cgen: auto cast sum type in array init. fixes #6907

vlib/v/ast/ast.v

@@ -825,6 +825,7 @@ pub:
 	has_cap         bool
 	has_default     bool
 pub mut:
+	expr_types      []table.Type // [Dog, Cat] // also used for interface_types
 	is_interface    bool // array of interfaces e.g. `[]Animal` `[Dog{}, Cat{}]`
 	interface_types []table.Type // [Dog, Cat]
 	interface_type  table.Type // Animal

vlib/v/checker/checker.v

@@ -2353,8 +2353,6 @@ pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 	if array_init.exprs.len > 0 && array_init.elem_type == table.void_type {
 		mut expected_value_type := table.void_type
 		mut expecting_interface_array := false
-		cap := array_init.exprs.len
-		mut interface_types := []table.Type{cap: cap}
 		if c.expected_type != 0 {
 			expected_value_type = c.table.value_type(c.expected_type)
 			if c.table.get_type_symbol(expected_value_type).kind == .interface_ {
@@ -2372,12 +2370,13 @@ pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 		// }
 		for i, expr in array_init.exprs {
 			typ := c.expr(expr)
+			array_init.expr_types << typ
+			// The first element's type
 			if expecting_interface_array {
 				if i == 0 {
 					elem_type = expected_value_type
 					c.expected_type = elem_type
 				}
-				interface_types << typ
 				continue
 			}
 			// The first element's type
@@ -2390,9 +2389,6 @@ pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 				c.error('invalid array element: $err', expr.position())
 			}
 		}
-		if expecting_interface_array {
-			array_init.interface_types = interface_types
-		}
 		if array_init.is_fixed {
 			idx := c.table.find_or_register_array_fixed(elem_type, array_init.exprs.len,
 				1)

vlib/v/gen/cgen.v

@@ -5844,11 +5844,11 @@ fn (mut g Gen) array_init(it ast.ArrayInit) {
 	}
 	for i, expr in it.exprs {
 		if it.is_interface {
-			// sym := g.table.get_type_symbol(it.interface_types[i])
+			// sym := g.table.get_type_symbol(it.expr_types[i])
 			// isym := g.table.get_type_symbol(it.interface_type)
-			g.interface_call(it.interface_types[i], it.interface_type)
+			g.interface_call(it.expr_types[i], it.interface_type)
 		}
-		g.expr(expr)
+		g.expr_with_cast(expr, it.expr_types[i], it.elem_type)
 		if it.is_interface {
 			g.write(')')
 		}

vlib/v/tests/array_init_test.v

@@ -194,3 +194,33 @@ fn test_array_init_direct_call() {
 	assert []int{len: 2, init: 0}.len == 2
 	assert []int{len: 3, init: 1}.map(it*2) == [2,2,2]
 }
+
+// test array init with sumtype
+type Alphabet = Abc | Xyz
+struct Abc {
+	val int
+}
+struct Xyz {
+	val int
+}
+fn test_array_init_with_sumtype () {
+	a := [Alphabet(Abc{1}), Xyz{2}]
+	a0 := a[0]
+	a1 := a[1]
+	match a0 {
+		Abc {
+			assert a0.val == 1
+		}
+		else {
+			assert false
+		}
+	}
+	match a1 {
+		Xyz {
+			assert a1.val == 2
+		}
+		else {
+			assert false
+		}
+	}
+}