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

[Copilot]

When the closing |} of an anonymous record type alias is vertically aligned with the opening {|, any postfix type operator on the same line causes a spurious parse error:

type T =
    {| Id: Guid
    |} []     // error FS0010: Unexpected symbol '[' in member definition
    
type U =
    {| Id: Guid
    |} seq    // error FS0010: Unexpected identifier in member definition

Workarounds were to either indent |} one extra space or use prefix generic syntax (array<{| Id: Guid |}>, etc.).

Root Cause

In LexFilter.fs, after |} (BAR_RBRACE) closes an anonymous record type, a synthetic ODUMMY BAR_RBRACE token is queued at that same position. The offside rule for type sequence blocks checks isTypeSeqBlockElementContinuator to decide whether to insert OBLOCKSEP. Since BAR_RBRACE was absent from that function, the dummy token at the same column as the outer CtxtSeqBlock triggered OBLOCKSEP insertion, causing the parser to enter class-member context — where [ and seq are invalid.

BAR_RBRACE was already present in isSeqBlockElementContinuator (expression contexts); the type context was simply missing the same treatment.

Changes

• src/Compiler/SyntaxTree/LexFilter.fs — add BAR_RBRACE to isTypeSeqBlockElementContinuator, preventing spurious OBLOCKSEP insertion after |} in type definition contexts.
• tests/FSharp.Compiler.ComponentTests/Conformance/Types/RecordTypes/AnonymousRecords.fs — add TypeAliasIndentation module with tests covering [], seq, list, option postfixes with column-aligned brackets, multi-field records, and the already-working single-line form.

[T-Gro]

Clean, well-targeted fix. The root cause analysis is correct: BAR_RBRACE was already handled in isSeqBlockElementContinuator (expression contexts) but was missing from isTypeSeqBlockElementContinuator (type definition contexts), causing spurious OBLOCKSEP insertion when |} is column-aligned.

The one-line change is minimal and mirrors the existing pattern for BAR in the same function. Tests cover the key variants (array, seq, list, option postfixes), multi-field records, and the already-working single-line form as a regression guard.

LGTM.

[github-actions]

❗ Release notes required

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✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/11.0.100.md