Some checks don't be performed on F#-style extension methods

[ijklam]

These checks don't be performed on F#-style extension methods.

fsharp/src/Compiler/Checking/PostInferenceChecks.fs

Lines 2407 to 2477 in a9d3ead

	for minfo in immediateMeths do
	let nm = minfo.LogicalName
	let m = (match minfo.ArbitraryValRef with None -> m | Some vref -> vref.DefinitionRange)
	let others = getOtherMethods minfo
	// abstract/default pairs of duplicate methods are OK
	let IsAbstractDefaultPair (x: MethInfo) (y: MethInfo) =
	x.IsDispatchSlot && y.IsDefiniteFSharpOverride
	let IsAbstractDefaultPair2 (minfo: MethInfo) (minfo2: MethInfo) =
	IsAbstractDefaultPair minfo minfo2 || IsAbstractDefaultPair minfo2 minfo
	let checkForDup erasureFlag (minfo2: MethInfo) =
	not (IsAbstractDefaultPair2 minfo minfo2)
	&& (minfo.IsInstance = minfo2.IsInstance)
	&& MethInfosEquivWrtUniqueness erasureFlag m minfo minfo2
	if others |> List.exists (checkForDup EraseAll) then
	if others |> List.exists (checkForDup EraseNone) then
	errorR(Error(FSComp.SR.chkDuplicateMethod(nm, NicePrint.minimalStringOfType cenv.denv ty), m))
	else
	errorR(Error(FSComp.SR.chkDuplicateMethodWithSuffix(nm, NicePrint.minimalStringOfType cenv.denv ty), m))
	let numCurriedArgSets = minfo.NumArgs.Length
	if numCurriedArgSets > 1 && others |> List.exists (fun minfo2 -> not (IsAbstractDefaultPair2 minfo minfo2)) then
	errorR(Error(FSComp.SR.chkDuplicateMethodCurried(nm, NicePrint.minimalStringOfType cenv.denv ty), m))
	if numCurriedArgSets > 1 &&
	(minfo.GetParamDatas(cenv.amap, m, minfo.FormalMethodInst)
	|> List.existsSquared (fun (ParamData(isParamArrayArg, _isInArg, isOutArg, optArgInfo, callerInfo, _, reflArgInfo, ty)) ->
	isParamArrayArg || isOutArg || reflArgInfo.AutoQuote || optArgInfo.IsOptional || callerInfo <> NoCallerInfo || isByrefLikeTy g m ty)) then
	errorR(Error(FSComp.SR.chkCurriedMethodsCantHaveOutParams(), m))
	if numCurriedArgSets = 1 then
	let inline tryDestOptionalTy g ty =
	if isOptionTy g ty then
	destOptionTy g ty |> ValueSome
	elif g.langVersion.SupportsFeature LanguageFeature.SupportValueOptionsAsOptionalParameters && isValueOptionTy g ty then
	destValueOptionTy g ty |> ValueSome
	else
	ValueNone
	let errorIfNotStringTy m ty callerInfo =
	if not (typeEquiv g g.string_ty ty) then
	errorR(Error(FSComp.SR.tcCallerInfoWrongType(callerInfo |> string, "string", NicePrint.minimalStringOfType cenv.denv ty), m))
	let errorIfNotOptional tyToCompare desiredTyName m ty callerInfo =
	match tryDestOptionalTy g ty with
	| ValueSome t when typeEquiv g tyToCompare t -> ()
	| ValueSome innerTy -> errorR(Error(FSComp.SR.tcCallerInfoWrongType(callerInfo |> string, desiredTyName, NicePrint.minimalStringOfType cenv.denv innerTy), m))
	| ValueNone -> errorR(Error(FSComp.SR.tcCallerInfoWrongType(callerInfo |> string, desiredTyName, NicePrint.minimalStringOfType cenv.denv ty), m))
	minfo.GetParamDatas(cenv.amap, m, minfo.FormalMethodInst)
	|> List.iterSquared (fun (ParamData(_, isInArg, _, optArgInfo, callerInfo, nameOpt, _, ty)) ->
	ignore isInArg
	let m =
	match nameOpt with
	| Some name -> name.idRange
	| None -> m
	match (optArgInfo, callerInfo) with
	| _, NoCallerInfo -> ()
	| NotOptional, _ -> errorR(Error(FSComp.SR.tcCallerInfoNotOptional(callerInfo |> string), m))
	| CallerSide _, CallerLineNumber ->
	if not (typeEquiv g g.int32_ty ty) then
	errorR(Error(FSComp.SR.tcCallerInfoWrongType(callerInfo |> string, "int", NicePrint.minimalStringOfType cenv.denv ty), m))
	| CalleeSide, CallerLineNumber -> errorIfNotOptional g.int32_ty "int" m ty callerInfo
	| CallerSide _, (CallerFilePath | CallerMemberName) -> errorIfNotStringTy m ty callerInfo
	| CalleeSide, (CallerFilePath | CallerMemberName) -> errorIfNotOptional g.string_ty "string" m ty callerInfo
	)

Repro steps

Put this code into fsi:

open System.Runtime.CompilerServices;;
  
[<Extension>]
type C =
    // FS0440: Methods with curried arguments cannot declare 'out', 'ParamArray', 'optional', 'ReflectedDefinition', 'byref', 'CallerLineNumber', 'CallerMemberName', or 'CallerFilePath' arguments
    [<Extension>]
    static member B(this: obj)(arg: string outref) = ()
    // FS1246: 'CallerLineNumber' must be applied to an argument of type 'int', but has been applied to an argument of type 'string'
    [<Extension>]
    static member C(this: obj, [<CallerLineNumber>] ?line: string) = ()
;;

type System.Object with
  // No error
  member this.B()(arg: string outref) = ()
  // No error
  member this.C([<CallerLineNumber>] ?line: string) = ()
;;

Expected behavior

Both C#-style and F#-style extension methods give the same error reports.

Actual behavior

Only C#-style extension methods gives the error reports.

Known workarounds

Not using F#-style extension methods.

Related information

• Microsoft (R) F# Interactive version F# 10.0 的 14.0.101.0
• .NET 10.0.101