Add primary associated type for MarkupVisitor

Author: Kyle-Ye

Sources/Markdown/Visitor/MarkupVisitor.swift

@@ -8,6 +8,292 @@
  See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
+
+#if swift(>=5.7)
+/// Visits `Markup` elements and returns a result.
+///
+/// - note: This interface only provides requirements for visiting each kind of element. It does not require each visit method to descend into child elements.
+///
+/// Generally, ``MarkupWalker`` is best for walking a ``Markup`` tree if the ``Result`` type is `Void` or is built up some other way, or ``MarkupRewriter`` for recursively changing a tree's structure. This type serves as a common interface to both. However, for building up other structured result types you can implement ``MarkupVisitor`` directly.
+public protocol MarkupVisitor<Result> {
+
+    /**
+     The result type returned when visiting a element.
+     */
+    associatedtype Result
+
+    /**
+     A default implementation to use when a visitor method isn't implemented for a particular element.
+     - parameter markup: the element to visit.
+     - returns: The result of the visit.
+     */
+    mutating func defaultVisit(_ markup: Markup) -> Result
+
+    /**
+     Visit any kind of `Markup` element and return the result.
+
+     - parameter markup: Any kind of `Markup` element.
+     - returns: The result of the visit.
+     */
+    mutating func visit(_ markup: Markup) -> Result
+
+    /**
+     Visit a `BlockQuote` element and return the result.
+
+     - parameter blockQuote: A `BlockQuote` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitBlockQuote(_ blockQuote: BlockQuote) -> Result
+
+    /**
+     Visit a `CodeBlock` element and return the result.
+
+     - parameter codeBlock: An `CodeBlock` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitCodeBlock(_ codeBlock: CodeBlock) -> Result
+
+    /**
+     Visit a `CustomBlock` element and return the result.
+
+     - parameter customBlock: An `CustomBlock` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitCustomBlock(_ customBlock: CustomBlock) -> Result
+
+    /**
+     Visit a `Document` element and return the result.
+
+     - parameter document: An `Document` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitDocument(_ document: Document) -> Result
+
+    /**
+     Visit a `Heading` element and return the result.
+
+     - parameter heading: An `Heading` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitHeading(_ heading: Heading) -> Result
+
+    /**
+     Visit a `ThematicBreak` element and return the result.
+
+     - parameter thematicBreak: An `ThematicBreak` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitThematicBreak(_ thematicBreak: ThematicBreak) -> Result
+    
+    /**
+     Visit an `HTML` element and return the result.
+
+     - parameter html: An `HTML` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitHTMLBlock(_ html: HTMLBlock) -> Result
+
+    /**
+     Visit a `ListItem` element and return the result.
+
+     - parameter listItem: An `ListItem` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitListItem(_ listItem: ListItem) -> Result
+
+    /**
+     Visit a `OrderedList` element and return the result.
+
+     - parameter orderedList: An `OrderedList` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitOrderedList(_ orderedList: OrderedList) -> Result
+
+    /**
+     Visit a `UnorderedList` element and return the result.
+
+     - parameter unorderedList: An `UnorderedList` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitUnorderedList(_ unorderedList: UnorderedList) -> Result
+
+    /**
+     Visit a `Paragraph` element and return the result.
+
+     - parameter paragraph: An `Paragraph` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitParagraph(_ paragraph: Paragraph) -> Result
+
+    /**
+     Visit a `BlockDirective` element and return the result.
+
+     - parameter blockDirective: A `BlockDirective` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitBlockDirective(_ blockDirective: BlockDirective) -> Result
+
+    /**
+     Visit a `InlineCode` element and return the result.
+
+     - parameter inlineCode: An `InlineCode` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitInlineCode(_ inlineCode: InlineCode) -> Result
+
+    /**
+     Visit a `CustomInline` element and return the result.
+
+     - parameter customInline: An `CustomInline` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitCustomInline(_ customInline: CustomInline) -> Result
