at-kwdef not working with const fields

[garborg]

using Base: @kwdef

@kwdef struct Foo
    a::Int
    b::Int=2
end
@kwdef mutable struct Bar
    a::Int
    b::Int=2
end
@kwdef mutable struct Baz
    const a::Int
    b::Int=2
end

a = 1
Foo(; a) # => Foo(1, 2)
Bar(; a) # => Bar(1, 2)
Baz(; a) # =>
# ERROR: MethodError: no method matching Baz(; a=1)
# Closest candidates are:
#   Baz(; b) at util.jl:493 got unsupported keyword argument "a"
#   Baz(::Int64, ::Int64) at Untitled-1:10 got unsupported keyword argument "a"
#   Baz(::Any, ::Any) at Untitled-1:10 got unsupported keyword argument "a"
# Stacktrace:
#  [1] kwerr(kw::NamedTuple{(:a,), Tuple{Int64}}, args::Type)
#    @ Base ./error.jl:165
#  [2] top-level scope
#    @ Untitled-1:16

julia> versioninfo()
Julia Version 1.8.0-rc1
Commit 6368fdc656 (2022-05-27 18:33 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: 2 × Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-13.0.1 (ORCJIT, sandybridge)
  Threads: 1 on 2 virtual cores
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 

[giordano]

I guess it's related to #45020