parser/checker: do not allow using private types from other modules

vlib/net/ftp/ftp.v

@@ -29,9 +29,9 @@ const (
 	OpenDataConnection = 150
 	CloseDataConnection = 226
 	CommandOk = 200
-	Denied = 550
+	denied = 550
 	PassiveMode = 227
-	Complete = 226
+	complete = 226
 )
 
 struct DTP {
@@ -173,13 +173,13 @@ pub fn (ftp FTP) pwd() string {
 pub fn (ftp FTP) cd(dir string) {
 	ftp.write('CWD $dir') or { return }
 	mut code, mut data := ftp.read()
-	match code {
-		Denied {
+	match int(code) {
+		denied {
 			$if debug {
 				println('CD $dir denied!')
 			}
 		}
-		Complete {
+		complete {
 			code, data = ftp.read()
 		}
 		else {}
@@ -233,7 +233,7 @@ pub fn (ftp FTP) dir() ?[]string {
 
 	ftp.write('LIST') or {}
 	code, _ := ftp.read()
-	if code == Denied {
+	if code == denied {
 		return error('LIST denied')
 	}
 	if code != OpenDataConnection {
@@ -267,7 +267,7 @@ pub fn (ftp FTP) get(file string) ?[]byte {
 	ftp.write('RETR $file') or {}
 	code, _ := ftp.read()
 
-	if code == Denied {
+	if code == denied {
 		return error('Permission denied')
 	}
 

vlib/os/os.v

@@ -393,6 +393,11 @@ fn vpclose(f voidptr) int {
 	}
 }
 
+struct Foo2 {
+	x int
+
+}
+
 pub struct Result {
 pub:
 	exit_code int

vlib/v/cflag/cflags.v

@@ -6,7 +6,7 @@ module cflag
 import os
 
 // parsed cflag
-struct CFlag {
+pub struct CFlag {
 	mod   string // the module in which the flag was given
 	os    string // eg. windows | darwin | linux
 	name  string // eg. -I

vlib/v/checker/checker.v

@@ -260,6 +260,9 @@ pub fn (mut c Checker) struct_init(struct_init mut ast.StructInit) table.Type {
 		struct_init.typ = c.expected_type
 	}
 	type_sym := c.table.get_type_symbol(struct_init.typ)
+	if !type_sym.is_public && type_sym.mod != c.mod {
+		c.warn('type `$type_sym.name` is private', struct_init.pos)
+	}
 	// println('check struct $typ_sym.name')
 	match type_sym.kind {
 		.placeholder {

vlib/v/parser/parser.v

@@ -12,7 +12,7 @@ import v.util
 import term
 import os
 
-struct Parser {
+pub struct Parser {
 	scanner           &scanner.Scanner
 	file_name         string // "/home/user/hello.v"
 	file_name_dir     string // "/home/user"
@@ -1202,6 +1202,7 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 			info: table.SumType{
 				variants: sum_variants
 			}
+			is_public: is_pub
 		})
 		return ast.SumTypeDecl{
 			name: name
@@ -1220,6 +1221,7 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 		info: table.Alias{
 			foo: ''
 		}
+		is_public: is_pub
 	})
 	return ast.AliasTypeDecl{
 		name: name

vlib/v/parser/struct.v

@@ -161,6 +161,7 @@ fn (mut p Parser) struct_decl() ast.StructDecl {
 			is_union: is_union
 		}
 		mod: p.mod
+		is_public: is_pub
 	}
 	mut ret := 0
 	if p.builtin_mod && t.name in table.builtin_type_names {

vlib/v/table/atypes.v

@@ -26,6 +26,7 @@ mut:
 	name       string
 	methods    []Fn
 	mod        string
+	is_public  bool
 }
 
 pub enum TypeFlag {
@@ -546,7 +547,7 @@ pub:
 // NB: FExpr here is a actually an ast.Expr .
 // It should always be used by casting to ast.Expr, using ast.fe2ex()/ast.ex2fe()
 // That hack is needed to break an import cycle between v.ast and v.table .
-type FExpr = byteptr | voidptr
+pub type FExpr = byteptr | voidptr
 
 pub struct Field {
 pub: