RFC: allow Tuple{Union{}}, returning Union{} #53452
Conversation
vtjnash
added
domain:types and dispatch
ararslan
added
backport 1.10
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I'd argue that this a bugfix and have marked it for backport to the active release branches accordingly. |
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My main question is: is this enough of a bug fix? It doesn't completely fix all of the regressed use-cases identified in #52385. At a minimum, I think we also need to have Then the fixes required for StructArrays are two ambiguous methods: staticschema(::Type{Union{}}) = Union{}
strip_params(::Type{Union{}}) = identityAnd the fixes required for TypedTables tests is just an ambiguity/unbound typevar around printing: columnnames(::AbstractArray{Union{}}) = ()
columnnames(::Table{<:Any,<:Any,<:NamedTuple{names}}) where {names} = names |
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Those seem like unambiguously bugfixes regardless of what we do with Tuple{Union{}}? |
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How are these "unambiguously bugfixes" if these methods could not even be triggered before this change in Julia? (that's for StructArrays, not too familiar with TypedTables) |
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Whoops, Oscar and I thought no changes would be necessary in inference with this change, but I found a counter-example today demonstrating that apply_type_tfunc would not be sound after this change: julia> const VT = Val{Tuple{T}} where T; code_typed((Type,)) do T; VT{T}; end
1-element Vector{Any}:
CodeInfo(
@ REPL[1]:1 within `#3`
1 ─ %1 = Core.apply_type(Main.VT, T)::Type{Val{Tuple{T}}} where T
└── return %1
) => Type{Val{Tuple{T}}} where T
julia> Val{Union{}} isa Type{Val{Tuple{T}}} where T
false |
The list of fixes from @mbauman above are equivalent to fixing the output of the ambiguity test checker. I suppose calling them a bugfix is a bit strong though, since it is not actually a bug to have ambiguities, even though their presence causes this test to fail. I believe many packages use |
| @test_throws ErrorException("Tuple field type cannot be Union{}") Tuple{Int, Vararg{Union{},1}} | ||
| @test_throws ErrorException("Tuple field type cannot be Union{}") Tuple{Vararg{Union{},1}} | ||
| @test Tuple{Int, Vararg{Union{},1}} === Union{} | ||
| @test Tuple{Vararg{Union{},1}} === Union{} | ||
| @test Tuple{} <: Tuple{Vararg{Union{},N}} where N | ||
| @test !(Tuple{} >: Tuple{Vararg{Union{},N}} where N) | ||
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| @testset "#52385" begin | |
| eagerzip() = error() | |
| function eagerzip(args::AbstractArray...) | |
| allequal(axes.(args)) || throw(DimensionMismatch()) | |
| Base.require_one_based_indexing(args...) | |
| res = similar(first(args), Tuple{eltype.(args)...}) | |
| for i in eachindex(args...) | |
| res[i] = getindex.(args, i) | |
| end | |
| res | |
| end | |
| @test isempty(eagerzip(Int[], [])) | |
| @test eltype(eagerzip(Int[], [])) === Tuple{Int64, Any} | |
| @test isempty(eagerzip(Union{}[], [])) | |
| @test eltype(eagerzip(Union{}[], [])) === Union{} | |
| end |
Seems worthwhile to grab @LilithHafner's test case from #52385 (comment)
How so? There is an issue on Aqua-detected ambiguities in StructArrays, and I don't see any overlap with @mbauman's methods: JuliaArrays/StructArrays.jl#293.
