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Syntax and semantic passes

Curb splits formatting work into two passes with different requirements. The split is not cosmetic — it determines when each pass can run and what it can safely do.

The syntax pass reads only the parse tree. It needs no compilation, no project file, no restored packages.

It handles:

  • All layout rules: indentation, spacing, brace placement, blank lines, reflow to max_line_length
  • Syntax-level code style: brace insertion, expression bodies, file-scoped namespaces, modifier order, using directive placement, file headers

Because it needs no build, it can run before the compiler — inside dotnet build, before CoreCompile. A file is formatted before the compiler reads it.

curb format <path> and curb check <path> both run the syntax pass.

The semantic pass fixes code style that requires knowing what names mean: unused usings, var where the type is apparent, readonly fields, and others.

Curb never loads a compilation of its own. Instead, it reads the diagnostics your build already reported and applies the fixes derivable from a rule ID and a span. No additional build step; the build you just ran already did the hard work.

Because it depends on a build having run, it cannot run before the compiler. The typical sequence:

dotnet build && curb cleanup

curb rules shows which rules the semantic pass fixes, and which it leaves for dotnet format style.

Naming conventions, unused members, and unread assignments are not touched by either pass. Their fixes delete declarations or rename symbols — changes that can compile and still alter which overload binds, or break a reflection string no compiler check catches. Curb reports these diagnostics and says why rather than guessing.

Curb reports these diagnostics and says why rather than guessing.

With the MSBuild package, the syntax pass runs automatically on every dotnet build. The semantic pass is a separate command you run after a build that produced diagnostics. This keeps the two passes independent: the syntax pass never waits for a compilation, and the semantic pass never re-does work the build already did.

See the build integration for how to configure both.