Closing `>` in nested multiline generic type applications violates offside rule

[nojaf]

Issue created from fantomas-online

Code

let makePipeline''
    (mode: ExecutionMode<Marker>)
    (resolver: IResolver option Marker)
    (args: Arguments Marker)
    (logging: Marker<ExtraLogging>)
    (processing:
        (PipelineStep<
            Map<string,
                ((Table * IStepMetadata)
                 * Operation seq
                 * FileInfo ResultKind seq
                 * (NodeInfo<string, string> * DayLogs) seq)>,
            PipelineCrate>)
            ->
        (Map<string,
            ((Table * IStepMetadata)
             * Operation seq
             * FileInfo ResultKind seq
             * (NodeInfo<string, string> * DayLogs) seq)> Marker)
            ->
        PipelineStep<unit>)
    =
    ()

Result

let makePipeline''
    (mode: ExecutionMode<Marker>)
    (resolver: IResolver option Marker)
    (args: Arguments Marker)
    (logging: Marker<ExtraLogging>)
    (processing:
        (PipelineStep<
            Map<
                string,
                ((Table * IStepMetadata) *
                Operation seq *
                FileInfo ResultKind seq *
                (NodeInfo<string, string> * DayLogs) seq)
             >,
            PipelineCrate
         >)
            -> (Map<
                string,
                ((Table * IStepMetadata) *
                Operation seq *
                FileInfo ResultKind seq *
                (NodeInfo<string, string> * DayLogs) seq)
             > Marker)
            -> PipelineStep<unit>)
    =
    ()

Problem description

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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.
• I would like a release if this problem is solved.

Options

Fantomas main branch at 2025-09-08T06:57:30Z - 31029b1

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[github-actions]

🤖 This is an automated response from Repo Assist.

Thanks for filing this, @nojaf. I attempted to load the fantomas-tools link using Playwright, but the Monaco editor did not finish rendering in time for me to capture the full input. I'm working from the issue body's code blocks.

Observed problem: The formatted output shows closing > brackets of nested generic type parameters (e.g. Map(string, ...) and PipelineStep<...>) indented with extra leading spaces, which changes the meaning of the code.

Probable area to investigate: Type.AppPrefix formatting in CodePrinter.fs around line 3243. When type arguments are multiline, the code does:

+> leadingExpressionIsMultiline (colGenericTypeParameters node.Arguments) (fun isMultiline ->
    onlyIf isMultiline (!-" "))
+> genSingleTextNode node.GreaterThan

The closing > relies on whatever column offset is in context at that point. In deeply nested complex function parameters (like the ones in this reproduction), the indentation context may accumulate extra offset from outer constructs, causing the > to be emitted at the wrong column.

This is likely an interaction between:

• The parameter indentation in genBinding / genPatLongIdentParen
• How colGenericTypeParameters calculates or inherits indent context
• Possibly: accumulated column offsets from deeply nested generic types

A good first step would be to write a minimal failing test with just the processing parameter's type signature, then bisect which level of nesting first produces the offset error.

Labelling as bug (soundness) since the formatted result breaks code (already set).

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