[clang][NFC] Refactor Sema::TagUseKind
#92689
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This patch makes `TagUseKind` a scoped enumeration, and moves it outside of `Sema` class, making it eligible for forward declaring.
llvmbot
added
clang
|
I'll merge this when CI passes. |
|
@llvm/pr-subscribers-clang Author: Vlad Serebrennikov (Endilll) ChangesThis patch makes Patch is 55.02 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/92689.diff 7 Files Affected:
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index af50164a8f93f..690b1ef66af9f 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -2814,7 +2814,7 @@ class Parser : public CodeCompletionHandler {
SourceLocation CorrectLocation);
void stripTypeAttributesOffDeclSpec(ParsedAttributes &Attrs, DeclSpec &DS,
- Sema::TagUseKind TUK);
+ TagUseKind TUK);
// FixItLoc = possible correct location for the attributes
void ProhibitAttributes(ParsedAttributes &Attrs,
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index d4d4a82525a02..071c0f8d9c406 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -445,6 +445,13 @@ enum class CheckedConversionKind {
ForBuiltinOverloadedOp
};
+enum class TagUseKind {
+ Reference, // Reference to a tag: 'struct foo *X;'
+ Declaration, // Fwd decl of a tag: 'struct foo;'
+ Definition, // Definition of a tag: 'struct foo { int X; } Y;'
+ Friend // Friend declaration: 'friend struct foo;'
+};
+
/// Sema - This implements semantic analysis and AST building for C.
/// \nosubgrouping
class Sema final : public SemaBase {
@@ -3161,13 +3168,6 @@ class Sema final : public SemaBase {
bool isDefinition, SourceLocation NewTagLoc,
const IdentifierInfo *Name);
- enum TagUseKind {
- TUK_Reference, // Reference to a tag: 'struct foo *X;'
- TUK_Declaration, // Fwd decl of a tag: 'struct foo;'
- TUK_Definition, // Definition of a tag: 'struct foo { int X; } Y;'
- TUK_Friend // Friend declaration: 'friend struct foo;'
- };
-
enum OffsetOfKind {
// Not parsing a type within __builtin_offsetof.
OOK_Outside,
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 8405b44685ae4..5873a2633fc80 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -1905,9 +1905,8 @@ void Parser::DiagnoseCXX11AttributeExtension(ParsedAttributes &Attrs) {
// variable.
// This function moves attributes that should apply to the type off DS to Attrs.
void Parser::stripTypeAttributesOffDeclSpec(ParsedAttributes &Attrs,
- DeclSpec &DS,
- Sema::TagUseKind TUK) {
- if (TUK == Sema::TUK_Reference)
+ DeclSpec &DS, TagUseKind TUK) {
+ if (TUK == TagUseKind::Reference)
return;
llvm::SmallVector<ParsedAttr *, 1> ToBeMoved;
@@ -5359,9 +5358,9 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
// enum foo {..}; void bar() { enum foo; } <- new foo in bar.
// enum foo {..}; void bar() { enum foo x; } <- use of old foo.
//
- Sema::TagUseKind TUK;
+ TagUseKind TUK;
if (AllowEnumSpecifier == AllowDefiningTypeSpec::No)
- TUK = Sema::TUK_Reference;
+ TUK = TagUseKind::Reference;
else if (Tok.is(tok::l_brace)) {
if (DS.isFriendSpecified()) {
Diag(Tok.getLocation(), diag::err_friend_decl_defines_type)
@@ -5373,9 +5372,9 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
ScopedEnumKWLoc = SourceLocation();
IsScopedUsingClassTag = false;
BaseType = TypeResult();
- TUK = Sema::TUK_Friend;
+ TUK = TagUseKind::Friend;
} else {
- TUK = Sema::TUK_Definition;
+ TUK = TagUseKind::Definition;
}
} else if (!isTypeSpecifier(DSC) &&
(Tok.is(tok::semi) ||
@@ -5384,7 +5383,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
// An opaque-enum-declaration is required to be standalone (no preceding or
// following tokens in the declaration). Sema enforces this separately by
// diagnosing anything else in the DeclSpec.
