checker: fix multi assignment for multiple fns (#5716)

vlib/v/checker/checker.v

@@ -1536,7 +1536,9 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 		}
 		if assign_stmt.right_types.len < assign_stmt.left.len { // first type or multi return types added above
 			right_type := c.expr(assign_stmt.right[i])
-			assign_stmt.right_types << c.check_expr_opt_call(assign_stmt.right[i], right_type)
+			if assign_stmt.right_types.len == i {
+				assign_stmt.right_types << c.check_expr_opt_call(assign_stmt.right[i], right_type)
+			}
 		}
 		right := if i < assign_stmt.right.len { assign_stmt.right[i] } else { assign_stmt.right[0] }
 		right_type := assign_stmt.right_types[i]

vlib/v/tests/fn_assignment_test.v

@@ -0,0 +1,55 @@
+fn test() int {
+	return 10
+}
+
+fn test1() int {
+	return 11
+}
+
+fn test_fn_assignment_var() {
+	mut a := 0
+	mut b := 0
+	a , b = test(), test1()
+	
+	assert a == 10 
+	assert b == 11
+
+	a, b = test(), test()
+	assert a == 10
+	assert b == 10
+
+	a, b = test(), 12
+
+	assert a == 10 
+	assert b == 12
+
+	a, b = 12, test()
+
+	assert a == 12
+	assert b == 10 
+}
+
+fn test_fn_assignment_array() {
+	mut a := [0, 1]
+
+	a[0], a[1] = test(), test1()
+
+	assert a[0] == 10 
+	assert a[1] == 11
+
+	a[0], a[1] = test() , test()
+
+	assert a[0] == 10 
+	assert a[1] == 10 
+
+	a[0], a[1] = test(), 12
+
+	assert a[0] == 10 
+	assert a[1] == 12 
+
+	a[0], a[1] = 12 , test() 
+	assert a[0] == 12 
+	assert a[1] == 10
+}
+
+