diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -126,6 +126,7 @@
   functions. Which include allowing non-literal types as return values and parameters, allow calling of
   non-constexpr functions and constructors.
 - Clang now supports `requires cplusplus23` for module maps.
+- Implemented `P2564R3: consteval needs to propagate up <https://wg21.link/P2564R3>`_.
 
 C++2c Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -2378,6 +2378,21 @@
     return getConstexprKind() == ConstexprSpecKind::Consteval;
   }
 
+  void setBodyContainsImmediateEscalatingExpressions(bool Set) {
+    FunctionDeclBits.BodyContainsImmediateEscalatingExpression = Set;
+  }
+
+  bool BodyContainsImmediateEscalatingExpressions() const {
+    return FunctionDeclBits.BodyContainsImmediateEscalatingExpression;
+  }
+
+  bool isImmediateEscalating() const;
+
+  // The function is a C++ immediate function.
+  // This can be either a consteval function, or an immediate escalating
+  // function containing an immediate escalating expression.
+  bool isImmediateFunction() const;
+
   /// Whether the instantiation of this function is pending.
   /// This bit is set when the decision to instantiate this function is made
   /// and unset if and when the function body is created. That leaves out
diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -1659,6 +1659,8 @@
 
     /// Kind of contexpr specifier as defined by ConstexprSpecKind.
     uint64_t ConstexprKind : 2;
+    uint64_t BodyContainsImmediateEscalatingExpression : 1;
+
     uint64_t InstantiationIsPending : 1;
 
     /// Indicates if the function uses __try.
@@ -1693,7 +1695,7 @@
   };
 
   /// Number of non-inherited bits in FunctionDeclBitfields.
-  enum { NumFunctionDeclBits = 29 };
+  enum { NumFunctionDeclBits = 30 };
 
   /// Stores the bits used by CXXConstructorDecl. If modified
   /// NumCXXConstructorDeclBits and the accessor
@@ -1705,12 +1707,12 @@
     /// For the bits in FunctionDeclBitfields.
     uint64_t : NumFunctionDeclBits;
 
-    /// 22 bits to fit in the remaining available space.
+    /// 21 bits to fit in the remaining available space.
     /// Note that this makes CXXConstructorDeclBitfields take
     /// exactly 64 bits and thus the width of NumCtorInitializers
     /// will need to be shrunk if some bit is added to NumDeclContextBitfields,
     /// NumFunctionDeclBitfields or CXXConstructorDeclBitfields.
-    uint64_t NumCtorInitializers : 19;
+    uint64_t NumCtorInitializers : 18;
     uint64_t IsInheritingConstructor : 1;
 
     /// Whether this constructor has a trail-allocated explicit specifier.
diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
--- a/clang/include/clang/AST/Expr.h
+++ b/clang/include/clang/AST/Expr.h
@@ -1436,6 +1436,14 @@
     return DeclRefExprBits.RefersToEnclosingVariableOrCapture;
   }
 
+  bool isImmediateEscalating() const {
+    return DeclRefExprBits.IsImmediateEscalating;
+  }
+
+  void setIsImmediateEscalating(bool Set) {
+    DeclRefExprBits.IsImmediateEscalating = Set;
+  }
+
   static bool classof(const Stmt *T) {
     return T->getStmtClass() == DeclRefExprClass;
   }
diff --git a/clang/include/clang/AST/ExprCXX.h b/clang/include/clang/AST/ExprCXX.h
--- a/clang/include/clang/AST/ExprCXX.h
+++ b/clang/include/clang/AST/ExprCXX.h
@@ -1681,6 +1681,14 @@
     getArgs()[Arg] = ArgExpr;
   }
 
+  bool isImmediateEscalating() const {
+    return CXXConstructExprBits.IsImmediateEscalating;
+  }
+
+  void setIsImmediateEscalating(bool Set) {
+    CXXConstructExprBits.IsImmediateEscalating = Set;
+  }
+
   SourceLocation getBeginLoc() const LLVM_READONLY;
   SourceLocation getEndLoc() const LLVM_READONLY;
   SourceRange getParenOrBraceRange() const { return ParenOrBraceRange; }
diff --git a/clang/include/clang/AST/Stmt.h b/clang/include/clang/AST/Stmt.h
--- a/clang/include/clang/AST/Stmt.h
+++ b/clang/include/clang/AST/Stmt.h
@@ -384,6 +384,7 @@
     unsigned HadMultipleCandidates : 1;
     unsigned RefersToEnclosingVariableOrCapture : 1;
     unsigned NonOdrUseReason : 2;
+    unsigned IsImmediateEscalating : 1;
 
     /// The location of the declaration name itself.
     SourceLocation Loc;
@@ -827,6 +828,7 @@
     unsigned StdInitListInitialization : 1;
     unsigned ZeroInitialization : 1;
     unsigned ConstructionKind : 3;
+    unsigned IsImmediateEscalating : 1;
 
     SourceLocation Loc;
   };
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2656,10 +2656,23 @@
   "in C++14; add 'const' to avoid a change in behavior">,
   InGroup<DiagGroup<"constexpr-not-const">>;
 def err_invalid_consteval_take_address : Error<
-  "cannot take address of consteval %select{function|call operator of}1 %0 outside"
+  "cannot take address of %select{immediate|consteval}2 "
+  "%select{function|call operator of}1 %0 outside"
   " of an immediate invocation">;
 def err_invalid_consteval_call : Error<
-  "call to consteval function %q0 is not a constant expression">;
+  "call to %select{immediate|consteval}1 function "
+  "%q0 is not a constant expression">;
+
+def err_immediate_function_used_before_definition : Error<
+  "immediate function %0 used before it is defined">;
+
+def note_immediate_function_reason : Note<
+  "%0 is an immediate function because its body "
+  "%select{evaluates the address of %select{an immediate|a consteval}2 "
+  "function %1|contains a call to %select{an immediate|a consteval}2 "
+  "%select{function|constructor}4 %1 and that call is not a constant "
+  "expression}3">;
+
 def note_invalid_consteval_initializer : Note<
   "in the default initalizer of %0">;
 def note_invalid_consteval_initializer_here : Note<
diff --git a/clang/include/clang/Sema/ScopeInfo.h b/clang/include/clang/Sema/ScopeInfo.h
--- a/clang/include/clang/Sema/ScopeInfo.h
+++ b/clang/include/clang/Sema/ScopeInfo.h
@@ -172,6 +172,9 @@
   /// in the function. One of co_return, co_await, or co_yield.
   unsigned char FirstCoroutineStmtKind : 2;
 
+  /// Whether we found an immediate-escalating expression.
+  bool FoundImmediateEscalatingExpression : 1;
+
   /// First coroutine statement in the current function.
   /// (ex co_return, co_await, co_yield)
   SourceLocation FirstCoroutineStmtLoc;
@@ -388,7 +391,8 @@
         HasPotentialAvailabilityViolations(false), ObjCShouldCallSuper(false),
         ObjCIsDesignatedInit(false), ObjCWarnForNoDesignatedInitChain(false),
         ObjCIsSecondaryInit(false), ObjCWarnForNoInitDelegation(false),
-        NeedsCoroutineSuspends(true), ErrorTrap(Diag) {}
+        NeedsCoroutineSuspends(true), FoundImmediateEscalatingExpression(false),
+        ErrorTrap(Diag) {}
 
   virtual ~FunctionScopeInfo();
 
