[clang][NFC] Improve locality of recently refactored enums (#70943)

This patch moves definition of recently refactored enums closer to the
types where they were originally defined. Since they are scoped enums at
namespace scope now, they can be forward-declared.

Refactorings in question are:
aaba376
50dec54
b120fe8
ae7b20b
4ad2ada
49fd28d

Author: Endilll

clang/include/clang/AST/Decl.h

@@ -4059,6 +4059,29 @@ class EnumDecl : public TagDecl {
   static bool classofKind(Kind K) { return K == Enum; }
 };
 
+/// Enum that represents the different ways arguments are passed to and
+/// returned from function calls. This takes into account the target-specific
+/// and version-specific rules along with the rules determined by the
+/// language.
+enum class ArgPassingKind {
+  /// The argument of this type can be passed directly in registers.
+  CanPassInRegs,
+
+  /// The argument of this type cannot be passed directly in registers.
+  /// Records containing this type as a subobject are not forced to be passed
+  /// indirectly. This value is used only in C++. This value is required by
+  /// C++ because, in uncommon situations, it is possible for a class to have
+  /// only trivial copy/move constructors even when one of its subobjects has
+  /// a non-trivial copy/move constructor (if e.g. the corresponding copy/move
+  /// constructor in the derived class is deleted).
+  CannotPassInRegs,
+
+  /// The argument of this type cannot be passed directly in registers.
+  /// Records containing this type as a subobject are forced to be passed
+  /// indirectly.
+  CanNeverPassInRegs
+};
+
 /// Represents a struct/union/class.  For example:
 ///   struct X;                  // Forward declaration, no "body".
 ///   union Y { int A, B; };     // Has body with members A and B (FieldDecls).

clang/include/clang/AST/DeclBase.h

@@ -1399,37 +1399,9 @@ enum class DeductionCandidate : unsigned char {
   Aggregate,
 };
 
-/// Enum that represents the different ways arguments are passed to and
-/// returned from function calls. This takes into account the target-specific
-/// and version-specific rules along with the rules determined by the
-/// language.
-enum class ArgPassingKind {
-  /// The argument of this type can be passed directly in registers.
-  CanPassInRegs,
-
-  /// The argument of this type cannot be passed directly in registers.
-  /// Records containing this type as a subobject are not forced to be passed
-  /// indirectly. This value is used only in C++. This value is required by
-  /// C++ because, in uncommon situations, it is possible for a class to have
-  /// only trivial copy/move constructors even when one of its subobjects has
-  /// a non-trivial copy/move constructor (if e.g. the corresponding copy/move
-  /// constructor in the derived class is deleted).
-  CannotPassInRegs,
-
-  /// The argument of this type cannot be passed directly in registers.
-  /// Records containing this type as a subobject are forced to be passed
-  /// indirectly.
-  CanNeverPassInRegs
-};
-
-enum class OMPDeclareReductionInitKind {
-  Call,   // Initialized by function call.
-  Direct, // omp_priv(<expr>)
-  Copy    // omp_priv = <expr>
-};
-
-enum class ObjCImplementationControl { None, Required, Optional };
-
+enum class ArgPassingKind;
+enum class OMPDeclareReductionInitKind;
+enum class ObjCImplementationControl;
 enum class LinkageSpecLanguageIDs;
 
 /// DeclContext - This is used only as base class of specific decl types that

clang/include/clang/AST/DeclObjC.h

@@ -115,6 +115,8 @@ class ObjCProtocolList : public ObjCList<ObjCProtocolDecl> {
            const SourceLocation *Locs, ASTContext &Ctx);
 };
 
+enum class ObjCImplementationControl { None, Required, Optional };
+
 /// ObjCMethodDecl - Represents an instance or class method declaration.
 /// ObjC methods can be declared within 4 contexts: class interfaces,
 /// categories, protocols, and class implementations. While C++ member

clang/include/clang/AST/DeclOpenMP.h

@@ -158,6 +158,12 @@ class OMPThreadPrivateDecl final : public OMPDeclarativeDirective<Decl> {
   static bool classofKind(Kind K) { return K == OMPThreadPrivate; }
 };
 
+enum class OMPDeclareReductionInitKind {
+  Call,   // Initialized by function call.
+  Direct, // omp_priv(<expr>)
+  Copy    // omp_priv = <expr>
+};
+
 /// This represents '#pragma omp declare reduction ...' directive.
 /// For example, in the following, declared reduction 'foo' for types 'int' and
 /// 'float':

clang/include/clang/AST/Type.h

@@ -1569,66 +1569,9 @@ enum class AutoTypeKeyword {
   GNUAutoType
 };
 
