Fix compile error

CHANGELOG.md

@@ -4,7 +4,12 @@ All notable changes to this project will be documented in this file.
 
 **Warning:** Features marked as *experimental* may change or be removed in a future release without notice. Use with caution.
 
-<!--## [Unreleased]-->
+## [Unreleased]
+
+### Fixed
+
+* [#139](https://github.com/readium/r2-shared-swift/pull/139) Compile error with Xcode 12.4
+
 
 ## [2.0.0]
 

r2-shared-swift/Toolkit/HTTP/DefaultHTTPClient.swift

@@ -336,9 +336,9 @@ public final class DefaultHTTPClient: NSObject, HTTPClient, Loggable, URLSession
                 // It was a HEAD request? We need to query the resource again to get the error body. The body is needed
                 // for example when the response is an OPDS Authentication Document.
                 if request.method == .head {
-                    var request = request
-                    request.method = .get
-                    session.dataTask(with: request.urlRequest) { data, _, error in
+                    var modifiedRequest = request
+                    modifiedRequest.method = .get
+                    session.dataTask(with: modifiedRequest.urlRequest) { data, _, error in
                         response.body = data
                         self.state = .failure(kind: kind, cause: error, response: response)
                         completionHandler(.cancel)