This query (`coverage_ids_info`) already determines which counter/expression IDs are unused, so it only takes a little extra effort to also determine which counters/expressions must have a value of zero.
TypingEnv
infcx
CrateCoverageContext
CguCoverageContext
&str
&[u8]
*const c_char
rustc_abi::Abi
BackendRepr
warn(unreachable_pub)
rustc_codegen_llvm