Make memberDeclListItem re-usable in SwiftParser

Author: StevenWong12

Sources/SwiftParser/Declarations.swift

@@ -733,6 +733,11 @@ extension Parser {
 
 extension Parser {
   mutating func parseMemberDeclListItem() -> RawMemberDeclListItemSyntax? {
+    let startToken = self.currentToken
+    if let syntax = self.loadCurrentSyntaxNodeFromCache(for: .memberDeclListItem) {
+      self.registerNodeForIncrementalParse(node: syntax.raw, startToken: startToken)
+      return RawMemberDeclListItemSyntax(syntax.raw)
+    }
     if let remainingTokens = remainingTokensIfMaximumNestingLevelReached() {
       let item = RawMemberDeclListItemSyntax(
         remainingTokens,
@@ -760,12 +765,16 @@ extension Parser {
       return nil
     }
 
-    return RawMemberDeclListItemSyntax(
+    let result = RawMemberDeclListItemSyntax(
       decl: decl,
       semicolon: semi,
       RawUnexpectedNodesSyntax(trailingSemis, arena: self.arena),
       arena: self.arena
     )
+
+    self.registerNodeForIncrementalParse(node: result.raw, startToken: startToken)
+
+    return result
   }
 
   /// `introducer` is the `struct`, `class`, ... keyword that is the cause that the member decl block is being parsed.

Tests/SwiftParserTest/IncrementalParsingTests.swift

@@ -17,11 +17,14 @@ import _SwiftSyntaxTestSupport
 
 public class IncrementalParsingTests: XCTestCase {
 
-  public func testIncrementalInvalid() {
+  public func testBrokenMemberFunction() {
     assertIncrementalParse(
       """
       struct A⏩️⏸️A⏪️ { func f() {
-      """
+      """,
+      reusedNodes: [
+        ReusedNodeSpec("func f() {", kind: .memberDeclListItem)
+      ]
     )
   }
 
@@ -174,8 +177,7 @@ public class IncrementalParsingTests: XCTestCase {
     )
   }
 
-  public func testAddProperty() throws {
-    try XCTSkipIf(true, "Swift parser does not handle node reuse yet")
+  public func testAddProperty() {
     assertIncrementalParse(
       """
       struct Foo {