diff --git a/lib/prism/node_ext.rb b/lib/prism/node_ext.rb
index 36a43b6327..fdd6ac200d 100644
--- a/lib/prism/node_ext.rb
+++ b/lib/prism/node_ext.rb
@@ -106,14 +106,23 @@ module Prism
     # local variable
     class DynamicPartsInConstantPathError < StandardError; end
 
+    # An error class raised when missing nodes are found while computing a
+    # constant path's full name. For example:
+    # Foo:: -> raises because the constant path is missing the last part
+    class MissingNodesInConstantPathError < StandardError; end
+
     # Returns the list of parts for the full name of this constant path.
     # For example: [:Foo, :Bar]
     def full_name_parts
-      parts = [child.name]
-      current = parent
+      parts = [] #: Array[Symbol]
+      current = self #: node?
 
       while current.is_a?(ConstantPathNode)
-        parts.unshift(current.child.name)
+        child = current.child
+        if child.is_a?(MissingNode)
+          raise MissingNodesInConstantPathError, "Constant path contains missing nodes. Cannot compute full name"
+        end
+        parts.unshift(child.name)
         current = current.parent
       end
 
@@ -134,14 +143,19 @@ module Prism
     # Returns the list of parts for the full name of this constant path.
     # For example: [:Foo, :Bar]
     def full_name_parts
-      parts = case parent
-      when ConstantPathNode, ConstantReadNode
-        parent.full_name_parts
-      when nil
-        [:""]
-      else
-        raise ConstantPathNode::DynamicPartsInConstantPathError,
-          "Constant path target contains dynamic parts. Cannot compute full name"
+      parts =
+        case parent
+        when ConstantPathNode, ConstantReadNode
+          parent.full_name_parts
+        when nil
+          [:""]
+        else
+          # e.g. self::Foo, (var)::Bar = baz
+          raise ConstantPathNode::DynamicPartsInConstantPathError, "Constant target path contains dynamic parts. Cannot compute full name"
+        end
+
+      if child.is_a?(MissingNode)
+        raise ConstantPathNode::MissingNodesInConstantPathError, "Constant target path contains missing nodes. Cannot compute full name"
       end
 
       parts.push(child.name)
@@ -169,7 +183,7 @@ module Prism
   class ParametersNode < Node
     # Mirrors the Method#parameters method.
     def signature
-      names = [] #: Array[[:req | :opt | :rest | :keyreq | :key | :keyrest | :block, Symbol] | [:req | :rest | :keyrest | :nokey]]
+      names = [] #: Array[[Symbol, Symbol] | [Symbol]]
 
       requireds.each do |param|
         names << (param.is_a?(MultiTargetNode) ? [:req] : [:req, param.name])
@@ -182,7 +196,14 @@ module Prism
       end
 
       posts.each do |param|
-        names << (param.is_a?(MultiTargetNode) ? [:req] : [:req, param.name])
+        if param.is_a?(MultiTargetNode)
+          names << [:req]
+        elsif param.is_a?(NoKeywordsParameterNode)
+          # Invalid syntax, e.g. "def f(**nil, ...)" moves the NoKeywordsParameterNode to posts
+          raise "Invalid syntax"
+        else
+          names << [:req, param.name]
+        end
       end
 
       # Regardless of the order in which the keywords were defined, the required
diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index 1d9e700882..c55b7b6685 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -281,7 +281,8 @@ module Prism
     # the beginning of the file. Useful for when you want a location object but
     # do not care where it points.
     def self.null
-      new(nil, 0, 0)
+      source = nil #: Source
+      new(source, 0, 0)
     end
   end
 
diff --git a/lib/prism/parse_result/comments.rb b/lib/prism/parse_result/comments.rb
index 314261ea47..4e1b9a68e5 100644
--- a/lib/prism/parse_result/comments.rb
+++ b/lib/prism/parse_result/comments.rb
@@ -188,7 +188,12 @@ module Prism
 
