Index X = Class.new(Super) constant assignments as classes

[apiology]

Fixes #1303.

Gems commonly build classes as X = Class.new(Parent) do ... end — Asana's entire error hierarchy is one example. Solargraph indexed the result as an untyped constant, so no method on such a class resolved, and the methods in the block were attached to the enclosing namespace instead of the new class. There was no annotation that worked around it: a @!parse stub declaring the same name contributed nothing, and @!override on the constant crashed the typechecker (#1302).

module Vendor
  Specific = Class.new(StandardError) do
    # @return [Integer]
    def retry_after
      5
    end
  end
end

# @param e [Vendor::Specific]
# @return [void]
def wait_for(e)
  e.retry_after   # Unresolved call to retry_after on Vendor::Specific
end

This adds a Convention::ClassDefinition following the existing StructDefinition / DataDefinition pattern: a :casgn node processor that pushes a Pin::Namespace for the assigned constant plus a Pin::Reference::Superclass, so block methods attach to the new class and the superclass is recorded. It registers after the Struct/Data processors and before ParserGem::NodeProcessors::CasgnNode, since registration order is precedence and Struct/Data must keep winning.

Negative controls verified in one file covering all four forms: S = Struct.new(:bar) and D = Data.define(:baz) still resolve through their own conventions, a plain Alias = Other is still an ordinary Pin::Constant, and C = Class.new(StandardError) do … end now resolves its block methods. Full suite green locally: 1632 examples, 0 failures, 60 pending. RuboCop clean; strong typecheck on both new lib files reports 0 problems.

Authored by Claude (Anthropic's Claude Code) on behalf of @apiology.