 /// Namespace for functions to parse swift source and retrieve a syntax tree.
 public enum SyntaxParser {
 
-  /// True if the parser library is compatible with the SwiftSyntax client;
+  /// True if the parser library is compatible with this SwiftSyntax version;
   /// false otherwise.
+  ///
+  /// Incompatibility can occur if the loaded `lib_InternalSwiftSyntaxParser.dylib/.so`
+  /// is from a toolchain that is not compatible with this version of SwiftSyntax.
   fileprivate static var nodeHashVerifyResult: Bool = verifyNodeDeclarationHash()
 
   /// Parses the string into a full-fidelity Syntax tree.

    case .invalidSyntaxData:
      return "parser created invalid syntax data"
    case .parserCompatibilityCheckFailed:
      return "SwiftSyntax parser library isn't compatible"
    }
  }
}

  /// normal circumstances, and it should be reported as a bug.
  case invalidSyntaxData

  /// The SwiftSyntax parser library isn't compatible with this SwiftSyntax version.
  ///
  /// Incompatibility can occur if the loaded `lib_InternalSwiftSyntaxParser.dylib/.so`
  /// is from a toolchain that is not compatible with this version of SwiftSyntax.
  case parserCompatibilityCheckFailed

  public var description: String {
