TRLS004 — Unsafe access to Result.Error

• Severity: Warning
• Category: Trellis

What it detects

Flags result.Error when the analyzer cannot prove that the access is guarded by a failure check or another safe Trellis pattern.

Why it matters

Result.Error throws when the result is a success. Unchecked access swaps a clean result flow for an exception.

Warning

This often appears in logging and HTTP mapping code. Make the failure path explicit before reading Error.

Bad example

using Trellis;

static class Example
{
    public static string Bad(Result<int> result) =>
        result.Error.Detail;
}

Good example

using Trellis;

static class Example
{
    public static string Good(Result<int> result)
    {
        if (result.IsFailure)
            return result.Error.Detail;

        return "No error";
    }
}

Code fix available

Yes — wraps the current usage in an if (result.IsFailure) guard.

Configuration

Use standard Roslyn configuration if you need to suppress this rule in a specific scope.

dotnet_diagnostic.TRLS004.severity = none

#pragma warning disable TRLS004
// Intentional: documented exception or test-only pattern.
#pragma warning restore TRLS004

Tip

When you need to translate both branches, Match and MatchError usually keep the code cleaner than a manual Error read.