[clang] Refactor: Move CTAD code from SemaTemplate.cpp to a dedicated file, NFC (llvm#98524)

Split out the deduction guide related code from SemaTemplate.cpp to a
dedicated file.

These code has grown significantly, and moving it to a separate file
will improve code organization.

Author: hokein

clang/include/clang/Sema/Sema.h

@@ -560,13 +560,14 @@ class Sema final : public SemaBase {
   // 23. Statement Attribute Handling (SemaStmtAttr.cpp)
   // 24. C++ Templates (SemaTemplate.cpp)
   // 25. C++ Template Argument Deduction (SemaTemplateDeduction.cpp)
-  // 26. C++ Template Instantiation (SemaTemplateInstantiate.cpp)
-  // 27. C++ Template Declaration Instantiation
+  // 26. C++ Template Deduction Guide (SemaTemplateDeductionGuide.cpp)
+  // 27. C++ Template Instantiation (SemaTemplateInstantiate.cpp)
+  // 28. C++ Template Declaration Instantiation
   //     (SemaTemplateInstantiateDecl.cpp)
-  // 28. C++ Variadic Templates (SemaTemplateVariadic.cpp)
-  // 29. Constraints and Concepts (SemaConcept.cpp)
-  // 30. Types (SemaType.cpp)
-  // 31. FixIt Helpers (SemaFixItUtils.cpp)
+  // 29. C++ Variadic Templates (SemaTemplateVariadic.cpp)
+  // 30. Constraints and Concepts (SemaConcept.cpp)
+  // 31. Types (SemaType.cpp)
+  // 32. FixIt Helpers (SemaFixItUtils.cpp)
 
   /// \name Semantic Analysis
   /// Implementations are in Sema.cpp
@@ -11347,6 +11348,10 @@ class Sema final : public SemaBase {
       bool &IsMemberSpecialization, bool &Invalid,
       bool SuppressDiagnostic = false);
 
+  /// Returns the template parameter list with all default template argument
+  /// information.
+  TemplateParameterList *GetTemplateParameterList(TemplateDecl *TD);
+
   DeclResult CheckClassTemplate(
       Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
       CXXScopeSpec &SS, IdentifierInfo *Name, SourceLocation NameLoc,
@@ -12009,15 +12014,6 @@ class Sema final : public SemaBase {
                                                  unsigned TemplateDepth,
                                                  const Expr *Constraint);
 
-  /// Declare implicit deduction guides for a class template if we've
-  /// not already done so.
-  void DeclareImplicitDeductionGuides(TemplateDecl *Template,
-                                      SourceLocation Loc);
-
-  FunctionTemplateDecl *DeclareAggregateDeductionGuideFromInitList(
-      TemplateDecl *Template, MutableArrayRef<QualType> ParamTypes,
-      SourceLocation Loc);
-
   /// Find the failed Boolean condition within a given Boolean
   /// constant expression, and describe it with a string.
   std::pair<Expr *, std::string> findFailedBooleanCondition(Expr *Cond);
@@ -12570,6 +12566,27 @@ class Sema final : public SemaBase {
   //
   //
 
+  /// \name C++ Template Deduction Guide
+  /// Implementations are in SemaTemplateDeductionGuide.cpp
+  ///@{
+
+  /// Declare implicit deduction guides for a class template if we've
+  /// not already done so.
+  void DeclareImplicitDeductionGuides(TemplateDecl *Template,
+                                      SourceLocation Loc);
+
+  FunctionTemplateDecl *DeclareAggregateDeductionGuideFromInitList(
+      TemplateDecl *Template, MutableArrayRef<QualType> ParamTypes,
+      SourceLocation Loc);
+
+  ///@}
+
+  //
+  //
+  // -------------------------------------------------------------------------
+  //
+  //
+
   /// \name C++ Template Instantiation
   /// Implementations are in SemaTemplateInstantiate.cpp
   ///@{

clang/lib/Sema/CMakeLists.txt

@@ -82,6 +82,7 @@ add_clang_library(clangSema
   SemaSystemZ.cpp
   SemaTemplate.cpp
   SemaTemplateDeduction.cpp
+  SemaTemplateDeductionGuide.cpp
   SemaTemplateInstantiate.cpp
   SemaTemplateInstantiateDecl.cpp
   SemaTemplateVariadic.cpp