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -1066,9 +1066,13 @@
       S.PushFunctionScope();
       S.PushExpressionEvaluationContext(
           Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
-      if (auto *FD = dyn_cast<FunctionDecl>(DC))
+      if (auto *FD = dyn_cast<FunctionDecl>(DC)) {
         FD->setWillHaveBody(true);
-      else
+        S.ExprEvalContexts.back().InImmediateFunctionContext =
+            FD->isImmediateFunction();
+        S.ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
+            S.getLangOpts().CPlusPlus20 && FD->isImmediateEscalating();
+      } else
         assert(isa<ObjCMethodDecl>(DC));
     }
 
@@ -1247,7 +1251,7 @@
 
     /// In addition of being constant evaluated, the current expression
     /// occurs in an immediate function context - either a consteval function
-    /// or a consteval if function.
+    /// or a consteval if statement.
     ImmediateFunctionContext,
 
     /// The current expression is potentially evaluated at run time,
@@ -1328,6 +1332,7 @@
     // an immediate function context, so they need to be tracked independently.
     bool InDiscardedStatement;
     bool InImmediateFunctionContext;
+    bool InImmediateEscalatingFunctionContext;
 
     bool IsCurrentlyCheckingDefaultArgumentOrInitializer = false;
 
@@ -1356,7 +1361,8 @@
         : Context(Context), ParentCleanup(ParentCleanup),
           NumCleanupObjects(NumCleanupObjects), NumTypos(0),
           ManglingContextDecl(ManglingContextDecl), ExprContext(ExprContext),
-          InDiscardedStatement(false), InImmediateFunctionContext(false) {}
+          InDiscardedStatement(false), InImmediateFunctionContext(false),
+          InImmediateEscalatingFunctionContext(false) {}
 
     bool isUnevaluated() const {
       return Context == ExpressionEvaluationContext::Unevaluated ||
@@ -6546,6 +6552,13 @@
   /// invocation.
   ExprResult CheckForImmediateInvocation(ExprResult E, FunctionDecl *Decl);
 
+  bool CheckImmediateEscalatingFunctionDefinition(
+      FunctionDecl *FD, bool HasImmediateEscalatingExpression);
+
+  void MarkExpressionAsImmediateEscalating(Expr *E);
+
+  void DiagnoseImmediateEscalatingReason(const clang::FunctionDecl *FD);
+
   bool CompleteConstructorCall(CXXConstructorDecl *Constructor,
                                QualType DeclInitType, MultiExprArg ArgsPtr,
                                SourceLocation Loc,
@@ -9159,6 +9172,9 @@
   bool DeduceReturnType(FunctionDecl *FD, SourceLocation Loc,
                         bool Diagnose = true);
 
+  bool CheckIfFunctionSpecializationIsImmediate(FunctionDecl *FD,
+                                                SourceLocation Loc);
+
   /// Declare implicit deduction guides for a class template if we've
   /// not already done so.
   void DeclareImplicitDeductionGuides(TemplateDecl *Template,
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -7126,6 +7126,7 @@
       E->getValueKind(), ToFoundD, ToResInfo, E->isNonOdrUse());
   if (E->hadMultipleCandidates())
     ToE->setHadMultipleCandidates(true);
+  ToE->setIsImmediateEscalating(E->isImmediateEscalating());
   return ToE;
 }
 
@@ -7943,12 +7944,14 @@
   if (Error Err = ImportContainerChecked(E->arguments(), ToArgs))
     return std::move(Err);
 
-  return CXXConstructExpr::Create(
+  CXXConstructExpr *ToE = CXXConstructExpr::Create(
       Importer.getToContext(), ToType, ToLocation, ToConstructor,
       E->isElidable(), ToArgs, E->hadMultipleCandidates(),
       E->isListInitialization(), E->isStdInitListInitialization(),
       E->requiresZeroInitialization(), E->getConstructionKind(),
       ToParenOrBraceRange);
+  ToE->setIsImmediateEscalating(E->isImmediateEscalating());
+  return ToE;
 }
 
 ExpectedStmt ASTNodeImporter::VisitExprWithCleanups(ExprWithCleanups *E) {
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3002,6 +3002,7 @@
   FunctionDeclBits.HasImplicitReturnZero = false;
   FunctionDeclBits.IsLateTemplateParsed = false;
   FunctionDeclBits.ConstexprKind = static_cast<uint64_t>(ConstexprKind);
+  FunctionDeclBits.BodyContainsImmediateEscalatingExpression = false;
   FunctionDeclBits.InstantiationIsPending = false;
   FunctionDeclBits.UsesSEHTry = false;
   FunctionDeclBits.UsesFPIntrin = UsesFPIntrin;
@@ -3167,6 +3168,44 @@
   return II && II->isStr(Str);
 }
 
+bool FunctionDecl::isImmediateEscalating() const {
+  // C++23 [expr.const]/p17
+  // An immediate-escalating function is
+  //  - the call operator of a lambda that is not declared with the consteval
+  //  specifier,
+  if (isLambdaCallOperator(this) && !isConsteval())
+    return true;
+  // - a defaulted special member function that is not declared with the
+  // consteval specifier,
+  if (isDefaulted() && !isConsteval())
+    return true;
+  // - a function that results from the instantiation of a templated entity
+  // defined with the constexpr specifier.
+  TemplatedKind TK = getTemplatedKind();
+  if (TK != TK_NonTemplate && TK != TK_DependentNonTemplate &&
+      isConstexprSpecified())
+    return true;
+  return false;
+}
+
+bool FunctionDecl::isImmediateFunction() const {
+  // C++23 [expr.const]/p18
+  // An immediate function is a function or constructor that is
+  // - declared with the consteval specifier
+  if (isConsteval())
+    return true;
+  // - an immediate-escalating function F whose function body contains an
+  // immediate-escalating expression
+  if (isImmediateEscalating() && BodyContainsImmediateEscalatingExpressions())
+    return true;
+
+  if (const auto *MD = dyn_cast<CXXMethodDecl>(this);
+      MD && MD->isLambdaStaticInvoker())
+    return MD->getParent()->getLambdaCallOperator()->isImmediateFunction();
+
+  return false;
+}
+
 bool FunctionDecl::isMain() const {
   const TranslationUnitDecl *tunit =
     dyn_cast<TranslationUnitDecl>(getDeclContext()->getRedeclContext());
diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -622,6 +622,8 @@
     if (D->isConstexprSpecified() && !D->isExplicitlyDefaulted())
       Out << "constexpr ";
     if (D->isConsteval())        Out << "consteval ";
+    else if (D->isImmediateFunction())
+      Out << "immediate ";
     ExplicitSpecifier ExplicitSpec = ExplicitSpecifier::getFromDecl(D);
     if (ExplicitSpec.isSpecified())
       printExplicitSpecifier(ExplicitSpec, Out, Policy, Indentation, Context);
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -492,6 +492,7 @@
   DeclRefExprBits.RefersToEnclosingVariableOrCapture =
       RefersToEnclosingVariableOrCapture;
   DeclRefExprBits.NonOdrUseReason = NOUR;
+  DeclRefExprBits.IsImmediateEscalating = false;
   DeclRefExprBits.Loc = L;
   setDependence(computeDependence(this, Ctx));
 }
@@ -529,6 +530,7 @@
     getTrailingObjects<ASTTemplateKWAndArgsInfo>()->initializeFrom(
         TemplateKWLoc);
   }
+  DeclRefExprBits.IsImmediateEscalating = false;
   DeclRefExprBits.HadMultipleCandidates = 0;
   setDependence(computeDependence(this, Ctx));
 }
diff --git a/clang/lib/AST/ExprCXX.cpp b/clang/lib/AST/ExprCXX.cpp
--- a/clang/lib/AST/ExprCXX.cpp
+++ b/clang/lib/AST/ExprCXX.cpp
@@ -1136,6 +1136,7 @@
   CXXConstructExprBits.StdInitListInitialization = StdInitListInitialization;
   CXXConstructExprBits.ZeroInitialization = ZeroInitialization;
   CXXConstructExprBits.ConstructionKind = ConstructKind;
+  CXXConstructExprBits.IsImmediateEscalating = false;
   CXXConstructExprBits.Loc = Loc;
 
