Argument conversion: Accept dicts matching TypedDicts as-is

Fixes #5114.

atest/robot/keywords/type_conversion/unions.robot

@@ -24,6 +24,9 @@ Union with subscripted generics and str
 Union with TypedDict
     Check Test Case    ${TESTNAME}
 
+Union with str and TypedDict
+    Check Test Case    ${TESTNAME}
+
 Union with item not liking isinstance
     Check Test Case    ${TESTNAME}
 

atest/testdata/keywords/type_conversion/unions.py

@@ -64,6 +64,10 @@ def union_with_typeddict(argument: Union[XD, None], expected):
     assert argument == eval(expected), '%r != %s' % (argument, expected)
 
 
+def union_with_str_and_typeddict(argument: Union[str, XD], expected):
+    assert argument == eval(expected), '%r != %s' % (argument, expected)
+
+
 def union_with_item_not_liking_isinstance(argument: Union[BadRational, int], expected):
     assert argument == expected, '%r != %r' % (argument, expected)
 

atest/testdata/keywords/type_conversion/unions.robot

@@ -52,6 +52,13 @@ Union with TypedDict
     NONE               None
     ${NONE}            None
 
+Union with str and TypedDict
+    [Template]    Union with str and TypedDict
+    {'x': 1}           "{'x': 1}"
+    ${{{'x': 1}}}      {'x': 1}
+    ${{{'bad': 1}}}    "{'bad': 1}"
+    ${{{'x': '1'}}}    "{'x': '1'}"
+
 Union with item not liking isinstance
     [Template]    Union with item not liking isinstance
     42                 ${42}

src/robot/running/arguments/typeconverters.py

@@ -526,7 +526,17 @@ def handles(cls, type_info: 'TypeInfo') -> bool:
         return type_info.is_typed_dict
 
     def no_conversion_needed(self, value):
-        return False
+        if not isinstance(value, dict):
+            return False
+        for key in value:
+            try:
+                converter = self.converters[key]
+            except KeyError:
+                return False
+            else:
+                if not converter.no_conversion_needed(value[key]):
+                    return False
+        return set(value).issuperset(self.type_info.required)
 
     def _non_string_convert(self, value):
         return self._convert_items(value)