with x <- 1 do :ok else _ -> ;0 end

Type: mismatch
Context: with_else_body

Code:
```elixir
with x <- 1 do :ok else _ ->
;0 end
```

Elixir AST:
```elixir
{:with,
[do: [line: 1, column: 13], end: [line: 2, column: 4], line: 1, column: 1],
[
{:<-, [line: 1, column: 8], [{:x, [line: 1, column: 6], nil}, 1]},
[
do: :ok,
else: [
{:->, [newlines: 1, line: 1, column: 27],
[[{:_, [line: 1, column: 25], nil}], {:__block__, [], [nil, 0]}]}
]
]
]}
```

Spitfire AST:
```elixir
{:with,
[do: [line: 1, column: 13], end: [line: 2, column: 4], line: 1, column: 1],
[
{:<-, [line: 1, column: 8], [{:x, [line: 1, column: 6], nil}, 1]},
[
do: :ok,
else: [
{:->, [newlines: 1, line: 1, column: 27],
[[{:_, [line: 1, column: 25], nil}], 0]}
]
]
]}
```

Reproduce the provided with/else expression and compare the Elixir AST with the Spitfire AST, focusing on the else branch's __block__ containing nil and 0. Trace the AST conversion entry point that handles this construct; done means Spitfire preserves the expected else-branch structure without changing the represented expression.

Written by the indexing model from the issue text.