improve NTuple show and cleanup code for Vararg and NTuple type parameter construction

[maleadt]

Refs #51228

@vtjnash Why did you mention that the printing of NTuple needs to be adjusted? Your example still works fine:

julia> Tuple{1,1,1,1}
NTuple{4, 1}

julia> NTuple{4, 1}
NTuple{4, 1}

... even though I guess the same validation could happen for NTuple, especially because it's just a Vararg:

julia> NTuple
Tuple{Vararg{T, N}} where {N, T}

julia> Vararg{4, 1}
ERROR: TypeError: in Vararg, in type, expected Type, got a value of type Int64

EDIT: AFAICT, it doesn't seem as easy to reject NTuple{1,2}, because instantiation happens in two steps: First, inst_tuple_w_ instantiates this to a fixed-length tuple, but the invalid T=2 doesn't seem known there (there's only T=T and N=1 in the type environment). Then, inst_datatype_inner instantiates the Tuple, but we can't reject T=2 there as Tuple{2} is valid.

[N5N3]

Is it possible to only apply this fix to method signature?
Our StaticArray ecosystem uses Tuple with Int parameters to store Size information, so I think it would be good to avoid inconsistency.

[maleadt]

Our StaticArray ecosystem uses Tuple with Int parameters to store Size information, so I think it would be good to avoid inconsistency.

The PR currently only addresses Vararg. I tried looking into restricting NTuple but not Tuple, but that didn't work out (see the edit above), so nothing should change wrt. Tuple behavior for now.

[vtjnash]

Current status of the testsuite with this added restriction looks like:

This can be fixed in Test:

Test Failed at /home/vtjnash/julia1/test/ambiguous.jl:360
  Expression: need_to_handle_undef_sparam == Set()
   Evaluated: Set(Method[_extrema_rf(x::Tuple{Vararg{T, 2}}, y::Tuple{Vararg{T, 2}}) where T<:Union{Float16, Float32, Float64} @ Base reduce.jl:867]) == Set{Any}()

This is a failure of inference, due to failure to evaluate nfields(NTuple{4}) === 4

Test Failed at /home/vtjnash/julia1/test/tuple.jl:761
  Expression: only(Base.return_types(g42457, (NTuple{3, Int}, NTuple{4}))) === Float64
   Evaluated: Union{Float64, Int64} === Float64
julia> code_warntype(Base.length, (NTuple{4},))
MethodInstance for length(::Tuple{Vararg{T, 4}} where T)
  from length(t::Tuple) @ Base tuple.jl:26
Arguments
  #self#::Core.Const(length)
  t::TUPLE{VARARG{T, 4}} WHERE T
Body::Int64
    @ tuple.jl:26 within `length`
1 ─      nothing
│   %2 = Base.nfields(t)::Int64
└──      return %2

These ones we meant to break here:

Error During Test at /home/vtjnash/julia1/test/core.jl:7845
  Test threw exception
  Expression: NTuple{3, 2} == Tuple{2, 2, 2}
  TypeError: in Vararg, in type, expected Type, got a value of type Int64
  Stacktrace:
   [1] macro expansion
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:676 [inlined]
   [2] top-level scope
     @ ~/julia1/test/core.jl:515
Error During Test at /home/vtjnash/julia1/test/show.jl:1376                                                                                                                                             
  Test threw exception                                                                                                                                                                                  
  Expression: repr(NTuple{4, :A}) == "NTuple{4, :A}"                                                                                                                                                    
  TypeError: in Vararg, in type, expected Type, got a value of type Symbol                                                                                                                              
  Stacktrace:                                                                                                                                                                                           
   [1] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:676 [inlined]                                                                                                                             
   [2] macro expansion                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1376 [inlined]                                                                                                                                                             
   [3] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:1599 [inlined]                                                                                                                            
   [4] top-level scope                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1376                                                                                                                                                                       
Error During Test at /home/vtjnash/julia1/test/show.jl:1377                                                                                                                                             
  Test threw exception                                                                                                                                                                                  
  Expression: repr(NTuple{3, :A}) == "Tuple{:A, :A, :A}"                                                                                                                                                
  TypeError: in Vararg, in type, expected Type, got a value of type Symbol                                                                                                                              
  Stacktrace:                                                                                                                                                                                           
   [1] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:676 [inlined]                                                                                                                             
   [2] macro expansion                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1377 [inlined]                                                                                                                                                             
   [3] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:1599 [inlined]                                                                                                                            
   [4] top-level scope                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1376                                                                                                                                                                       
Error During Test at /home/vtjnash/julia1/test/show.jl:1378                                                                                                                                             
  Test threw exception                                                                                                                                                                                  
  Expression: repr(NTuple{2, :A}) == "Tuple{:A, :A}"                                                                                                                                                    
  TypeError: in Vararg, in type, expected Type, got a value of type Symbol                                                                                                                              
  Stacktrace:                                                                                                                                                                                           
   [1] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:676 [inlined]                                                                                                                             
   [2] macro expansion                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1378 [inlined]                                                                                                                                                             
   [3] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:1599 [inlined]                                                                                                                               [4] top-level scope                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1376                                                                                                                                                                       
Error During Test at /home/vtjnash/julia1/test/show.jl:1379                                                                                                                                             
  Test threw exception                                                                                                                                                                                  
  Expression: repr(NTuple{1, :A}) == "Tuple{:A}"                                                                                                                                                        
  TypeError: in Vararg, in type, expected Type, got a value of type Symbol                                                                                                                              
  Stacktrace:                                                                                                                                                                                           
   [1] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:676 [inlined]                                                                                                                             
   [2] macro expansion                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1379 [inlined]                                                                                                                                                             
   [3] macro expansion                                                                                                                                                                                  
     @ ~/julia1/usr/share/julia/stdlib/v1.11/Test/src/Test.jl:1599 [inlined]                                                                                                                            
   [4] top-level scope                                                                                                                                                                                  
     @ ~/julia1/test/show.jl:1376                                                                                                                                                                       

[maleadt]

These ones we meant to break here:

I fixed those.

