Fix signature of fixed size arrays

Author: smonicas

slither/utils/type.py

@@ -10,6 +10,8 @@
 )
 from slither.core.solidity_types.type import Type
 from slither.core.variables.variable import Variable
+from slither.core.expressions.literal import Literal
+from slither.core.expressions.identifier import Identifier
 
 
 def _convert_type_for_solidity_signature_to_string(
@@ -27,7 +29,14 @@ def _convert_type_for_solidity_signature_to_string(
             underlying_type_str = _convert_type_for_solidity_signature_to_string(
                 underlying_type, seen
             )
-            return underlying_type_str + "[]"
+
+            if types.length is None:
+                return underlying_type_str + "[]"
+            if isinstance(types.length, Literal):
+                return underlying_type_str + f"[{types.length}]"
+            # At this point it must be an Identifier and constant either a TopLevelVariable or a StateVariable
+            assert isinstance(types.length, Identifier) and types.length.value.is_constant
+            return underlying_type_str + f"[{types.length.value.expression}]"
 
         return str(types)