Implement checks for thread model violations

Source/Swift/Environment.swift

@@ -18,6 +18,7 @@
 // EmacsSwiftModule. If not, see <https://www.gnu.org/licenses/>.
 //
 import EmacsModule
+import Foundation
 
 public enum EmacsVersion: Int, Comparable {
   case Emacs25 = 25
@@ -54,9 +55,13 @@ public final class Environment {
       guard valid else {
         throw EmacsError.lifetimeViolation
       }
+      guard thread == Thread.current else {
+        throw EmacsError.threadModelViolation
+      }
       return raw.pointee
     }
   }
+  let thread = Thread.current
 
   var valid = true
   /// Mark this environment as invalid

Source/Swift/Error.swift

@@ -79,6 +79,10 @@ public enum EmacsError: Error {
   ///
   /// See <doc:Lifetimes> for more details.
   case lifetimeViolation
+  /// Using ``Environment`` in a different thread than issued it.
+  ///
+  /// See <doc:Lifetimes> for more details.
+  case threadModelViolation
   /// If everything went to hell...
   case unknown
 }

Test/TestModule/Test.swift

@@ -109,6 +109,12 @@ class TestModule: Module {
     try env.defun("swift-env-misuse-lifetime") {
       try env.funcall("message", with: "Some message")
     }
+    try env.defun("swift-env-misuse-thread") {
+      (env: Environment, callback: PersistentEmacsValue) throws in
+      Task.detached {
+        try env.funcall(callback)
+      }
+    }
 
     if env.version >= .Emacs28 {
       let channel = try env.openChannel(name: "test")

Test/swift-module-test.el

@@ -149,6 +149,9 @@
         (should (equal x 32))
         (funcall done))))
 
-(ert-deftest swift-module:lifetime-checks ()
+(ert-deftest-async-tagged swift-module:lifetime-checks (done)
   :tags '(emacs-all)
-  (should-error (swift-env-misuse-lifetime) :type 'swift-error))
+  (should-error (swift-env-misuse-lifetime) :type 'swift-error)
+  (swift-env-misuse-thread
+   (lambda () (funcall done "Shouldn't have called the callback")))
+  (funcall done))