Factor Tree-Sitter Extensions

Don't build.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/TreeSitterExtensions/Extensions.swift

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+// p4rse, Copyright 2026, Will Hawkins
+//
+// This file is part of p4rse.
+
+// This file is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+import SwiftTreeSitter
+
+extension MutableTree {
+  public func isError(lang: Language) -> Bool {
+    guard
+      let parser_error_query = try? SwiftTreeSitter.Query(
+        language: lang,
+        data: String(
+          "(ERROR)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return false
+    }
+
+    let error_qr = parser_error_query.execute(in: self)
+    for _ in error_qr {
+      return true
+    }
+    return false
+  }
+}
+