diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
index 05dec109828d83..b48f7e4f9308b5 100644
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -465,6 +465,10 @@ class alignas(8) Decl {
 
   ASTContext &getASTContext() const LLVM_READONLY;
 
+  /// Helper to get the language options from the ASTContext.
+  /// Defined out of line to avoid depending on ASTContext.h.
+  const LangOptions &getLangOpts() const LLVM_READONLY;
+
   void setAccess(AccessSpecifier AS) {
     Access = AS;
     assert(AccessDeclContextSanity());
diff --git a/clang/include/clang/AST/DeclCXX.h b/clang/include/clang/AST/DeclCXX.h
index 60d99f1a487f85..d914bd10663ed7 100644
--- a/clang/include/clang/AST/DeclCXX.h
+++ b/clang/include/clang/AST/DeclCXX.h
@@ -15,7 +15,6 @@
 #ifndef LLVM_CLANG_AST_DECLCXX_H
 #define LLVM_CLANG_AST_DECLCXX_H
 
-#include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTUnresolvedSet.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
@@ -40,6 +39,7 @@
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/TinyPtrVector.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compiler.h"
@@ -53,6 +53,7 @@
 
 namespace clang {
 
+class ASTContext;
 class ClassTemplateDecl;
 class ConstructorUsingShadowDecl;
 class CXXBasePath;
@@ -1166,7 +1167,7 @@ class CXXRecordDecl : public RecordDecl {
   bool defaultedDefaultConstructorIsConstexpr() const {
     return data().DefaultedDefaultConstructorIsConstexpr &&
            (!isUnion() || hasInClassInitializer() || !hasVariantMembers() ||
-            getASTContext().getLangOpts().CPlusPlus2a);
+            getLangOpts().CPlusPlus2a);
   }
 
   /// Determine whether this class has a constexpr default constructor.
@@ -1258,7 +1259,7 @@ class CXXRecordDecl : public RecordDecl {
   /// would be constexpr.
   bool defaultedDestructorIsConstexpr() const {
     return data().DefaultedDestructorIsConstexpr &&
-           getASTContext().getLangOpts().CPlusPlus2a;
+           getLangOpts().CPlusPlus2a;
   }
 
   /// Determine whether this class has a constexpr destructor.
@@ -1355,10 +1356,10 @@ class CXXRecordDecl : public RecordDecl {
   ///
   /// Only in C++17 and beyond, are lambdas literal types.
   bool isLiteral() const {
-    ASTContext &Ctx = getASTContext();
-    return (Ctx.getLangOpts().CPlusPlus2a ? hasConstexprDestructor()
+    const LangOptions &LangOpts = getLangOpts();
+    return (LangOpts.CPlusPlus2a ? hasConstexprDestructor()
                                           : hasTrivialDestructor()) &&
-           (!isLambda() || Ctx.getLangOpts().CPlusPlus17) &&
+           (!isLambda() || LangOpts.CPlusPlus17) &&
            !hasNonLiteralTypeFieldsOrBases() &&
            (isAggregate() || isLambda() ||
             hasConstexprNonCopyMoveConstructor() ||
@@ -2035,7 +2036,8 @@ class CXXMethodDecl : public FunctionDecl {
   method_iterator end_overridden_methods() const;
   unsigned size_overridden_methods() const;
 
-  using overridden_method_range= ASTContext::overridden_method_range;
+  using overridden_method_range = llvm::iterator_range<
+      llvm::TinyPtrVector<const CXXMethodDecl *>::const_iterator>;
 
   overridden_method_range overridden_methods() const;
 
diff --git a/clang/include/clang/AST/GlobalDecl.h b/clang/include/clang/AST/GlobalDecl.h
index bf30d9b942357f..d8ac498be54fd3 100644
--- a/clang/include/clang/AST/GlobalDecl.h
+++ b/clang/include/clang/AST/GlobalDecl.h
@@ -150,9 +150,8 @@ class GlobalDecl {
   }
 
   static KernelReferenceKind getDefaultKernelReference(const FunctionDecl *D) {
-    return D->getASTContext().getLangOpts().CUDAIsDevice
-               ? KernelReferenceKind::Kernel
-               : KernelReferenceKind::Stub;
+    return D->getLangOpts().CUDAIsDevice ? KernelReferenceKind::Kernel
+                                         : KernelReferenceKind::Stub;
   }
 
   GlobalDecl getWithDecl(const Decl *D) {
diff --git a/clang/include/clang/Serialization/ASTRecordReader.h b/clang/include/clang/Serialization/ASTRecordReader.h
index 5bdc9ca2ddbfce..52de383b0ebfce 100644
--- a/clang/include/clang/Serialization/ASTRecordReader.h
+++ b/clang/include/clang/Serialization/ASTRecordReader.h
@@ -14,6 +14,7 @@
 #ifndef LLVM_CLANG_SERIALIZATION_ASTRECORDREADER_H
 #define LLVM_CLANG_SERIALIZATION_ASTRECORDREADER_H
 