   Stmt **TrailingArgs = getTrailingArgs();
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2163,13 +2163,12 @@
     }
   }
 
-  if (auto *FD = dyn_cast_or_null<FunctionDecl>(BaseVD)) {
-    if (FD->isConsteval()) {
-      Info.FFDiag(Loc, diag::note_consteval_address_accessible)
-          << !Type->isAnyPointerType();
-      Info.Note(FD->getLocation(), diag::note_declared_at);
-      return false;
-    }
+  if (auto *FD = dyn_cast_or_null<FunctionDecl>(BaseVD);
+      FD && FD->isImmediateFunction()) {
+    Info.FFDiag(Loc, diag::note_consteval_address_accessible)
+        << !Type->isAnyPointerType();
+    Info.Note(FD->getLocation(), diag::note_declared_at);
+    return false;
   }
 
   // Check that the object is a global. Note that the fake 'this' object we
@@ -2305,7 +2304,7 @@
   const auto *FD = dyn_cast_or_null<CXXMethodDecl>(Member);
   if (!FD)
     return true;
-  if (FD->isConsteval()) {
+  if (FD->isImmediateFunction()) {
     Info.FFDiag(Loc, diag::note_consteval_address_accessible) << /*pointer*/ 0;
     Info.Note(FD->getLocation(), diag::note_declared_at);
     return false;
diff --git a/clang/lib/AST/JSONNodeDumper.cpp b/clang/lib/AST/JSONNodeDumper.cpp
--- a/clang/lib/AST/JSONNodeDumper.cpp
+++ b/clang/lib/AST/JSONNodeDumper.cpp
@@ -889,6 +889,7 @@
   attributeOnlyIfTrue("explicitlyDeleted", FD->isDeletedAsWritten());
   attributeOnlyIfTrue("constexpr", FD->isConstexpr());
   attributeOnlyIfTrue("variadic", FD->isVariadic());
+  attributeOnlyIfTrue("immediate", FD->isImmediateFunction());
 
   if (FD->isDefaulted())
     JOS.attribute("explicitlyDefaulted",
@@ -1249,6 +1250,7 @@
   case NOUR_Constant: JOS.attribute("nonOdrUseReason", "constant"); break;
   case NOUR_Discarded: JOS.attribute("nonOdrUseReason", "discarded"); break;
   }
+  attributeOnlyIfTrue("isImmediateEscalating", DRE->isImmediateEscalating());
 }
 
 void JSONNodeDumper::VisitSYCLUniqueStableNameExpr(
@@ -1408,6 +1410,7 @@
   attributeOnlyIfTrue("initializer_list", CE->isStdInitListInitialization());
   attributeOnlyIfTrue("zeroing", CE->requiresZeroInitialization());
   attributeOnlyIfTrue("hadMultipleCandidates", CE->hadMultipleCandidates());
+  attributeOnlyIfTrue("isImmediateEscalating", CE->isImmediateEscalating());
 
   switch (CE->getConstructionKind()) {
   case CXXConstructExpr::CK_Complete:
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -283,6 +283,8 @@
       OS << " constexpr";
     if (FD->isConsteval())
       OS << " consteval";
+    else if (FD->isImmediateFunction())
+      OS << " immediate";
     if (FD->isMultiVersion())
       OS << " multiversion";
   }
@@ -1046,6 +1048,8 @@
   case NOUR_Constant: OS << " non_odr_use_constant"; break;
   case NOUR_Discarded: OS << " non_odr_use_discarded"; break;
   }
+  if (Node->isImmediateEscalating())
+    OS << " immediate-escalating";
 }
 
 void TextNodeDumper::VisitUnresolvedLookupExpr(
@@ -1227,6 +1231,8 @@
     OS << " std::initializer_list";
   if (Node->requiresZeroInitialization())
     OS << " zeroing";
+  if (Node->isImmediateEscalating())
+    OS << " immediate-escalating";
 }
 
 void TextNodeDumper::VisitCXXBindTemporaryExpr(
diff --git a/clang/lib/AST/VTableBuilder.cpp b/clang/lib/AST/VTableBuilder.cpp
--- a/clang/lib/AST/VTableBuilder.cpp
+++ b/clang/lib/AST/VTableBuilder.cpp
@@ -2259,7 +2259,7 @@
 VTableLayout::~VTableLayout() { }
 
 bool VTableContextBase::hasVtableSlot(const CXXMethodDecl *MD) {
-  return MD->isVirtual() && !MD->isConsteval();
+  return MD->isVirtual() && !MD->isImmediateFunction();
 }
 
 ItaniumVTableContext::ItaniumVTableContext(
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4231,8 +4231,8 @@
                                                  bool ForVTable,
                                                  bool DontDefer,
                                               ForDefinition_t IsForDefinition) {
-  assert(!cast<FunctionDecl>(GD.getDecl())->isConsteval() &&
-         "consteval function should never be emitted");
+  assert(!cast<FunctionDecl>(GD.getDecl())->isImmediateFunction() &&
+         "an immediate function should never be emitted");
   // If there was no specific requested type, just convert it now.
   if (!Ty) {
     const auto *FD = cast<FunctionDecl>(GD.getDecl());
@@ -6333,9 +6333,8 @@
     return;
 