-/// Capture whether this is a normal array (e.g. int X[4])
-/// an array with a static size (e.g. int X[static 4]), or an array
-/// with a star size (e.g. int X[*]).
-/// 'static' is only allowed on function parameters.
-enum class ArraySizeModifier { Normal, Static, Star };
-
-/// The elaboration keyword that precedes a qualified type name or
-/// introduces an elaborated-type-specifier.
-enum class ElaboratedTypeKeyword {
-  /// The "struct" keyword introduces the elaborated-type-specifier.
-  Struct,
-
-  /// The "__interface" keyword introduces the elaborated-type-specifier.
-  Interface,
-
-  /// The "union" keyword introduces the elaborated-type-specifier.
-  Union,
-
-  /// The "class" keyword introduces the elaborated-type-specifier.
-  Class,
-
-  /// The "enum" keyword introduces the elaborated-type-specifier.
-  Enum,
-
-  /// The "typename" keyword precedes the qualified type name, e.g.,
-  /// \c typename T::type.
-  Typename,
-
-  /// No keyword precedes the qualified type name.
-  None
-};
-
-enum class VectorKind {
-  /// not a target-specific vector type
-  Generic,
-
-  /// is AltiVec vector
-  AltiVecVector,
-
-  /// is AltiVec 'vector Pixel'
-  AltiVecPixel,
-
-  /// is AltiVec 'vector bool ...'
-  AltiVecBool,
-
-  /// is ARM Neon vector
-  Neon,
-
-  /// is ARM Neon polynomial vector
-  NeonPoly,
-
-  /// is AArch64 SVE fixed-length data vector
-  SveFixedLengthData,
-
-  /// is AArch64 SVE fixed-length predicate vector
-  SveFixedLengthPredicate,
-
-  /// is RISC-V RVV fixed-length data vector
-  RVVFixedLengthData,
-};
+enum class ArraySizeModifier;
+enum class ElaboratedTypeKeyword;
+enum class VectorKind;
 
 /// The base class of the type hierarchy.
 ///
@@ -3145,6 +3088,12 @@ class MemberPointerType : public Type, public llvm::FoldingSetNode {
   }
 };
 
+/// Capture whether this is a normal array (e.g. int X[4])
+/// an array with a static size (e.g. int X[static 4]), or an array
+/// with a star size (e.g. int X[*]).
+/// 'static' is only allowed on function parameters.
+enum class ArraySizeModifier { Normal, Static, Star };
+
 /// Represents an array type, per C99 6.7.5.2 - Array Declarators.
 class ArrayType : public Type, public llvm::FoldingSetNode {
 private:
@@ -3474,6 +3423,34 @@ class DependentSizedExtVectorType : public Type, public llvm::FoldingSetNode {
                       QualType ElementType, Expr *SizeExpr);
 };
 
+enum class VectorKind {
+  /// not a target-specific vector type
+  Generic,
+
+  /// is AltiVec vector
+  AltiVecVector,
+
+  /// is AltiVec 'vector Pixel'
+  AltiVecPixel,
+
+  /// is AltiVec 'vector bool ...'
+  AltiVecBool,
+
+  /// is ARM Neon vector
+  Neon,
+
+  /// is ARM Neon polynomial vector
+  NeonPoly,
+
+  /// is AArch64 SVE fixed-length data vector
+  SveFixedLengthData,
+
+  /// is AArch64 SVE fixed-length predicate vector
+  SveFixedLengthPredicate,
+
+  /// is RISC-V RVV fixed-length data vector
+  RVVFixedLengthData,
+};
 
 /// Represents a GCC generic vector type. This type is created using
 /// __attribute__((vector_size(n)), where "n" specifies the vector size in
@@ -5667,6 +5644,32 @@ class InjectedClassNameType : public Type {
   }
 };
 
+/// The elaboration keyword that precedes a qualified type name or
+/// introduces an elaborated-type-specifier.
+enum class ElaboratedTypeKeyword {
+  /// The "struct" keyword introduces the elaborated-type-specifier.
+  Struct,
+
+  /// The "__interface" keyword introduces the elaborated-type-specifier.
+  Interface,
+
+  /// The "union" keyword introduces the elaborated-type-specifier.
+  Union,
+
+  /// The "class" keyword introduces the elaborated-type-specifier.
+  Class,
+
+  /// The "enum" keyword introduces the elaborated-type-specifier.
+  Enum,
+
+  /// The "typename" keyword precedes the qualified type name, e.g.,
+  /// \c typename T::type.
+  Typename,
+
+  /// No keyword precedes the qualified type name.
+  None
+};
+
 /// The kind of a tag type.
 enum TagTypeKind {
   /// The "struct" keyword.