diff --git a/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h b/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowAnalysis.h
@@ -49,10 +49,8 @@
 ///
 ///  `LatticeT` is a bounded join-semilattice that is used by `Derived` and must
 ///  provide the following public members:
-///   * `LatticeJoinEffect join(const LatticeT &)` - joins the object and the
-///     argument by computing their least upper bound, modifies the object if
-///     necessary, and returns an effect indicating whether any changes were
-///     made to it;
+///   * `void join(const LatticeT &)` - joins the object and the argument by
+///     computing their least upper bound and modifies the object if necessary;
 ///   * `bool operator==(const LatticeT &) const` - returns true if and only if
 ///     the object is equal to the argument.
 ///
@@ -84,11 +82,11 @@
     return {static_cast<Derived *>(this)->initialElement()};
   }
 
-  LatticeJoinEffect joinTypeErased(TypeErasedLattice &E1,
-                                   const TypeErasedLattice &E2) final {
+  void joinTypeErased(TypeErasedLattice &E1,
+                      const TypeErasedLattice &E2) final {
     Lattice &L1 = llvm::any_cast<Lattice &>(E1.Value);
     const Lattice &L2 = llvm::any_cast<const Lattice &>(E2.Value);
-    return L1.join(L2);
+    L1.join(L2);
   }
 
   void widenTypeErased(TypeErasedLattice &E1,
diff --git a/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h b/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
@@ -21,7 +21,6 @@
 #include "clang/AST/Type.h"
 #include "clang/Analysis/FlowSensitive/ControlFlowContext.h"
 #include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
-#include "clang/Analysis/FlowSensitive/DataflowLattice.h"
 #include "clang/Analysis/FlowSensitive/StorageLocation.h"
 #include "clang/Analysis/FlowSensitive/Value.h"
 #include "llvm/ADT/DenseMap.h"
@@ -169,8 +168,7 @@
   /// Requirements:
   ///
   ///  `Other` and `this` must use the same `DataflowAnalysisContext`.
-  LatticeJoinEffect join(const Environment &Other,
-                         Environment::ValueModel &Model);
+  void join(const Environment &Other, Environment::ValueModel &Model);
 
   // FIXME: Rename `createOrGetStorageLocation` to `getOrCreateStorageLocation`,
   // `getStableStorageLocation`, or something more appropriate.
diff --git a/clang/include/clang/Analysis/FlowSensitive/DataflowLattice.h b/clang/include/clang/Analysis/FlowSensitive/DataflowLattice.h
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowLattice.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowLattice.h
@@ -17,7 +17,11 @@
 namespace clang {
 namespace dataflow {
 
+/// DEPRECATED: Not meaningfully used.
+///
 /// Effect indicating whether a lattice join operation resulted in a new value.
+///
+/// FIXME: Delete this file once all references are removed.
 enum class LatticeJoinEffect {
   Unchanged,
   Changed,
diff --git a/clang/include/clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h b/clang/include/clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h
--- a/clang/include/clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h
+++ b/clang/include/clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h
@@ -22,7 +22,6 @@
 #include "clang/Analysis/CFG.h"
 #include "clang/Analysis/FlowSensitive/ControlFlowContext.h"
 #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
-#include "clang/Analysis/FlowSensitive/DataflowLattice.h"
 #include "clang/Analysis/FlowSensitive/Transfer.h"
 #include "llvm/ADT/Any.h"
 #include "llvm/ADT/Optional.h"
@@ -74,8 +73,8 @@
   /// Joins two type-erased lattice elements by computing their least upper
   /// bound. Places the join result in the left element and returns an effect
   /// indicating whether any changes were made to it.
-  virtual LatticeJoinEffect joinTypeErased(TypeErasedLattice &,
-                                           const TypeErasedLattice &) = 0;
+  virtual void joinTypeErased(TypeErasedLattice &,
+                              const TypeErasedLattice &) = 0;
 
   /// Relaxes the constraints in `A` to subsume the state in `B`.
   virtual void widenTypeErased(TypeErasedLattice &A,
diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -16,7 +16,6 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/Type.h"
-#include "clang/Analysis/FlowSensitive/DataflowLattice.h"
 #include "clang/Analysis/FlowSensitive/Value.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
@@ -299,33 +298,21 @@
   return true;
 }
 
-LatticeJoinEffect Environment::join(const Environment &Other,
-                                    Environment::ValueModel &Model) {
+void Environment::join(const Environment &Other,
+                       Environment::ValueModel &Model) {
   assert(DACtx == Other.DACtx);
   assert(ReturnLoc == Other.ReturnLoc);
   assert(ThisPointeeLoc == Other.ThisPointeeLoc);
 
-  auto Effect = LatticeJoinEffect::Unchanged;
-
   Environment JoinedEnv(*DACtx);
 
   JoinedEnv.ReturnLoc = ReturnLoc;
   JoinedEnv.ThisPointeeLoc = ThisPointeeLoc;
 
   JoinedEnv.DeclToLoc = intersectDenseMaps(DeclToLoc, Other.DeclToLoc);
-  if (DeclToLoc.size() != JoinedEnv.DeclToLoc.size())
-    Effect = LatticeJoinEffect::Changed;
-
   JoinedEnv.ExprToLoc = intersectDenseMaps(ExprToLoc, Other.ExprToLoc);
-  if (ExprToLoc.size() != JoinedEnv.ExprToLoc.size())
-    Effect = LatticeJoinEffect::Changed;
-
   JoinedEnv.MemberLocToStruct =
       intersectDenseMaps(MemberLocToStruct, Other.MemberLocToStruct);
-  if (MemberLocToStruct.size() != JoinedEnv.MemberLocToStruct.size())
-    Effect = LatticeJoinEffect::Changed;
-
-  // FIXME: set `Effect` as needed.
   JoinedEnv.FlowConditionToken = &DACtx->joinFlowConditions(
       *FlowConditionToken, *Other.FlowConditionToken);
 
@@ -350,12 +337,8 @@
             Loc->getType(), Val, *this, It->second, Other, JoinedEnv, Model))
       JoinedEnv.LocToVal.insert({Loc, MergedVal});
   }
-  if (LocToVal.size() != JoinedEnv.LocToVal.size())
-    Effect = LatticeJoinEffect::Changed;
 
   *this = std::move(JoinedEnv);
-
-  return Effect;
 }
 
 StorageLocation &Environment::createStorageLocation(QualType Type) {