The compiler panics with internal error: entered unreachable code: This type cannot be encoded in src/codegen/encoding/mod.rs:1453 when an internal function reference is passed to abi.encode or abi.encodePacked. Sema only rejects mapping and recursive argument types for the variadic abi.encode* family, so Type::InternalFunction slips through to the encoder where it is explicitly listed as unreachable.

MRE:

contract Foo {
    function f() public {
        abi.encodePacked(f);
    }
}

Reproduce: save as mre.sol, run solang compile --target polkadot mre.sol.

Output:

thread 'main' panicked at src/codegen/encoding/mod.rs:1453:36:
internal error: entered unreachable code: This type cannot be encoded
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expected behavior: sema rejects internal function references in abi.encode* arguments with a proper diagnostic.

Also reproduces on --target evm and --target solana. abi.encode(f) triggers the symmetric panic at src/codegen/encoding/mod.rs:291.

Git commit: 901bfb9
Build: release
rustc 1.96.0-nightly (562dee482 2026-03-21)