init_sum_type_without_init_value_and_len_err.vv:7:13: error: cannot initialize sum type array without default value
+    5 |     println(a)
+    6 | 
+    7 |     fixed_a := [10]Foo{}
+      |                ~~~~~~~~~
+    8 |     println(fixed_a)
+    9 | }

vlib/v/checker/tests/array_init_sum_type_without_init_value_and_len_err.vv

@@ -1,7 +1,9 @@
-type Foo = string | int
+type Foo = int | string
 
 fn main() {
 	a := []Foo{len: 10}
 	println(a)
 
+	fixed_a := [10]Foo{}
+	println(fixed_a)
 }