rigor-mangrove

Sharpens Mangrove Result / Option unwrap-family return types from untyped to the concrete type-argument carried at the call site, and synthesises the subclasses an Enum’s variants do … end DSL generates at runtime so they resolve statically. It layers on top of rigor-sorbet (which ingests Mangrove’s sig / RBI surface); this plugin adds the two precision steps sig-level types can’t reach. No runtime dependency.

It ships bundled in rigortype. Activate it under plugins: (alongside rigor-sorbet, which supplies the carrier types):

plugins:
  - rigor-sorbet
  - rigor-mangrove

What it infers — no diagnostics, no config

The plugin emits no diagnostics of its own and has no configuration. It contributes types in two places; the engine’s ordinary method-existence check then catches typos on the now-known types.

Unwrap-family return types. When the receiver is a Mangrove carrier carrying a type argument, the unwrap return narrows to that argument:

# token : Result::Ok[String, StandardError]
session.token.unwrap!.uppercaze   # error: undefined method `uppercaze' for String

Enum variant synthesis (ADR-36 Slice A). The variants DSL emits nested subclasses at runtime; the plugin synthesises them statically — the variant constant resolves, .new dispatches, and a typed #inner reader returns the declared payload type:

class Shape
  extend Mangrove::Enum
  variants do
    variant Circle, Float
  end
end

Shape::Circle.new(1.5).inner.floor                # ok — Float
Shape::Circle.new(1.5).inner.no_such_float_method # error: undefined for Float

Limitations

• No generic inference from constructors. Result::Ok.new("x") yields a carrier with no type argument, so unwrap there contributes nothing (a conservative no-op, never a false positive).
• Downcast narrowing keeps no type args (ADR-36 Slice B, deferred). Narrowing a parent generic to a variant via is_a? doesn’t yet carry the type arguments through the inheritance edge.
• Non-constant payload shapes degrade. A variant whose payload is a shape hash ({ name: String }) falls back to Dynamic[Top].

Plugin internals

The carrier-generic instantiation, the NestedClassTemplate variant synthesis, and the relationship to rigor-sorbet are in the plugin’s README; the synthesis tier is ADR-36. To write a plugin, see examples/ and the rigor-plugin-author skill.