Pass through world age for kwargs MethodError

Fixes #50200

base/errorshow.jl

@@ -243,7 +243,7 @@ function showerror(io::IO, ex::MethodError)
         ft = typeof(f)
         arg_types_param = arg_types_param[3:end]
         kwargs = pairs(ex.args[1])
-        ex = MethodError(f, ex.args[3:end::Int])
+        ex = MethodError(f, ex.args[3:end::Int], ex.world)
     end
     name = ft.name.mt.name
     if f === Base.convert && length(arg_types_param) == 2 && !is_arg_types

test/errorshow.jl

@@ -578,7 +578,7 @@ let
     end
 end
 
-@testset "show for manually thrown MethodError" begin
+@testset "show for MethodError with world age issue" begin
     global f21006
 
     f21006() = nothing
@@ -620,6 +620,31 @@ end
     end
 end
 
+# Issue #50200
+using Base.Experimental: @opaque
+@testset "show for MethodError with world age issue (kwarg)" begin
+    test_no_error(f) = @test f() === nothing
+    function test_worldage_error(f)
+        ex = try; f(); error("Should not have been reached") catch ex; ex; end
+        @test occursin("The applicable method may be too new", sprint(Base.showerror, ex))
+    end
+
+    global callback50200
+
+    # First the no-kwargs version
+    callback50200 = (args...)->nothing
+    f = @opaque ()->callback50200()
+    test_no_error(f)
+    callback50200 = (args...)->nothing
+    test_worldage_error(f)
+
+    callback50200 = (args...; kwargs...)->nothing
+    f = @opaque ()->callback50200(;a=1)
+    test_no_error(f)
+    callback50200 = (args...; kwargs...)->nothing
+    test_worldage_error(f)
+end
+
 # Custom hints
 struct HasNoOne end
 function recommend_oneunit(io, ex, arg_types, kwargs)