Fix parser error for anonymous record type aliases with postfix type operators when closing bracket is column-aligned (#19762)

* Initial plan

* Fix anonymous record type alias with array/generic type suffix error when closing bracket is aligned with opening bracket

Add BAR_RBRACE to isTypeSeqBlockElementContinuator in LexFilter.fs to prevent incorrect OBLOCKSEP insertion after closing |} in type alias contexts. This fixes the error 'Unexpected symbol [' in member definition' when writing:

    type T =
        {| Id: Guid
        |} []  // or |} seq, |} list, |} option

Add tests covering the fixed cases in AnonymousRecords.fs.

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Co-authored-by: T-Gro <46543583+T-Gro@users.noreply.github.com>

* Add release notes for anonymous record type alias parser fix

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: T-Gro <46543583+T-Gro@users.noreply.github.com>
Co-authored-by: Tomas Grosup <tomasgrosup@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Tomas Grosup <Tomas.Grosup@gmail.com>

Author: 3 people

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -64,6 +64,7 @@
 * Fix parallel compilation of scripts ([PR #19649](https://github.com/dotnet/fsharp/pull/19649))
 * Fix parser recovery, name resolution, and code completion for unfinished enum patterns ([PR #19708](https://github.com/dotnet/fsharp/pull/19708))
 * Parser: fix unexpected diagnostics in debug builds, improve error messages ([PR #19730](https://github.com/dotnet/fsharp/pull/19730))
+* Fix parser error for anonymous record type aliases with postfix type operators (e.g. `{| Id: Guid |} []`) when closing bracket is column-aligned with opening bracket. ([Issue #17407](https://github.com/dotnet/fsharp/issues/17407), [PR #19762](https://github.com/dotnet/fsharp/pull/19762))
 * Fix internal error when resolving SRTP `get_Item` witness for `string` indexers (`unknown builtin witness 'get_ItemDynamic'`). ([Issue #18093](https://github.com/dotnet/fsharp/issues/18093), [PR #19757](https://github.com/dotnet/fsharp/pull/19757))
 * Allow `| null` nullable annotation on a `[<MeasureAnnotatedAbbreviation>]` over a reference type (e.g. the FSharp.UMX `type string<[<Measure>] 'm> = string` pattern). ([Issue #19657](https://github.com/dotnet/fsharp/issues/19657))
 * Fix `[<Struct>] ?param` optional parameters could not be passed using the explicit `?param = expr` caller-side syntax with a `ValueOption` value. ([Issue #19711](https://github.com/dotnet/fsharp/issues/19711), [PR #19742](https://github.com/dotnet/fsharp/pull/19742))

src/Compiler/SyntaxTree/LexFilter.fs

@@ -352,6 +352,14 @@ let rec isTypeSeqBlockElementContinuator token =
     //   member x.M1
     //   member x.M2
     | BAR -> true
+    // Closing tokens for anonymous record types and struct types in type aliases, e.g.
+    //   type T =
+    //       {| Id: int
+    //       |} []          <-- BAR_RBRACE here should not trigger OBLOCKSEP for '[]'
+    //   type T =
+    //       {| Id: int
+    //       |} seq         <-- BAR_RBRACE here should not trigger OBLOCKSEP for 'seq'
+    | BAR_RBRACE -> true
     | OBLOCKBEGIN | ORIGHT_BLOCK_END _ | OBLOCKEND _ | ODECLEND (_, _) -> true // The following arise during reprocessing of the inserted tokens when we hit a DONE
     | ODUMMY token -> isTypeSeqBlockElementContinuator token
     | _ -> false

tests/FSharp.Compiler.ComponentTests/Conformance/Types/RecordTypes/AnonymousRecords.fs

@@ -673,3 +673,73 @@ let nested2 : {| A: {| B: Expr<int> |}; C: Expr |} =
             (Error 3350, Line 8, Col 22, Line 8, Col 24, "Feature 'Support for better anonymous record parsing' is not available in F# 9.0. Please use language version 10.0 or greater.")
             (Error 3350, Line 8, Col 44, Line 8, Col 49, "Feature 'Support for better anonymous record parsing' is not available in F# 9.0. Please use language version 10.0 or greater.")
         ]
+
+module TypeAliasIndentation =
+
+    // https://github.com/dotnet/fsharp/issues/17992
+    [<Fact>]
+    let ``Anonymous record type alias with array suffix - closing bracket aligned with opening``() =
+        FSharp """
+module M
+type T =
+    {| Id: System.Guid
+    |} []
+"""
+        |> typecheck
+        |> shouldSucceed
+
+    [<Fact>]
+    let ``Anonymous record type alias with seq postfix - closing bracket aligned with opening``() =
+        FSharp """
+module M
+type T =
+    {| Id: System.Guid
+    |} seq
+"""
+        |> typecheck
+        |> shouldSucceed
+
+    [<Fact>]
+    let ``Anonymous record type alias with list postfix - closing bracket aligned with opening``() =
+        FSharp """
+module M
+type T =
+    {| Id: System.Guid
+    |} list
+"""
+        |> typecheck
+        |> shouldSucceed
+
+    [<Fact>]
+    let ``Anonymous record type alias with option postfix - closing bracket aligned with opening``() =
+        FSharp """
+module M
+type T =
+    {| Id: System.Guid
+    |} option
+"""
+        |> typecheck
+        |> shouldSucceed
+
+    [<Fact>]
+    let ``Anonymous record type alias with multiple fields and array suffix``() =
+        FSharp """
+module M
+type T =
+    {| Id: System.Guid
+       Name: string
+    |} []
+"""
+        |> typecheck
+        |> shouldSucceed
+
+    [<Fact>]
+    let ``Anonymous record type alias all on same line still works``() =
+        FSharp """
+module M
+type T = {| Id: System.Guid |} []
+type U = {| Id: System.Guid |} seq
+type V = {| Id: System.Guid |} list
+"""
+        |> typecheck
+        |> shouldSucceed