Aborted (core dumped)

[Fuhj-better]

I don't quite understand why the following content appears:

root@ :~# ebmc $SVWin/fifo.sv --top fifo --bound 10  
Parsing fifo.sv
Converting
Type-checking Verilog::fifo
--- begin invariant violation report ---
Invariant check failed
File: verilog_elaborate.cpp:862 function: collect_symbols
Condition: false
Reason: unexpected module item: clk
Backtrace:
ebmc(+0x16fb62) [0x564b35a0ab62]
ebmc(+0x1708dd) [0x564b35a0b8dd]
ebmc(+0xab452) [0x564b35946452]
ebmc(+0x421905) [0x564b35cbc905]
ebmc(+0x421a5f) [0x564b35cbca5f]
ebmc(+0x4222ec) [0x564b35cbd2ec]
ebmc(+0x3d7563) [0x564b35c72563]
ebmc(+0x48e402) [0x564b35d29402]
ebmc(+0x3d872b) [0x564b35c7372b]
ebmc(+0x39f250) [0x564b35c3a250]
ebmc(+0x2545b4) [0x564b35aef5b4]
ebmc(+0x25520f) [0x564b35af020f]
ebmc(+0x113a21) [0x564b359aea21]
ebmc(+0x114f00) [0x564b359aff00]
ebmc(+0xcd019) [0x564b35968019]
ebmc(+0x9da0f) [0x564b35938a0f]
ebmc(+0x9ba69) [0x564b35936a69]
/lib/x86_64-linux-gnu/libc.so.6(+0x29d90) [0x7f0b267d6d90]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x80) [0x7f0b267d6e40]
ebmc(+0xa63f5) [0x564b359413f5]


--- end invariant violation report ---
Aborted (core dumped)

This is the RTL code:

fifo.zip