diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ConstraintManager.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ConstraintManager.h
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ConstraintManager.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/ConstraintManager.h
@@ -94,35 +94,18 @@
   /// not perfectly precise and this may happen very rarely.)
   ProgramStatePair assumeDual(ProgramStateRef State, DefinedSVal Cond);
 
-  virtual ProgramStateRef assumeInclusiveRange(ProgramStateRef State,
-                                               NonLoc Value,
-                                               const llvm::APSInt &From,
-                                               const llvm::APSInt &To,
-                                               bool InBound) = 0;
-
-  virtual ProgramStatePair assumeInclusiveRangeDual(ProgramStateRef State,
-                                                    NonLoc Value,
-                                                    const llvm::APSInt &From,
-                                                    const llvm::APSInt &To) {
-    ProgramStateRef StInRange =
-        assumeInclusiveRange(State, Value, From, To, true);
-
-    // If StTrue is infeasible, asserting the falseness of Cond is unnecessary
-    // because the existing constraints already establish this.
-    if (!StInRange)
-      return ProgramStatePair((ProgramStateRef)nullptr, State);
-
-    ProgramStateRef StOutOfRange =
-        assumeInclusiveRange(State, Value, From, To, false);
-    if (!StOutOfRange) {
-      // We are careful to return the original state, /not/ StTrue,
-      // because we want to avoid having callers generate a new node
-      // in the ExplodedGraph.
-      return ProgramStatePair(State, (ProgramStateRef)nullptr);
-    }
-
-    return ProgramStatePair(StInRange, StOutOfRange);
-  }
+  ProgramStateRef assumeInclusiveRange(ProgramStateRef State, NonLoc Value,
+                                       const llvm::APSInt &From,
+                                       const llvm::APSInt &To, bool InBound);
+
+  /// Returns a pair of states (StInRange, StOutOfRange) where the given value
+  /// is assumed to be in the range or out of the range, respectively.
+  /// (Note that these two states might be equal if the parent state turns out
+  /// to be infeasible. This may happen if the underlying constraint solver is
+  /// not perfectly precise and this may happen very rarely.)
+  ProgramStatePair assumeInclusiveRangeDual(ProgramStateRef State, NonLoc Value,
+                                            const llvm::APSInt &From,
+                                            const llvm::APSInt &To);
 
   /// If a symbol is perfectly constrained to a constant, attempt
   /// to return the concrete value.
@@ -163,6 +146,12 @@
   virtual ProgramStateRef assumeInternal(ProgramStateRef state,
                                          DefinedSVal Cond, bool Assumption) = 0;
 
+  virtual ProgramStateRef assumeInclusiveRangeInternal(ProgramStateRef State,
+                                                       NonLoc Value,
+                                                       const llvm::APSInt &From,
+                                                       const llvm::APSInt &To,
+                                                       bool InBound) = 0;
+
   /// canReasonAbout - Not all ConstraintManagers can accurately reason about
   ///  all SVal values.  This method returns true if the ConstraintManager can
   ///  reasonably handle a given SVal value.  This is typically queried by
diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SimpleConstraintManager.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SimpleConstraintManager.h
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SimpleConstraintManager.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SimpleConstraintManager.h
@@ -39,10 +39,11 @@
   ProgramStateRef assumeInternal(ProgramStateRef State, DefinedSVal Cond,
                                  bool Assumption) override;
 
-  ProgramStateRef assumeInclusiveRange(ProgramStateRef State, NonLoc Value,
-                                       const llvm::APSInt &From,
-                                       const llvm::APSInt &To,
-                                       bool InRange) override;
+  ProgramStateRef assumeInclusiveRangeInternal(ProgramStateRef State,
+                                               NonLoc Value,
+                                               const llvm::APSInt &From,
+                                               const llvm::APSInt &To,
+                                               bool InRange) override;
 
 protected:
   //===------------------------------------------------------------------===//
diff --git a/clang/lib/StaticAnalyzer/Core/ConstraintManager.cpp b/clang/lib/StaticAnalyzer/Core/ConstraintManager.cpp
--- a/clang/lib/StaticAnalyzer/Core/ConstraintManager.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ConstraintManager.cpp
@@ -71,8 +71,49 @@
   return ProgramStatePair(StTrue, StFalse);
 }
 
+ConstraintManager::ProgramStatePair
+ConstraintManager::assumeInclusiveRangeDual(ProgramStateRef State, NonLoc Value,
+                                            const llvm::APSInt &From,
+                                            const llvm::APSInt &To) {
+  ProgramStateRef StInRange =
+      assumeInclusiveRangeInternal(State, Value, From, To, true);
+  if (!StInRange) {
+    ProgramStateRef StOutOfRange =
+        assumeInclusiveRangeInternal(State, Value, From, To, false);
+    if (LLVM_UNLIKELY(!StOutOfRange)) { // both infeasible
+      ProgramStateRef StInfeasible = State->cloneAsPosteriorlyOverconstrained();
+      assert(StInfeasible->isPosteriorlyOverconstrained());
+      // Checkers might rely on the API contract that both returned states
+      // cannot be null. Thus, we return StInfeasible for both branches because
+      // it might happen that a Checker uncoditionally uses one of them if the
+      // other is a nullptr. This may also happen with the non-dual and
+      // adjacent `assume(true)` and `assume(false)` calls. By implementing
+      // assume in therms of assumeDual, we can keep our API contract there as
+      // well.
+      return ProgramStatePair(StInfeasible, StInfeasible);
+    }
+  }
+
+  ProgramStateRef StOutOfRange =
+      assumeInclusiveRangeInternal(State, Value, From, To, false);
+  if (!StOutOfRange) {
+    return ProgramStatePair(StInRange, nullptr);
+  }
+
+  return ProgramStatePair(StInRange, StOutOfRange);
+}
+
 ProgramStateRef ConstraintManager::assume(ProgramStateRef State,
                                           DefinedSVal Cond, bool Assumption) {
   ConstraintManager::ProgramStatePair R = assumeDual(State, Cond);
   return Assumption ? R.first : R.second;
 }
+
+ProgramStateRef
+ConstraintManager::assumeInclusiveRange(ProgramStateRef State, NonLoc Value,
+                                        const llvm::APSInt &From,
+                                        const llvm::APSInt &To, bool InBound) {
+  ConstraintManager::ProgramStatePair R =
+      assumeInclusiveRangeDual(State, Value, From, To);
+  return InBound ? R.first : R.second;
+}
diff --git a/clang/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp b/clang/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
--- a/clang/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
@@ -91,7 +91,7 @@
   } // end switch
 }
 
-ProgramStateRef SimpleConstraintManager::assumeInclusiveRange(
+ProgramStateRef SimpleConstraintManager::assumeInclusiveRangeInternal(
     ProgramStateRef State, NonLoc Value, const llvm::APSInt &From,
     const llvm::APSInt &To, bool InRange) {