From 6803436d873e53c45a84a9ae2b135ca8f9b0e94b Mon Sep 17 00:00:00 2001
From: inju2403 <56947879+inju2403@users.noreply.github.com>
Date: Fri, 29 May 2026 15:46:12 +0900
Subject: [PATCH] [SwiftIDEUtils] Fix infinite loop in NameMatcher for
 whitespace positions in string segments

The `while let baseNamePosition = positionsToResolve.first(where:)` loop in the `.stringSegment` branch of `visit(_:TokenSyntax)` only mutated `positionsToResolve` via `addResolvedLocIfRequested`. When `getFirstTokenLength` returned `nil` (the position landed on whitespace inside the string segment, so the parser saw leading trivia) the loop hit `continue` without removing the position, and `first(where:)` found the same position again on every subsequent iteration -- an infinite loop.

Iterate a snapshot of the matching positions instead, so a position for which `getFirstTokenLength` returns `nil` is simply skipped to the next one.

This is the same class of bug as the one fixed in 528257fe4 for the trivia loop earlier in the same function.

Adds a regression test (`testStringLiteralWithPositionOnWhitespace`) that hangs against `main` and passes in <5ms with this change.
---
 Sources/SwiftIDEUtils/NameMatcher.swift        | 7 ++++++-
 Tests/SwiftIDEUtilsTest/NameMatcherTests.swift | 9 +++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Sources/SwiftIDEUtils/NameMatcher.swift b/Sources/SwiftIDEUtils/NameMatcher.swift
index 5ba9ab4fba3..284762be39c 100644
--- a/Sources/SwiftIDEUtils/NameMatcher.swift
+++ b/Sources/SwiftIDEUtils/NameMatcher.swift
@@ -252,7 +252,12 @@ public class NameMatcher: SyntaxAnyVisitor {
     }
 
     if case .stringSegment = token.tokenKind {
-      while let baseNamePosition = positionsToResolve.first(where: { token.rangeWithoutTrivia.contains($0) }) {
+      // Iterate a snapshot: `addResolvedLocIfRequested` is the only path that
+      // removes a position from `positionsToResolve`, and it is skipped when
+      // `getFirstTokenLength` returns `nil`. A `while let .first(where:)` loop
+      // would re-pick any such position forever.
+      let positionsInToken = positionsToResolve.filter { token.rangeWithoutTrivia.contains($0) }
+      for baseNamePosition in positionsInToken {
         let positionOffsetInStringSegment = baseNamePosition.utf8Offset - token.position.utf8Offset
         guard let tokenLength = getFirstTokenLength(in: token.syntaxTextBytes[positionOffsetInStringSegment...]) else {
           continue
diff --git a/Tests/SwiftIDEUtilsTest/NameMatcherTests.swift b/Tests/SwiftIDEUtilsTest/NameMatcherTests.swift
index e5856339b18..9d49cab768b 100644
--- a/Tests/SwiftIDEUtilsTest/NameMatcherTests.swift
+++ b/Tests/SwiftIDEUtilsTest/NameMatcherTests.swift
@@ -152,6 +152,15 @@ class NameMatcherTests: XCTestCase {
     )
   }
 
+  func testStringLiteralWithPositionOnWhitespace() {
+    assertNameMatcherResult(
+      """
+      "hello1️⃣ world"
+      """,
+      expected: []
+    )
+  }
+
   func testWildcardParameter() {
     assertNameMatcherResult(
       "func 0️⃣foo1(_ x: Int) {}",