checker: fix `function x is private` error in main, for `pub const abc = x()` in a (sub)module

vlib/v/checker/checker.v

@@ -3818,9 +3818,13 @@ pub fn (mut c Checker) ident(mut node ast.Ident) ast.Type {
 					}
 					mut typ := obj.typ
 					if typ == 0 {
+						old_c_mod := c.mod
+						c.mod = obj.mod
 						c.inside_const = true
 						typ = c.expr(obj.expr)
 						c.inside_const = false
+						c.mod = old_c_mod
+
 						if obj.expr is ast.CallExpr {
 							if obj.expr.or_block.kind != .absent {
 								typ = typ.clear_flag(.optional)

vlib/v/tests/project_with_modules_having_submodules/bin/a_program_under_bin_can_find_mod1_test.v

@@ -4,6 +4,11 @@ fn test_mod1_can_still_be_found_through_parent_project_vmod() {
 	assert 1051 == m.f()
 }
 
+fn test_pub_const_using_private_fn_for_its_initialisation() {
+	println(m.my_version)
+	assert m.my_version == '0.0.1'
+}
+
 /*
 NB: this main program is under bin/ , but it still
 can find mod1, because the parent project has v.mod,

vlib/v/tests/project_with_modules_having_submodules/mod1/submodule/m.v

@@ -13,3 +13,9 @@ import v.tests.project_with_modules_having_submodules.mod1.mod14
 pub fn f() int {
 	return 1000 + mod11.f() + mod12.f() + mod13.f() + mod14.f()
 }
+
+pub const my_version = get_version()
+
+fn get_version() string {
+	return '0.0.1'
+}