Function specialize_function 

pub fn specialize_function(
    func_name: &str,
    ops: &[WasmOp],
    block_arity: &[(u8, u8)],
    facts: &[WscFact],
) -> FactSpecResult

Specialize one function’s op stream against its wsc.facts premises.

block_arity is the decoder’s ordinal side-table (one (params, results) entry per Block/Loop/If in op order); facts is the per-function slice (CompileConfig::current_func_facts). Total: every input yields a result — inapplicable shapes surface as loud declines, never errors.