cor3ntin created this revision.
Herald added a subscriber: jeroen.dobbelaere.
cor3ntin requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Implement P2360R0 in C++23 mode and as an extension in older
languages mode.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D111175
Files:
clang/include/clang/Basic/DiagnosticParseKinds.td
clang/include/clang/Parse/Parser.h
clang/lib/Parse/ParseExprCXX.cpp
clang/lib/Parse/ParseStmt.cpp
clang/lib/Parse/ParseTentative.cpp
clang/test/Parser/cxx2b-init-statement.cpp
clang/test/SemaCXX/cxx2b-init-statement.cpp
clang/www/cxx_status.html
Index: clang/www/cxx_status.html
===================================================================
--- clang/www/cxx_status.html
+++ clang/www/cxx_status.html
@@ -1365,7 +1365,7 @@
<tr>
<td>Extend init-statement to allow alias-declaration</td>
<td><a href="https://wg21.link/P2360R0";>P2360R0</a></td>
- <td class="none" align="center">No</td>
+ <td class="unreleased" align="center">Clang 14</td>
</tr>
</table>
Index: clang/test/SemaCXX/cxx2b-init-statement.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/cxx2b-init-statement.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -verify -std=c++2b -Wall -Wshadow %s
+
+void f() {
+
+ for (using foo = int;true;) {} //expected-warning {{unused type alias 'foo'}}
+
+ switch(using foo = int; 0) { //expected-warning {{unused type alias 'foo'}}
+ case 0: break;
+ }
+
+ if(using foo = int; false) {} // expected-warning {{unused type alias 'foo'}}
+
+ int x; // expected-warning {{unused variable 'x'}}
+ if(using x = int; true) {} // expected-warning {{unused type alias 'x'}}
+
+ using y = int; // expected-warning {{unused type alias 'y'}} \
+ // expected-note 2{{previous declaration is here}}
+
+ if(using y = double; true) {} // expected-warning {{unused type alias 'y'}} \
+ // expected-warning {{declaration shadows a type alias in function 'f'}}
+
+ for(using y = double; true;) { // expected-warning {{declaration shadows a type alias in function 'f'}}
+ y foo = 0;
+ (void)foo;
+ constexpr y var = 0;
+ static_assert(var == 0);
+ }
+}
Index: clang/test/Parser/cxx2b-init-statement.cpp
===================================================================
--- /dev/null
+++ clang/test/Parser/cxx2b-init-statement.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -fsyntax-only -verify=expected -std=c++2b -Wall %s
+// RUN: %clang_cc1 -fsyntax-only -verify=expected,expected-cxx20 -std=c++20 -Wall %s
+
+namespace ns {
+ int i;
+ enum class e {};
+}
+void f() {
+
+ for (using foo = int;true;); //expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+
+ switch(using foo = int; 0) { //expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+ case 0: break;
+ }
+
+ if(using foo = int; false) {} //expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+
+
+ if (using enum ns::e; false){} // expected-error {{expected alias declaration after using in init statement}} \
+ // expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+
+
+ for (using ns::i; true;); // expected-error {{expected alias declaration after using in init statement}} \
+ // expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+
+ if (using ns::i; false){} // expected-error {{expected alias declaration after using in init statement}} \
+ // expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+
+ switch(using ns::i; 0) { // expected-error {{expected alias declaration after using in init statement}} \
+ // expected-cxx20-warning {{alias declaration in init statements is a C++2b extension}}
+ case 0: break;
+ }
+
+}
Index: clang/lib/Parse/ParseTentative.cpp
===================================================================
--- clang/lib/Parse/ParseTentative.cpp
+++ clang/lib/Parse/ParseTentative.cpp
@@ -483,7 +483,9 @@
ConditionDeclarationOrInitStatementState State(*this, CanBeInitStatement,
CanBeForRangeDecl);
- if (State.update(isCXXDeclarationSpecifier()))
+ if (CanBeInitStatement && Tok.is(tok::kw_using)) {
+ return ConditionOrInitStatement::InitStmtDecl;
+ } else if (State.update(isCXXDeclarationSpecifier()))
return State.result();
// It might be a declaration; we need tentative parsing.
