tests: add submodules tests (#9640)

vlib/v/tests/modules/submodules/submodules.v

@@ -0,0 +1,10 @@
+module submodules
+
+pub struct Main {
+pub:
+	a string
+}
+
+fn init() {
+	println('init submodules')
+}

vlib/v/tests/modules/submodules/submodules_test.v

@@ -0,0 +1,21 @@
+import submodules
+import submodules.test
+import submodules.test.test2
+
+fn test_main() {
+	println('main')
+	main := submodules.Main{
+		a: 'main'
+	}
+	assert 'main' == main.a
+
+	test := test.Test{
+		a: 'test'
+	}
+	assert 'test' == test.a
+
+	test2 := test2.Test2{
+		a: 'test2'
+	}
+	assert 'test2' == test2.a
+}

vlib/v/tests/modules/submodules/test/test.v

@@ -0,0 +1,10 @@
+module test
+
+pub struct Test {
+pub:
+	a string
+}
+
+fn init() {
+	println('init submodules.test')
+}

vlib/v/tests/modules/submodules/test/test2/test2.v

@@ -0,0 +1,10 @@
+module test2
+
+pub struct Test2 {
+pub:
+	a string
+}
+
+fn init() {
+	println('init submodules.test.test2')
+}