+
+    /**
+     Visit a `Emphasis` element and return the result.
+
+     - parameter emphasis: An `Emphasis` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitEmphasis(_ emphasis: Emphasis) -> Result
+
+    /**
+     Visit a `Image` element and return the result.
+
+     - parameter image: An `Image` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitImage(_ image: Image) -> Result
+
+    /**
+     Visit a `InlineHTML` element and return the result.
+
+     - parameter inlineHTML: An `InlineHTML` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitInlineHTML(_ inlineHTML: InlineHTML) -> Result
+
+    /**
+     Visit a `LineBreak` element and return the result.
+
+     - parameter lineBreak: An `LineBreak` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitLineBreak(_ lineBreak: LineBreak) -> Result
+
+    /**
+     Visit a `Link` element and return the result.
+
+     - parameter link: An `Link` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitLink(_ link: Link) -> Result
+    
+    /**
+     Visit a `SoftBreak` element and return the result.
+
+     - parameter softBreak: An `SoftBreak` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitSoftBreak(_ softBreak: SoftBreak) -> Result
+
+    /**
+     Visit a `Strong` element and return the result.
+
+     - parameter strong: An `Strong` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitStrong(_ strong: Strong) -> Result
+
+    /**
+     Visit a `Text` element and return the result.
+
+     - parameter text: A `Text` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitText(_ text: Text) -> Result
+
+    /**
+     Visit a `Strikethrough` element and return the result.
+
+     - parameter strikethrough: A `Strikethrough` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitStrikethrough(_ strikethrough: Strikethrough) -> Result
+
+    /**
+     Visit a `Table` element and return the result.
+
+     - parameter table: A `Table` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitTable(_ table: Table) -> Result
+
+    /**
+     Visit a `Table.Head` element and return the result.
+
+     - parameter tableHead: A `Table.Head` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitTableHead(_ tableHead: Table.Head) -> Result
+
+    /**
+     Visit a `Table.Body` element and return the result.
+
+     - parameter tableBody: A `Table.Body` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitTableBody(_ tableBody: Table.Body) -> Result
+
+    /**
+     Visit a `Table.Row` element and return the result.
+
+     - parameter tableRow: A `Table.Row` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitTableRow(_ tableRow: Table.Row) -> Result
+
+    /**
+     Visit a `Table.Cell` element and return the result.
+
+     - parameter tableCell: A `Table.Cell` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitTableCell(_ tableCell: Table.Cell) -> Result
+
+    /**
+     Visit a `SymbolLink` element and return the result.
+
+     - parameter symbolLink: A `SymbolLink` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitSymbolLink(_ symbolLink: SymbolLink) -> Result
+
+    /**
+    Visit an `InlineAttributes` element and return the result.
+
+    - parameter attribute: An `InlineAttributes` element.
+    - returns: The result of the visit.
+     */
+     mutating func visitInlineAttributes(_ attributes: InlineAttributes) -> Result
+
+    /**
+     Visit a `DoxygenParam` element and return the result.
+
+     - parameter doxygenParam: A `DoxygenParam` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitDoxygenParameter(_ doxygenParam: DoxygenParameter) -> Result
+
+    /**
+     Visit a `DoxygenReturns` element and return the result.
+
+     - parameter doxygenReturns: A `DoxygenReturns` element.
+     - returns: The result of the visit.
+     */
+    mutating func visitDoxygenReturns(_ doxygenReturns: DoxygenReturns) -> Result
+}
+#else
 /// Visits `Markup` elements and returns a result.
 ///
 /// - note: This interface only provides requirements for visiting each kind of element. It does not require each visit method to descend into child elements.
@@ -291,6 +577,7 @@ public protocol MarkupVisitor {
      */
     mutating func visitDoxygenReturns(_ doxygenReturns: DoxygenReturns) -> Result
 }
+#endif
 
 extension MarkupVisitor {
     // Default implementation: call `accept` on the markup element,