   // Consteval function shouldn't be emitted.
-  if (auto *FD = dyn_cast<FunctionDecl>(D))
-    if (FD->isConsteval())
-      return;
+  if (auto *FD = dyn_cast<FunctionDecl>(D); FD && FD->isImmediateFunction())
+    return;
 
   switch (D->getKind()) {
   case Decl::CXXConversion:
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -683,7 +683,7 @@
     // Refer to the discussion of this at https://reviews.llvm.org/D128619.
     Builder.defineMacro("__cpp_concepts", "201907L");
     Builder.defineMacro("__cpp_conditional_explicit", "201806L");
-    //Builder.defineMacro("__cpp_consteval", "201811L");
+    // Builder.defineMacro("__cpp_consteval", "202211L");
     Builder.defineMacro("__cpp_constexpr_dynamic_alloc", "201907L");
     Builder.defineMacro("__cpp_constinit", "201907L");
     Builder.defineMacro("__cpp_impl_coroutine", "201902L");
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -3215,6 +3215,7 @@
           ? Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed
           : Sema::ExpressionEvaluationContext::PotentiallyEvaluated,
       D);
+  Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext = true;
   if (TryConsumeToken(tok::equal, EqualLoc)) {
     if (Tok.is(tok::kw_delete)) {
       // In principle, an initializer of '= delete p;' is legal, but it will
diff --git a/clang/lib/Sema/ScopeInfo.cpp b/clang/lib/Sema/ScopeInfo.cpp
--- a/clang/lib/Sema/ScopeInfo.cpp
+++ b/clang/lib/Sema/ScopeInfo.cpp
@@ -39,6 +39,7 @@
   FirstReturnLoc = SourceLocation();
   FirstCXXOrObjCTryLoc = SourceLocation();
   FirstSEHTryLoc = SourceLocation();
+  FoundImmediateEscalatingExpression = false;
 
   // Coroutine state
   FirstCoroutineStmtLoc = SourceLocation();
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -15198,6 +15198,8 @@
   // function is entered, we need to reset this tracking, since the entered
   // function might be not an immediate function.
   ExprEvalContexts.back().InImmediateFunctionContext = FD->isConsteval();
+  ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
+      getLangOpts().CPlusPlus20 && FD->isImmediateEscalating();
 
   // Check for defining attributes before the check for redefinition.
   if (const auto *Attr = FD->getAttr<AliasAttr>()) {
@@ -15507,10 +15509,11 @@
     // one is already popped when finishing the lambda in BuildLambdaExpr().
     // This is meant to pop the context added in ActOnStartOfFunctionDef().
     ExitFunctionBodyRAII ExitRAII(*this, isLambdaCallOperator(FD));
-
     if (FD) {
       FD->setBody(Body);
       FD->setWillHaveBody(false);
+      CheckImmediateEscalatingFunctionDefinition(
+          FD, FSI->FoundImmediateEscalatingExpression);
 
       if (getLangOpts().CPlusPlus14) {
         if (!FD->isInvalidDecl() && Body && !FD->isDependentContext() &&
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -2437,6 +2437,88 @@
   return true;
 }
 
+bool Sema::CheckImmediateEscalatingFunctionDefinition(
+    FunctionDecl *FD, bool HasImmediateEscalatingExpression) {
+  if (!FD->hasBody() || !getLangOpts().CPlusPlus20 ||
+      !FD->isImmediateEscalating())
+    return true;
+  FD->setBodyContainsImmediateEscalatingExpressions(
+      HasImmediateEscalatingExpression);
+  if (HasImmediateEscalatingExpression) {
+    auto it = UndefinedButUsed.find(FD->getCanonicalDecl());
+    if (it != UndefinedButUsed.end()) {
+      Diag(it->second, diag::err_immediate_function_used_before_definition)
+          << it->first;
+      Diag(FD->getLocation(), diag::note_defined_here) << FD;
+      if (FD->isImmediateFunction() && !FD->isConsteval())
+        DiagnoseImmediateEscalatingReason(FD);
+      return false;
+    }
+  }
+  return true;
+}
+
+void Sema::DiagnoseImmediateEscalatingReason(const FunctionDecl *FD) {
+  assert(FD->isImmediateEscalating() && !FD->isConsteval() &&
+         "expected an immediate function");
+  assert(FD->hasBody() && "expected the function to have a body");
+  struct ImmediateEscalatingExpressionsVisitor
+      : public RecursiveASTVisitor<ImmediateEscalatingExpressionsVisitor> {
+    using Base = RecursiveASTVisitor<ImmediateEscalatingExpressionsVisitor>;
+    Sema &SemaRef;
+    const FunctionDecl *FD;
+    ImmediateEscalatingExpressionsVisitor(Sema &SemaRef, const FunctionDecl *FD)
+        : SemaRef(SemaRef), FD(FD) {}
+
+    bool shouldVisitImplicitCode() const { return true; }
+    bool shouldVisitLambdaBody() const { return false; }
+
+    bool TraverseCallExpr(CallExpr *E) {
+      if (const auto *DR =
+              dyn_cast<DeclRefExpr>(E->getCallee()->IgnoreImplicit());
+          DR && DR->isImmediateEscalating()) {
+        SemaRef.Diag(E->getBeginLoc(), diag::note_immediate_function_reason)
+            << FD << E->getDirectCallee() << E->getDirectCallee()->isConsteval()
+            << /*Call*/ 1 << /*Function*/ 0 << E->getSourceRange();
+      }
+      for (auto A : E->arguments()) {
+        getDerived().TraverseStmt(A);
+      }
+      return true;
+    }
+    bool VisitDeclRefExpr(DeclRefExpr *E) {
+      if (const auto *ReferencedFn = dyn_cast<FunctionDecl>(E->getDecl());
+          ReferencedFn && E->isImmediateEscalating()) {
+        SemaRef.Diag(E->getBeginLoc(), diag::note_immediate_function_reason)
+            << FD << ReferencedFn << ReferencedFn->isConsteval()
+            << /*Address*/ 0 << /*Function*/ 0 << E->getSourceRange();
+      }
+      return true;
+    }
+    bool VisitCXXConstructExpr(CXXConstructExpr *E) {
+      CXXConstructorDecl *D = E->getConstructor();
+      if (E->isImmediateEscalating()) {
+        SemaRef.Diag(E->getBeginLoc(), diag::note_immediate_function_reason)
+            << FD << D << D->isConsteval() << /*Call*/ 1 << /*Constructor*/ 1
+            << E->getSourceRange();
+      }
+      return true;
+    }
+
+    // These nodes can never contain an immediate escalating expression,
+    // we can skip them to avoid unecessary work.
+    bool TraverseDecl(Decl *D) {
+      if (isa<FunctionDecl, RecordDecl>(D))
+        return true;
+      return Base::TraverseDecl(D);
+    }
+    bool TraverseType(QualType T) { return true; }
+    bool VisitBlockExpr(BlockExpr *T) { return true; }
+
+  } Visitor(*this, FD);
+  Visitor.TraverseStmt(FD->getBody());
+}
+
 /// Get the class that is directly named by the current context. This is the
 /// class for which an unqualified-id in this scope could name a constructor
 /// or destructor.
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6007,8 +6007,9 @@
   //   is a function parameter scope of an immediate function.
   EnterExpressionEvaluationContext EvalContext(
       *this,
-      FD->isConsteval() ? ExpressionEvaluationContext::ImmediateFunctionContext
-                        : ExpressionEvaluationContext::PotentiallyEvaluated,
+      FD->isImmediateFunction()
+          ? ExpressionEvaluationContext::ImmediateFunctionContext
+          : ExpressionEvaluationContext::PotentiallyEvaluated,
       Param);
   ExprEvalContexts.back().IsCurrentlyCheckingDefaultArgumentOrInitializer =
       SkipImmediateInvocations;
@@ -6019,13 +6020,21 @@
 }
 
 struct ImmediateCallVisitor : public RecursiveASTVisitor<ImmediateCallVisitor> {
+  const ASTContext &Context;
+  ImmediateCallVisitor(const ASTContext &Ctx) : Context(Ctx) {}
+
   bool HasImmediateCalls = false;
+  bool IsImmediateInvocation = false;
 
   bool shouldVisitImplicitCode() const { return true; }
 
   bool VisitCallExpr(CallExpr *E) {
-    if (const FunctionDecl *FD = E->getDirectCallee())
-      HasImmediateCalls |= FD->isConsteval();
+    if (const FunctionDecl *FD = E->getDirectCallee()) {
+      HasImmediateCalls |= FD->isImmediateFunction();
+      if (FD->isConsteval() && !E->isCXX11ConstantExpr(Context))
+        IsImmediateInvocation = true;
+    }
+
     return RecursiveASTVisitor<ImmediateCallVisitor>::VisitStmt(E);
   }
 