- TUK = DS.isFriendSpecified() ? Sema::TUK_Friend : Sema::TUK_Declaration;
+ TUK = DS.isFriendSpecified() ? TagUseKind::Friend : TagUseKind::Declaration;
if (Tok.isNot(tok::semi)) {
// A semicolon was missing after this declaration. Diagnose and recover.
ExpectAndConsume(tok::semi, diag::err_expected_after, "enum");
@@ -5392,21 +5391,21 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
Tok.setKind(tok::semi);
}
} else {
- TUK = Sema::TUK_Reference;
+ TUK = TagUseKind::Reference;
}
bool IsElaboratedTypeSpecifier =
- TUK == Sema::TUK_Reference || TUK == Sema::TUK_Friend;
+ TUK == TagUseKind::Reference || TUK == TagUseKind::Friend;
// If this is an elaborated type specifier nested in a larger declaration,
// and we delayed diagnostics before, just merge them into the current pool.
- if (TUK == Sema::TUK_Reference && shouldDelayDiagsInTag) {
+ if (TUK == TagUseKind::Reference && shouldDelayDiagsInTag) {
diagsFromTag.redelay();
}
MultiTemplateParamsArg TParams;
if (TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate &&
- TUK != Sema::TUK_Reference) {
+ TUK != TagUseKind::Reference) {
if (!getLangOpts().CPlusPlus11 || !SS.isSet()) {
// Skip the rest of this declarator, up until the comma or semicolon.
Diag(Tok, diag::err_enum_template);
@@ -5427,7 +5426,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
SS.setTemplateParamLists(TParams);
}
- if (!Name && TUK != Sema::TUK_Definition) {
+ if (!Name && TUK != TagUseKind::Definition) {
Diag(Tok, diag::err_enumerator_unnamed_no_def);
DS.SetTypeSpecError();
@@ -5460,7 +5459,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
stripTypeAttributesOffDeclSpec(attrs, DS, TUK);
SkipBodyInfo SkipBody;
- if (!Name && TUK == Sema::TUK_Definition && Tok.is(tok::l_brace) &&
+ if (!Name && TUK == TagUseKind::Definition && Tok.is(tok::l_brace) &&
NextToken().is(tok::identifier))
SkipBody = Actions.shouldSkipAnonEnumBody(getCurScope(),
NextToken().getIdentifierInfo(),
@@ -5481,7 +5480,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
OffsetOfState, &SkipBody).get();
if (SkipBody.ShouldSkip) {
- assert(TUK == Sema::TUK_Definition && "can only skip a definition");
+ assert(TUK == TagUseKind::Definition && "can only skip a definition");
BalancedDelimiterTracker T(*this, tok::l_brace);
T.consumeOpen();
@@ -5523,7 +5522,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
if (!TagDecl) {
// The action failed to produce an enumeration tag. If this is a
// definition, consume the entire definition.
- if (Tok.is(tok::l_brace) && TUK != Sema::TUK_Reference) {
+ if (Tok.is(tok::l_brace) && TUK != TagUseKind::Reference) {
ConsumeBrace();
SkipUntil(tok::r_brace, StopAtSemi);
}
@@ -5532,7 +5531,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
return;
}
- if (Tok.is(tok::l_brace) && TUK == Sema::TUK_Definition) {
+ if (Tok.is(tok::l_brace) && TUK == TagUseKind::Definition) {
Decl *D = SkipBody.CheckSameAsPrevious ? SkipBody.New : TagDecl;
ParseEnumBody(StartLoc, D);
if (SkipBody.CheckSameAsPrevious &&
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 5eaec2b621e6f..805651e4ab069 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1961,11 +1961,11 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
MaybeParseCXX11Attributes(Attributes);
const PrintingPolicy &Policy = Actions.getASTContext().getPrintingPolicy();
- Sema::TagUseKind TUK;
+ TagUseKind TUK;
if (isDefiningTypeSpecifierContext(DSC, getLangOpts().CPlusPlus) ==
AllowDefiningTypeSpec::No ||
(getLangOpts().OpenMP && OpenMPDirectiveParsing))
- TUK = Sema::TUK_Reference;
+ TUK = TagUseKind::Reference;
else if (Tok.is(tok::l_brace) ||
(DSC != DeclSpecContext::DSC_association &&
getLangOpts().CPlusPlus && Tok.is(tok::colon)) ||
@@ -1980,10 +1980,10 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// Skip everything up to the semicolon, so that this looks like a proper
// friend class (or template thereof) declaration.