Index: clang/lib/Parse/ParseStmt.cpp
===================================================================
--- clang/lib/Parse/ParseStmt.cpp
+++ clang/lib/Parse/ParseStmt.cpp
@@ -1823,6 +1823,7 @@
/// [C++] for-init-statement:
/// [C++] expression-statement
/// [C++] simple-declaration
+/// [C++2b] alias-declaration
///
/// [C++0x] for-range-declaration:
/// [C++0x] attribute-specifier-seq[opt] type-specifier-seq declarator
@@ -1928,36 +1929,41 @@
Diag(Tok, diag::ext_c99_variable_decl_in_for_loop);
Diag(Tok, diag::warn_gcc_variable_decl_in_for_loop);
}
+ DeclGroupPtrTy DG;
+ if (Tok.is(tok::kw_using)) {
+ DG = ParseAliasDeclarationInInitStatement(attrs);
+ } else {
+ // In C++0x, "for (T NS:a" might not be a typo for ::
+ bool MightBeForRangeStmt = getLangOpts().CPlusPlus;
+ ColonProtectionRAIIObject ColonProtection(*this, MightBeForRangeStmt);
- // In C++0x, "for (T NS:a" might not be a typo for ::
- bool MightBeForRangeStmt = getLangOpts().CPlusPlus;
- ColonProtectionRAIIObject ColonProtection(*this, MightBeForRangeStmt);
-
- SourceLocation DeclStart = Tok.getLocation(), DeclEnd;
- DeclGroupPtrTy DG = ParseSimpleDeclaration(
- DeclaratorContext::ForInit, DeclEnd, attrs, false,
- MightBeForRangeStmt ? &ForRangeInfo : nullptr);
- FirstPart = Actions.ActOnDeclStmt(DG, DeclStart, Tok.getLocation());
- if (ForRangeInfo.ParsedForRangeDecl()) {
- Diag(ForRangeInfo.ColonLoc, getLangOpts().CPlusPlus11 ?
- diag::warn_cxx98_compat_for_range : diag::ext_for_range);
- ForRangeInfo.LoopVar = FirstPart;
- FirstPart = StmtResult();
- } else if (Tok.is(tok::semi)) { // for (int x = 4;
- ConsumeToken();
- } else if ((ForEach = isTokIdentifier_in())) {
- Actions.ActOnForEachDeclStmt(DG);
- // ObjC: for (id x in expr)
- ConsumeToken(); // consume 'in'
-
- if (Tok.is(tok::code_completion)) {
- cutOffParsing();
- Actions.CodeCompleteObjCForCollection(getCurScope(), DG);
- return StmtError();
+ SourceLocation DeclStart = Tok.getLocation(), DeclEnd;
+ DG = ParseSimpleDeclaration(
+ DeclaratorContext::ForInit, DeclEnd, attrs, false,
+ MightBeForRangeStmt ? &ForRangeInfo : nullptr);
+ FirstPart = Actions.ActOnDeclStmt(DG, DeclStart, Tok.getLocation());
+ if (ForRangeInfo.ParsedForRangeDecl()) {
+ Diag(ForRangeInfo.ColonLoc, getLangOpts().CPlusPlus11
+ ? diag::warn_cxx98_compat_for_range
+ : diag::ext_for_range);
+ ForRangeInfo.LoopVar = FirstPart;
+ FirstPart = StmtResult();
+ } else if (Tok.is(tok::semi)) { // for (int x = 4;
+ ConsumeToken();
+ } else if ((ForEach = isTokIdentifier_in())) {
+ Actions.ActOnForEachDeclStmt(DG);
+ // ObjC: for (id x in expr)
+ ConsumeToken(); // consume 'in'
+
+ if (Tok.is(tok::code_completion)) {
+ cutOffParsing();
+ Actions.CodeCompleteObjCForCollection(getCurScope(), DG);
+ return StmtError();
+ }
+ Collection = ParseExpression();
+ } else {
+ Diag(Tok, diag::err_expected_semi_for);
}
- Collection = ParseExpression();
- } else {
- Diag(Tok, diag::err_expected_semi_for);
}
} else {
ProhibitAttributes(attrs);
Index: clang/lib/Parse/ParseExprCXX.cpp
===================================================================