Sure, it's better if there are no ambiguities in methods at all. But achieving this in practice is both nontrivial, and not even clearly useful. For example, take StructArrays and the aforementioned issue on ambiguities. Those ambiguities don't even seem realizable in practice, and potential new methods added to resolve them would be dead weight (or even unreachable and untestable). This appears to be a very common position among devs: there are many issues with the same title by the same author over Julia packages, and almost all of them remain open. Even worse, these ambiguity detectors don't catch some real problems. See JuliaArrays/StructArrays.jl#279 with a short example exhibiting the ambiguity. This issue is clearly relevant, and remains open just because it's not clear how to best resolve it. This is somewhat off-topic wrt this issue, but yet, ambiguities are also a pain point (related to multiple dispatch) – but that's for real ambiguities that can actually be realized. Relationship with "detected" ones is unclear imo. |
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This is quite tangential now, but there is actually a performance benefit now to solving those, even though they may seem completely pointless, their presence documents to the compiler that they are pointless, which allows it to skip a lot of work when inferring or loading the package. The added method does need to a slightly peculiar exact form though, with a Secondly, the default ambiguity checker is quite conservative, even though that means it may miss many relevant cases. You can make it less conservative by passing |
Backported PRs: - [x] #39071 <!-- Add a lazy `logrange` function and `LogRange` type --> - [x] #51802 <!-- Allow AnnotatedStrings in log messages --> - [x] #53369 <!-- Orthogonalize re-indexing for FastSubArrays --> - [x] #48050 <!-- improve `--heap-size-hint` arg handling --> - [x] #53482 <!-- add IR encoding for EnterNode --> - [x] #53499 <!-- Avoid compiler warning about redefining jl_globalref_t --> - [x] #53507 <!-- update staled `Core.Compiler.Effects` documentation --> - [x] #53408 <!-- task splitting: change additive accumulation to multiplicative --> - [x] #53523 <!-- add back an alias for `check_top_bit` --> - [x] #53377 <!-- add _readdirx for returning more object info gathered during dir scan --> - [x] #53525 <!-- fix InteractiveUtils call in Base.runtests on failure --> - [x] #53540 <!-- use more efficient `_readdirx` for tab completion --> - [x] #53545 <!-- use `_readdirx` for `walkdir` --> - [x] #53551 <!-- revert "Add @create_log_macro for making custom styled logging macros (#52196)" --> - [x] #53554 <!-- Always return a value in 1-d circshift! of abstractarray.jl --> - [x] #53424 <!-- yet more atomics & cache-line fixes on work-stealing queue --> - [x] #53571 <!-- Update Documenter to v1.3 for inventory writing --> - [x] #53403 <!-- Move parallel precompilation to Base --> - [x] #53589 <!-- add back `unsafe_convert` to pointer for arrays --> - [x] #53596 <!-- build: remove extra .a file --> - [x] #53606 <!-- fix error path in `precompilepkgs` --> - [x] #53004 <!-- Unexport with, at_with, and ScopedValue from Base --> - [x] #53629 <!-- typo fix in scoped values docs --> - [x] #53630 <!-- sroa: Fix incorrect scope counting --> - [x] #53598 <!-- Use Base parallel precompilation to build stdlibs --> - [x] #53649 <!-- precompilepkgs: package in boths deps and weakdeps are in fact only weak --> - [x] #53671 <!-- Fix bootstrap Base precompile in cross compile configuration --> - [x] #52125 <!-- Load Pkg if not already to reinstate missing package add prompt --> - [x] #53602 <!-- Handle zero on arrays of unions of number types and missings --> - [x] #53516 <!-- permit NamedTuple{<:Any, Union{}} to be created --> - [x] #53643 <!-- Bump CSL to 1.1.1 to fix libgomp bug --> - [x] #53679 <!-- move precompile workload back from Base --> - [x] #53663 <!-- add isassigned methods for reinterpretarray --> - [x] #53662 <!-- [REPL] fix incorrectly cleared line after completions accepted --> - [x] #53611 <!-- Linalg: matprod_dest for Diagonal and adjvec --> - [x] #53659 <!-- fix #52025, re-allow all implicit pointer casts in cconvert for Array --> - [x] #53631 <!-- LAPACK: validate input parameters to throw informative errors --> - [x] #53628 <!