Thread safety analysis: Implement MutexLocker factory functions in documentation

We skipped adding definitions in 54bfd04 because we'd emit false
positive warnings on the closing braces. But these have been fixed in
commit e64ef63.

Author: aaronpuchert

clang/docs/ThreadSafetyAnalysis.rst

@@ -933,11 +933,25 @@ implementation.
     MutexLocker(Mutex *mu, defer_lock_t) EXCLUDES(mu) : mut(mu), locked(false) {}
 
     // Same as constructors, but without tag types. (Requires C++17 copy elision.)
-    static MutexLocker Lock(Mutex *mu) ACQUIRE(mu);
-    static MutexLocker Adopt(Mutex *mu) REQUIRES(mu);
-    static MutexLocker ReaderLock(Mutex *mu) ACQUIRE_SHARED(mu);
-    static MutexLocker AdoptReaderLock(Mutex *mu) REQUIRES_SHARED(mu);
-    static MutexLocker DeferLock(Mutex *mu) EXCLUDES(mu);
+    static MutexLocker Lock(Mutex *mu) ACQUIRE(mu) {
+      return MutexLocker(mu);
+    }
+
+    static MutexLocker Adopt(Mutex *mu) REQUIRES(mu) {
+      return MutexLocker(mu, adopt_lock);
+    }
+
+    static MutexLocker ReaderLock(Mutex *mu) ACQUIRE_SHARED(mu) {
+      return MutexLocker(mu, shared_lock);
+    }
+
+    static MutexLocker AdoptReaderLock(Mutex *mu) REQUIRES_SHARED(mu) {
+      return MutexLocker(mu, adopt_lock, shared_lock);
+    }
+
+    static MutexLocker DeferLock(Mutex *mu) EXCLUDES(mu) {
+      return MutexLocker(mu, defer_lock);
+    }
 
     // Release *this and all associated mutexes, if they are still held.
     // There is no warning if the scope was already unlocked before.