SkipUntil(tok::semi, StopBeforeMatch);
- TUK = Sema::TUK_Friend;
+ TUK = TagUseKind::Friend;
} else {
// Okay, this is a class definition.
- TUK = Sema::TUK_Definition;
+ TUK = TagUseKind::Definition;
}
} else if (isClassCompatibleKeyword() &&
(NextToken().is(tok::l_square) ||
@@ -2024,15 +2024,15 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
}
if (Tok.isOneOf(tok::l_brace, tok::colon))
- TUK = Sema::TUK_Definition;
+ TUK = TagUseKind::Definition;
else
- TUK = Sema::TUK_Reference;
+ TUK = TagUseKind::Reference;
PA.Revert();
} else if (!isTypeSpecifier(DSC) &&
(Tok.is(tok::semi) ||
(Tok.isAtStartOfLine() && !isValidAfterTypeSpecifier(false)))) {
- TUK = DS.isFriendSpecified() ? Sema::TUK_Friend : Sema::TUK_Declaration;
+ TUK = DS.isFriendSpecified() ? TagUseKind::Friend : TagUseKind::Declaration;
if (Tok.isNot(tok::semi)) {
const PrintingPolicy &PPol = Actions.getASTContext().getPrintingPolicy();
// A semicolon was missing after this declaration. Diagnose and recover.
@@ -2042,11 +2042,11 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
Tok.setKind(tok::semi);
}
} else
- TUK = Sema::TUK_Reference;
+ TUK = TagUseKind::Reference;
// Forbid misplaced attributes. In cases of a reference, we pass attributes
// to caller to handle.
- if (TUK != Sema::TUK_Reference) {
+ if (TUK != TagUseKind::Reference) {
// If this is not a reference, then the only possible
// valid place for C++11 attributes to appear here
// is between class-key and class-name. If there are
@@ -2072,7 +2072,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
if (!Name && !TemplateId &&
(DS.getTypeSpecType() == DeclSpec::TST_error ||
- TUK != Sema::TUK_Definition)) {
+ TUK != TagUseKind::Definition)) {
if (DS.getTypeSpecType() != DeclSpec::TST_error) {
// We have a declaration or reference to an anonymous class.
Diag(StartLoc, diag::err_anon_type_definition)
@@ -2082,7 +2082,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// If we are parsing a definition and stop at a base-clause, continue on
// until the semicolon. Continuing from the comma will just trick us into
// thinking we are seeing a variable declaration.
- if (TUK == Sema::TUK_Definition && Tok.is(tok::colon))
+ if (TUK == TagUseKind::Definition && Tok.is(tok::colon))
SkipUntil(tok::semi, StopBeforeMatch);
else
SkipUntil(tok::comma, StopAtSemi);
@@ -2103,7 +2103,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
if (TemplateId->isInvalid()) {
// Can't build the declaration.
} else if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation &&
- TUK == Sema::TUK_Declaration) {
+ TUK == TagUseKind::Declaration) {
// This is an explicit instantiation of a class template.
ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
diag::err_keyword_not_allowed,
@@ -2119,8 +2119,8 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// they have template headers, in which case they're ill-formed
// (FIXME: "template <class T> friend class A<T>::B<int>;").
