Highly confusing error with single whitespace change in a list expression

1. Open `StructureTests.fs`
2. Modify an existing test to offset some whitespace in the list expression

```fsharp
[]
let ``match``() =
"""
match None with // 2
| Some _ -> // 3
() // 4
| None -> // 5
match None with // 6
| Some _ -> () // 7
| None -> // 8
let x = () // 9
() // 10
"""
=> [ (1, 0, 11, 0), (1, 0, 11, 0) // Note this is one space over
(2, 0, 10, 10), (2, 15, 10, 10)
(6, 4, 10, 10), (5, 6, 10, 10)
(6, 4, 10, 10), (6, 19, 10, 10)
(9, 8, 10, 10), (8, 10, 10, 10) ]
```

Result:

Type mismatch error.