refactor: move more metadata handling into meta

src/awkward/_meta/recordmeta.py

@@ -71,11 +71,11 @@ def dimension_optiontype(self) -> bool:
         return False
 
     @property
-    def is_leaf(self):
+    def is_leaf(self) -> bool:
         return len(self._contents) == 0
 
     @property
-    def contents(self):
+    def contents(self) -> list[T]:
         return self._contents
 
     @property
@@ -85,7 +85,7 @@ def fields(self) -> list[str]:
         else:
             return self._fields
 
-    def index_to_field(self, index):
+    def index_to_field(self, index: int) -> str:
         if 0 <= index < len(self._contents):
             if self._fields is None:
                 return str(index)
@@ -96,7 +96,7 @@ def index_to_field(self, index):
                 f"no index {index} in record with {len(self._contents)} fields"
             )
 
-    def field_to_index(self, field):
+    def field_to_index(self, field: str) -> int:
         if self._fields is None:
             try:
                 i = int(field)
@@ -116,7 +116,7 @@ def field_to_index(self, field):
             f"no field {field!r} in record with {len(self._contents)} fields"
         )
 
-    def has_field(self, field):
+    def has_field(self, field: str) -> bool:
         if self._fields is None:
             try:
                 i = int(field)
@@ -127,7 +127,7 @@ def has_field(self, field):
         else:
             return field in self._fields
 
-    def content(self, index_or_field):
+    def content(self, index_or_field: int | str) -> T:
         if is_integer(index_or_field):
             index = index_or_field
         elif isinstance(index_or_field, str):

src/awkward/_meta/unionmeta.py

@@ -94,3 +94,6 @@ def dimension_optiontype(self) -> bool:
             if content.dimension_optiontype:
                 return True
         return False
+
+    def content(self, index: int) -> T:
+        return self._contents[index]

src/awkward/forms/unionform.py

@@ -108,9 +108,6 @@ def _union_of_optionarrays(self, index, parameters):
             .form
         )
 
-    def content(self, index):
-        return self._contents[index]
-
     def __repr__(self):
         args = [
             repr(self._tags),

src/awkward/types/recordtype.py

@@ -10,8 +10,10 @@
 import awkward._prettyprint
 from awkward._behavior import find_record_typestr
 from awkward._parameters import parameters_are_equal, type_parameters_equal
+from awkward._regularize import is_integer
 from awkward._typing import Any, JSONMapping, Self, cast, final
 from awkward._util import UNSET, Sentinel
+from awkward.errors import FieldNotFoundError
 from awkward.types.type import Type
 
 
@@ -225,13 +227,56 @@ def _is_equal_to(self, other: Any, all_parameters: bool) -> bool:
             return False
 
     def index_to_field(self, index: int) -> str:
-        return ak.forms.RecordForm.index_to_field(self, index)  # type: ignore[arg-type]
+        if 0 <= index < len(self._contents):
+            if self._fields is None:
+                return str(index)
+            else:
+                return self._fields[index]
+        else:
+            raise IndexError(
+                f"no index {index} in record with {len(self._contents)} fields"
+            )
 
     def field_to_index(self, field: str) -> int:
-        return ak.forms.RecordForm.field_to_index(self, field)  # type: ignore[arg-type]
+        if self._fields is None:
+            try:
+                i = int(field)
+            except ValueError:
+                pass
+            else:
+                if 0 <= i < len(self._contents):
+                    return i
+        else:
+            try:
+                i = self._fields.index(field)
+            except ValueError:
+                pass
+            else:
+                return i
+        raise FieldNotFoundError(
+            f"no field {field!r} in record with {len(self._contents)} fields"
+        )
 
     def has_field(self, field: str) -> bool:
-        return ak.forms.RecordForm.has_field(self, field)  # type: ignore[arg-type]
+        if self._fields is None:
+            try:
+                i = int(field)
+            except ValueError:
+                return False
+            else:
+                return 0 <= i < len(self._contents)
+        else:
+            return field in self._fields
 
-    def content(self, index_or_field: str | int) -> Type:
-        return ak.forms.RecordForm.content(self, index_or_field)  # type: ignore[arg-type]
+    def content(self, index_or_field: int | str) -> Type:
+        if is_integer(index_or_field):
+            index = int(index_or_field)
+        elif isinstance(index_or_field, str):
+            index = self.field_to_index(index_or_field)
+        else:
+            raise TypeError(
+                "index_or_field must be an integer (index) or string (field), not {}".format(
+                    repr(index_or_field)
+                )
+            )
+        return self._contents[index]