     # Attach the list of comments to their respective locations in the tree.
     def attach_comments!
-      Comments.new(self).attach!
+      if ProgramNode === value
+        this = self #: ParseResult[ProgramNode]
+        Comments.new(this).attach!
+      else
+        raise
+      end
     end
   end
 end
diff --git a/lib/prism/prism.gemspec b/lib/prism/prism.gemspec
index 16ae553e32..905cd1b90b 100644
--- a/lib/prism/prism.gemspec
+++ b/lib/prism/prism.gemspec
@@ -122,7 +122,6 @@ Gem::Specification.new do |spec|
     "src/options.c",
     "src/prism.c",
     "prism.gemspec",
-    "sig/manifest.yaml",
     "sig/prism.rbs",
     "sig/prism/compiler.rbs",
     "sig/prism/dispatcher.rbs",
diff --git a/lib/prism/ripper_compat.rb b/lib/prism/ripper_compat.rb
new file mode 100644
index 0000000000..caab9a8549
--- /dev/null
+++ b/lib/prism/ripper_compat.rb
@@ -0,0 +1,208 @@
+# frozen_string_literal: true
+
+require "ripper"
+
+module Prism
+  # Note: This integration is not finished, and therefore still has many
+  # inconsistencies with Ripper. If you'd like to help out, pull requests would
+  # be greatly appreciated!
+  #
+  # This class is meant to provide a compatibility layer between prism and
+  # Ripper. It functions by parsing the entire tree first and then walking it
+  # and executing each of the Ripper callbacks as it goes.
+  #
+  # This class is going to necessarily be slower than the native Ripper API. It
+  # is meant as a stopgap until developers migrate to using prism. It is also
+  # meant as a test harness for the prism parser.
+  #
+  # To use this class, you treat `Prism::RipperCompat` effectively as you would
+  # treat the `Ripper` class.
+  class RipperCompat < Visitor
+    # This class mirrors the ::Ripper::SexpBuilder subclass of ::Ripper that
+    # returns the arrays of [type, *children].
+    class SexpBuilder < RipperCompat
+      private
+
+      Ripper::PARSER_EVENTS.each do |event|
+        define_method(:"on_#{event}") do |*args|
+          [event, *args]
+        end
+      end
+
+      Ripper::SCANNER_EVENTS.each do |event|
+        define_method(:"on_#{event}") do |value|
+          [:"@#{event}", value, [lineno, column]]
+        end
+      end
+    end
+
+    # This class mirrors the ::Ripper::SexpBuilderPP subclass of ::Ripper that
+    # returns the same values as ::Ripper::SexpBuilder except with a couple of
+    # niceties that flatten linked lists into arrays.
+    class SexpBuilderPP < SexpBuilder
+      private
+
+      def _dispatch_event_new # :nodoc:
+        []
+      end
+
+      def _dispatch_event_push(list, item) # :nodoc:
+        list << item
+        list
+      end
+
+      Ripper::PARSER_EVENT_TABLE.each do |event, arity|
+        case event
+        when /_new\z/
+          alias_method :"on_#{event}", :_dispatch_event_new if arity == 0
+        when /_add\z/
+          alias_method :"on_#{event}", :_dispatch_event_push
+        end
+      end
+    end
+
+    # The source that is being parsed.
+    attr_reader :source
+
+    # The current line number of the parser.
+    attr_reader :lineno
+
+    # The current column number of the parser.
+    attr_reader :column
+
+    # Create a new RipperCompat object with the given source.
+    def initialize(source)
+      @source = source
+      @result = nil
+      @lineno = nil
+      @column = nil
+    end
+
+    ############################################################################
+    # Public interface
+    ############################################################################
+
+    # True if the parser encountered an error during parsing.
+    def error?
+      result.failure?
+    end
+
+    # Parse the source and return the result.
+    def parse
+      result.magic_comments.each do |magic_comment|
+        on_magic_comment(magic_comment.key, magic_comment.value)
+      end
+
+      if error?
+        result.errors.each do |error|
+          on_parse_error(error.message)
+        end
+      else
+        result.value.accept(self)
+      end
+    end
+
+    ############################################################################
+    # Visitor methods
+    ############################################################################
+
+    # Visit a CallNode node.
+    def visit_call_node(node)
+      message = node.message
+      if message && message.match?(/^[[:alpha:]_]/) && node.opening_loc.nil? && node.arguments && node.arguments.arguments && node.arguments.arguments.length == 1
+        left = visit(node.receiver)
+        right = visit(node.arguments.arguments.first)
+
+        bounds(node.location)
+        on_binary(left, node.name, right)
+      else
+        raise NotImplementedError
+      end
+    end
+
+    # Visit a FloatNode node.
+    def visit_float_node(node)
+      bounds(node.location)
+      on_float(node.slice)
+    end
+
+    # Visit a ImaginaryNode node.
+    def visit_imaginary_node(node)
+      bounds(node.location)
+      on_imaginary(node.slice)
+    end
+
+    # Visit an IntegerNode node.
+    def visit_integer_node(node)
+      bounds(node.location)
+      on_int(node.slice)
+    end
+
+    # Visit a RationalNode node.
+    def visit_rational_node(node)
+      bounds(node.location)
+      on_rational(node.slice)
+    end
+
+    # Visit a StatementsNode node.
+    def visit_statements_node(node)
+      bounds(node.location)
+      node.body.inject(on_stmts_new) do |stmts, stmt|
+        on_stmts_add(stmts, visit(stmt))
+      end
+    end
+
+    # Visit a ProgramNode node.
+    def visit_program_node(node)
+      statements = visit(node.statements)
+      bounds(node.location)
+      on_program(statements)
+    end
+
+    ############################################################################
+    # Entrypoints for subclasses
+    ############################################################################
+
+    # This is a convenience method that runs the SexpBuilder subclass parser.
+    def self.sexp_raw(source)
+      SexpBuilder.new(source).parse
+    end
+
+    # This is a convenience method that runs the SexpBuilderPP subclass parser.
+    def self.sexp(source)
+      SexpBuilderPP.new(source).parse
+    end
+
+    private
+
+    # This method is responsible for updating lineno and column information
+    # to reflect the current node.
+    #
+    # This method could be drastically improved with some caching on the start
+    # of every line, but for now it's good enough.
+    def bounds(location)
+      @lineno = location.start_line
+      @column = location.start_column
+    end
+
+    # Lazily initialize the parse result.
+    def result
+      @result ||= Prism.parse(source)
+    end
+
+    def _dispatch0; end # :nodoc:
+    def _dispatch1(_); end # :nodoc:
+    def _dispatch2(_, _); end # :nodoc:
+    def _dispatch3(_, _, _); end # :nodoc:
+    def _dispatch4(_, _, _, _); end # :nodoc:
+    def _dispatch5(_, _, _, _, _); end # :nodoc:
+    def _dispatch7(_, _, _, _, _, _, _); end # :nodoc:
+
+    alias_method :on_parse_error, :_dispatch1
+    alias_method :on_magic_comment, :_dispatch2
+
+    (Ripper::SCANNER_EVENT_TABLE.merge(Ripper::PARSER_EVENT_TABLE)).each do |event, arity|
+      alias_method :"on_#{event}", :"_dispatch#{arity}"
+    end
+  end
+end
diff --git a/prism/templates/lib/prism/dsl.rb.erb b/prism/templates/lib/prism/dsl.rb.erb
index 7c55fb10bc..4c139ca281 100644
--- a/prism/templates/lib/prism/dsl.rb.erb
+++ b/prism/templates/lib/prism/dsl.rb.erb
@@ -36,6 +36,7 @@ module Prism
 
