Extract and display RBS type signatures in documentation

Add support for displaying RBS type signatures in both HTML and RI
output. Type information is sourced from inline `#:` annotations
(parsed by the Prism parser) and from `.rbs` files in the project's
`sig/` directory plus RBS stdlib declarations.

Implementation:
- `RDoc::RbsHelper` module: loads RBS signatures, validates types,
  renders type signatures as HTML with linked type names
- Parser extracts `#:` annotation lines via `RBS_SIG_LINE` constant,
  validates them, and attaches to `MethodAttr#type_signature`
- `Store#merge_rbs_signatures` fills in signatures from `.rbs` files
  where inline annotations are absent
- `Store#type_name_lookup` maps qualified and unambiguous unqualified
  names to documentation paths for type linking
- Aliki theme: type signatures render as styled `<pre>` blocks under
  method headings, with linked type names using `a.rbs-type` class
- RI driver: type signatures display as verbatim blocks
- `MARSHAL_VERSION` bumped to 4 for `AnyMethod` and `Attr`

Author: st0012

lib/rdoc/code_object/any_method.rb

@@ -14,7 +14,7 @@ class RDoc::AnyMethod < RDoc::MethodAttr
   #   RDoc 4.1
   #   Added is_alias_for
 
-  MARSHAL_VERSION = 3 # :nodoc:
+  MARSHAL_VERSION = 4 # :nodoc:
 
   ##
   # Don't rename \#initialize to \::new
@@ -166,6 +166,7 @@ def marshal_dump
       @parent.class,
       @section.title,
       is_alias_for,
+      @type_signature,
     ]
   end
 
@@ -204,6 +205,7 @@ def marshal_load(array)
     @parent_title  = array[13]
     @section_title = array[14]
     @is_alias_for  = array[15]
+    @type_signature = array[16]
 
     array[8].each do |new_name, document|
       add_alias RDoc::Alias.new(nil, @name, new_name, RDoc::Comment.from_document(document), singleton: @singleton)

lib/rdoc/code_object/attr.rb

@@ -11,7 +11,7 @@ class RDoc::Attr < RDoc::MethodAttr
   #    Added parent name and class
   #    Added section title
 
-  MARSHAL_VERSION = 3 # :nodoc:
+  MARSHAL_VERSION = 4 # :nodoc:
 
   ##
   # Is the attribute readable ('R'), writable ('W') or both ('RW')?
@@ -108,7 +108,8 @@ def marshal_dump
       @file.relative_name,
       @parent.full_name,
       @parent.class,
-      @section.title
+      @section.title,
+      @type_signature,
     ]
   end
 
@@ -140,6 +141,7 @@ def marshal_load(array)
     @parent_name   = array[8]
     @parent_class  = array[9]
     @section_title = array[10]
+    @type_signature = array[11]
 
     @file = RDoc::TopLevel.new array[7] if version > 1
 

lib/rdoc/code_object/method_attr.rb

@@ -58,6 +58,18 @@ class RDoc::MethodAttr < RDoc::CodeObject
 
   attr_accessor :call_seq
 
+  ##
+  # RBS type signature from inline annotations or loaded .rbs files
+
+  attr_accessor :type_signature
+
+  ##
+  # Returns the type signature split into individual lines.
+
+  def type_signature_lines
+    @type_signature&.split("\n")
+  end
+
   ##
   # The call_seq or the param_seq with method name, if there is no call_seq.
 
@@ -86,6 +98,7 @@ def initialize(text, name, singleton: false)
     @block_params = nil
     @call_seq     = nil
     @params       = nil
+    @type_signature = nil
   end
 
   ##

lib/rdoc/generator/aliki.rb

@@ -117,6 +117,21 @@ def write_search_index
     File.write search_index_path, "var search_data = #{JSON.generate(data)};"
   end
 
+  ##
+  # Returns the type signature of +method_attr+ as HTML with linked type names.
+  # Returns nil if no type signature is present.
+
+  def type_signature_html(method_attr, from_path)
+    lines = method_attr.type_signature_lines
+    return unless lines
+
+    RDoc::RbsHelper.signature_to_html(
+      lines,
+      lookup: @store.type_name_lookup,
+      from_path: from_path
+    )
+  end
+
   ##
   # Resolves a URL for use in templates. Absolute URLs are returned unchanged.
   # Relative URLs are prefixed with rel_prefix to ensure they resolve correctly from any page.