-- Make some improvements to the Scoped Values documentation. --> - [x] #53655 <!-- Change tbaa of ptr_phi to tbaa_value --> - [x] #53391 <!-- Default to the medium code model in x86 linux --> - [x] #53699 <!-- Move `isexecutable, isreadable, iswritable` to `filesystem.jl` --> - [x] #41232 <!-- Fix linear indexing for ReshapedArray if the parent has offset axes --> - [x] #53527 <!-- Enable analyzegc checks for try catch and fix found issues --> - [x] #52092 - [x] #53682 <!-- Increase build precompilation --> - [x] #53720 - [x] #53553 <!-- typeintersect: fix `UnionAll` unaliasing bug caused by innervars. --> Contains multiple commits, manual intervention needed: - [ ] #53305 <!-- Propagate inbounds in isassigned with CartesianIndex indices --> Non-merged PRs with backport label: - [ ] #53736 <!-- fix literal-pow to return the right type when the base is -1 --> - [ ] #53707 <!-- Make ScopedValue public --> - [ ] #53696 <!-- add invokelatest to on_done callback in bracketed paste --> - [ ] #53660 <!-- put Logging back in default sysimage --> - [ ] #53509 <!-- revert moving "creating packages" from Pkg.jl --> - [ ] #53452 <!-- RFC: allow Tuple{Union{}}, returning Union{} --> - [ ] #53402 <!-- Add `jl_getaffinity` and `jl_setaffinity` --> - [ ] #52694 <!-- Reinstate similar for AbstractQ for backward compatibility --> - [ ] #51928 <!-- Styled markdown, with a few tweaks --> - [ ] #51816 <!-- User-themable stacktraces --> - [ ] #51811 <!-- Make banner size depend on terminal size --> - [ ] #51479 <!-- prevent code loading from lookin in the versioned environment when building Julia -->
Backported PRs: - [x] #53665 <!-- use afoldl instead of tail recursion for tuples --> - [x] #53976 <!-- LinearAlgebra: LazyString in interpolated error messages --> - [x] #54005 <!-- make `view(::Memory, ::Colon)` produce a Vector --> - [x] #54010 <!-- Overload `Base.literal_pow` for `AbstractQ` --> - [x] #54069 <!-- Allow PrecompileTools to see MI's inferred by foreign abstract interpreters --> - [x] #53750 <!-- inference correctness: fields and globals can revert to undef --> - [x] #53984 <!-- Profile: fix heap snapshot is valid char check --> - [x] #54102 <!-- Explicitly compute stride in unaliascopy for SubArray --> - [x] #54070 <!-- Fix integer overflow in `skip(s::IOBuffer, typemax(Int64))` --> - [x] #54013 <!-- Support case-changes to Annotated{String,Char}s --> - [x] #53941 <!-- Fix writing of AnnotatedChars to AnnotatedIOBuffer --> - [x] #54137 <!-- Fix typo in docs for `partialsortperm` --> - [x] #54129 <!-- use correct size when creating output data from an IOBuffer --> - [x] #54153 <!-- Fixup IdSet docstring --> - [x] #54143 <!-- Fix `make install` from tarballs --> - [x] #54151 <!-- LinearAlgebra: Correct zero element in `_generic_matvecmul!` for block adj/trans --> - [x] #54213 <!-- Add `public` statement to `Base.GC` --> - [x] #54222 <!-- Utilize correct tbaa when emitting stores of unions. --> - [x] #54233 <!-- set MAX_OS_WRITE on unix --> - [x] #54255 <!-- fix `_checked_mul_dims` in the presence of 0s and overflow. --> - [x] #54259 <!-- Fix typo in `readuntil` --> - [x] #54251 <!-- fix typo in gc_mark_memory8 when chunking a large array --> - [x] #54276 <!-- Fix solve for complex `Hermitian` with non-vanishing imaginary part on diagonal --> - [x] #54248 <!-- ensure package callbacks are invoked when no valid precompile file exists for an "auto loaded" stdlib --> - [x] #54308 <!-- Implement eval-able AnnotatedString 2-arg show --> - [x] #54302 <!-- Specialised substring equality for annotated strs --> - [x] #54243 <!-- prevent `package_callbacks` to run multiple time for a single package --> - [x] #54350 <!-- add a precompile signature to Artifacts code that is used by JLLs --> - [x] #54331 <!-- correctly track freed bytes in jl_genericmemory_to_string --> - [x] #53509 <!-- revert moving "creating packages" from Pkg.jl --> - [x] #54335 <!-- When accessing the data pointer for an array, first decay it to a Derived Pointer --> - [x] #54239 <!-- Make sure `fieldcount` constant-folds for `Tuple{...}` --> - [x] #54288 - [x] #54067 - [x] #53715 <!-- Add read/write specialisation for IOContext{AnnIO} --> - [x] #54289 <!-- Rework annotation ordering/optimisations --> - [x] #53815 <!-- create phantom task for GC threads --> - [x] #54130 <!-- inference: handle `LimitedAccuracy` in `handle_global_assignment!