--- clang/lib/Parse/ParseExprCXX.cpp
+++ clang/lib/Parse/ParseExprCXX.cpp
@@ -1910,6 +1910,31 @@
}
}
+Parser::DeclGroupPtrTy
+Parser::ParseAliasDeclarationInInitStatement(ParsedAttributesWithRange &attrs) {
+ assert(Tok.is(tok::kw_using) && "Expected using");
+ DeclGroupPtrTy DG;
+ SourceLocation DeclStart = ConsumeToken(), DeclEnd;
+
+ DG = ParseUsingDeclaration(DeclaratorContext::SelectionInit, {}, DeclStart,
+ DeclEnd, attrs, AS_none);
+ if (!DG)
+ return DG;
+
+ const Decl *InitDecl = DG.get().getSingleDecl();
+ if (!isa<TypeAliasDecl>(InitDecl)) {
+ Diag(DeclStart, diag::err_expected_alias_after_using_in_init_statement)
+ << SourceRange(DeclStart, DeclEnd);
+ }
+
+ if (!getLangOpts().CPlusPlus2b) {
+ Diag(DeclStart, diag::ext_alias_in_init_statement)
+ << SourceRange(DeclStart, DeclEnd);
+ }
+
+ return DG;
+}
+
/// ParseCXXCondition - if/switch/while condition expression.
///
/// condition:
@@ -2017,9 +2042,14 @@
case ConditionOrInitStatement::InitStmtDecl: {
WarnOnInit();
+ DeclGroupPtrTy DG;
SourceLocation DeclStart = Tok.getLocation(), DeclEnd;
- DeclGroupPtrTy DG = ParseSimpleDeclaration(
- DeclaratorContext::SelectionInit, DeclEnd, attrs, /*RequireSemi=*/true);
+ if (Tok.is(tok::kw_using)) {
+ DG = ParseAliasDeclarationInInitStatement(attrs);
+ } else {
+ DG = ParseSimpleDeclaration(DeclaratorContext::SelectionInit, DeclEnd,
+ attrs, /*RequireSemi=*/true);
+ }
*InitStmt = Actions.ActOnDeclStmt(DG, DeclStart, DeclEnd);
return ParseCXXCondition(nullptr, Loc, CK);
}
Index: clang/include/clang/Parse/Parser.h
===================================================================
--- clang/include/clang/Parse/Parser.h
+++ clang/include/clang/Parse/Parser.h
@@ -1977,6 +1977,8 @@
Sema::ConditionKind CK,
ForRangeInfo *FRI = nullptr,
bool EnterForConditionScope = false);
+ DeclGroupPtrTy
+ ParseAliasDeclarationInInitStatement(ParsedAttributesWithRange &attrs);
//===--------------------------------------------------------------------===//
// C++ Coroutines
@@ -2396,7 +2398,8 @@
if (getLangOpts().OpenMP)
Actions.startOpenMPLoop();
if (getLangOpts().CPlusPlus)
- return isCXXSimpleDeclaration(/*AllowForRangeDecl=*/true);
+ return isCXXSimpleDeclaration(/*AllowForRangeDecl=*/true) ||
+ Tok.is(tok::kw_using);
return isDeclarationSpecifier(true);
}
Index: clang/include/clang/Basic/DiagnosticParseKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticParseKinds.td
+++ clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -549,6 +549,11 @@
"variable declaration in condition cannot have a parenthesized initializer">;
def err_extraneous_rparen_in_condition : Error<
"extraneous ')' after condition, expected a statement">;
+def err_expected_alias_after_using_in_init_statement : Error<
+ "expected alias declaration after using in init statement">;
+def ext_alias_in_init_statement : ExtWarn<
+ "alias declaration in init statements is a C++2b extension">,
+ InGroup<CXX2b>;
def warn_dangling_else : Warning<
"add explicit braces to avoid dangling else">,
InGroup<DanglingElse>;
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