// We diagnose this error in ActOnClassTemplateSpecialization.
- } else if (TUK == Sema::TUK_Reference ||
- (TUK == Sema::TUK_Friend &&
+ } else if (TUK == TagUseKind::Reference ||
+ (TUK == TagUseKind::Friend &&
TemplateInfo.Kind == ParsedTemplateInfo::NonTemplate)) {
ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
diag::err_keyword_not_allowed,
@@ -2145,10 +2145,10 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// It this is friend declaration however, since it cannot have a
// template header, it is most likely that the user meant to
// remove the 'template' keyword.
- assert((TUK == Sema::TUK_Definition || TUK == Sema::TUK_Friend) &&
+ assert((TUK == TagUseKind::Definition || TUK == TagUseKind::Friend) &&
"Expected a definition here");
- if (TUK == Sema::TUK_Friend) {
+ if (TUK == TagUseKind::Friend) {
Diag(DS.getFriendSpecLoc(), diag::err_friend_explicit_instantiation);
TemplateParams = nullptr;
} else {
@@ -2179,7 +2179,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
&SkipBody);
}
} else if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation &&
- TUK == Sema::TUK_Declaration) {
+ TUK == TagUseKind::Declaration) {
// Explicit instantiation of a member of a class template
// specialization, e.g.,
//
@@ -2190,7 +2190,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
TagOrTempResult = Actions.ActOnExplicitInstantiation(
getCurScope(), TemplateInfo.ExternLoc, TemplateInfo.TemplateLoc,
TagType, StartLoc, SS, Name, NameLoc, attrs);
- } else if (TUK == Sema::TUK_Friend &&
+ } else if (TUK == TagUseKind::Friend &&
TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate) {
ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
diag::err_keyword_not_allowed,
@@ -2202,12 +2202,12 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
MultiTemplateParamsArg(TemplateParams ? &(*TemplateParams)[0] : nullptr,
TemplateParams ? TemplateParams->size() : 0));
} else {
- if (TUK != Sema::TUK_Declaration && TUK != Sema::TUK_Definition)
+ if (TUK != TagUseKind::Declaration && TUK != TagUseKind::Definition)
ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
diag::err_keyword_not_allowed,
/* DiagnoseEmptyAttrs=*/true);
- if (TUK == Sema::TUK_Definition &&
+ if (TUK == TagUseKind::Definition &&
TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation) {
// If the declarator-id is not a template-id, issue a diagnostic and
// recover by ignoring the 'template' keyword.
@@ -2222,7 +2222,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// reference. For example, we don't need the template parameters here:
// template <class T> class A *makeA(T t);
MultiTemplateParamsArg TParams;
- if (TUK != Sema::TUK_Reference && TemplateParams)
+ if (TUK != TagUseKind::Reference && TemplateParams)
TParams =
MultiTemplateParamsArg(&(*TemplateParams)[0], TemplateParams->size());
@@ -2241,7 +2241,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// If ActOnTag said the type was dependent, try again with the
// less common call.
if (IsDependent) {
- assert(TUK == Sema::TUK_Reference || TUK == Sema::TUK_Friend);
+ assert(TUK == TagUseKind::Reference || TUK == TagUseKind::Friend);
TypeResult = Actions.ActOnDependentTag(getCurScope(), TagType, TUK, SS,
Name, StartLoc, NameLoc);
}
@@ -2252,13 +2252,13 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
// just merge them into the current pool.
if (shouldDelayDiagsInTag) {
diagsFromTag.done();
- if (TUK == Sema::TUK_Reference &&
+ if (TUK == TagUseKind::Reference &&
TemplateInfo.Kind == ParsedTemplateInfo::Template)
diagsFromTag.redelay();
}
// If there is a body, parse it and inform the actions module.
