Add support for SE-0460 @specialized

CodeGeneration/Sources/SyntaxSupport/AttributeNodes.swift

@@ -74,6 +74,11 @@ public let ATTRIBUTE_NODES: [Node] = [
             // Special arguments for keyword decl name e.g. 'subscript(_:)', and availability arguments.
             kind: .node(kind: .specializeAttributeArgumentList)
           ),
+          Child(
+            name: "specializedArguments",
+            // Special arguments for generic where clause.
+            kind: .node(kind: .specializedAttributeArgument)
+          ),
           Child(
             name: "objCName",
             // Special arguments for Objective-C names. e.g. 'methodNameWithArg1:Arg2:'
@@ -717,6 +722,19 @@ public let ATTRIBUTE_NODES: [Node] = [
     ]
   ),
 
+  Node(
+    kind: .specializedAttributeArgument,
+    base: .syntax,
+    nameForDiagnostics: "argument to '@specialized",
+    documentation: "The generic where clause for the `@specialized` attribute",
+    children: [
+      Child(
+        name: "genericWhereClause",
+        kind: .node(kind: .genericWhereClause)
+      )
+    ]
+  ),
+
   Node(
     kind: .specializeTargetFunctionArgument,
     base: .syntax,

CodeGeneration/Sources/SyntaxSupport/KeywordSpec.swift

@@ -104,6 +104,7 @@ public enum Keyword: CaseIterable {
   case _PackageDescription
   case _read
   case _RefCountedObject
+  case specialized
   case _specialize
   case _spi_available
   case _Trivial
@@ -340,6 +341,8 @@ public enum Keyword: CaseIterable {
       return KeywordSpec("_read")
     case ._RefCountedObject:
       return KeywordSpec("_RefCountedObject")
+    case .specialized:
+      return KeywordSpec("specialized")
     case ._specialize:
       return KeywordSpec("_specialize")
     case ._spi_available:

CodeGeneration/Sources/SyntaxSupport/SyntaxNodeKind.swift

@@ -259,6 +259,7 @@ public enum SyntaxNodeKind: String, CaseIterable, IdentifierConvertible, TypeCon
   case simpleStringLiteralSegmentList
   case someOrAnyType
   case sourceFile
+  case specializedAttributeArgument
   case specializeAttributeArgumentList
   case specializeAvailabilityArgument
   case specializeTargetFunctionArgument
@@ -454,6 +455,7 @@ public enum SyntaxNodeKind: String, CaseIterable, IdentifierConvertible, TypeCon
     case .someOrAnyType: return "constrainedSugarType"
     case .simpleTypeSpecifier: return "typeSpecifier"
     case .specializeAttributeArgumentList: return "specializeAttributeSpecList"
+    case .specializedAttributeArgument: return "specializedAttribute"
     case .specializeAvailabilityArgument: return "availabilityEntry"
     case .specializeTargetFunctionArgument: return "targetFunctionEntry"
     case .stringLiteralSegmentList: return "stringLiteralSegments"

Sources/SwiftParser/Attributes.swift

@@ -41,6 +41,7 @@ extension Parser {
     case _effects
     case _implements
     case _originallyDefinedIn
+    case specialized
     case _specialize
     case _spi_available
     case `rethrows`
@@ -63,6 +64,7 @@ extension Parser {
       case TokenSpec(._effects): self = ._effects
       case TokenSpec(._implements): self = ._implements
       case TokenSpec(._originallyDefinedIn): self = ._originallyDefinedIn
+      case TokenSpec(.specialized): self = .specialized
       case TokenSpec(._specialize): self = ._specialize
       case TokenSpec(._spi_available): self = ._spi_available
       case TokenSpec(.`rethrows`): self = .rethrows
@@ -89,6 +91,7 @@ extension Parser {
       case ._effects: return .keyword(._effects)
       case ._implements: return .keyword(._implements)
       case ._originallyDefinedIn: return .keyword(._originallyDefinedIn)
+      case .specialized: return .keyword(.specialized)
       case ._specialize: return .keyword(._specialize)
       case ._spi_available: return .keyword(._spi_available)
       case .`rethrows`: return .keyword(.rethrows)
@@ -254,6 +257,10 @@ extension Parser {
       return parseAttribute(argumentMode: .optional) { parser in
         return (nil, .objCName(parser.parseObjectiveCSelector()))
       }
+    case .specialized:
+      return parseAttribute(argumentMode: .required) { parser in
+        return (nil, .specializedArguments(parser.parseSpecializedAttributeArgument()))
+      }
     case ._specialize:
       return parseAttribute(argumentMode: .required) { parser in
         return (nil, .specializeArguments(parser.parseSpecializeAttributeArgumentList()))
@@ -645,6 +652,11 @@ extension Parser {
 }
 
 extension Parser {
+  mutating func parseSpecializedAttributeArgument() -> RawSpecializedAttributeArgumentSyntax {
+    let whereClause = self.parseGenericWhereClause()
+    return RawSpecializedAttributeArgumentSyntax(genericWhereClause: whereClause, arena: self.arena)
+  }
+
   mutating func parseSpecializeAttributeArgumentList() -> RawSpecializeAttributeArgumentListSyntax {
     var elements = [RawSpecializeAttributeArgumentListSyntax.Element]()
     // Parse optional "exported" and "kind" labeled parameters.

Sources/SwiftParser/TokenPrecedence.swift

@@ -267,6 +267,7 @@ enum TokenPrecedence: Comparable {
       ._effects,
       ._implements,
       ._originallyDefinedIn,
+      .specialized,
       ._specialize,
       ._spi_available,
       .abi,