` --> - [x] #54428 <!-- Move ConsoleLogging.jl into Base --> - [x] #54332 <!-- Revert "add unsetindex support to more copyto methods (#51760)" --> - [x] #53826 <!-- Make all command-line options documented in all related files --> - [x] #54465 <!-- typeintersect: conservative typevar subtitution during `finish_unionall` --> - [x] #54514 <!-- typeintersect: followup cleanup for the nothrow path of type instantiation --> - [x] #54499 <!-- make `@doc x` work without REPL loaded --> - [x] #54210 <!-- attach finalizer in `mmap` to the correct object --> - [x] #54359 <!-- Pkg REPL: cache `pkg_mode` lookup --> Non-merged PRs with backport label: - [ ] #54471 <!-- Actually setup jit targets when compiling packageimages instead of targeting only one --> - [ ] #54457 <!-- Make `String(::Memory)` copy --> - [ ] #54323 <!-- inference: fix too conservative effects for recursive cycles --> - [ ] #54322 <!-- effects: add new `@consistent_overlay` macro --> - [ ] #54191 <!-- make `AbstractPipe` public --> - [ ] #53957 <!-- tweak how filtering is done for what packages should be precompiled --> - [ ] #53882 <!-- Warn about cycles in extension precompilation --> - [ ] #53707 <!-- Make ScopedValue public --> - [ ] #53452 <!-- RFC: allow Tuple{Union{}}, returning Union{} --> - [ ] #53402 <!-- Add `jl_getaffinity` and `jl_setaffinity` --> - [ ] #53286 <!-- Raise an error when using `include_dependency` with non-existent file or directory --> - [ ] #52694 <!-- Reinstate similar for AbstractQ for backward compatibility --> - [ ] #51479 <!-- prevent code loading from lookin in the versioned environment when building Julia -->
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What's the status of this? It has backport labels, but also is marked as a draft / RFC, and has a merge conflict... |
Backported PRs: - [x] #54010 <!-- Overload `Base.literal_pow` for `AbstractQ` --> - [x] #54143 <!-- Fix `make install` from tarballs --> - [x] #54151 <!-- LinearAlgebra: Correct zero element in `_generic_matvecmul!` for block adj/trans --> - [x] #54233 <!-- set MAX_OS_WRITE on unix --> - [x] #54251 <!-- fix typo in gc_mark_memory8 when chunking a large array --> - [x] #54363 <!-- typeintersect: fix another stack overflow caused by circular constraints --> - [x] #54497 <!-- Make TestLogger thread-safe (introduce a lock) --> - [x] #53796 <!-- Add a missing doc --> - [x] #54465 <!-- typeintersect: conservative typevar subtitution during `finish_unionall` --> - [x] #54514 <!-- typeintersect: followup cleanup for the nothrow path of type instantiation --> Need manual backport: - [ ] #52505 <!-- fix alignment of emit_unbox_store copy --> - [ ] #53373 <!-- fix sysimage-native-code=no option with pkgimages --> - [ ] #53815 <!-- create phantom task for GC threads --> - [ ] #53984 <!-- Profile: fix heap snapshot is valid char check --> - [ ] #54276 <!-- Fix solve for complex `Hermitian` with non-vanishing imaginary part on diagonal --> Contains multiple commits, manual intervention needed: - [ ] #52854 <!-- Change to streaming out the heap snapshot data --> - [ ] #53218 <!-- Fix interpreter_exec.jl test --> - [ ] #53833 <!-- Profile: make heap snapshots viewable in vscode viewer --> - [ ] #54303 <!-- LinearAlgebra: improve type-inference in Symmetric/Hermitian matmul --> - [ ] #52694 <!-- Reinstate similar for AbstractQ for backward compatibility --> Non-merged PRs with backport label: - [ ] #54471 <!-- Actually setup jit targets when compiling packageimages instead of targeting only one --> - [ ] #53452 <!-- RFC: allow Tuple{Union{}}, returning Union{} --> - [ ] #51479 <!-- prevent code loading from lookin in the versioned environment when building Julia -->
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What happened here? I thought that the plan from #52385 was a good one. Could you summarize why this isn't the way forward? |
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I believe #54792 is the replacement. |
