dont show #unused# for unnamed arguments in stacktraces (#49058)

Author: KristofferC

base/stacktraces.jl

@@ -224,6 +224,7 @@ function show_spec_linfo(io::IO, frame::StackFrame)
         if isa(def, Method)
             sig = linfo.specTypes
             argnames = Base.method_argnames(def)
+            argnames = replace(argnames, :var"#unused#" => :var"")
             if def.nkw > 0
                 # rearrange call kw_impl(kw_args..., func, pos_args...) to func(pos_args...)
                 kwarg_types = Any[ fieldtype(sig, i) for i = 2:(1+def.nkw) ]

test/errorshow.jl

@@ -934,6 +934,12 @@ let err_str
     @test occursin("String concatenation is performed with *", err_str)
 end
 
+@testset "unused argument names" begin
+    g(::Int) = backtrace()
+    bt = g(1)
+    @test !contains(sprint(Base.show_backtrace, bt), "#unused#")
+end
+
 # issue #49002
 let buf = IOBuffer()
     Base.show_method_candidates(buf, Base.MethodError(typeof, (17,)), pairs((foo = :bar,)))