Solidity Compiler Error 9467: Inline Assembly Variables With 'slot' Suffix Causing False Identifier Not Found Errors

[s4bot3ur]

Description

The Solidity compiler is incorrectly interpreting variable names in inline assembly that end with "_slot" (e.g., "from_slot") as attempts to access storage variables rather than as locally declared assembly variables. This causes compilation error 9467: "Identifier not found. Use '.slot' and '.offset' to access storage or transient storage variables."

When using variable names like "from_slot" or "to_slot" in inline assembly, the compiler mistakenly interprets these as attempts to access storage slot properties. However, when the same variables are renamed to "slot_from" or "slot_to" (moving the word "slot" to the beginning), the code compiles successfully. This suggests the compiler is incorrectly parsing variable names that end with "_slot".

Environment

• Compiler version:0.8.28

Steps to Reproduce

// SPDX-License-Identifier: MIT
pragma solidity 0.8.28;
contract test{
      function transfer(address _to, uint256 _value)public{
        assembly{
            let ptr:=mload(0x40)
            mstore(ptr,caller())
            mstore(add(ptr,0x20),1)
            let from_slot:=keccak256(ptr,0x40)
            let from_Balance:=sload(from_slot)
        }
}

-->

[Saw-mon-and-Natalie]

issue is from here:

solidity/libsolidity/analysis/ReferencesResolver.cpp

Lines 364 to 376 in 584cdcc

	else if (declarations.size() == 0)
	{
	if (
	boost::algorithm::ends_with(_identifier.name.str(), "_slot") ||
	boost::algorithm::ends_with(_identifier.name.str(), "_offset")
	)
	m_errorReporter.declarationError(
	9467_error,
	nativeLocationOf(_identifier),
	"Identifier not found. Use \".slot\" and \".offset\" to access storage or transient storage variables."
	);
	return;
	}

and here is a simplified example:

contract C {
    function f() public {
        assembly{
            let _slot := 0
            pop(_slot)
        }
    }
}

The following does not cause an error:

contract C {
    function f() public {
        uint256 _slot;
        assembly{
            pop(_slot)
        }
    }
}

since declarations would be non-emtpy:

solidity/libsolidity/analysis/ReferencesResolver.cpp

Line 341 in 584cdcc

auto declarations = m_resolver.nameFromCurrentScope(_identifier.name.str());

related:

• [BREAKING] Change _slot and _offset to use dot in inline assembly #9285