Refine Slot on setfield!

Author: serenity4

Compiler/src/abstractinterpretation.jl

@@ -2665,12 +2665,20 @@ function abstract_call_known(interp::AbstractInterpreter, @nospecialize(f),
         end
         pushfirst!(argtypes, ft)
         refinements = nothing
-        if sv isa InferenceState && f === typeassert
-            # perform very limited back-propagation of invariants after this type assertion
-            if rt !== Bottom && isa(fargs, Vector{Any})
+        if sv isa InferenceState
+            if f === typeassert
+                # perform very limited back-propagation of invariants after this type assertion
+                if rt !== Bottom && isa(fargs, Vector{Any})
+                    farg2 = ssa_def_slot(fargs[2], sv)
+                    if farg2 isa SlotNumber
+                        refinements = SlotRefinement(farg2, rt)
+                    end
+                end
+            elseif f === setfield! && length(argtypes) == 4 && isa(argtypes[3], Const)
                 farg2 = ssa_def_slot(fargs[2], sv)
                 if farg2 isa SlotNumber
-                    refinements = SlotRefinement(farg2, rt)
+                    refined = form_partially_defined_struct(argtypes[2], argtypes[3])
+                    refinements = SlotRefinement(farg2, refined)
                 end
             end
         end