allow external AbstractInterpreter to overload throw-call handling (

#52498)

By defining new `abstract_throw` interface, which allows external
`AbstractInterpreter` to customize the behavior of `throw`-call handling
just by overloading `abstract_throw` method. This is particularly useful
for JET.

base/compiler/abstractinterpretation.jl

@@ -2046,13 +2046,30 @@ function abstract_finalizer(interp::AbstractInterpreter, argtypes::Vector{Any},
     return CallMeta(Nothing, Any, Effects(), NoCallInfo())
 end
 
+function abstract_throw(interp::AbstractInterpreter, argtypes::Vector{Any}, ::AbsIntState)
+    na = length(argtypes)
+    𝕃ᵢ = typeinf_lattice(interp)
+    if na == 2
+        argtype2 = argtypes[2]
+        if isvarargtype(argtype2)
+            exct = tmerge(𝕃ᵢ, unwrapva(argtype2), ArgumentError)
+        else
+            exct = argtype2
+        end
+    elseif na == 3 && isvarargtype(argtypes[3])
+        exct = tmerge(𝕃ᵢ, argtypes[2], ArgumentError)
+    else
+        exct = ArgumentError
+    end
+    return CallMeta(Union{}, exct, EFFECTS_THROWS, NoCallInfo())
+end
+
 # call where the function is known exactly
 function abstract_call_known(interp::AbstractInterpreter, @nospecialize(f),
         arginfo::ArgInfo, si::StmtInfo, sv::AbsIntState,
         max_methods::Int = get_max_methods(interp, f, sv))
     (; fargs, argtypes) = arginfo
     la = length(argtypes)
-
     𝕃ᵢ = typeinf_lattice(interp)
     if isa(f, Builtin)
         if f === _apply_iterate
@@ -2066,19 +2083,7 @@ function abstract_call_known(interp::AbstractInterpreter, @nospecialize(f),
         elseif f === applicable
             return abstract_applicable(interp, argtypes, sv, max_methods)
         elseif f === throw
-            if la == 2
-                arg2 = argtypes[2]
-                if isvarargtype(arg2)
-                    exct = tmerge(𝕃ᵢ, unwrapva(argtypes[2]), ArgumentError)
-                else
-                    exct = arg2
-                end
-            elseif la == 3 && isvarargtype(argtypes[3])
-                exct = tmerge(𝕃ᵢ, argtypes[2], ArgumentError)
-            else
-                exct = ArgumentError
-            end
-            return CallMeta(Union{}, exct, EFFECTS_THROWS, NoCallInfo())
+            return abstract_throw(interp, argtypes, sv)
         end
         rt = abstract_call_builtin(interp, f, arginfo, sv)
         ft = popfirst!(argtypes)