Add a check `consider-using-set-comprehension` which is emitted if for set initialization

the old style with list comprehensions is used.

3 files changed, 26 insertions, 7 deletions

diff --git a/pylint/checkers/refactoring.py b/pylint/checkers/refactoring.py
index e775dfbb4..96dc278e8 100644
--- a/pylint/checkers/refactoring.py
+++ b/pylint/checkers/refactoring.py
@@ -167,6 +167,13 @@ class RefactoringChecker(checkers.BaseTokenChecker):
                   'Also it is faster since you don\'t need to create another '
                   'transient list',
                  ),
+        'R1718': ('Consider using a set comprehension',
+                  'consider-using-set-comprehension',
+                  'Although there is nothing syntactically wrong with this code, '
+                  'it is hard to read and can be simplified to a set comprehension.'
+                  'Also it is faster since you don\'t need to create another '
+                  'transient list',
+                  ),
     }
     options = (('max-nested-blocks',
                 {'default': 5, 'type': 'int', 'metavar': '<int>',
@@ -441,18 +448,20 @@ class RefactoringChecker(checkers.BaseTokenChecker):
         stopiteration_qname = '{}.StopIteration'.format(utils.EXCEPTIONS_MODULE)
         return any(_class.qname() == stopiteration_qname for _class in exc.mro())
 
-    def _check_consider_using_dict_comprehension(self, node):
+    def _check_consider_using_comprehension_constructor(self, node):
         if (isinstance(node.func, astroid.Name) and
-                node.func.name == 'dict' and
-                node.args and
-                isinstance(node.args[0], astroid.ListComp)):
-            self.add_message('consider-using-dict-comprehension', node=node)
+                node.args
+                and node.func.name in {'dict', 'set'}
+                and isinstance(node.args[0], astroid.ListComp)):
+            message_name = 'consider-using-{}-comprehension'.format(node.func.name)
+            self.add_message(message_name, node=node)
 
     @utils.check_messages('stop-iteration-return',
-                          'consider-using-dict-comprehension')
+                          'consider-using-dict-comprehension',
+                          'consider-using-set-comprehension')
     def visit_call(self, node):
         self._check_raising_stopiteration_in_generator_next_call(node)
-        self._check_consider_using_dict_comprehension(node)
+        self._check_consider_using_comprehension_constructor(node)
 
     def _check_raising_stopiteration_in_generator_next_call(self, node):
         """Check if a StopIteration exception is raised by the call to next function
diff --git a/pylint/test/functional/consider_using_set_comprehension.py b/pylint/test/functional/consider_using_set_comprehension.py
new file mode 100644
index 000000000..2c42ef2fd
--- /dev/null
+++ b/pylint/test/functional/consider_using_set_comprehension.py
@@ -0,0 +1,9 @@
+# pylint: disable=missing-docstring, invalid-name
+
+numbers = [1, 2, 3, 4, 5, 6]
+
+set()
+
+set([])
+
+set([number for number in numbers])  # [consider-using-set-comprehension]
diff --git a/pylint/test/functional/consider_using_set_comprehension.txt b/pylint/test/functional/consider_using_set_comprehension.txt
new file mode 100644
index 000000000..225d37ae8
--- /dev/null
+++ b/pylint/test/functional/consider_using_set_comprehension.txt
@@ -0,0 +1 @@
+consider-using-set-comprehension:9::Consider using a set comprehension
\ No newline at end of file