[mypyc] Support unpacking mappings in dict display (#15203)

Fixes mypyc/mypyc#994.

mypyc/primitives/dict_ops.py

@@ -113,7 +113,7 @@
 # Operation used for **value in dict displays.
 # This is mostly like dict.update(obj), but has customized error handling.
 dict_update_in_display_op = custom_op(
-    arg_types=[dict_rprimitive, dict_rprimitive],
+    arg_types=[dict_rprimitive, object_rprimitive],
     return_type=c_int_rprimitive,
     c_function_name="CPyDict_UpdateInDisplay",
     error_kind=ERR_NEG_INT,

mypyc/test-data/run-misc.test

@@ -158,7 +158,7 @@ exit! a ohno
 caught
 
 [case testDisplays]
-from typing import List, Set, Tuple, Sequence, Dict, Any
+from typing import List, Set, Tuple, Sequence, Dict, Any, Mapping
 
 def listDisplay(x: List[int], y: List[int]) -> List[int]:
     return [1, 2, *x, *y, 3]
@@ -172,12 +172,17 @@ def tupleDisplay(x: Sequence[str], y: Sequence[str]) -> Tuple[str, ...]:
 def dictDisplay(x: str, y1: Dict[str, int], y2: Dict[str, int]) -> Dict[str, int]:
     return {x: 2, **y1, 'z': 3, **y2}
 
+def dictDisplayUnpackMapping(obj: Mapping[str, str]) -> Dict[str, str]:
+    return {**obj, "env": "value"}
+
 [file driver.py]
-from native import listDisplay, setDisplay, tupleDisplay, dictDisplay
+import os
+from native import listDisplay, setDisplay, tupleDisplay, dictDisplay, dictDisplayUnpackMapping
 assert listDisplay([4], [5, 6]) == [1, 2, 4, 5, 6, 3]
 assert setDisplay({4}, {5}) == {1, 2, 3, 4, 5}
 assert tupleDisplay(['4', '5'], ['6']) == ('1', '2', '4', '5', '6', '3')
 assert dictDisplay('x', {'y1': 1}, {'y2': 2, 'z': 5}) == {'x': 2, 'y1': 1, 'y2': 2, 'z': 5}
+assert dictDisplayUnpackMapping(os.environ) == {**os.environ, "env": "value"}
 
 [case testArbitraryLvalues]
 from typing import List, Dict, Any