Backported PRs: - [x] #54361 <!-- [LBT] Upgrade to v5.9.0 --> - [x] #54474 <!-- Unalias source from dest in copytrito --> - [x] #54548 <!-- Fixes for bitcast bugs with LLVM 17 / opaque pointers --> - [x] #54191 <!-- make `AbstractPipe` public --> - [x] #53402 <!-- Add `jl_getaffinity` and `jl_setaffinity` --> - [x] #53356 <!-- Rename at-scriptdir project argument to at-script and search upwards for Project.toml --> - [x] #54545 <!-- typeintersect: fix incorrect innervar handling under circular env --> - [x] #54586 <!-- Set storage class of julia globals to dllimport on windows to avoid auto-import weirdness. Forward port of #54572 --> - [x] #54587 <!-- Accomodate for rectangular matrices in `copytrito!` --> - [x] #54617 <!-- CLI: Use `GetModuleHandleExW` to locate libjulia.dll --> - [x] #54605 <!-- Allow libquadmath to also fail as it is not available on all systems --> - [x] #54634 <!-- Fix trampoline assembly for build on clang 18 on apple silicon --> - [x] #54635 <!-- Aggressive constprop in trevc! to stabilize triangular eigvec --> - [x] #54645 <!-- ensure we set the right value to gc_first_tid --> - [x] #54554 <!-- make elsize public --> - [x] #54648 <!-- Construct LazyString in error paths for tridiag --> - [x] #54658 <!-- fix missing uuid check on extension when finding the location of an extension --> - [x] #54594 <!-- Switch to Pkg mode prompt immediately and load Pkg in the background --> - [x] #54669 <!-- Improve error message in inplace transpose --> - [x] #54671 <!-- Add boundscheck in bindingkey_eq to avoid OOB access due to data race --> - [x] #54672 <!-- make: Fix `sed` command for LLVM libraries with no symbol versioning --> - [x] #54624 <!-- more precise aliasing checks for SubArray --> - [x] #54679 <!-- 🤖 [master] Bump the Distributed stdlib from 6a07d98 to 6c7cdb5 --> - [x] #54604 <!-- Fix tbaa annotation on union selector bytes inside of structs --> - [x] #54690 <!-- Fix assertion/crash when optimizing function with dead basic block --> - [x] #54704 <!-- LazyString in reinterpretarray error messages --> - [x] #54718 <!-- fix prepend StackOverflow issue --> - [x] #54674 <!-- Reimplement dummy pkg prompt as standard prompt --> - [x] #54737 <!-- LazyString in interpolated error messages involving types --> - [x] #54642 <!-- Document GenericMemory and AtomicMemory --> - [x] #54713 <!-- make: use `readelf` for LLVM symbol version detection --> - [x] #54760 <!-- REPL: improve prompt! async function handler --> - [x] #54606 <!-- fix double-counting and non-deterministic results in `summarysize` --> - [x] #54759 <!-- REPL: Fully populate the dummy Pkg prompt --> - [x] #54702 <!-- lowering: Recognize argument destructuring inside macro hygiene --> - [x] #54678 <!-- Don't let setglobal! implicitly create bindings --> - [x] #54730 <!-- Fix uuidkey of exts in fast path of `require_stdlib` --> - [x] #54765 <!-- Handle no-postdominator case in finalizer pass --> - [x] #54591 <!-- Don't expose guard pages to malloc_stack API consumers --> - [x] #54755 <!-- [TOML] remove Dates hack, replace with explicit usage --> - [x] #54721 <!-- add try/catch around scheduler to reset sleep state --> - [x] #54631 <!-- Avoid concatenating LazyString in setindex! for triangular matrices --> - [x] #54322 <!-- effects: add new `@consistent_overlay` macro --> - [x] #54785 - [x] #54865 - [x] #54815 - [x] #54795 - [x] #54779 - [x] #54837 Contains multiple commits, manual intervention needed: - [ ] #52694 <!-- Reinstate similar for AbstractQ for backward compatibility --> - [ ] #54649 <!-- Less restrictive copyto! signature for triangular matrices --> Non-merged PRs with backport label: - [ ] #54779 <!-- make recommendation clearer on manifest version mismatch --> - [ ] #54739 <!-- finish implementation of upgradable stdlibs --> - [ ] #54738 <!-- serialization: fix relocatability bug --> - [ ] #54574 <!-- Make ScopedValues public --> - [ ] #54457 <!-- Make `String(::Memory)` copy --> - [ ] #53957 <!-- tweak how filtering is done for what packages should be precompiled --> - [ ] #53452 <!-- RFC: allow Tuple{Union{}}, returning Union{} --> - [ ] #53286 <!-- Raise an error when using `include_dependency` with non-existent file or directory --> - [ ] #51479 <!-- prevent code loading from lookin in the versioned environment when building Julia -->
KristofferC
removed
backport 1.10
@oscardssmith requested that I put this up as a PR, where instead of throwing an exception, the call instead returns
Union{}. It appears this is actually already consistent with the way we had been choosing to represent this particular operation in inference (specific to Tuple, since other types do not use exactly the same code path there), so no changes appear to be necessary there.Fixes #52385