[mypyc] Faster dict true test (#10333)

Closes mypyc/mypyc#768.

mypyc/irbuild/ll_builder.py

@@ -32,7 +32,7 @@
     is_list_rprimitive, is_tuple_rprimitive, is_dict_rprimitive, is_set_rprimitive, PySetObject,
     none_rprimitive, RTuple, is_bool_rprimitive, is_str_rprimitive, c_int_rprimitive,
     pointer_rprimitive, PyObject, PyListObject, bit_rprimitive, is_bit_rprimitive,
-    object_pointer_rprimitive, c_size_t_rprimitive
+    object_pointer_rprimitive, c_size_t_rprimitive, dict_rprimitive
 )
 from mypyc.ir.func_ir import FuncDecl, FuncSignature
 from mypyc.ir.class_ir import ClassIR, all_concrete_classes
@@ -960,7 +960,8 @@ def add_bool_branch(self, value: Value, true: BasicBlock, false: BasicBlock) ->
             return
         elif is_same_type(value.type, str_rprimitive):
             value = self.call_c(str_check_if_true, [value], value.line)
-        elif is_same_type(value.type, list_rprimitive):
+        elif (is_same_type(value.type, list_rprimitive)
+                or is_same_type(value.type, dict_rprimitive)):
             length = self.builtin_len(value, value.line)
             zero = Integer(0)
             value = self.binary_op(length, zero, '!=', value.line)

mypyc/test-data/run-dicts.test

@@ -253,3 +253,26 @@ def test_dict_subclass_setdefault() -> None:
     assert d.setdefault('a') == 1
     assert d.setdefault('e') == None
     assert d.setdefault('e', 100) == 110
+
+[case testDictToBool]
+from typing import Dict, List
+
+def is_true(x: dict) -> bool:
+    if x:
+        return True
+    else:
+        return False
+
+def is_false(x: dict) -> bool:
+    if not x:
+        return True
+    else:
+        return False
+
+def test_dict_to_bool() -> None:
+    assert is_false({})
+    assert not is_true({})
+    tmp_list: List[Dict] = [{2: bool}, {'a': 'b'}]
+    for x in tmp_list:
+        assert is_true(x)
+        assert not is_false(x)