@@ -6104,7 +6113,7 @@
     //   scope is a function parameter scope of an immediate function.
     EnterExpressionEvaluationContext EvalContext(
         *this,
-        FD->isConsteval()
+        FD->isImmediateFunction()
             ? ExpressionEvaluationContext::ImmediateFunctionContext
             : ExpressionEvaluationContext::PotentiallyEvaluated,
         Param);
@@ -6117,7 +6126,7 @@
     // An immediate invocation that is not evaluated where it appears is
     // evaluated and checked for whether it is a constant expression at the
     // point where the enclosing initializer is used in a function call.
-    ImmediateCallVisitor V;
+    ImmediateCallVisitor V(getASTContext());
     if (!NestedDefaultChecking)
       V.TraverseDecl(Param);
     if (V.HasImmediateCalls) {
@@ -6198,10 +6207,17 @@
   // evaluated and checked for whether it is a constant expression at the
   // point where the enclosing initializer is used in a [...] a constructor
   // definition, or an aggregate initialization.
-  ImmediateCallVisitor V;
+  ImmediateCallVisitor V(getASTContext());
   if (!NestedDefaultChecking)
     V.TraverseDecl(Field);
   if (V.HasImmediateCalls) {
+    // C++23 [expr.const]/p15
+    // An aggregate initialization is an immediate invocation
+    // if it evaluates a default member initializer that has a subexpression
+    // that is an immediate-escalating expression.
+    ExprEvalContexts.back().InImmediateFunctionContext |=
+        V.IsImmediateInvocation;
+
     ExprEvalContexts.back().DelayedDefaultInitializationContext = {Loc, Field,
                                                                    CurContext};
     ExprEvalContexts.back().IsCurrentlyCheckingDefaultArgumentOrInitializer =
@@ -17925,9 +17941,17 @@
   ExprEvalContexts.back().InDiscardedStatement =
       ExprEvalContexts[ExprEvalContexts.size() - 2]
           .isDiscardedStatementContext();
+
+  // C++23 [expr.const]/p15
+  // An expression or conversion is in an immediate function context if [...]
+  // it is a subexpression of a manifestly constant-evaluated expression or
+  // conversion.
+  const auto &Prev = ExprEvalContexts[ExprEvalContexts.size() - 2];
   ExprEvalContexts.back().InImmediateFunctionContext =
-      ExprEvalContexts[ExprEvalContexts.size() - 2]
-          .isImmediateFunctionContext();
+      Prev.isImmediateFunctionContext() || Prev.isConstantEvaluated();
+
+  ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
+      Prev.InImmediateEscalatingFunctionContext;
 
   Cleanup.reset();
   if (!MaybeODRUseExprs.empty())
@@ -18006,9 +18030,30 @@
   }
 }
 
+void Sema::MarkExpressionAsImmediateEscalating(Expr *E) {
+  assert(!FunctionScopes.empty() && "Expected a function scope");
+  assert(getLangOpts().CPlusPlus20 &&
+         ExprEvalContexts.back().InImmediateEscalatingFunctionContext &&
+         "Cannot mark an immediate escalating expression outside of an "
+         "immediate escalating context");
+  if (auto *Call = dyn_cast<CallExpr>(E->IgnoreImplicit());
+      Call && Call->getCallee()) {
+    if (auto *DeclRef =
+            dyn_cast<DeclRefExpr>(Call->getCallee()->IgnoreImplicit()))
+      DeclRef->setIsImmediateEscalating(true);
+  } else if (auto *Ctr = dyn_cast<CXXConstructExpr>(E->IgnoreImplicit())) {
+    Ctr->setIsImmediateEscalating(true);
+  } else if (auto *DeclRef = dyn_cast<DeclRefExpr>(E->IgnoreImplicit())) {
+    DeclRef->setIsImmediateEscalating(true);
+  } else {
+    assert(false && "expected an immediately escalating expression");
+  }
+  getCurFunction()->FoundImmediateEscalatingExpression = true;
+}
+
 ExprResult Sema::CheckForImmediateInvocation(ExprResult E, FunctionDecl *Decl) {
   if (isUnevaluatedContext() || !E.isUsable() || !Decl ||
-      !Decl->isConsteval() || isConstantEvaluated() ||
+      !Decl->isImmediateFunction() || isConstantEvaluated() ||
       isCheckingDefaultArgumentOrInitializer() ||
       RebuildingImmediateInvocation || isImmediateFunctionContext())
     return E;
@@ -18022,6 +18067,32 @@
             dyn_cast<DeclRefExpr>(Call->getCallee()->IgnoreImplicit()))
       ExprEvalContexts.back().ReferenceToConsteval.erase(DeclRef);
 
+  // C++23 [expr.const]/p16
+  // An expression or conversion is immediate-escalating if it is not initially
+  // in an immediate function context and it is [...] an immediate invocation
+  // that is not a constant expression and is not a subexpression of an
+  // immediate invocation.
+  APValue Cached;
+  auto CheckConstantExpressionAndKeepResult = [&]() {
+    llvm::SmallVector<PartialDiagnosticAt, 8> Notes;
+    Expr::EvalResult Eval;
+    Eval.Diag = &Notes;
+    bool Res = E.get()->EvaluateAsConstantExpr(
+        Eval, getASTContext(), ConstantExprKind::ImmediateInvocation);
+    if (Res && Notes.empty()) {
+      Cached = std::move(Eval.Val);
+      return true;
+    }
+    return false;
+  };
+
+  if (!E.get()->isValueDependent() &&
+      ExprEvalContexts.back().InImmediateEscalatingFunctionContext &&
+      !CheckConstantExpressionAndKeepResult()) {
+    MarkExpressionAsImmediateEscalating(E.get());
+    return E;
+  }
+
   E = MaybeCreateExprWithCleanups(E);
 
