Add WithOptionalCodeBlock trait and adopt it where there's a body

Author: DougGregor

CodeGeneration/Sources/SyntaxSupport/DeclNodes.swift

@@ -82,7 +82,10 @@ public let DECL_NODES: [Node] = [
     base: .decl,
     nameForDiagnostics: "accessor",
     parserFunction: "parseAccessorDecl",
-    traits: ["WithAttributes"],
+    traits: [
+      "WithOptionalCodeBlock",
+      "WithAttributes",
+    ],
     children: [
       Child(
         name: "attributes",
@@ -493,6 +496,7 @@ public let DECL_NODES: [Node] = [
     traits: [
       "WithAttributes",
       "WithModifiers",
+      "WithOptionalCodeBlock",
     ],
     children: [
       Child(
@@ -879,6 +883,7 @@ public let DECL_NODES: [Node] = [
       "WithAttributes",
       "WithGenericParameters",
       "WithModifiers",
+      "WithOptionalCodeBlock",
     ],
     children: [
       Child(
@@ -1217,6 +1222,7 @@ public let DECL_NODES: [Node] = [
       "WithAttributes",
       "WithGenericParameters",
       "WithModifiers",
+      "WithOptionalCodeBlock",
     ],
     children: [
       Child(

CodeGeneration/Sources/SyntaxSupport/Traits.swift

@@ -151,6 +151,12 @@ public let TRAITS: [Trait] = [
       Child(name: "modifiers", kind: .node(kind: .declModifierList))
     ]
   ),
+  Trait(
+    traitName: "WithOptionalCodeBlock",
+    children: [
+      Child(name: "body", kind: .node(kind: .codeBlock), isOptional: true)
+    ]
+  ),
   Trait(
     traitName: "WithStatements",
     children: [