diff --git a/slither/core/declarations/function.py b/slither/core/declarations/function.py
index f8d8c8158..dbc8c3921 100644
--- a/slither/core/declarations/function.py
+++ b/slither/core/declarations/function.py
@@ -127,10 +127,10 @@ class Function(metaclass=ABCMeta):  # pylint: disable=too-many-public-methods
         self._slithir_variables: Set["SlithIRVariable"] = set()
         self._parameters: List["LocalVariable"] = []
         self._parameters_ssa: List["LocalIRVariable"] = []
-        self._parameters_src: Optional[SourceMapping] = None
+        self._parameters_src: SourceMapping = SourceMapping()
         self._returns: List["LocalVariable"] = []
         self._returns_ssa: List["LocalIRVariable"] = []
-        self._returns_src: Optional[SourceMapping] = None
+        self._returns_src: SourceMapping = SourceMapping()
         self._return_values: Optional[List["SlithIRVariable"]] = None
         self._return_values_ssa: Optional[List["SlithIRVariable"]] = None
         self._vars_read: List["Variable"] = []
@@ -570,6 +570,9 @@ class Function(metaclass=ABCMeta):  # pylint: disable=too-many-public-methods
     def add_parameter_ssa(self, var: "LocalIRVariable"):
         self._parameters_ssa.append(var)
 
+    def parameters_src(self) -> SourceMapping:
+        return self._parameters_src
+
     # endregion
     ###################################################################################
     ###################################################################################
@@ -588,6 +591,9 @@ class Function(metaclass=ABCMeta):  # pylint: disable=too-many-public-methods
             return [r.type for r in returns]
         return None
 
+    def returns_src(self) -> SourceMapping:
+        return self._returns_src
+
     @property
     def type(self) -> Optional[List[Type]]:
         """
diff --git a/slither/formatters/attributes/const_functions.py b/slither/formatters/attributes/const_functions.py
index 282e9077c..95fc6d8c8 100644
--- a/slither/formatters/attributes/const_functions.py
+++ b/slither/formatters/attributes/const_functions.py
@@ -22,10 +22,10 @@ def custom_format(slither, result):
                     result,
                     element["source_mapping"]["filename_absolute"],
                     int(
-                        function.parameters_src.source_mapping["start"]
-                        + function.parameters_src.source_mapping["length"]
+                        function.parameters_src().source_mapping["start"]
+                        + function.parameters_src().source_mapping["length"]
                     ),
-                    int(function.returns_src.source_mapping["start"]),
+                    int(function.returns_src().source_mapping["start"]),
                 )
 
 
diff --git a/slither/formatters/functions/external_function.py b/slither/formatters/functions/external_function.py
index da557e41e..dd2eaf362 100644
--- a/slither/formatters/functions/external_function.py
+++ b/slither/formatters/functions/external_function.py
@@ -17,8 +17,8 @@ def custom_format(slither, result):
                     slither,
                     result,
                     element["source_mapping"]["filename_absolute"],
-                    int(function.parameters_src.source_mapping["start"]),
-                    int(function.returns_src.source_mapping["start"]),
+                    int(function.parameters_src().source_mapping["start"]),
+                    int(function.returns_src().source_mapping["start"]),
                 )
 
 
diff --git a/slither/solc_parsing/declarations/function.py b/slither/solc_parsing/declarations/function.py
index e437bdda3..4c21e72f1 100644
--- a/slither/solc_parsing/declarations/function.py
+++ b/slither/solc_parsing/declarations/function.py
@@ -26,7 +26,6 @@ from slither.utils.expression_manipulations import SplitTernaryExpression
 from slither.visitors.expression.export_values import ExportValues
 from slither.visitors.expression.has_conditional import HasConditional
 from slither.solc_parsing.exceptions import ParsingError
-from slither.core.source_mapping.source_mapping import SourceMapping
 
 if TYPE_CHECKING:
     from slither.core.expressions.expression import Expression
@@ -85,9 +84,6 @@ class FunctionSolc:
 
         self._analyze_type()
 
-        self.parameters_src = SourceMapping()
-        self.returns_src = SourceMapping()
-
         self._node_to_nodesolc: Dict[Node, NodeSolc] = dict()
         self._node_to_yulobject: Dict[Node, YulBlock] = dict()
 
@@ -1089,7 +1085,7 @@ class FunctionSolc:
     def _parse_params(self, params: Dict):
         assert params[self.get_key()] == "ParameterList"
 
-        self.parameters_src.set_offset(params["src"], self._function.slither)
+        self._function.parameters_src().set_offset(params["src"], self._function.slither)
 
         if self.is_compact_ast:
             params = params["parameters"]
@@ -1105,7 +1101,7 @@ class FunctionSolc:
 
         assert returns[self.get_key()] == "ParameterList"
 
-        self.returns_src.set_offset(returns["src"], self._function.slither)
+        self._function.returns_src().set_offset(returns["src"], self._function.slither)
 
         if self.is_compact_ast:
             returns = returns["parameters"]
diff --git a/slither/tools/flattening/flattening.py b/slither/tools/flattening/flattening.py
index 7790f9af1..2e3d6c650 100644
--- a/slither/tools/flattening/flattening.py
+++ b/slither/tools/flattening/flattening.py
@@ -5,9 +5,8 @@ from enum import Enum as PythonEnum
 from pathlib import Path
 from typing import List, Set, Dict, Optional
 
-from slither.core.declarations import SolidityFunction, Enum
+from slither.core.declarations import SolidityFunction, EnumContract, StructureContract
 from slither.core.declarations.contract import Contract
-from slither.core.declarations.structure import Structure
 from slither.core.solidity_types import MappingType, ArrayType
 from slither.core.solidity_types.user_defined_type import UserDefinedType
 from slither.exceptions import SlitherException
@@ -100,10 +99,10 @@ class Flattening:
                     continue
                 if f.visibility == "external":
                     attributes_start = (
-                        f.parameters_src.source_mapping["start"]
-                        + f.parameters_src.source_mapping["length"]
+                        f.parameters_src().source_mapping["start"]
+                        + f.parameters_src().source_mapping["length"]
                     )
-                    attributes_end = f.returns_src.source_mapping["start"]
+                    attributes_end = f.returns_src().source_mapping["start"]
                     attributes = content[attributes_start:attributes_end]
                     regex = re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes)
                     if regex:
@@ -197,7 +196,7 @@ class Flattening:
 
     def _export_from_type(self, t, contract, exported, list_contract):
         if isinstance(t, UserDefinedType):
-            if isinstance(t.type, (Enum, Structure)):
+            if isinstance(t.type, (EnumContract, StructureContract)):
                 if t.type.contract != contract and t.type.contract not in exported:
                     self._export_list_used_contracts(t.type.contract, exported, list_contract)
             else: