Fix StructLayout Size for struct discriminated unions#19946
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KirtiRamchandani wants to merge 2 commits into
Open
Fix StructLayout Size for struct discriminated unions#19946KirtiRamchandani wants to merge 2 commits into
KirtiRamchandani wants to merge 2 commits into
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Struct DUs carry a compiler-generated tag field but were emitted with StructLayout Size=1 when they had no declared instance fields. Fixes dotnet#18125
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Fixes #18125
Struct unions get a compiler-generated
_tagfield butdefaultLayoutwas still emittingStructLayout(..., Size = 1)when there are no declared instance fields.This adds
tycon.IsUnionTyconto the condition that omits an explicit size, matching what we already do for structs with instance fields.Added
StructUnionLayout18125.fswhich checkssizeof<ABC> = 4for a three-case struct DU.