   ConstantExpr *Res = ConstantExpr::Create(
@@ -18029,6 +18100,8 @@
       ConstantExpr::getStorageKind(Decl->getReturnType().getTypePtr(),
                                    getASTContext()),
       /*IsImmediateInvocation*/ true);
+  if (Cached.hasValue())
+    Res->MoveIntoResult(Cached, getASTContext());
   /// Value-dependent constant expressions should not be immediately
   /// evaluated until they are instantiated.
   if (!Res->isValueDependent())
@@ -18056,14 +18129,17 @@
       FD = Call->getConstructor();
     else
       llvm_unreachable("unhandled decl kind");
-    assert(FD && FD->isConsteval());
-    SemaRef.Diag(CE->getBeginLoc(), diag::err_invalid_consteval_call) << FD;
+    assert(FD && FD->isImmediateFunction());
+    SemaRef.Diag(CE->getBeginLoc(), diag::err_invalid_consteval_call)
+        << FD << FD->isConsteval();
     if (auto Context =
             SemaRef.InnermostDeclarationWithDelayedImmediateInvocations()) {
       SemaRef.Diag(Context->Loc, diag::note_invalid_consteval_initializer)
           << Context->Decl;
       SemaRef.Diag(Context->Decl->getBeginLoc(), diag::note_declared_at);
     }
+    if (!FD->isConsteval())
+      SemaRef.DiagnoseImmediateEscalatingReason(FD);
     for (auto &Note : Notes)
       SemaRef.Diag(Note.first, Note.second);
     return;
@@ -18209,13 +18285,36 @@
     if (!CE.getInt())
       EvaluateAndDiagnoseImmediateInvocation(SemaRef, CE);
   for (auto *DR : Rec.ReferenceToConsteval) {
-    NamedDecl *ND = cast<FunctionDecl>(DR->getDecl());
-    if (auto *MD = llvm::dyn_cast<CXXMethodDecl>(ND);
+    const auto *FD = cast<FunctionDecl>(DR->getDecl());
+    const NamedDecl *ND = FD;
+    if (const auto *MD = dyn_cast<CXXMethodDecl>(ND);
         MD && (MD->isLambdaStaticInvoker() || isLambdaCallOperator(MD)))
       ND = MD->getParent();
-    SemaRef.Diag(DR->getBeginLoc(), diag::err_invalid_consteval_take_address)
-        << ND << isa<CXXRecordDecl>(ND);
-    SemaRef.Diag(ND->getLocation(), diag::note_declared_at);
+
+    // C++23 [expr.const]/p16
+    // An expression or conversion is immediate-escalating if it is not
+    // initially in an immediate function context and it is [...] a
+    // potentially-evaluated id-expression that denotes an immediate function
+    // that is not a subexpression of an immediate invocation.
+    bool ImmediateEscalating = false;
+    bool IsPotentiallyEvaluated =
+        Rec.Context ==
+            Sema::ExpressionEvaluationContext::PotentiallyEvaluated ||
+        Rec.Context ==
+            Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed;
+    if (SemaRef.inTemplateInstantiation() && IsPotentiallyEvaluated)
+      ImmediateEscalating = Rec.InImmediateEscalatingFunctionContext;
+
+    if (!Rec.InImmediateEscalatingFunctionContext ||
+        (SemaRef.inTemplateInstantiation() && !ImmediateEscalating)) {
+      SemaRef.Diag(DR->getBeginLoc(), diag::err_invalid_consteval_take_address)
+          << ND << isa<CXXRecordDecl>(ND) << FD->isConsteval();
+      SemaRef.Diag(ND->getLocation(), diag::note_declared_at);
+      if (FD->isImmediateEscalating() && !FD->isConsteval())
+        SemaRef.DiagnoseImmediateEscalatingReason(FD);
+    } else {
+      SemaRef.MarkExpressionAsImmediateEscalating(DR);
+    }
   }
 }
 
@@ -20299,12 +20398,14 @@
         !Method->getDevirtualizedMethod(Base, getLangOpts().AppleKext))
       OdrUse = false;
 
-  if (auto *FD = dyn_cast<FunctionDecl>(E->getDecl()))
+  if (auto *FD = dyn_cast<FunctionDecl>(E->getDecl())) {
     if (!isUnevaluatedContext() && !isConstantEvaluated() &&
         !isImmediateFunctionContext() &&
-        !isCheckingDefaultArgumentOrInitializer() && FD->isConsteval() &&
-        !RebuildingImmediateInvocation && !FD->isDependentContext())
+        !isCheckingDefaultArgumentOrInitializer() &&
+        FD->isImmediateFunction() && !RebuildingImmediateInvocation &&
+        !FD->isDependentContext())
       ExprEvalContexts.back().ReferenceToConsteval.insert(E);
+  }
   MarkExprReferenced(*this, E->getLocation(), E->getDecl(), E, OdrUse,
                      RefsMinusAssignments);
 }
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1421,6 +1421,10 @@
       LSI->CallOperator->isConsteval()
           ? ExpressionEvaluationContext::ImmediateFunctionContext
           : ExpressionEvaluationContext::PotentiallyEvaluated);
+  ExprEvalContexts.back().InImmediateFunctionContext =
+      LSI->CallOperator->isConsteval();
+  ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
+      getLangOpts().CPlusPlus20 && LSI->CallOperator->isImmediateEscalating();
 }
 
 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -932,11 +932,12 @@
   }
 
   if (ConstevalOrNegatedConsteval) {
-    bool Immediate = isImmediateFunctionContext();
+    bool Immediate = ExprEvalContexts.back().Context ==
+                     ExpressionEvaluationContext::ImmediateFunctionContext;
     if (CurContext->isFunctionOrMethod()) {
       const auto *FD =
           dyn_cast<FunctionDecl>(Decl::castFromDeclContext(CurContext));
-      if (FD && FD->isConsteval())
+      if (FD && FD->isImmediateFunction())
         Immediate = true;
     }
     if (isUnevaluatedContext() || Immediate)
@@ -4753,6 +4754,7 @@
 
   PushExpressionEvaluationContext(
       ExpressionEvaluationContext::PotentiallyEvaluated);
+  ExprEvalContexts.back().InImmediateEscalatingFunctionContext = false;
 }
 
 void Sema::ActOnCapturedRegionStart(SourceLocation Loc, Scope *CurScope,
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4390,6 +4390,12 @@
       DeduceReturnType(Specialization, Info.getLocation(), false))
     return TDK_MiscellaneousDeductionFailure;
 
+  if (IsAddressOfFunction && getLangOpts().CPlusPlus20 &&
+      Specialization->isImmediateEscalating() &&
+      CheckIfFunctionSpecializationIsImmediate(Specialization,
+                                               Info.getLocation()))
+    return TDK_MiscellaneousDeductionFailure;
+
   // If the function has a dependent exception specification, resolve it now,
   // so we can check that the exception specification matches.
   auto *SpecializationFPT =
@@ -5011,6 +5017,33 @@
   return StillUndeduced;
 }
 
