[mypyc] Fix comparison of tuples with different lengths (#19372)

When comparing tuples, their lengths are now compared and their contents
are only compared if their lengths are equal. Otherwise, when they have
different lengths, the comparison always evaluates to `False`.

Author: p-sawicki

mypyc/irbuild/ll_builder.py

@@ -1507,6 +1507,10 @@ def compare_tuples(self, lhs: Value, rhs: Value, op: str, line: int = -1) -> Val
         assert isinstance(lhs.type, RTuple) and isinstance(rhs.type, RTuple)
         equal = True if op == "==" else False
         result = Register(bool_rprimitive)
+        # tuples of different lengths
+        if len(lhs.type.types) != len(rhs.type.types):
+            self.add(Assign(result, self.false() if equal else self.true(), line))
+            return result
         # empty tuples
         if len(lhs.type.types) == 0 and len(rhs.type.types) == 0:
             self.add(Assign(result, self.true() if equal else self.false(), line))

mypyc/test-data/run-tuples.test

@@ -203,6 +203,22 @@ def f7(x: List[Tuple[int, int]]) -> int:
 def test_unbox_tuple() -> None:
     assert f7([(5, 6)]) == 11
 
+def test_comparison() -> None:
+    assert ('x','y') == ('x','y')
+    assert not(('x','y') != ('x','y'))
+
+    assert ('x','y') != ('x','y',1)
+    assert not(('x','y') == ('x','y',1))
+
+    assert ('x','y',1) != ('x','y')
+    assert not(('x','y',1) == ('x','y'))
+
+    assert ('x','y') != ()
+    assert not(('x','y') == ())
+
+    assert () != ('x','y')
+    assert not(() == ('x','y'))
+
 # Test that order is irrelevant to unions. Really I only care that this builds.
 
 class A: