Unify let, let!, use, use! LetOrUse AST representation.

docs/release-notes/.FSharp.Compiler.Service/10.0.100.md

@@ -21,6 +21,7 @@
 
 ### Changed
 * Use `errorR` instead of `error` in `CheckDeclarations.fs` when possible. ([PR #18645](https://github.com/dotnet/fsharp/pull/18645))
+* Unify `let`, `let!`, `use` and `use!` AST representation. ([PR #18825](https://github.com/dotnet/fsharp/pull/18825))
 
 ### Breaking Changes
 

src/Compiler/Checking/CheckRecordSyntaxHelpers.fs

@@ -180,4 +180,13 @@ let BindOriginalRecdExpr (withExpr: SynExpr * BlockSeparator) mkRecdExpr =
              None,
              SynBindingTrivia.Zero)
 
-    SynExpr.LetOrUse(false, false, [ binding ], mkRecdExpr (Some withExpr), mOrigExprSynth, SynExprLetOrUseTrivia.Zero)
+    SynExpr.LetOrUse(
+        isRecursive = false,
+        isUse = false,
+        isFromSource = false, // compiler generated during desugaring
+        isBang = false,
+        bindings = [ binding ],
+        body = mkRecdExpr (Some withExpr),
+        range = mOrigExprSynth,
+        trivia = SynExprLetOrUseTrivia.Zero
+    )

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -6072,7 +6072,7 @@ and TcExprUndelayed (cenv: cenv) (overallTy: OverallTy) env tpenv (synExpr: SynE
     | SynExpr.DoBang (trivia = { DoBangKeyword = m })
     | SynExpr.MatchBang (trivia = { MatchBangKeyword = m })
     | SynExpr.WhileBang (range = m)
-    | SynExpr.LetOrUseBang (trivia = { LetOrUseKeyword = m }) ->
+    | SynExpr.LetOrUse (isBang = true; trivia = { LetOrUseKeyword = m }) ->
         error(Error(FSComp.SR.tcConstructRequiresComputationExpression(), m))
 
     | SynExpr.IndexFromEnd (rightExpr, m) ->
@@ -9199,7 +9199,7 @@ and TcImplicitOpItemThen (cenv: cenv) overallTy env id sln tpenv mItem delayed =
         | SynExpr.YieldOrReturn _
         | SynExpr.YieldOrReturnFrom _
         | SynExpr.MatchBang _
-        | SynExpr.LetOrUseBang _
+        | SynExpr.LetOrUse (isBang = true)
         | SynExpr.DoBang _
         | SynExpr.WhileBang _
         | SynExpr.TraitCall _
@@ -10614,7 +10614,7 @@ and TcLinearExprs bodyChecker cenv env overallTy tpenv isCompExpr synExpr cont =
         TcLinearExprs bodyChecker cenv env2 overallTy tpenv isCompExpr expr2 (fun (expr2R, tpenv) ->
             cont (Expr.Sequential (expr1R, expr2R, NormalSeq, m), tpenv))
 
-    | SynExpr.LetOrUse (isRec, isUse, binds, body, m, _) when not (isUse && isCompExpr) ->
+    | SynExpr.LetOrUse (isRecursive = isRec; isUse= isUse; bindings = binds; body = body; range = m) when not (isUse && isCompExpr) ->
         if isRec then
             // TcLinearExprs processes at most one recursive binding, this is not tailcalling
             CheckRecursiveBindingIds binds

src/Compiler/Checking/Expressions/CheckExpressionsOps.fs

@@ -202,9 +202,6 @@ let YieldFree (cenv: TcFileState) expr =
             | SynExpr.While(doExpr = body)
             | SynExpr.WhileBang(doExpr = body)
             | SynExpr.ForEach(bodyExpr = body) -> YieldFree body
-
-            | SynExpr.LetOrUseBang(body = body) -> YieldFree body
-
             | SynExpr.YieldOrReturn(flags = (true, _)) -> false
 
             | _ -> true
@@ -232,7 +229,7 @@ let YieldFree (cenv: TcFileState) expr =
             | SynExpr.WhileBang(doExpr = body)
             | SynExpr.ForEach(bodyExpr = body) -> YieldFree body
 
-            | SynExpr.LetOrUseBang _
+            | SynExpr.LetOrUse(isBang = true)
             | SynExpr.YieldOrReturnFrom _
             | SynExpr.YieldOrReturn _
             | SynExpr.ImplicitZero _
@@ -256,7 +253,6 @@ let inline IsSimpleSemicolonSequenceElement expr cenv acceptDeprecated =
     | SynExpr.LetOrUse _
     | SynExpr.Do _
     | SynExpr.MatchBang _
-    | SynExpr.LetOrUseBang _
     | SynExpr.While _
     | SynExpr.WhileBang _ -> false
     | _ -> true

src/Compiler/Checking/Expressions/CheckSequenceExpressions.fs

@@ -263,7 +263,7 @@ let TcSequenceExpression (cenv: TcFileState) env tpenv comp (overallTy: OverallT
             // The 'mBind' is attached to the lambda
             Some(mkSeqUsing cenv env wholeExprMark bindPatTy genOuterTy inputExpr consumeExpr, tpenv)
 
-        | SynExpr.LetOrUseBang(range = m) -> error (Error(FSComp.SR.tcUseForInSequenceExpression (), m))
+        | SynExpr.LetOrUse(isBang = true; range = m) -> error (Error(FSComp.SR.tcUseForInSequenceExpression (), m))
 
         | SynExpr.Match(spMatch, expr, clauses, _m, _trivia) ->
             let inputExpr, inputTy, tpenv = TcExprOfUnknownType cenv env tpenv expr

src/Compiler/Driver/GraphChecking/FileContentMapping.fs

@@ -505,21 +505,6 @@ let visitSynExpr (e: SynExpr) : FileContentEntry list =
             Continuation.concatenate continuations continuation
         | SynExpr.YieldOrReturn(expr = expr) -> visit expr continuation
         | SynExpr.YieldOrReturnFrom(expr = expr) -> visit expr continuation
-        | SynExpr.LetOrUseBang(pat = pat; rhs = rhs; andBangs = andBangs; body = body) ->
-            let continuations =
-                let andBangExprs = List.map (fun (SynBinding(expr = body)) -> body) andBangs
-                List.map visit (body :: rhs :: andBangExprs)
-
-            let finalContinuation nodes =
-                [
-                    yield! List.concat nodes
-                    yield! visitPat pat
-                    for SynBinding(headPat = pat) in andBangs do
-                        yield! visitPat pat
-                ]
-                |> continuation
-
-            Continuation.sequence continuations finalContinuation
         | SynExpr.MatchBang(expr = expr; clauses = clauses) ->
             visit expr (fun exprNodes ->
                 [ yield! exprNodes; yield! List.collect visitSynMatchClause clauses ]

src/Compiler/Service/FSharpParseFileResults.fs

@@ -762,15 +762,6 @@ type FSharpParseFileResults(diagnostics: FSharpDiagnostic[], input: ParsedInput,
                             yield! walkExpr false e2
                             yield! walkExpr false e3
 
-                        | SynExpr.LetOrUseBang(spBind, _, _, _, rhsExpr, andBangs, bodyExpr, _, _) ->
-                            yield! walkBindSeqPt spBind
-                            yield! walkExpr true rhsExpr
-
-                            for SynBinding(debugPoint = andBangSpBind; expr = eAndBang) in andBangs do
-                                yield! walkBindSeqPt andBangSpBind
-                                yield! walkExpr true eAndBang
-
-                            yield! walkExpr true bodyExpr
                 ]
 
             // Process a class declaration or F# type declaration

src/Compiler/Service/ServiceInterfaceStubGenerator.fs

@@ -956,15 +956,6 @@ module InterfaceStubGenerator =
                 | SynExpr.YieldOrReturnFrom(expr = synExpr)
                 | SynExpr.DoBang(expr = synExpr) -> walkExpr synExpr
 
-                | SynExpr.LetOrUseBang(rhs = synExpr1; andBangs = synExprAndBangs; body = synExpr2) ->
-                    [
-                        yield synExpr1
-                        for SynBinding(expr = eAndBang) in synExprAndBangs do
-                            yield eAndBang
-                        yield synExpr2
-                    ]
-                    |> List.tryPick walkExpr
-
                 | SynExpr.LibraryOnlyILAssembly _
                 | SynExpr.LibraryOnlyStaticOptimization _
                 | SynExpr.LibraryOnlyUnionCaseFieldGet _

src/Compiler/Service/ServiceParseTreeWalk.fs

@@ -745,20 +745,6 @@ module SyntaxTraversal =
                     ]
                     |> pick expr
 
-                | SynExpr.LetOrUseBang(pat = synPat; rhs = synExpr; andBangs = andBangSynExprs; body = synExpr2) ->
-                    [
-                        yield dive synPat synPat.Range traversePat
-                        yield dive synExpr synExpr.Range traverseSynExpr
-                        yield!
-                            [
-                                for SynBinding(headPat = andBangSynPat; expr = andBangSynExpr) in andBangSynExprs do
-                                    yield (dive andBangSynPat andBangSynPat.Range traversePat)
-                                    yield (dive andBangSynExpr andBangSynExpr.Range traverseSynExpr)
-                            ]
-                        yield dive synExpr2 synExpr2.Range traverseSynExpr
-                    ]
-                    |> pick expr
-
                 | SynExpr.Dynamic _
                 | SynExpr.Ident _
                 | SynExpr.LongIdent _

src/Compiler/Service/ServiceParsedInputOps.fs

@@ -848,15 +848,6 @@ module ParsedInput =
 
             | SynExpr.Ident ident -> ifPosInRange ident.idRange (fun _ -> Some(EntityKind.FunctionOrValue false))
 
-            | SynExpr.LetOrUseBang(rhs = e1; andBangs = es; body = e2) ->
-                [
-                    yield e1
-                    for SynBinding(expr = eAndBang) in es do
-                        yield eAndBang
-                    yield e2
-                ]
-                |> List.tryPick (walkExprWithKind parentKind)
-
             | SynExpr.TraitCall(TypesForTypar ts, sign, e, _) ->
                 List.tryPick walkType ts
                 |> Option.orElseWith (fun () -> walkMemberSig sign)
@@ -2155,16 +2146,6 @@ module ParsedInput =
                 walkExpr e2
                 walkExpr e3
 
-            | SynExpr.LetOrUseBang(pat = pat; rhs = e1; andBangs = es; body = e2) ->
-                walkPat pat
-                walkExpr e1
-
-                for SynBinding(headPat = patAndBang; expr = eAndBang) in es do
-                    walkPat patAndBang
-                    walkExpr eAndBang
-
-                walkExpr e2
-
             | SynExpr.TraitCall(TypesForTypar ts, sign, e, _) ->
                 List.iter walkType ts
                 walkMemberSig sign

src/Compiler/Service/ServiceStructure.fs

@@ -258,25 +258,6 @@ module Structure =
                 rcheck Scope.Do Collapse.Below r <| Range.modStart 3 r
                 parseExpr e
 
-            | SynExpr.LetOrUseBang(pat = pat; rhs = eLet; andBangs = es; body = eBody) ->
-                let exprs =
-                    [
-                        eLet
-                        for SynBinding(expr = eAndBang) in es do
-                            eAndBang
-                    ]
-
-                for e in exprs do
-                    // for `let!`, `use!` or `and!` the pattern begins at the end of the
-                    // keyword so that this scope can be used without adjustment if there is no `=`
-                    // on the same line. If there is an `=` the range will be adjusted during the
-                    // tooltip creation
-                    let r = Range.endToEnd pat.Range e.Range
-                    rcheck Scope.LetOrUseBang Collapse.Below r r
-                    parseExpr e
-
-                parseExpr eBody
-
             | SynExpr.For(doBody = e; range = r)
             | SynExpr.ForEach(_, _, _, _, _, _, e, r) ->
                 rcheck Scope.For Collapse.Below r r

src/Compiler/Service/SynExpr.fs

@@ -444,8 +444,7 @@ module SynExpr =
         [<return: Struct>]
         let (|LetOrUse|_|) =
             dangling (function
-                | SynExpr.LetOrUse _
-                | SynExpr.LetOrUseBang _ as expr -> Some expr
+                | SynExpr.LetOrUse _ as expr -> Some expr
                 | _ -> None)
 
         /// Matches a dangling sequential expression.
@@ -697,7 +696,6 @@ module SynExpr =
         | _, SyntaxNode.SynExpr(SynExpr.Lazy _ as outer) :: _
         | _, SyntaxNode.SynExpr(SynExpr.App(argExpr = SynExpr.Paren(expr = Is expr)) as outer) :: _
         | _, SyntaxNode.SynExpr(SynExpr.LetOrUse _ as outer) :: _
-        | _, SyntaxNode.SynExpr(SynExpr.LetOrUseBang _ as outer) :: _
         | _, SyntaxNode.SynExpr(SynExpr.TryWith _ as outer) :: _
         | _, SyntaxNode.SynExpr(SynExpr.TryFinally _ as outer) :: _
         | _, SyntaxNode.SynExpr(SynExpr.For _ as outer) :: _
@@ -1211,7 +1209,6 @@ module SynExpr =
             | SynExpr.Match _, _
             | SynExpr.MatchBang _, _
             | SynExpr.LetOrUse _, _
-            | SynExpr.LetOrUseBang _, _
             | SynExpr.Sequential _, _
             | SynExpr.Do _, _
             | SynExpr.DoBang _, _

src/Compiler/Service/SynPat.fs

@@ -92,11 +92,17 @@ module SynPat =
         //     set (x: …, y: …) = …
         | SynPat.Typed _, SyntaxNode.SynPat(Rightmost(SynPat.Paren(Is pat, _))) :: SyntaxNode.SynMatchClause _ :: _
         | Rightmost(SynPat.Typed _), SyntaxNode.SynMatchClause _ :: _
-        | SynPat.Typed _, SyntaxNode.SynExpr(SynExpr.LetOrUseBang _) :: _
-        | SynPat.Typed _, SyntaxNode.SynPat(SynPat.Tuple(isStruct = false)) :: SyntaxNode.SynExpr(SynExpr.LetOrUseBang _) :: _
-        | SynPat.Tuple(isStruct = false; elementPats = AnyTyped), SyntaxNode.SynExpr(SynExpr.LetOrUseBang _) :: _
+        | SynPat.Typed _, SyntaxNode.SynExpr(SynExpr.LetOrUse(isBang = true)) :: _
+        | SynPat.Typed _, SyntaxNode.SynPat(SynPat.Tuple(isStruct = false)) :: SyntaxNode.SynExpr(SynExpr.LetOrUse(isBang = true)) :: _
+        | SynPat.Tuple(isStruct = false; elementPats = AnyTyped), SyntaxNode.SynExpr(SynExpr.LetOrUse(isBang = true)) :: _
         | SynPat.Typed _, SyntaxNode.SynPat(SynPat.Tuple(isStruct = false)) :: SyntaxNode.SynBinding _ :: _
         | SynPat.Tuple(isStruct = false; elementPats = AnyTyped), SyntaxNode.SynBinding _ :: _
+
+        //     let! (_ : obj) = …
+        | SynPat.Typed _, SyntaxNode.SynBinding _ :: SyntaxNode.SynExpr(SynExpr.LetOrUse(isBang = true)) :: _ -> true
+
+        //     let! (A _) = …
+        | SynPat.LongIdent _, SyntaxNode.SynBinding _ :: SyntaxNode.SynExpr(SynExpr.LetOrUse(isBang = true)) :: _ -> false
         | SynPat.LongIdent(argPats = SynArgPats.Pats(_ :: _)), SyntaxNode.SynBinding _ :: _
         | SynPat.LongIdent(argPats = SynArgPats.Pats(_ :: _)), SyntaxNode.SynExpr(SynExpr.Lambda _) :: _
         | SynPat.Tuple(isStruct = false), SyntaxNode.SynExpr(SynExpr.Lambda(parsedData = Some _)) :: _
@@ -144,7 +150,6 @@ module SynPat =
 
                     | SyntaxNode.SynExpr(SynExpr.Lambda(body = rhs)) :: _
                     | SyntaxNode.SynExpr(SynExpr.LetOrUse(body = rhs)) :: _
-                    | SyntaxNode.SynExpr(SynExpr.LetOrUseBang(body = rhs)) :: _
                     | SyntaxNode.SynBinding(SynBinding(expr = rhs)) :: _
                     | SyntaxNode.SynMatchClause(SynMatchClause(resultExpr = rhs)) :: _ ->
                         let rhsRange = rhs.Range
@@ -243,7 +248,7 @@ module SynPat =
         //     fun (x) -> …
         | _, SyntaxNode.SynBinding _ :: _
         | _, SyntaxNode.SynExpr(SynExpr.ForEach _) :: _
-        | _, SyntaxNode.SynExpr(SynExpr.LetOrUseBang _) :: _
+        | _, SyntaxNode.SynExpr(SynExpr.LetOrUse(isBang = true)) :: _
         | _, SyntaxNode.SynMatchClause _ :: _
         | Atomic, SyntaxNode.SynExpr(SynExpr.Lambda(parsedData = Some _)) :: _ -> false