+bool Sema::CheckIfFunctionSpecializationIsImmediate(FunctionDecl *FD,
+                                                    SourceLocation Loc) {
+  assert(FD->isImmediateEscalating());
+
+  if (isLambdaConversionOperator(FD)) {
+    CXXRecordDecl *Lambda = cast<CXXMethodDecl>(FD)->getParent();
+    FunctionDecl *CallOp = Lambda->getLambdaCallOperator();
+
+    // For a generic lambda, instantiate the call operator if needed.
+    if (auto *Args = FD->getTemplateSpecializationArgs()) {
+      CallOp = InstantiateFunctionDeclaration(
+          CallOp->getDescribedFunctionTemplate(), Args, Loc);
+      if (!CallOp || CallOp->isInvalidDecl())
+        return true;
+      runWithSufficientStackSpace(
+          Loc, [&] { InstantiateFunctionDefinition(Loc, CallOp); });
+    }
+    return CallOp->isInvalidDecl();
+  }
+
+  if (FD->getTemplateInstantiationPattern()) {
+    runWithSufficientStackSpace(
+        Loc, [&] { InstantiateFunctionDefinition(Loc, FD); });
+  }
+  return false;
+}
+
 /// If this is a non-static member function,
 static void
 AddImplicitObjectParameterType(ASTContext &Context,
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -595,6 +595,7 @@
   E->DeclRefExprBits.HadMultipleCandidates = Record.readInt();
   E->DeclRefExprBits.RefersToEnclosingVariableOrCapture = Record.readInt();
   E->DeclRefExprBits.NonOdrUseReason = Record.readInt();
+  E->DeclRefExprBits.IsImmediateEscalating = Record.readInt();
   unsigned NumTemplateArgs = 0;
   if (E->hasTemplateKWAndArgsInfo())
     NumTemplateArgs = Record.readInt();
@@ -1703,6 +1704,7 @@
   E->CXXConstructExprBits.StdInitListInitialization = Record.readInt();
   E->CXXConstructExprBits.ZeroInitialization = Record.readInt();
   E->CXXConstructExprBits.ConstructionKind = Record.readInt();
+  E->CXXConstructExprBits.IsImmediateEscalating = Record.readInt();
   E->CXXConstructExprBits.Loc = readSourceLocation();
   E->Constructor = readDeclAs<CXXConstructorDecl>();
   E->ParenOrBraceRange = readSourceRange();
@@ -2933,12 +2935,14 @@
 
     case EXPR_DECL_REF:
       S = DeclRefExpr::CreateEmpty(
-        Context,
-        /*HasQualifier=*/Record[ASTStmtReader::NumExprFields],
-        /*HasFoundDecl=*/Record[ASTStmtReader::NumExprFields + 1],
-        /*HasTemplateKWAndArgsInfo=*/Record[ASTStmtReader::NumExprFields + 2],
-        /*NumTemplateArgs=*/Record[ASTStmtReader::NumExprFields + 2] ?
-          Record[ASTStmtReader::NumExprFields + 6] : 0);
+          Context,
+          /*HasQualifier=*/Record[ASTStmtReader::NumExprFields],
+          /*HasFoundDecl=*/Record[ASTStmtReader::NumExprFields + 1],
+          /*HasTemplateKWAndArgsInfo=*/Record[ASTStmtReader::NumExprFields + 2],
+          /*NumTemplateArgs=*/
+          Record[ASTStmtReader::NumExprFields + 2]
+              ? Record[ASTStmtReader::NumExprFields + 7]
+              : 0);
       break;
 
     case EXPR_INTEGER_LITERAL:
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -580,7 +580,7 @@
 }
 
 void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
-  static_assert(DeclContext::NumFunctionDeclBits == 29,
+  static_assert(DeclContext::NumFunctionDeclBits == 30,
                 "You need to update the serializer after you change the "
                 "FunctionDeclBits");
 
@@ -1495,7 +1495,7 @@
 }
 
 void ASTDeclWriter::VisitCXXConstructorDecl(CXXConstructorDecl *D) {
-  static_assert(DeclContext::NumCXXConstructorDeclBits == 22,
+  static_assert(DeclContext::NumCXXConstructorDeclBits == 21,
                 "You need to update the serializer after you change the "
                 "CXXConstructorDeclBits");
 
@@ -2425,6 +2425,7 @@
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //HadMultipleCandidates
   Abv->Add(BitCodeAbbrevOp(0)); // RefersToEnclosingVariableOrCapture
   Abv->Add(BitCodeAbbrevOp(0)); // NonOdrUseReason
+  Abv->Add(BitCodeAbbrevOp(0)); // IsImmediateEscalating
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // DeclRef
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Location
   DeclRefExprAbbrev = Stream.EmitAbbrev(std::move(Abv));
diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -613,6 +613,7 @@
   Record.push_back(E->hadMultipleCandidates());
   Record.push_back(E->refersToEnclosingVariableOrCapture());
   Record.push_back(E->isNonOdrUse());
+  Record.push_back(E->isImmediateEscalating());
 
   if (E->hasTemplateKWAndArgsInfo()) {
     unsigned NumTemplateArgs = E->getNumTemplateArgs();
@@ -624,7 +625,8 @@
   if ((!E->hasTemplateKWAndArgsInfo()) && (!E->hasQualifier()) &&
       (E->getDecl() == E->getFoundDecl()) &&
       nk == DeclarationName::Identifier &&
-      !E->refersToEnclosingVariableOrCapture() && !E->isNonOdrUse()) {
+      !E->refersToEnclosingVariableOrCapture() && !E->isNonOdrUse() &&
+      !E->isImmediateEscalating()) {
     AbbrevToUse = Writer.getDeclRefExprAbbrev();
   }
 
@@ -1601,6 +1603,7 @@
   Record.push_back(E->isStdInitListInitialization());
   Record.push_back(E->requiresZeroInitialization());
   Record.push_back(E->getConstructionKind()); // FIXME: stable encoding
+  Record.push_back(E->isImmediateEscalating());
   Record.AddSourceLocation(E->getLocation());
   Record.AddDeclRef(E->getConstructor());
   Record.AddSourceRange(E->getParenOrBraceRange());
diff --git a/clang/test/SemaCXX/cxx2a-consteval-default-params.cpp b/clang/test/SemaCXX/cxx2a-consteval-default-params.cpp
--- a/clang/test/SemaCXX/cxx2a-consteval-default-params.cpp
+++ b/clang/test/SemaCXX/cxx2a-consteval-default-params.cpp
@@ -1,21 +1,13 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++23 %s
 
-consteval int undefined();  // expected-note 4 {{declared here}}
+consteval int undefined();  // expected-note 2 {{declared here}}
 
 void check_lambdas_unused(
-    int a = []
-    {
-        // The body of a lambda is not a subexpression of the lambda
-        // so this is immediately evaluated even if the parameter
-        // is never used.
-        return undefined();  // expected-error {{not a constant expression}} \
-                             // expected-note  {{undefined function 'undefined'}}
-    }(),
-    int b = [](int no_error = undefined()) {
+    int a = [](int no_error = undefined()) {
         return no_error;
     }(0),
-    int c = [](int defaulted = undefined()) {
+    int b = [](int defaulted = undefined()) {
         return defaulted;
     }()
 ) {}
@@ -40,8 +32,7 @@
 
 struct UnusedInitWithLambda {
     int a = [] {
-        return undefined();  // expected-error {{not a constant expression}} \
-                             // expected-note  {{undefined function 'undefined'}}
+        return undefined(); // never evaluated because immediate escalating
     }();
     // UnusedInitWithLambda is never constructed, so the initializer
     // of b and undefined() are never evaluated.
@@ -50,22 +41,19 @@
     }();
 };
 