[maleadt]

@nanosoldier runtests()

[nanosoldier]

The package evaluation job you requested has completed - possible new issues were detected.
The full report is available.

[vtjnash]

Ah, right, this approach will probably never work, since StaticArrays assumes this is valid to use to represent array dimension tuples. For example, an SMatrix{2, 2, Int64} is actually an SArray{Tuple{2, 2}, Int64, 2, 4}

[maleadt]

StaticArrays assumes this is valid to use to represent array dimension tuples. For example, an SMatrix{2, 2, Int64} is actually an SArray{Tuple{2, 2}, Int64, 2, 4}

We're only disallowing NTuple{2,2} though; Tuple{2,2} still works. However, it looks like packages are using the former, e.g. RegionTrees.jl has NTuple{N, 2} where N, which accounts for most of the failures in the PkgEval run.

I guess it doesn't make sense to disallow NTuple{2,2} if we're still allowing Tuple{2,2}... I'll revert that part of the changes and see if just the Vararg change is breaking.

[maleadt]

@nanosoldier runtests()

[nanosoldier]

The package evaluation job you requested has completed - possible new issues were detected.
The full report is available.

[maleadt]

OK, that didn't work because NTuple is of course defined as Tuple{Vararg{T, N}}, so the new restriction on Vararg breaks NTuple{2,2}.

Working around this now by special-casing the Vararg handling when contained in a NTuple (by temporarily swapping in a valid type for T, which is a hack, but we cannot simply disable check because N still needs to be checked). This makes NTuple{2,2} work, however, Tuple{Vararg{2,2}} doesn't because the types are applied separately. So all pretty unsatisfying.

[maleadt]

@nanosoldier runtests(["RegionTrees", "ChaoticEncryption", "MIRTjim", "ClusterDepth", "MRIReco", "Roentgen", "Test", "ImageHashes", "MRIFiles", "LASindex", "SMLMFrameConnection", "MiseEnPage", "CellSegmentation", "SSIMLoss", "WGPUgfx", "Dynesty", "Eikonal", "ImageUtils", "StructuredLight", "Images", "MRICoilSensitivities", "SMLMSim", "FatDatasets", "AvailablePotentialEnergyFramework", "FinEtoolsVoxelMesher", "LineIntegralConvolution", "NeuroAnalysis", "Mellan", "ImageSegmentation", "OVERT", "SMLMMetrics", "MRISimulation", "HiQGA", "QuantumCumulants", "Fable", "Colocalization", "ImageProjectiveGeometry", "ImagineFormat", "EditorsRepo", "HmtArchive", "BundlerIO", "PyBraket", "GIFImages", "MaterialReconstruction", "AztecDiamonds", "PlutoStaticHTML", "PerceptualColourMaps", "RemoteSensingToolbox", "ImageFeatures", "ColorSchemeTools", "CorrelationTrackers", "SMLMData", "CitableImage", "FaceDetection", "SyntacticModels", "MPITestImages", "CorrelationFunctions", "RoentgenPlots", "BM3DDenoise", "DiffEqCallbacks", "MixtureDensityNetworks", "RetentionParameterEstimator"])

[nanosoldier]

The package evaluation job you requested has completed - possible new issues were detected.
The full report is available.

[maleadt]

@nanosoldier runtests(["RegionTrees", "ChaoticEncryption", "MIRTjim", "ClusterDepth", "MRIReco", "Roentgen", "Test", "ImageHashes", "MRIFiles", "LASindex", "SMLMFrameConnection", "MiseEnPage", "CellSegmentation", "SSIMLoss", "WGPUgfx", "Dynesty", "Eikonal", "ImageUtils", "StructuredLight", "Images", "MRICoilSensitivities", "SMLMSim", "FatDatasets", "AvailablePotentialEnergyFramework", "FinEtoolsVoxelMesher", "LineIntegralConvolution", "NeuroAnalysis", "Mellan", "ImageSegmentation", "OVERT", "SMLMMetrics", "MRISimulation", "HiQGA", "QuantumCumulants", "Fable", "Colocalization", "ImageProjectiveGeometry", "ImagineFormat", "EditorsRepo", "HmtArchive", "BundlerIO", "PyBraket", "GIFImages", "MaterialReconstruction", "AztecDiamonds", "PlutoStaticHTML", "PerceptualColourMaps", "RemoteSensingToolbox", "ImageFeatures", "ColorSchemeTools", "CorrelationTrackers", "SMLMData", "CitableImage", "FaceDetection", "SyntacticModels", "MPITestImages", "CorrelationFunctions", "RoentgenPlots", "BM3DDenoise", "DiffEqCallbacks", "MixtureDensityNetworks", "RetentionParameterEstimator"])

[nanosoldier]

The package evaluation job you requested has completed - possible new issues were detected.
The full report is available.

[vtjnash]

I have moved the minimal bugfix to #51300 instead, and kept this PR as just the code cleanups. It also now implements a better show method still as well, which handles fixed length Vararg and bound NTuple more naturally.