Add new linter: dict-iter-missing-items

Add a new linter to check against forgotten calls to `.items()` when
iterating through a dictionary in a `for` loop.

Close #2761 

2 files changed, 24 insertions, 0 deletions

diff --git a/pylint/test/functional/dict_iter_missing_items.py b/pylint/test/functional/dict_iter_missing_items.py
new file mode 100644
index 000000000..333f58990
--- /dev/null
+++ b/pylint/test/functional/dict_iter_missing_items.py
@@ -0,0 +1,23 @@
+# pylint: disable=invalid-name, consider-iterating-dictionary, missing-docstring, import-error
+from unknown import Uninferable
+
+d = {1: 1, 2: 2}
+l = [1, 2]
+s1 = {1, 2}
+s2 = {1, 2, 3}
+
+# Positive
+for k, v in d:  # [dict-iter-missing-items]
+    pass
+
+# Negative
+for k, v in d.items():
+    pass
+for k in d.keys():
+    pass
+for i, v in enumerate(l):
+    pass
+for i, v in s1.intersection(s2):
+    pass
+for k, v in Uninferable:
+    pass
diff --git a/pylint/test/functional/dict_iter_missing_items.txt b/pylint/test/functional/dict_iter_missing_items.txt
new file mode 100644
index 000000000..0e939ee33
--- /dev/null
+++ b/pylint/test/functional/dict_iter_missing_items.txt
@@ -0,0 +1 @@
+dict-iter-missing-items:10::Unpacking a dictionary in iteration without calling .items()