checker: make pub field check an error

vlib/os/inode.v

@@ -14,12 +14,14 @@ enum FileType {
 }
 
 struct FilePermission {
+pub:
 	read bool
 	write bool
 	execute bool
 }
 
 struct FileMode {
+pub:
 	typ FileType
 	owner FilePermission
 	group FilePermission

vlib/v/builder/builder.v

@@ -27,11 +27,12 @@ pub:
 	module_path         string
 mut:
 	pref                &pref.Preferences
-	module_search_paths []string
 	parsed_files        []ast.File
 	global_scope        &ast.Scope
 	out_name_c          string
 	out_name_js         string
+pub mut:
+	module_search_paths []string
 }
 
 pub fn new_builder(pref &pref.Preferences) Builder {

vlib/v/checker/checker.v

@@ -1011,7 +1011,7 @@ pub fn (mut c Checker) selector_expr(selector_expr mut ast.SelectorExpr) table.T
 	}
 	if field := c.table.struct_find_field(typ_sym, field_name) {
 	if typ_sym.mod != c.mod && !field.is_pub{
-		c.warn('field `${typ_sym.name}.$field_name` is not public', selector_expr.pos)
+		c.error('field `${typ_sym.name}.$field_name` is not public', selector_expr.pos)
 	}
 		return field.typ
 	}