Merge pull request #1443 from crytic/0xpaladinsecurity-dev

Constants detector: Also detect Contract types

slither/detectors/variables/possible_const_state_variables.py

@@ -1,15 +1,40 @@
 """
 Module detecting state variables that could be declared as constant
 """
+from typing import Set, List, Dict
+
 from slither.core.compilation_unit import SlitherCompilationUnit
 from slither.core.solidity_types.elementary_type import ElementaryType
+from slither.core.solidity_types.user_defined_type import UserDefinedType
+from slither.core.variables.variable import Variable
 from slither.detectors.abstract_detector import AbstractDetector, DetectorClassification
+from slither.utils.output import Output
 from slither.visitors.expression.export_values import ExportValues
+from slither.core.declarations import Contract, Function
 from slither.core.declarations.solidity_variables import SolidityFunction
 from slither.core.variables.state_variable import StateVariable
 from slither.formatters.variables.possible_const_state_variables import custom_format
 
 
+def _is_valid_type(v: StateVariable) -> bool:
+    t = v.type
+    if isinstance(t, ElementaryType):
+        return True
+    if isinstance(t, UserDefinedType) and isinstance(t.type, Contract):
+        return True
+    return False
+
+
+def _valid_candidate(v: StateVariable) -> bool:
+    return _is_valid_type(v) and not (v.is_constant or v.is_immutable)
+
+
+def _is_constant_var(v: Variable) -> bool:
+    if isinstance(v, StateVariable):
+        return v.is_constant
+    return False
+
+
 class ConstCandidateStateVars(AbstractDetector):
     """
     State variables that could be declared as constant detector.
@@ -29,10 +54,6 @@ class ConstCandidateStateVars(AbstractDetector):
     WIKI_DESCRIPTION = "Constant state variables should be declared constant to save gas."
     WIKI_RECOMMENDATION = "Add the `constant` attributes to state variables that never change."
 
-    @staticmethod
-    def _valid_candidate(v):
-        return isinstance(v.type, ElementaryType) and not (v.is_constant or v.is_immutable)
-
     # https://solidity.readthedocs.io/en/v0.5.2/contracts.html#constant-state-variables
     valid_solidity_function = [
         SolidityFunction("keccak256()"),
@@ -46,13 +67,7 @@ class ConstCandidateStateVars(AbstractDetector):
         SolidityFunction("mulmod(uint256,uint256,uint256)"),
     ]
 
-    @staticmethod
-    def _is_constant_var(v):
-        if isinstance(v, StateVariable):
-            return v.is_constant
-        return False
-
-    def _constant_initial_expression(self, v):
+    def _constant_initial_expression(self, v: Variable) -> bool:
         if not v.expression:
             return True
 
@@ -60,34 +75,39 @@ class ConstCandidateStateVars(AbstractDetector):
         values = export.result()
         if not values:
             return True
-        if all(
-            (val in self.valid_solidity_function or self._is_constant_var(val) for val in values)
-        ):
+        if all((val in self.valid_solidity_function or _is_constant_var(val) for val in values)):
             return True
         return False
 
-    def _detect(self):
+    def _detect(self) -> List[Output]:
         """Detect state variables that could be const"""
         results = []
 
-        all_variables = [c.state_variables for c in self.compilation_unit.contracts]
-        all_variables = {item for sublist in all_variables for item in sublist}
-        all_non_constant_elementary_variables = {
-            v for v in all_variables if self._valid_candidate(v)
+        all_variables_l = [c.state_variables for c in self.compilation_unit.contracts]
+        all_variables: Set[StateVariable] = {
+            item for sublist in all_variables_l for item in sublist
         }
-
-        all_functions = [c.all_functions_called for c in self.compilation_unit.contracts]
-        all_functions = list({item for sublist in all_functions for item in sublist})
+        all_non_constant_elementary_variables = {v for v in all_variables if _valid_candidate(v)}
+
+        all_functions_nested = [c.all_functions_called for c in self.compilation_unit.contracts]
+        all_functions = list(
+            {
+                item1
+                for sublist in all_functions_nested
+                for item1 in sublist
+                if isinstance(item1, Function)
+            }
+        )
 
         all_variables_written = [
             f.state_variables_written for f in all_functions if not f.is_constructor_variables
         ]
         all_variables_written = {item for sublist in all_variables_written for item in sublist}
 
-        constable_variables = [
+        constable_variables: List[Variable] = [
             v
             for v in all_non_constant_elementary_variables
-            if (not v in all_variables_written) and self._constant_initial_expression(v)
+            if (v not in all_variables_written) and self._constant_initial_expression(v)
         ]
         # Order for deterministic results
         constable_variables = sorted(constable_variables, key=lambda x: x.canonical_name)
@@ -101,5 +121,5 @@ class ConstCandidateStateVars(AbstractDetector):
         return results
 
     @staticmethod
-    def _format(compilation_unit: SlitherCompilationUnit, result):
+    def _format(compilation_unit: SlitherCompilationUnit, result: Dict) -> None:
         custom_format(compilation_unit, result)