make sure rand(sampler, dims) works (JuliaLang#51643)

For any object `x` from which one can sample, the `Random` API also
requires that `rand(rng, Sampler(typeof(rng), x), [dims])` works. So add
tests for that, and fix `rand(Tuple{...})` accordingly, which was not
using `SamplerTag` fully correctly.

More precisely, the `Sampler` constructor for tuple types was returning
a `SamplerTag` object whose `gentype` was returning the wrong type,
leading to the wrong eltype of the output array for a call like
`rand(rng, Sampler(rng, Tuple{...}), dims)`, so filling this array with
random values was failing.

stdlib/Random/src/generation.jl

@@ -171,18 +171,19 @@ end
 
 function Sampler(::Type{RNG}, ::Type{T}, n::Repetition) where {T<:Tuple, RNG<:AbstractRNG}
  tail_sp_ = Sampler(RNG, Tuple{Base.tail(fieldtypes(T))...}, n)
- SamplerTag{T}((Sampler(RNG, fieldtype(T, 1), n), tail_sp_.data...))
+ SamplerTag{Ref{T}}((Sampler(RNG, fieldtype(T, 1), n), tail_sp_.data...))
+ # Ref so that the gentype is `T` in SamplerTag's constructor
 end
 
 function Sampler(::Type{RNG}, ::Type{Tuple{Vararg{T, N}}}, n::Repetition) where {T, N, RNG<:AbstractRNG}
  if N > 0
- SamplerTag{Tuple{Vararg{T, N}}}((Sampler(RNG, T, n),))
+ SamplerTag{Ref{Tuple{Vararg{T, N}}}}((Sampler(RNG, T, n),))
  else
- SamplerTag{Tuple{}}(())
+ SamplerTag{Ref{Tuple{}}}(())
  end
 end
 
-function rand(rng::AbstractRNG, sp::SamplerTag{T}) where T<:Tuple
+function rand(rng::AbstractRNG, sp::SamplerTag{Ref{T}}) where T<:Tuple
  ntuple(i -> rand(rng, sp.data[min(i, length(sp.data))]), Val{fieldcount(T)}())::T
 end
 

stdlib/Random/test/runtests.jl

@@ -283,6 +283,7 @@ end
 
 # test all rand APIs
 for rng in ([], [MersenneTwister(0)], [RandomDevice()], [Xoshiro()])
+ realrng = rng == [] ? default_rng() : only(rng)
  ftypes = [Float16, Float32, Float64, FakeFloat64, BigFloat]
  cftypes = [ComplexF16, ComplexF32, ComplexF64, ftypes...]
  types = [Bool, Char, BigFloat, Tuple{Bool, Tuple{Int, Char}}, Pair{Int8, UInt32},
@@ -321,42 +322,47 @@ for rng in ([], [MersenneTwister(0)], [RandomDevice()], [Xoshiro()])
  @test size(f2) == (5,)
  @test size(f3) == size(f4) == (2, 3)
  for T in functypes[f]
- a0 = f(rng..., T) ::T
- a1 = f(rng..., T, 5) ::Vector{T}
- a2 = f(rng..., T, 2, 3) ::Array{T, 2}
- a3 = f(rng..., T, b2, u3) ::Array{T, 2}
- a4 = f(rng..., T, (2, 3)) ::Array{T, 2}
- if T <: Number
- @test size(a0) == ()
- end
- @test size(a1) == (5,)
- @test size(a2) == size(a3) == size(a4) == (2, 3)
- if T <: AbstractFloat && f === rand
- for a in T[a0, a1..., a2..., a3..., a4...]
- @test 0.0 <= a < 1.0
+ tts = f == rand ? (T, Sampler(realrng, T, Val(1)), Sampler(realrng, T, Val(Inf))) : (T,)
+ for tt in tts
+ a0 = f(rng..., tt) ::T
+ a1 = f(rng..., tt, 5) ::Vector{T}
+ a2 = f(rng..., tt, 2, 3) ::Array{T, 2}
+ a3 = f(rng..., tt, b2, u3) ::Array{T, 2}
+ a4 = f(rng..., tt, (2, 3)) ::Array{T, 2}
+ if T <: Number
+ @test size(a0) == ()
+ end
+ @test size(a1) == (5,)
+ @test size(a2) == size(a3) == size(a4) == (2, 3)
+ if T <: AbstractFloat && f === rand
+ for a in T[a0, a1..., a2..., a3..., a4...]
+ @test 0.0 <= a < 1.0
+ end
  end
  end
  end
  end
  for (C, T) in collections
- a0 = rand(rng..., C) ::T
- a1 = rand(rng..., C, 5) ::Vector{T}
- a2 = rand(rng..., C, 2, 3) ::Array{T, 2}
- a3 = rand(rng..., C, (2, 3)) ::Array{T, 2}
- a4 = rand(rng..., C, b2, u3) ::Array{T, 2}
- a5 = rand!(rng..., Array{T}(undef, 5), C) ::Vector{T}
- a6 = rand!(rng..., Array{T}(undef, 2, 3), C) ::Array{T, 2}
- a7 = rand!(rng..., GenericArray{T}(undef, 5), C) ::GenericArray{T, 1}
- a8 = rand!(rng..., GenericArray{T}(undef, 2, 3), C) ::GenericArray{T, 2}
- a9 = rand!(rng..., OffsetArray(Array{T}(undef, 5), 9), C) ::OffsetArray{T, 1}
- a10 = rand!(rng..., OffsetArray(Array{T}(undef, 2, 3), (-2, 4)), C) ::OffsetArray{T, 2}
- @test size(a1) == (5,)
- @test size(a2) == size(a3) == (2, 3)
- for a in [a0, a1..., a2..., a3..., a4..., a5..., a6..., a7..., a8..., a9..., a10...]
- if C isa Type
- @test a isa C
- else
- @test a in C
+ for cc = (C, Sampler(realrng, C, Val(1)), Sampler(realrng, C, Val(Inf)))
+ a0 = rand(rng..., cc) ::T
+ a1 = rand(rng..., cc, 5) ::Vector{T}
+ a2 = rand(rng..., cc, 2, 3) ::Array{T, 2}
+ a3 = rand(rng..., cc, (2, 3)) ::Array{T, 2}
+ a4 = rand(rng..., cc, b2, u3) ::Array{T, 2}
+ a5 = rand!(rng..., Array{T}(undef, 5), cc) ::Vector{T}
+ a6 = rand!(rng..., Array{T}(undef, 2, 3), cc) ::Array{T, 2}
+ a7 = rand!(rng..., GenericArray{T}(undef, 5), cc) ::GenericArray{T, 1}
+ a8 = rand!(rng..., GenericArray{T}(undef, 2, 3), cc) ::GenericArray{T, 2}
+ a9 = rand!(rng..., OffsetArray(Array{T}(undef, 5), 9), cc) ::OffsetArray{T, 1}
+ a10 = rand!(rng..., OffsetArray(Array{T}(undef, 2, 3), (-2, 4)), cc) ::OffsetArray{T, 2}
+ @test size(a1) == (5,)
+ @test size(a2) == size(a3) == (2, 3)
+ for a in [a0, a1..., a2..., a3..., a4..., a5..., a6..., a7..., a8..., a9..., a10...]
+ if C isa Type
+ @test a isa C
+ else
+ @test a in C
+ end
  end
  end
  end