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add enumStyle helper macro (#189)
For serialization and parsing, distinguishing enums with numeric values from enums with associated strings for each value is useful. This adds foundational helpers to allow such distinction.
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‎stew/enums.nim‎

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# stew
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# Copyright 2023 Status Research & Development GmbH
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# Licensed under either of
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#
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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#
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import std/[macros, options]
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type EnumStyle* {.pure.} = enum
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Numeric,
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AssociatedStrings
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func setMode(style: var Option[EnumStyle], s: EnumStyle, typ: auto) =
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if style.isNone:
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style = some s
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elif style.get != s:
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error("Mixed enum styles not supported for deserialization: " & $typ)
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else:
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discard
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macro enumStyle*(t: typedesc[enum]): untyped =
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let
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typ = t.getTypeInst[1]
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impl = typ.getImpl[2]
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expectKind impl, nnkEnumTy
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var style: Option[EnumStyle]
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for f in impl:
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case f.kind
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of nnkEmpty:
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continue
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of nnkIdent:
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when (NimMajor, NimMinor) < (1, 4): # `nnkSym` in Nim 1.2
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style.setMode(EnumStyle.Numeric, typ)
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else:
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error("Unexpected enum node for deserialization: " & $f.kind)
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of nnkSym:
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style.setMode(EnumStyle.Numeric, typ)
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of nnkEnumFieldDef:
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case f[1].kind
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of nnkIntLit:
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style.setMode(EnumStyle.Numeric, typ)
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of nnkStrLit:
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style.setMode(EnumStyle.AssociatedStrings, typ)
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else: error("Unexpected enum tuple for deserialization: " & $f[1].kind)
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else: error("Unexpected enum node for deserialization: " & $f.kind)
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if style.isNone:
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error("Cannot determine enum style for deserialization: " & $typ)
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case style.get
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of EnumStyle.Numeric:
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quote do:
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EnumStyle.Numeric
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of EnumStyle.AssociatedStrings:
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quote do:
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EnumStyle.AssociatedStrings

‎stew/shims/enumutils.nim‎

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when (NimMajor, NimMinor) > (1, 4):
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import std/enumutils
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export enumutils
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else: # Copy from `std/enumutils`
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#
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#
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# Nim's Runtime Library
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# (c) Copyright 2020 Nim contributors
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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import macros
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from typetraits import OrdinalEnum, HoleyEnum
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export typetraits
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# xxx `genEnumCaseStmt` needs tests and runnableExamples
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macro genEnumCaseStmt*(typ: typedesc, argSym: typed, default: typed,
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userMin, userMax: static[int], normalizer: static[proc(s :string): string]): untyped =
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# generates a case stmt, which assigns the correct enum field given
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# a normalized string comparison to the `argSym` input.
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# string normalization is done using passed normalizer.
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# NOTE: for an enum with fields Foo, Bar, ... we cannot generate
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# `of "Foo".nimIdentNormalize: Foo`.
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# This will fail, if the enum is not defined at top level (e.g. in a block).
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# Thus we check for the field value of the (possible holed enum) and convert
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# the integer value to the generic argument `typ`.
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let typ = typ.getTypeInst[1]
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let impl = typ.getImpl[2]
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expectKind impl, nnkEnumTy
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let normalizerNode = quote: `normalizer`
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expectKind normalizerNode, nnkSym
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result = nnkCaseStmt.newTree(newCall(normalizerNode, argSym))
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# stores all processed field strings to give error msg for ambiguous enums
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var foundFields: seq[string] = @[]
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var fStr = "" # string of current field
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var fNum = BiggestInt(0) # int value of current field
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for f in impl:
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case f.kind
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of nnkEmpty: continue # skip first node of `enumTy`
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of nnkSym, nnkIdent: fStr = f.strVal
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of nnkAccQuoted:
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fStr = ""
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for ch in f:
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fStr.add ch.strVal
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of nnkEnumFieldDef:
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case f[1].kind
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of nnkStrLit: fStr = f[1].strVal
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of nnkTupleConstr:
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fStr = f[1][1].strVal
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fNum = f[1][0].intVal
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of nnkIntLit:
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fStr = f[0].strVal
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fNum = f[1].intVal
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else: error("Invalid tuple syntax!", f[1])
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else: error("Invalid node for enum type `" & $f.kind & "`!", f)
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# add field if string not already added
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if fNum >= userMin and fNum <= userMax:
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fStr = normalizer(fStr)
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if fStr notin foundFields:
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result.add nnkOfBranch.newTree(newLit fStr, nnkCall.newTree(typ, newLit fNum))
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foundFields.add fStr
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else:
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error("Ambiguous enums cannot be parsed, field " & $fStr &
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" appears multiple times!", f)
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inc fNum
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# finally add else branch to raise or use default
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if default == nil:
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let raiseStmt = quote do:
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raise newException(ValueError, "Invalid enum value: " & $`argSym`)
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result.add nnkElse.newTree(raiseStmt)
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else:
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expectKind(default, nnkSym)
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result.add nnkElse.newTree(default)

‎stew/shims/typetraits.nim‎

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import std/typetraits
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export typetraits
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when (NimMajor, NimMinor) < (1, 6): # Copy from `std/typetraits`
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#
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#
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# Nim's Runtime Library
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# (c) Copyright 2012 Nim Contributors
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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type HoleyEnum* = (not Ordinal) and enum ## Enum with holes.
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type OrdinalEnum* = Ordinal and enum ## Enum without holes.

‎tests/all_tests.nim‎

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# stew
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# Copyright 2018-2022 Status Research & Development GmbH
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# Copyright 2018-2023 Status Research & Development GmbH
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# Licensed under either of
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#
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
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test_byteutils,
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test_ctops,
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test_endians2,
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test_enums,
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test_io2,
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test_keyed_queue,
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test_sorted_set,

‎tests/test_enums.nim‎

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# stew
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# Copyright 2023 Status Research & Development GmbH
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# Licensed under either of
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#
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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#
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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{.used.}
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import
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unittest2,
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../stew/enums
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suite "enumStyle":
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test "OrdinalEnum":
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type EnumTest = enum
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x0,
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x1,
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x2
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check EnumTest.enumStyle == EnumStyle.Numeric
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test "HoleyEnum":
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type EnumTest = enum
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y1 = 1,
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y3 = 3,
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y4,
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y6 = 6
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check EnumTest.enumStyle == EnumStyle.Numeric
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test "StringEnum":
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type EnumTest = enum
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z1 = "aaa",
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z2 = "bbb",
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z3 = "ccc"
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check EnumTest.enumStyle == EnumStyle.AssociatedStrings

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