fix: naming-convention false positive on ERC-7201 $ storage pointer

slither/detectors/naming_convention/naming_convention.py

@@ -16,6 +16,7 @@ class NamingConvention(AbstractDetector):
     Exceptions:
     - Allow constant variables name/symbol/decimals to be lowercase (ERC20)
     - Allow '_' at the beginning of the mixed_case match for private variables and unused parameters
+    - Allow '$' (the ERC-7201 namespaced-storage pointer name) for the mixed_case match
     - Ignore echidna properties (functions with names starting 'echidna_' or 'crytic_'
     """
 
@@ -33,7 +34,8 @@ class NamingConvention(AbstractDetector):
 Solidity defines a [naming convention](https://solidity.readthedocs.io/en/v0.4.25/style-guide.html#naming-conventions) that should be followed.
 #### Rule exceptions
 - Allow constant variable name/symbol/decimals to be lowercase (`ERC20`).
-- Allow `_` at the beginning of the `mixed_case` match for private variables and unused parameters."""
+- Allow `_` at the beginning of the `mixed_case` match for private variables and unused parameters.
+- Allow `$` (the [ERC-7201](https://eips.ethereum.org/EIPS/eip-7201) namespaced-storage pointer name) for the `mixed_case` match."""
     # endregion wiki_description
 
     WIKI_RECOMMENDATION = "Follow the Solidity [naming convention](https://solidity.readthedocs.io/en/v0.4.25/style-guide.html#naming-conventions)."
@@ -54,12 +56,21 @@ def is_state_naming(name: str) -> bool:
 
     @staticmethod
     def is_mixed_case(name: str) -> bool:
+        if name == "$":
+            # `$` is a valid Solidity identifier and the conventional name for
+            # the ERC-7201 namespaced-storage struct pointer (used by
+            # OpenZeppelin, Solady, ...). It has no letters to case, so it
+            # trivially conforms to mixedCase.
+            return True
         return re.search("^[a-z]([A-Za-z0-9]+)?_?$", name) is not None
 
     @staticmethod
     def is_mixed_case_with_underscore(name: str) -> bool:
         # Allow _ at the beginning to represent private variable
         # or unused parameters
+        if name == "$":
+            # ERC-7201 namespaced-storage pointer, see `is_mixed_case`.
+            return True
         return re.search("^[_]?[a-z]([A-Za-z0-9]+)?_?$", name) is not None
 
     @staticmethod

tests/e2e/detectors/snapshots/detectors__detector_NamingConvention_0_8_20_naming_convention_dollar_storage_sol__0.txt

@@ -0,0 +1,2 @@
+Parameter LibExample.tripwire(uint256).bad_param (tests/e2e/detectors/test_data/naming-convention/0.8.20/naming_convention_dollar_storage.sol#33) is not in mixedCase
+

tests/e2e/detectors/test_data/naming-convention/0.8.20/naming_convention_dollar_storage.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.20;
+
+/// Regression coverage for the `naming-convention` fix on the ERC-7201
+/// namespaced-storage pointer name `$`.
+///
+/// `$` is a valid Solidity identifier and the de-facto convention for the
+/// storage-struct pointer (OpenZeppelin upgradeable, Solady, ...). It carries
+/// no letters to case, so the mixedCase checks must not flag it. Before the
+/// fix, every `function f(SomeStorage storage $)` reported a `Parameter ... .$
+/// is not in mixedCase` false positive (24+ on Solady alone).
+///
+/// Expected output after fix: exactly one finding, for the deliberately
+/// snake_cased parameter `bad_param` (the tripwire proving the detector still
+/// flags genuine Solidity-level violations).
+
+library LibExample {
+    struct BytesStorage {
+        bytes32 _spacer;
+    }
+
+    // `$` is read here -> exercises `is_mixed_case` on the storage pointer.
+    function length(BytesStorage storage $) internal view returns (uint256 result) {
+        assembly {
+            result := shr(224, sload($.slot))
+        }
+    }
+
+    // `$` is unused here -> exercises `is_mixed_case_with_underscore`.
+    function clear(BytesStorage storage $) internal {}
+
+    // Tripwire: a snake_cased parameter must still be reported.
+    function tripwire(uint256 bad_param) internal pure returns (uint256) {
+        return bad_param;
+    }
+}

tests/e2e/detectors/test_detectors.py

@@ -644,6 +644,11 @@ def id_test(test_item: Test):
         "naming_convention_yul_local.sol",
         "0.8.20",
     ),
+    Test(
+        all_detectors.NamingConvention,
+        "naming_convention_dollar_storage.sol",
+        "0.8.20",
+    ),
     Test(
         all_detectors.ControlledDelegateCall,
         "controlled_delegatecall.sol",