- if (TUK == Sema::TUK_Definition) {
+ if (TUK == TagUseKind::Definition) {
assert(Tok.is(tok::l_brace) ||
(getLangOpts().CPlusPlus && Tok.is(tok::colon)) ||
isClassCompatibleKeyword());
@@ -2316,7 +2316,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
//
// After a type-specifier, we don't expect a semicolon. This only happens in
// C, since definitions are not permitted in this context in C++.
- if (TUK == Sema::TUK_Definition &&
+ if (TUK == TagUseKind::Definition &&
(getLangOpts().CPlusPlus || !isTypeSpecifier(DSC)) &&
(TemplateInfo.Kind || !isValidAfterTypeSpecifier(false))) {
if (Tok.isNot(tok::semi)) {
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index f2b9202255cd4..b74cf189d88aa 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4985,7 +4985,7 @@ void Sema::setTagNameForLinkagePurposes(TagDecl *TagFromDeclSpec,
if (TagFromDeclSpec->hasNameForLinkage())
return;
- // A well-formed anonymous tag must always be a TUK_Definition.
+ // A well-formed anonymous tag must always be a TagUseKind::Definition.
assert(TagFromDeclSpec->isThisDeclarationADefinition());
// The type must match the tag exactly; no qualifiers allowed.
@@ -17237,9 +17237,9 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
OffsetOfKind OOK, SkipBodyInfo *SkipBody) {
// If this is not a definition, it must have a name.
IdentifierInfo *OrigName = Name;
- assert((Name != nullptr || TUK == TUK_Definition) &&
+ assert((Name != nullptr || TUK == TagUseKind::Definition) &&
"Nameless record must be a definition!");
- assert(TemplateParameterLists.size() == 0 || TUK != TUK_Reference);
+ assert(TemplateParameterLists.size() == 0 || TUK != TagUseKind::Reference);
OwnedDecl = false;
TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForTypeSpec(TagSpec);
@@ -17253,11 +17253,11 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
// or a scope specifier, which also conveniently avoids this work
// for non-C++ cases.
if (TemplateParameterLists.size() > 0 ||
- (SS.isNotEmpty() && TUK != TUK_Reference)) {
+ (SS.isNotEmpty() && TUK != TagUseKind::Reference)) {
TemplateParameterList *TemplateParams =
MatchTemplateParametersToScopeSpecifier(
KWLoc, NameLoc, SS, nullptr, TemplateParameterLists,
- TUK == TUK_Friend, isMemberSpecialization, Invalid);
+ TUK == TagUseKind::Friend, isMemberSpecialization, Invalid);
// C++23 [dcl.type.elab] p2:
// If an elaborated-type-specifier is the sole constituent of a
@@ -17272,7 +17272,8 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
// FIXME: Class template partial specializations can be forward declared
// per CWG2213, but the resolution failed to allow qualified forward
// declarations. This is almost certainly unintentional, so we allow them.
- if (TUK == TUK_Declaration && SS.isNotEmpty() && !isMemberSpecialization)
+ if (TUK == TagUseKind::Declaration && SS.isNotEmpty() &&
+ !isMemberSpecialization)
Diag(SS.getBeginLoc(), diag::err_standalone_class_nested_name_specifier)
<< TypeWithKeyword::getTagTypeKindName(Kind) << SS.getRange();
@@ -17309,7 +17310,7 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
return true;
}
- if (TUK == TUK_Friend && Kind == TagTypeKind::Enum) {
+ if (TUK == TagUseKind::Friend && Kind == TagTypeKind::Enum) {
// C++23 [dcl.type.elab]p4:
// If an elaborated-type-specifier appears with the friend specifier as
// an entire member-declaration, the member-declaration shall have one
@@ -17360,7 +17361,7 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
// of 'int'. However, if this is an unfixed forward declaration, don't set
// the underlying type unless the user enables -fms-compatibility. This
// makes unfixed forward declared enums incomplet...
[truncated]
|
cor3ntin
approved these changes
May 20, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This patch makes
TagUseKinda scoped enumeration, and moves it outside ofSemaclass, making it eligible for forward declaring.