     # Create a new Location object
     def Location(source = nil, start_offset = 0, length = 0)
+      # @type var source: Source
       Location.new(source, start_offset, length)
     end
     <%- nodes.each do |node| -%>
diff --git a/prism/templates/lib/prism/node.rb.erb b/prism/templates/lib/prism/node.rb.erb
index 98048989f2..32134f8820 100644
--- a/prism/templates/lib/prism/node.rb.erb
+++ b/prism/templates/lib/prism/node.rb.erb
@@ -56,6 +56,7 @@ module Prism
 
     # Convert this node into a graphviz dot graph string.
     def to_dot
+      # @type self: node
       DotVisitor.new.tap { |visitor| accept(visitor) }.to_dot
     end
 
diff --git a/prism/templates/lib/prism/visitor.rb.erb b/prism/templates/lib/prism/visitor.rb.erb
index 04156cc7a9..4b30a1815b 100644
--- a/prism/templates/lib/prism/visitor.rb.erb
+++ b/prism/templates/lib/prism/visitor.rb.erb
@@ -7,16 +7,19 @@ module Prism
     # Calls `accept` on the given node if it is not `nil`, which in turn should
     # call back into this visitor by calling the appropriate `visit_*` method.
     def visit(node)
+      # @type self: _Visitor
       node&.accept(self)
     end
 
     # Visits each node in `nodes` by calling `accept` on each one.
     def visit_all(nodes)
+      # @type self: _Visitor
       nodes.each { |node| node&.accept(self) }
     end
 
     # Visits the child nodes of `node` by calling `accept` on each one.
     def visit_child_nodes(node)
+      # @type self: _Visitor
       node.compact_child_nodes.each { |node| node.accept(self) }
     end
   end