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Concise check if cases of DU are the same
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open System | |
open System.Collections.Concurrent | |
open Microsoft.FSharp.Reflection | |
open Microsoft.FSharp.Quotations.Patterns | |
type UnionUtils = | |
static member private isTypeUnionCache = ConcurrentDictionary<Type, bool>() | |
static member private tagGetterCache = ConcurrentDictionary<Type, obj -> int>() | |
static member private getUnionCaseInfo expr = | |
match expr with | |
| Lambda(_, expr) -> UnionUtils.getUnionCaseInfo expr | |
| Let(_, _, expr) -> UnionUtils.getUnionCaseInfo expr | |
| NewUnionCase(unionCaseInfo, _) -> unionCaseInfo | |
| _ -> failwith "no way" | |
static member private IsSameCase<'a>(x: 'a, unionCaseInfo: UnionCaseInfo) = | |
let t = typeof<'a> | |
let isUnion = UnionUtils.isTypeUnionCache.GetOrAdd(t, FSharpType.IsUnion) | |
if not isUnion then failwithf "Type %s is not union!" t.Name | |
let getTag = UnionUtils.tagGetterCache.GetOrAdd(key = t, valueFactory = Func<_,_>(fun _ -> | |
let m = t.GetProperty("Tag").GetGetMethod() | |
fun o -> m.Invoke(o, null) :?> int | |
)) | |
getTag x = unionCaseInfo.Tag | |
static member IsSameCase<'a>(x: 'a, y: Quotations.Expr<'a>) = | |
UnionUtils.IsSameCase(x, UnionUtils.getUnionCaseInfo y) | |
static member IsSameCase<'a,'b>(x: 'a, y: Quotations.Expr<'b -> 'a>) = | |
UnionUtils.IsSameCase(x, UnionUtils.getUnionCaseInfo y) | |
type Foo = | |
| A of string * int | |
| B | |
UnionUtils.IsSameCase(B, <@A@>) |
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