Define valtype(::NamedTuple) and keytype(::NamedTuple) (#46555)

Author: Tokazama

base/namedtuple.jl

@@ -219,6 +219,12 @@ eltype(::Type{T}) where T<:NamedTuple = nteltype(T)
 nteltype(::Type) = Any
 nteltype(::Type{NamedTuple{names,T}} where names) where {T} = eltype(T)
 
+keytype(@nospecialize nt::NamedTuple) = keytype(typeof(nt))
+keytype(@nospecialize T::Type{<:NamedTuple}) = Symbol
+
+valtype(@nospecialize nt::NamedTuple) = valtype(typeof(nt))
+valtype(@nospecialize T::Type{<:NamedTuple}) = eltype(T)
+
 ==(a::NamedTuple{n}, b::NamedTuple{n}) where {n} = Tuple(a) == Tuple(b)
 ==(a::NamedTuple, b::NamedTuple) = false
 

test/namedtuple.jl

@@ -84,6 +84,9 @@ end
 @test eltype(NamedTuple{(:x, :y),Tuple{Union{Missing, Int},Union{Missing, Float64}}}(
     (missing, missing))) === Union{Real, Missing}
 
+@test valtype((a=[1,2], b=[3,4])) === Vector{Int}
+@test keytype((a=[1,2], b=[3,4])) === Symbol
+
 @test Tuple((a=[1,2], b=[3,4])) == ([1,2], [3,4])
 @test Tuple(NamedTuple()) === ()
 @test Tuple((x=4, y=5, z=6)) == (4,5,6)