lib/rdoc/generator/template/aliki/class.rhtml

@@ -93,6 +93,9 @@
             <span class="method-name"><%= h attrib.name %></span>
             <span class="attribute-access-type">[<%= attrib.rw %>]</span>
           </a>
+          <%- if attrib.type_signature %>
+          <span class="method-type-signature"><code><%= type_signature_html(attrib, klass.path) %></code></span>
+          <%- end %>
         </div>
 
         <div class="method-description">
@@ -150,6 +153,10 @@
               </a>
             </div>
           <%- end %>
+
+          <%- if method.type_signature %>
+          <pre class="method-type-signature"><code><%= type_signature_html(method, klass.path) %></code></pre>
+          <%- end %>
         </div>
 
         <%- if method.token_stream %>

lib/rdoc/generator/template/aliki/css/rdoc.css

@@ -1075,6 +1075,20 @@ main h6 a:hover {
   font-style: italic;
 }
 
+/* RBS Type Signature Links — linked types get subtle underline */
+a.rbs-type {
+  color: inherit;
+  text-decoration: underline;
+  text-decoration-color: var(--color-border-default);
+  text-underline-offset: 0.2em;
+  transition: text-decoration-color var(--transition-fast), color var(--transition-fast);
+}
+
+a.rbs-type:hover {
+  color: var(--color-link-hover);
+  text-decoration-color: var(--color-link-hover);
+}
+
 /* Emphasis */
 em {
   text-decoration-color: var(--color-emphasis-decoration);
@@ -1335,6 +1349,49 @@ main .method-heading .method-args {
   font-weight: var(--font-weight-normal);
 }
 
+/* Type signatures — overloads stack as a code block under the method name */
+pre.method-type-signature {
+  position: relative;
+  margin: var(--space-2) 0 0;
+  padding: var(--space-2) 0 0;
+  background: transparent;
+  border: none;
+  border-radius: 0;
+  overflow: visible;
+  font-family: var(--font-code);
+  font-size: var(--font-size-sm);
+  color: var(--color-text-tertiary);
+  line-height: var(--line-height-tight);
+  white-space: pre-wrap;
+  overflow-wrap: break-word;
+}
+
+pre.method-type-signature::before {
+  content: '';
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  border-top: 1px dotted var(--color-border-default);
+}
+
+pre.method-type-signature code {
+  font-family: inherit;
+  font-size: inherit;
+  color: inherit;
+  background: transparent;
+  padding: 0;
+}
+
+/* Attribute type sigs render inline after the [RW] badge */
+main .method-heading > .method-type-signature {
+  display: inline;
+  margin-left: var(--space-2);
+  font-family: var(--font-code);
+  font-size: var(--font-size-sm);
+  color: var(--color-text-secondary);
+}
+
 main .method-controls {
   position: absolute;
   top: var(--space-3);
@@ -1444,6 +1501,10 @@ main .attribute-access-type {
     font-size: var(--font-size-base);
   }
 
+  pre.method-type-signature {
+    font-size: var(--font-size-xs);
+  }
+
   main .method-header {
     padding: var(--space-2);
     padding-right: var(--space-2);

lib/rdoc/generator/template/aliki/js/aliki.js

@@ -435,8 +435,8 @@ function wrapCodeBlocksWithCopyButton() {
   //   not directly in rhtml templates
   // - Modifying the formatter would require extending RDoc's core internals
 
-  // Find all pre elements that are not already wrapped
-  const preElements = document.querySelectorAll('main pre:not(.code-block-wrapper pre)');
+  // Target code examples and source code; skip type signature blocks
+  const preElements = document.querySelectorAll('main pre:not(.method-type-signature)');
 
   preElements.forEach((pre) => {
     // Skip if already wrapped

lib/rdoc/markdown.kpeg

@@ -617,8 +617,8 @@ BlockQuote = BlockQuoteRaw:a
 
 BlockQuoteRaw =  @StartList:a
                  (( ">" " "? Line:l { a << l } )
-                  ( !">" !@BlankLine Line:c { a << c } )*
-                  ( @BlankLine:n { a << n } )*
+                  ( !">" !@BlankLine !(AtxStart @Spacechar) !Bullet !Enumerator !( &{ github? } Ticks3 ) Line:c { a << c } )*
+                  ( ">" @BlankLine:n { a << n } )*
                  )+
                  { inner_parse a.join }