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check issimpleenoughtype for PartialStruct during issimplertype#61130

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vtjnash merged 5 commits intoJuliaLang:masterfrom
adienes:fast_path_tmerge_partialstruct
Mar 31, 2026
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check issimpleenoughtype for PartialStruct during issimplertype#61130
vtjnash merged 5 commits intoJuliaLang:masterfrom
adienes:fast_path_tmerge_partialstruct

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@adienes adienes commented Feb 23, 2026

fixes #60715

tmerge_types_slow would check issimpleenoughtype(u) after the PartialStructs were stripped from the types, but that path wasn't getting hit as it would early return via tmerge_fast_path

Claude assisted the analysis but the proposed fix is mine

@adienes adienes added bugfix This change fixes an existing bug compiler:inference Type inference labels Feb 23, 2026
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vtjnash commented Feb 23, 2026

This looks inaccurate of a fix. The tmerge_fast_path code checks issimplertype which should already be a sufficient and superior fix to this. Any idea what input is there? We should add a unit test for that, and not just this integration test

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adienes commented Feb 23, 2026

let T(n) = Tuple{Int, Union{Int, Tuple{Int, Union{...}}}} to a nesting depth of 2n (so each of Tuple, Union occurs n times)

then IIUC typea = PartialStruct(T(n), [Const(0), Union{Int, T(n-1)}]) and typeb = PartialStruct(T(n+1), [Const(0), Union{Int, T(n)}])

@adienes adienes changed the title enforce issimpleenoughtype in fast path for tmerge for PartialStruct check issimpleenoughtype for PartialStruct during issimplertype Feb 23, 2026
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vtjnash reviewed Feb 23, 2026
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adienes and others added 2 commits February 23, 2026 15:59
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Update Compiler/src/typelimits.jl
0696471 
Co-authored-by: Jameson Nash <vtjnash@gmail.com>
@adienes
fixup
4ab4c38
@KristofferC KristofferC added backport 1.12 Change should be backported to release-1.12 backport 1.13 Change should be backported to release-1.13 labels Feb 24, 2026
@KristofferC KristofferC mentioned this pull request Feb 25, 2026
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@adienes adienes requested a review from vtjnash February 25, 2026 14:16
@KristofferC KristofferC mentioned this pull request Mar 3, 2026
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adienes commented Mar 12, 2026

look ok now?

@KristofferC KristofferC mentioned this pull request Mar 13, 2026
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@vtjnash vtjnash merged commit e820849 into JuliaLang:master Mar 31, 2026
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@adienes adienes deleted the fast_path_tmerge_partialstruct branch March 31, 2026 02:31
aviatesk pushed a commit that referenced this pull request Mar 31, 2026
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check issimpleenoughtype for PartialStruct during issimplertype (#…
fb9683b 
…61130)

fixes #60715

`tmerge_types_slow` would check `issimpleenoughtype(u)` after the
`PartialStruct`s were stripped from the types, but that path wasn't
getting hit as it would early return via `tmerge_fast_path`

Claude assisted the analysis but the proposed fix is mine
@aviatesk aviatesk removed the backport 1.13 Change should be backported to release-1.13 label Mar 31, 2026
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backport 1.12 Change should be backported to release-1.12 bugfix This change fixes an existing bug compiler:inference Type inference

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Type inference hangs on recursive varargs function returning nested tuples

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