-consteval int ub(int n) {
-    return 0/n; // expected-note  {{division}}
+consteval int ub(int n) { // expected-note {{declared here}}
+    return 0/n;
 }
 
 struct InitWithLambda {
-    int b = [](int error = undefined()) { // expected-error {{not a constant expression}} \
-                              // expected-note  {{declared here}} \
-                              // expected-note  {{undefined function 'undefined'}}
+    int b = [](int error = undefined()) { // expected-error {{cannot take address of consteval function 'undefined' outside of an immediate invocation}}
         return error;
-    }(); // expected-note {{in the default initalizer of 'error'}}
-    int c = [](int error = sizeof(undefined()) + ub(0)) { // expected-error {{'ub' is not a constant expression}} \
-                                                          // expected-note  {{declared here}} \
-                                                          // expected-note {{in call to 'ub(0)}}
+    }();
+    int c = [](int error = sizeof(undefined()) + ub(0)) { // expected-error {{cannot take address of consteval function 'ub' outside of an immediate invocation}}
+
         return error;
-    }(); // expected-note {{in the default initalizer of 'error'}}
-} i; // expected-note {{in implicit default constructor}}
+    }();
+} i;
 
 namespace ShouldNotCrash {
     template<typename T>
diff --git a/clang/test/SemaCXX/cxx2a-consteval.cpp b/clang/test/SemaCXX/cxx2a-consteval.cpp
--- a/clang/test/SemaCXX/cxx2a-consteval.cpp
+++ b/clang/test/SemaCXX/cxx2a-consteval.cpp
@@ -250,14 +250,14 @@
   return f(i);
 };
 
-auto l1 = [](int i) constexpr {
-// expected-note@-1 {{declared here}}
+auto l1 = [](int i) constexpr { // expected-error{{cannot take address of immediate call operator}} \
+                                // expected-note {{declared here}}
   int t = f(i);
-// expected-error@-1 {{is not a constant expression}}
-// expected-note@-2 {{function parameter}}
-  return f(0);  
+  return f(0);
 };
 
+int(*test)(int)  = l1;
+
 }
 
 namespace std {
diff --git a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
@@ -0,0 +1,166 @@
+// RUN: %clang_cc1 -std=c++2a -emit-llvm-only -Wno-unused-value %s -verify
+// RUN: %clang_cc1 -std=c++2b -emit-llvm-only -Wno-unused-value %s -verify
+
+consteval int id(int i) { return i; }
+constexpr char id(char c) { return c; }
+
+template <typename T>
+constexpr int f(T t) { // expected-note {{declared here}}
+    return t + id(t);  // expected-note 2{{'f<int>' is an immediate function because its body contains a call to a consteval function 'id' and that call is not a constant expression}}
+}
+
+namespace examples {
+
+auto a = &f<char>; // ok, f<char> is not an immediate function
+auto b = &f<int>;  // expected-error {{cannot take address of immediate function 'f<int>' outside of an immediate invocation}}
+
+static_assert(f(3) == 6); // ok
+
+template <typename T>
+constexpr int g(T t) {    // g<int> is not an immediate function
+    return t + id(42);    // because id(42) is already a constant
+}
+
+template <typename T, typename F>
+constexpr bool is_not(T t, F f) {
+    return not f(t);
+}
+
+consteval bool is_even(int i) { return i % 2 == 0; }
+
+static_assert(is_not(5, is_even));
+
+int x = 0; // expected-note {{declared here}}
+
+template <typename T>
+constexpr T h(T t = id(x)) { // expected-note {{read of non-const variable 'x' is not allowed in a constant expression}} \
+                             // expected-note 2{{'hh<int>' is an immediate function because its body contains a call to a consteval function 'id' and that call is not a constant expression}}
+    return t;
+}
+
+template <typename T>
+constexpr T hh() {           // hh<int> is an immediate function
+    [[maybe_unused]] auto x = h<T>();
+    return h<T>();
+}
+
+int i = hh<int>(); // expected-error {{call to immediate function 'examples::hh<int>' is not a constant expression}} \
+                   // expected-note {{in call to 'hh()'}}
+
+struct A {
+  int x;
+  int y = id(x);
+};
+
+template <typename T>
+constexpr int k(int) {
+  return A(42).y;
+}
+
+}
+
+namespace nested {
+
+template <typename T>
+constexpr int fdupe(T t) {
+    return id(t);
+}
+
+struct a {
+  constexpr a(int) { }
+};
+
+a aa(fdupe<int>((f<int>(7))));
+
+template <typename T>
+constexpr int foo(T t);     // expected-note {{declared here}}
+
+a bb(f<int>(foo<int>(7))); // expected-error{{call to immediate function 'f<int>' is not a constant expression}} \
+                           // expected-note{{undefined function 'foo<int>' cannot be used in a constant expression}}
+
+}
+
+namespace e2{
+template <typename T>
+constexpr int f(T t);
+auto a = &f<char>;
+auto b = &f<int>;
+}
+
+namespace forward_declare_constexpr{
+template <typename T>
+constexpr int f(T t);
+
+auto a = &f<char>;
+auto b = &f<int>;
+
+template <typename T>
+constexpr int f(T t) {
+    return id(0);
+}
+}
+
+namespace forward_declare_consteval{
+template <typename T>
+constexpr int f(T t);  // expected-note {{'f<int>' defined here}}
+
+auto a = &f<char>;
+auto b = &f<int>; // expected-error {{immediate function 'f<int>' used before it is defined}} \
+                  // expected-note {{in instantiation of function template specialization}}
+
+template <typename T>
+constexpr int f(T t) {
+    return id(t); // expected-note {{'f<int>' is an immediate function because its body contains a call to a consteval function 'id' and that call is not a constant expression}}
+}
+}
+
+namespace constructors {
+consteval int f(int) {
+  return 0;
+}
+struct S {
+  constexpr S(auto i) {
+    f(i);
+  }
+};
+constexpr void g(auto i) {
+  [[maybe_unused]] S s{i};
+}
+void test() {
+  g(0);
+}
+}
+
+namespace aggregate {
+consteval int f(int);
+struct S{
+    int a = 0;
+    int b = f(a);
+};
+
+constexpr bool test(auto i) {
+    S s{i};
+    return s.b == 2 *i;
+}
+consteval int f(int i) {
+    return 2 * i;
+}
+
+void test() {
+    static_assert(test(42));
+}
+
+}
+
+namespace ConstevalConstructor{
+int x = 0; // expected-note {{declared here}}
+struct S {
+    consteval S(int) {};
+};
+constexpr int g(auto t) {
+    S s(t); // expected-note {{'g<int>' is an immediate function because its body contains a call to a consteval constructor 'S' and that call is not a constant expression}}
+    return 0;
+}
+int i = g(x); // expected-error {{call to immediate function 'ConstevalConstructor::g<int>' is not a constant expression}} \
+              // expected-note {{read of non-const variable 'x' is not allowed in a constant expression}}
+}
diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -363,7 +363,7 @@
     <tr>
       <td>consteval needs to propagate up</td>
       <td><a href="https://wg21.link/P2564R3">P2564R3</a> (<a href="#dr">DR</a>)</td>
-      <td class="none" align="center">No</td>
+      <td class="unreleased" align="center">Clang 17</td>
     </tr>
     <tr>
       <td>Lifetime extension in range-based for loops</td>