`begin`/`end` are replaced with parens

[auduchinok]

Issue created from fantomas-online

Code

do
    begin 1 end

Result

do (1)

Problem description

Please describe here the Fantomas problem you encountered.
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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 2022-07-15T14:30:45Z - 87cd212

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]

The AST is identical to do (1), so without any additional trivia in the syntax tree, we cannot reconstruct the original result.

[auduchinok]

The AST is identical to do (1)

It looks like that indeed, but there's still a small difference. The only case where SynExpr.Paren is produced for something not starting with ( is beginEndExpr, and as a workaround we could check leftParenRange length to see if it's longer than a paren. I agree, though, that it'd be better to have it properly shown in the tree in the long-term. 🙂

[auduchinok]

I've seen begin/end expressions used for scoping (and using disposables), so here's a bit less minimal case to show the change:

do
    let a = 1
    begin
        use b = f ()
        ()
    end
    let c = 2
    ()

Which gets formatted to:

do
    let a = 1

    (use b = f ()
     ())

    let c = 2
    ()