Fix false positive dict-iter-missing-items for tuple keys (#4939)

This fixes a false positive emitted for dictionaries that contain only
tuples as keys. This makes unpacking the dictionary without calling
`.items()` valid.
This closes #3283

ChangeLog

@@ -45,6 +45,10 @@ Release date: TBA
 
 * Fix false positive for ``protected-access`` if a protected member is used in type hints of function definitions
 
+* Fix false positive ``dict-iter-missing-items`` for dictionaries only using tuples as keys
+
+  Closes #3282
+
 
 What's New in Pylint 2.10.3?
 ============================

doc/whatsnew/2.11.rst

@@ -51,3 +51,7 @@ Other Changes
   Closes #4936
 
 * Fix false positive for ``protected-access`` if a protected member is used in type hints of function definitions
+
+* Fix false positive ``dict-iter-missing-items`` for dictionaries only using tuples as keys
+
+  Closes #3282

pylint/checkers/typecheck.py

@@ -1862,6 +1862,10 @@ def visit_for(self, node):
             # the iterable is not a dict
             return
 
+        if all(isinstance(i[0], nodes.Tuple) for i in inferred.items):
+            # if all keys are tuples
+            return
+
         self.add_message("dict-iter-missing-items", node=node)
 
 

tests/functional/d/dict_iter_missing_items.py

@@ -2,6 +2,7 @@
 from unknown import Uninferable
 
 d = {1: 1, 2: 2}
+d_tuple = {(1, 2): 3, (4, 5): 6}
 l = [1, 2]
 s1 = {1, 2}
 s2 = {1, 2, 3}
@@ -21,3 +22,5 @@
     pass
 for k, v in Uninferable:
     pass
+for a, b in d_tuple:
+    pass

tests/functional/d/dict_iter_missing_items.txt

@@ -1 +1 @@
-dict-iter-missing-items:10:0::Unpacking a dictionary in iteration without calling .items()
+dict-iter-missing-items:11:0::Unpacking a dictionary in iteration without calling .items()