+#include "clang/AST/ASTContext.h"
 #include "clang/AST/AbstractBasicReader.h"
 #include "clang/Lex/Token.h"
 #include "clang/Serialization/ASTReader.h"
diff --git a/clang/lib/AST/CommentSema.cpp b/clang/lib/AST/CommentSema.cpp
index 8102f0115cc78e..7642e73fa17149 100644
--- a/clang/lib/AST/CommentSema.cpp
+++ b/clang/lib/AST/CommentSema.cpp
@@ -691,7 +691,7 @@ void Sema::checkDeprecatedCommand(const BlockCommandComment *Command) {
         FD->doesThisDeclarationHaveABody())
       return;
 
-    const LangOptions &LO = FD->getASTContext().getLangOpts();
+    const LangOptions &LO = FD->getLangOpts();
     const bool DoubleSquareBracket = LO.CPlusPlus14 || LO.C2x;
     StringRef AttributeSpelling =
         DoubleSquareBracket ? "[[deprecated]]" : "__attribute__((deprecated))";
diff --git a/clang/lib/AST/ComparisonCategories.cpp b/clang/lib/AST/ComparisonCategories.cpp
index 07673230357f63..6b6826c02a123e 100644
--- a/clang/lib/AST/ComparisonCategories.cpp
+++ b/clang/lib/AST/ComparisonCategories.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/AST/ComparisonCategories.h"
+#include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/Type.h"
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index a59873cbc9fc0a..0eb88e07f9bc05 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -378,6 +378,12 @@ ASTContext &Decl::getASTContext() const {
   return getTranslationUnitDecl()->getASTContext();
 }
 
+/// Helper to get the language options from the ASTContext.
+/// Defined out of line to avoid depending on ASTContext.h.
+const LangOptions &Decl::getLangOpts() const {
+  return getASTContext().getLangOpts();
+}
+
 ASTMutationListener *Decl::getASTMutationListener() const {
   return getASTContext().getASTMutationListener();
 }
diff --git a/clang/lib/Analysis/PathDiagnostic.cpp b/clang/lib/Analysis/PathDiagnostic.cpp
index 53235ba0769946..c88e6c1e1535f6 100644
--- a/clang/lib/Analysis/PathDiagnostic.cpp
+++ b/clang/lib/Analysis/PathDiagnostic.cpp
@@ -20,6 +20,7 @@
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/OperationKinds.h"
 #include "clang/AST/ParentMap.h"
+#include "clang/AST/PrettyPrinter.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/Type.h"
 #include "clang/Analysis/AnalysisDeclContext.h"
@@ -909,7 +910,7 @@ static void describeClass(raw_ostream &Out, const CXXRecordDecl *D,
   Out << Prefix << '\'' << *D;
   if (const auto T = dyn_cast<ClassTemplateSpecializationDecl>(D))
     describeTemplateParameters(Out, T->getTemplateArgs().asArray(),
-                               D->getASTContext().getLangOpts(), "<", ">");
+                               D->getLangOpts(), "<", ">");
 
   Out << '\'';
 }
@@ -975,8 +976,8 @@ static bool describeCodeDecl(raw_ostream &Out, const Decl *D,
   if (const auto FD = dyn_cast<FunctionDecl>(D))
     if (const TemplateArgumentList *TAList =
                                     FD->getTemplateSpecializationArgs())
-      describeTemplateParameters(Out, TAList->asArray(),
-                                 FD->getASTContext().getLangOpts(), "<", ">");
+      describeTemplateParameters(Out, TAList->asArray(), FD->getLangOpts(), "<",
+                                 ">");
 
   Out << '\'';
   return true;
diff --git a/clang/lib/Analysis/ProgramPoint.cpp b/clang/lib/Analysis/ProgramPoint.cpp
index 0783fbed531554..2a91749affd2a6 100644
--- a/clang/lib/Analysis/ProgramPoint.cpp
+++ b/clang/lib/Analysis/ProgramPoint.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Analysis/ProgramPoint.h"
+#include "clang/AST/ASTContext.h"
 #include "clang/Basic/JsonSupport.h"
 
 using namespace clang;
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index 1deca074954fc4..4915e19753c653 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -17,6 +17,7 @@
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExternalASTSource.h"
+#include "clang/AST/PrettyPrinter.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeOrdering.h"
 #include "clang/Basic/CodeGenOptions.h"
diff --git a/clang/lib/Tooling/Core/Lookup.cpp b/clang/lib/Tooling/Core/Lookup.cpp
index aa83e567b7743d..712724a268fb28 100644
--- a/clang/lib/Tooling/Core/Lookup.cpp
+++ b/clang/lib/Tooling/Core/Lookup.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Tooling/Core/Lookup.h"
+#include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclarationName.h"