feat(parsing): support 0.8.35 erc7201 comptime builtin

slither/core/declarations/solidity_variables.py

@@ -72,6 +72,8 @@
     "log3(bytes32,bytes32,bytes32,bytes32)": [],
     "blockhash(uint256)": ["bytes32"],
     "prevrandao()": ["uint256"],
+    # Solidity 0.8.35 comptime builtin: ERC-7201 namespaced storage base slot
+    "erc7201(string)": ["uint256"],
     # the following need a special handling
     # as they are recognized as a SolidityVariableComposed
     # and converted to a SolidityFunction by SlithIR

slither/visitors/expression/constants_folding.py

@@ -98,7 +98,10 @@ def _post_identifier(self, expression: Identifier) -> None:
                     cf = ConstantFolding(expr, self._type)
                     expr = cf.result()
                 assert isinstance(expr, Literal)
-                set_val(expression, convert_string_to_int(expr.converted_value))
+                if str(expr.type) == "string":
+                    set_val(expression, expr.converted_value)
+                else:
+                    set_val(expression, convert_string_to_int(expr.converted_value))
             else:
                 raise NotConstant
         elif isinstance(expression.value, SolidityFunction):
@@ -276,6 +279,16 @@ def _post_call_expression(self, expression: expressions.CallExpression) -> None:
             digest = keccak.new(digest_bits=256)
             digest.update(str(args[0]).encode("utf8"))
             set_val(expression, digest.digest())
+        elif called.name == "erc7201(string)":
+            # Solidity 0.8.35 comptime builtin
+            # keccak256(keccak256(id) - 1) & ~0xff
+            inner = keccak.new(digest_bits=256)
+            inner.update(str(args[0]).encode("utf8"))
+            inner_int = int.from_bytes(inner.digest(), "big")
+            minus_one = (inner_int - 1) & ((1 << 256) - 1)
+            outer = keccak.new(digest_bits=256)
+            outer.update(minus_one.to_bytes(32, "big"))
+            set_val(expression, int.from_bytes(outer.digest(), "big") & ~0xFF)
         else:
             raise NotConstant
 

tests/unit/core/test_data/storage_layout/storage_layout-0.8.35.sol

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.35;
+
+string constant NS = "openzeppelin.storage.MyContract";
+
+contract MyContract layout at erc7201(NS) {
+    uint256 x;
+    uint256 y;
+}

tests/unit/core/test_storage_layout.py

@@ -15,6 +15,11 @@ def test_custom_storage_layout(solc_binary_path):
     _test_storage_layout(solc_binary_path, "0.8.33", "storage_layout-0.8.33.sol")
 
 
+def test_erc7201_storage_layout(solc_binary_path):
+    # 0.8.35 erc7201 comptime builtin used as the base slot of `layout at`
+    _test_storage_layout(solc_binary_path, "0.8.35", "storage_layout-0.8.35.sol")
+
+
 def _test_storage_layout(solc_binary_path, solc_version, test_file):
     # the storage layout has not yet changed between solidity versions so we will test with one version of the compiler
     solc_path = solc_binary_path(solc_version)