AddBackticksToIdentifierIfNeeded adds ticks for `not` word.

[nojaf]

Please provide a succinct description of the issue.

Repro steps

Local fsi:

#r @"C:\Users\fverdonck\Projects\fsharp\artifacts\bin\FSharp.Core\Debug\netstandard2.0\FSharp.Core.dll"
#r @"C:\Users\fverdonck\Projects\fsharp\artifacts\bin\FSharp.Compiler.Service\Debug\netstandard2.0\FSharp.Compiler.Service.dll"

FSharp.Compiler.Syntax.PrettyNaming.AddBackticksToIdentifierIfNeeded "not"
|> printfn "FSharp.Compiler.Syntax.PrettyNaming.AddBackticksToIdentifierIfNeeded :  %s"

dotnet artifacts\bin\fsi\Debug\net5.0\fsi.dll C:\Users\fverdonck\Projects\scripts\fsharp\ast-from-local-compiler.fsx

Expected behavior

In previews version of FCS, no ticks are added.

Actual behavior

``not``

Known workarounds

Provide a description of any known workarounds.

Related information

Provide any related information (optional):

FCS 41.0.0-preview.21472.3

[nojaf]

params and parallel should get ticks and do not get them.

[vzarytovskii]

Hm, interesting, it got changed in #12072, keywordsWithDescription was moved from the lexhelp to the PrettyNaming module, as a lookup table when we check whether we need to add backticks and not is in it (we didn't use it there prior to this change):

And here's the new logic by which we check whether we need to wrap it:

fsharp/src/fsharp/PrettyNaming.fs

Lines 257 to 265 in b3d46d4

	let IsIdentifierName (name: string) =
	not (keywordLookup.Contains name) &&
	not (IsUnencodedOpName name) &&
	not (IsUnencodedLegacyOpName name) &&
	let nameLen = name.Length
	nameLen > 0 &&
	IsIdentifierFirstCharacter name.[0] &&
	let rec loop i = (i >= nameLen || (IsIdentifierPartCharacter(name.[i]) && loop (i+1)))
	loop 1

The lookup in keywordLookup is new.

cc @dsyme

[dsyme]

Hmmm yes I see, it was incorrect to use "keywordsWithDescription", which is mis-named - some of the entries in that table are not keywords (e.g. not, which is a function in the standard library), and not all keywords are present (e.g. reserved ones like params and parallel).

[nojaf]

