Generate RBI methods inherited from Struct and other anonymous superclasses

[DaneHarrison]

Motivation

Fixes #1384 - When a class inherits from an anonymous superclass like class SSLOptions < Struct.new(:verify_hostname), Tapioca skips everything defined on the anonymous class. So we get verify? but not verify_hostname/verify_hostname=. Same thing happens with Data.define and Class.new { }.

Implementation

Methods from the anonymous superclass are now compiled onto the named class, so class Foo < Struct.new(:bar) becomes class Foo < ::Struct with bar and bar=.

There are ~800 lines of tests; commits highlight the tests that turn green after the changes.

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• New Pipeline#anonymous_superclasses_of caches and returns the unnamed superclasses compile_superclass skips.

  • Singleton classes map to their attached class so self. methods work.
  • Abstract and generic superclasses stop the walk, since their abstract methods and type members can't go on the subclass.

• Only the gem that first defines the class gets these superclasses. Otherwise a gem that reopens the class repeats all the Struct methods in its RBI.

  • When the superclass is a named struct defined in another gem, or is built by another gem's method (class Foo < LibA.Base(:x)), this gem gets the members and class methods but not the methods defined in its block (def helper in Struct.new("Shared", :key) { ... }). Those are defined in the other gem, so they're skipped here. That gem doesn't have them either, since it writes a named struct as Shared = Struct.

• method_defined_by_constant now accepts methods owned by those superclasses, through the new Pipeline#anonymous_superclass_owning (also used by SourceLocation) after the constant itself is checked.

• Method definitions are tracked against the anonymous class, not the named one, so method_definitions_for falls back to source_location. That returned the sig wrapper or a prepended module's method, so those methods were dropped. fallback_source_method: passes in the method compile_method already found on the anonymous superclass.

  • I tried calling method_definition_in_gem with the anonymous superclass as the owner instead (like SourceLocation does), but that broke tests
    • "compiles named Struct superclasses defined in other gems"
    • "compiles DelegateClass"
    • "does not compile methods a DelegateClass superclass delegates"
    • "compiles public methods ActiveSupport defines in an anonymous superclass"

• Visibility falls back to the anonymous superclass, so a prepended module's private doesn't override the original.

• For loc comments (--include-loc), SourceLocation looks the method up under the anonymous superclass, so the comment points to the right line.

• Mixins only drops ancestors from the first named superclass, so an include/extend inside the Struct.new block ends up on the class. Mixin locations are looked up on the anonymous superclass too, so mixins done by other gems still get filtered.

• Named structs (Struct::Foo) count as anonymous too, since name_of writes them as Struct. named_struct? also checks that the class really inherits from Struct. Mixins also skips the superclasses themselves so they don't show up as an include ::Struct::Foo.

Further Considerations:

• Unrelated to this issue, I fixed a minor issue in my last PR (Fix method signatures being overwritten by prepended modules #2718): owner checks in methods.rb used ==/!=, which a class can override. I switched them to are_equal?, which the rest of Tapioca uses to compare modules by identity.
• Since most classes won't have an anonymous superclass, I tried to memoize and short-circuit when possible.

Tests

• Updated the S1 and S4 expectations in the existing Structs, Classes, and Modules spec
• SSLOptions from the issue matches the Struct.new block form
• A Data.define subclass matches the Data.define block form
• A copy of aws-sdk-core's class EmptyStructure < Struct.new('AwsEmptyStructure')
  • One of the edge cases that got the previous fix (Generate better Struct definitions #247) reverted in Revert "Generate better Struct definitions" #465
• Named structs defined in another gem and subclassed in this one
• A Struct subclass reopened by another gem doesn't repeat the Struct methods
• Struct methods overridden by the subclass, or made private with private :y=
• Sigs defined in the Struct.new block (plain, sig(:final) and attr_accessor)
• Source locations for methods from the anonymous superclass
• Modules prepended onto the subclass, inside the Struct.new block, and from another gem
• A prepended module's private doesn't change the Struct method's visibility
• include/extend inside a Struct.new block, and include inside a Data.define block
• include/prepend/extend on the anonymous superclass from another gem are skipped
• Grandchild of a Struct subclass doesn't repeat the methods
• Data anonymous superclass matches the block form
• Class.new superclasses: plain, with a named parent, and nested
• Abstract and generic anonymous superclasses aren't compiled into the subclass
• initialize from Struct, Data and Class.new superclasses
• public/protected/private and private_class_method in the block
• DelegateClass methods are still left out
• ActiveSupport delegate and class_attribute in the block

[DaneHarrison]

• The RBI's superclass already brings in its ancestors, so they're dropped: Reflection#inherited_ancestors_of, Mixins#interesting_ancestors_of

• class Foo < Struct.new(:a) is written as class Foo < ::Struct: Pipeline#compile_superclass

• Only Struct's ancestors are dropped, since it's the superclass of the last (topmost) anonymous superclass: Pipeline#anonymous_superclasses_of, Mixins#interesting_ancestors_of

• Mixins added inside Struct.new/Data.define are kept: tested by "compiles mixins of Struct and Data anonymous superclasses"

• The anonymous superclasses themselves are dropped, otherwise named structs show up as include ::Struct::Foo: Mixins#interesting_ancestors_of, tested by "compiles Structs, Classes, and Modules", "compiles named Struct superclasses like aws-sdk-core's EmptyStructure", and "compiles named Struct superclasses defined in other gems"