Idempotency problem when using set and spread syntax

[MangelMaxime]

Issue created from fantomas-online

Formatted code

let numeric =
    set['0' .. '9']
    + set['+'
    '-'
    '.'
    'e'
    'E']

let whitespace =
    set[','
    ':'
    '\u0009'
    '\u000a'
    '\u000d'
    '\u0020']

Reformatted code

let numeric = set['0' .. '9'] + set['+' '-' '.' 'e' 'E']

let whitespace = set[',' ':' '\u0009' '\u000a' '\u000d' '\u0020']

This code is invalid because it is missing ; separator.

Another problem with this code, is that it gives a compiler warning because there should be a space between set and the bracket [

The syntax 'expr1[expr2]' is used for indexing. Consider adding a type annotation to enable indexing, or if calling a function add a space, e.g. 'expr1 [expr2]'

Problem description

Fantomas was not able to produce the same code after reformatting the result.

Extra information

• The formatted result breaks my code.
• The formatted result gives compiler warnings.
• I or my company would be willing to help fix this.

Options

Fantomas master branch at 2022-07-28T06:18:27Z - 9f5feff

Default Fantomas configuration

_{Did you know that you can ignore files when formatting from fantomas-tool or the FAKE targets by using a .fantomasignore file?}

[nojaf]

Hello, this is a duplicate of #2158.
In short, calling set[expr] is considered to be an indexer expression (like foo[1]) in the new F# 6 syntax.
You need to add a space in your code to tell the compiler this is a function application instead of an indexer expression. (Example)

[nojaf]

Fixed by #2446