[ICE] via-IR: internal compiler error when emitting an event with an indexed external function parameter that requires a mutability conversion

Description

Emitting an event whose indexed parameter has an external function type triggers an internal compiler error under --via-ir, when the argument's function type differs from the declared parameter type by state mutability. Here this.f has type function () external payable while the event parameter is declared function () external, so the emit requires the implicit payable to non-payable function conversion. That conversion is legal, and the legacy pipeline compiles the contract without error and produces bytecode. via-IR instead aborts with an assertion.

Removing indexed, or removing the conversion (declaring f non-payable, or declaring the event parameter payable as well), makes the contract compile under via-IR. Assigning the pointer to a local variable before the emit also avoids it. Optimization settings make no difference.

Steps to Reproduce

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract C {
    event E(function() external indexed);

    function f() public payable {
        emit E(this.f);
    }
}

solc --via-ir --bin ice.sol

The same error occurs through standard-JSON with "viaIR": true.

Internal compiler error:
/solidity/libsolidity/codegen/ir/IRGeneratorForStatements.cpp(1094): Throw in function virtual void solidity::frontend::IRGeneratorForStatements::endVisit(const solidity::frontend::FunctionCall&)
Dynamic exception type: boost::wrapexcept<solidity::langutil::InternalCompilerError>
std::exception::what: Solidity assertion failed
[solidity::util::tag_comment*] = Solidity assertion failed

Environment

• Compiler version: 0.8.36+commit.8a079791.Linux.g++
• Target EVM version: osaka (default)