So a fix would be to renamed keywordsWithDescription and update

fsharp/src/fsharp/PrettyNaming.fs

Lines 158 to 235 in b3d46d4

	let keywordsWithDescription : (string * string) list =
	[ "abstract", FSComp.SR.keywordDescriptionAbstract()
	"and", FSComp.SR.keyworkDescriptionAnd()
	"as", FSComp.SR.keywordDescriptionAs()
	"assert", FSComp.SR.keywordDescriptionAssert()
	"base", FSComp.SR.keywordDescriptionBase()
	"begin", FSComp.SR.keywordDescriptionBegin()
	"class", FSComp.SR.keywordDescriptionClass()
	"const", FSComp.SR.keywordDescriptionConst()
	"default", FSComp.SR.keywordDescriptionDefault()
	"delegate", FSComp.SR.keywordDescriptionDelegate()
	"do", FSComp.SR.keywordDescriptionDo()
	"done", FSComp.SR.keywordDescriptionDone()
	"downcast", FSComp.SR.keywordDescriptionDowncast()
	"downto", FSComp.SR.keywordDescriptionDownto()
	"elif", FSComp.SR.keywordDescriptionElif()
	"else", FSComp.SR.keywordDescriptionElse()
	"end", FSComp.SR.keywordDescriptionEnd()
	"exception", FSComp.SR.keywordDescriptionException()
	"extern", FSComp.SR.keywordDescriptionExtern()
	"false", FSComp.SR.keywordDescriptionTrueFalse()
	"finally", FSComp.SR.keywordDescriptionFinally()
	"for", FSComp.SR.keywordDescriptionFor()
	"fun", FSComp.SR.keywordDescriptionFun()
	"function", FSComp.SR.keywordDescriptionFunction()
	"global", FSComp.SR.keywordDescriptionGlobal()
	"if", FSComp.SR.keywordDescriptionIf()
	"in", FSComp.SR.keywordDescriptionIn()
	"inherit", FSComp.SR.keywordDescriptionInherit()
	"inline", FSComp.SR.keywordDescriptionInline()
	"interface", FSComp.SR.keywordDescriptionInterface()
	"internal", FSComp.SR.keywordDescriptionInternal()
	"lazy", FSComp.SR.keywordDescriptionLazy()
	"let", FSComp.SR.keywordDescriptionLet()
	"let!", FSComp.SR.keywordDescriptionLetBang()
	"match", FSComp.SR.keywordDescriptionMatch()
	"match!", FSComp.SR.keywordDescriptionMatchBang()
	"member", FSComp.SR.keywordDescriptionMember()
	"module", FSComp.SR.keywordDescriptionModule()
	"mutable", FSComp.SR.keywordDescriptionMutable()
	"namespace", FSComp.SR.keywordDescriptionNamespace()
	"new", FSComp.SR.keywordDescriptionNew()
	"not", FSComp.SR.keywordDescriptionNot()
	"null", FSComp.SR.keywordDescriptionNull()
	"of", FSComp.SR.keywordDescriptionOf()
	"open", FSComp.SR.keywordDescriptionOpen()
	"or", FSComp.SR.keywordDescriptionOr()
	"override", FSComp.SR.keywordDescriptionOverride()
	"private", FSComp.SR.keywordDescriptionPrivate()
	"public", FSComp.SR.keywordDescriptionPublic()
	"rec", FSComp.SR.keywordDescriptionRec()
	"return", FSComp.SR.keywordDescriptionReturn()
	"return!", FSComp.SR.keywordDescriptionReturnBang()
	"static", FSComp.SR.keywordDescriptionStatic()
	"struct", FSComp.SR.keywordDescriptionStruct()
	"then", FSComp.SR.keywordDescriptionThen()
	"to", FSComp.SR.keywordDescriptionTo()
	"true", FSComp.SR.keywordDescriptionTrueFalse()
	"try", FSComp.SR.keywordDescriptionTry()
	"type", FSComp.SR.keywordDescriptionType()
	"upcast", FSComp.SR.keywordDescriptionUpcast()
	"use", FSComp.SR.keywordDescriptionUse()
	"use!", FSComp.SR.keywordDescriptionUseBang()
	"val", FSComp.SR.keywordDescriptionVal()
	"void", FSComp.SR.keywordDescriptionVoid()
	"when", FSComp.SR.keywordDescriptionWhen()
	"while", FSComp.SR.keywordDescriptionWhile()
	"with", FSComp.SR.keywordDescriptionWith()
	"yield", FSComp.SR.keywordDescriptionYield()
	"yield!", FSComp.SR.keywordDescriptionYieldBang()
	"->", FSComp.SR.keywordDescriptionRightArrow()
	"<-", FSComp.SR.keywordDescriptionLeftArrow()
	":>", FSComp.SR.keywordDescriptionCast()
	":?>", FSComp.SR.keywordDescriptionDynamicCast()
	"<@", FSComp.SR.keywordDescriptionTypedQuotation()
	"@>", FSComp.SR.keywordDescriptionTypedQuotation()
	"<@@", FSComp.SR.keywordDescriptionUntypedQuotation()
	"@@>", FSComp.SR.keywordDescriptionUntypedQuotation() ]

Remove not and add params and parallel?

[Happypig375]

Consider not in when 'T: not struct. Here, not is a keyword.

[dsyme]

Well, sort of. But in any case for the purposes of backtick escape it's not a keyword.