`Request textDocument/completion failed` with Interpolated Bitstring

[pjdiiori]

I had the following in a test setup block:

subaccounts =
  for letter <- ?A..?Z,
      do:
        organization_fixture(%{parent_id: parent_org.id, name: "Subaccount #{<<letter>>}"})

That caused the following error to occur on every following keystroke:

2025-12-12 10:15:07.897 [info] [Error - 10:15:07 AM] Request textDocument/completion failed.
2025-12-12 10:06:25.599 [info]   Message: ** (FunctionClauseError) no function clause matching in XPForge.Ast.Tokens.get_start_pos/1
    (xp_forge 0.1.0) XPForge.Ast.Tokens.get_start_pos([{:"<<", {815, 84, nil}}, {:identifier, {815, 86, ~c"letter"}, :letter}, {:">>", {815, 92, nil}}])
    (xp_forge 0.1.0) lib/forge/ast/tokens.ex:158: anonymous fn/2 in XPForge.Ast.Tokens.interpolation_ranges/1
    (elixir 1.18.1) lib/enum.ex:2546: Enum."-reduce/3-lists^foldl/2-0-"/3
    (xp_forge 0.1.0) lib/forge/ast/tokens.ex:151: XPForge.Ast.Tokens.interpolation_ranges/1
    (xp_forge 0.1.0) lib/forge/ast/tokens.ex:97: XPForge.Ast.Tokens.normalize_token/1
    (elixir 1.18.1) lib/stream.ex:626: anonymous fn/4 in Stream.map/2
    (elixir 1.18.1) lib/enum.ex:4964: Enumerable.List.reduce/3
    (elixir 1.18.1) lib/stream.ex:1612: Stream.do_list_resource/6

changing the code in the setup block to the following fixed the issue for me:

subaccounts =
  for letter <- ?A..?Z,
      do:
        organization_fixture(%{parent_id: parent_org.id, name: "Subaccount " <> <<letter>>})

Using VS Code on MacOS Sequoia 15.3.2
Elixir Version:

Erlang/OTP 27 [erts-15.2] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit]

Elixir 1.18.1 (compiled with Erlang/OTP 27)

Issue also occurred with Lexical after disabling Expert.

Let me know if you need any other info, thanks.