be more aggressive at type-inferring cfunction than is generally a go…

…od idea

this is required by the threadcall function

src/codegen.cpp

@@ -3532,11 +3532,17 @@ static Function *gen_cfun_wrapper(jl_function_t *ff, jl_value_t *jlrettype, jl_t
  // infer it first, if necessary
  if (lam) {
  name = jl_symbol_name(lam->def->name);
- jl_llvm_functions_t decls = jl_compile_linfo(lam, NULL);
- if (decls.functionObject == NULL || lam->jlcall_api != 1) {
- lam = NULL; // TODO: use emit_invoke framework to dispatch these
+ jl_source_info_t *src = NULL;
+ if (!lam->inferred) // TODO: this isn't ideal to be unconditionally calling type inference from here
+ src = jl_type_infer(lam, 0);
+ jl_compile_linfo(lam, src);
+ if (lam->jlcall_api != 2) {
+ if (lam->functionObjectsDecls.functionObject == NULL ||
+ jl_jlcall_api(lam->functionObjectsDecls.functionObject) != 1) {
+ lam = NULL; // TODO: use emit_invoke framework to dispatch these
+ }
  }
- else {
+ if (lam) {
  astrt = lam->rettype;
  if (astrt != (jl_value_t*)jl_bottom_type &&
  jl_type_intersection(astrt, declrt) == jl_bottom_type) {