invalidate internal code cache anyway when JET hasn't analyzed it yet

this will of course slow down analysis peformance, but should give us 
more correct analysis

it reveals the truth of lots of hidden false positives though ...

src/jetcache.jl

@@ -14,16 +14,26 @@ CC.WorldView(tpc::JETCache, args...) = WorldView(tpc, WorldRange(args...))
 
 CC.haskey(tpc::JETCache, mi::MethodInstance) = CC.haskey(tpc.native, mi)
 
+const ANALYZED_LINFOS   = IdSet{MethodInstance}()         # keeps `MethodInstances` analyzed by JET
+const ERRORNEOUS_LINFOS = IdDict{MethodInstance,Symbol}() # keeps `MethodInstances` analyzed as "errorneous" by JET
+
 function CC.get(tpc::JETCache, mi::MethodInstance, default)
-    force_invalidate_self_code_cache(mi) && return default
+    # if we haven't analyzed this linfo, just invalidate native code cache and force analysis by JET
+    if mi ∉ ANALYZED_LINFOS
+        push!(ANALYZED_LINFOS, mi)
+        return default
+    end
 
     ret = CC.get(tpc.native, mi, default)
 
-    isa(ret, CodeInstance) || return default
+    # cache isn't really found
+    if ret === default
+        return ret
+    end
 
     # cache hit, now we need to invalidate the cache lookup if this `mi` has been profiled
-    # as erroneous by JET or is seemingly erroneous (checked by its return type annotation);
-    # otherwise the error reports that can occur from this frame will just be ignored
+    # as erroneous by JET analysis; otherwise the error reports that can occur from this
+    # frame will just be ignored
     force_inference = false
 
     if haskey(ERRORNEOUS_LINFOS, mi)
@@ -32,9 +42,6 @@ function CC.get(tpc::JETCache, mi::MethodInstance, default)
         if ERRORNEOUS_LINFOS[mi] !== get_id(tpc.interp)
             force_inference = true
         end
-    elseif isdefined(ret, :rettype) && ret.rettype === Bottom
-        # return type is annotated as `Bottom` (by native compiler), let's force inference
-        force_inference = true
     end
 
     return force_inference ? default : ret

src/reports.jl

@@ -92,8 +92,6 @@ const Lineage = IdSet{MethodInstance}
 is_lineage(linfo::MethodInstance, report::InferenceErrorReport) = is_lineage(linfo, report.lineage)
 is_lineage(linfo::MethodInstance, lineage::Lineage)             = linfo in lineage
 
-const ERRORNEOUS_LINFOS = IdDict{MethodInstance,Symbol}()
-
 macro reportdef(ex, kwargs...)
     T = first(ex.args)
     args = map(ex.args) do x