clang/lib/Sema/SemaCoroutine.cpp

   1 //===-- SemaCoroutine.cpp - Semantic Analysis for Coroutines --------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file implements semantic analysis for C++ Coroutines.
  10 //
  11 //  This file contains references to sections of the Coroutines TS, which
  12 //  can be found at http://wg21.link/coroutines.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "CoroutineStmtBuilder.h"
  17 #include "clang/AST/ASTLambda.h"
  18 #include "clang/AST/Decl.h"
  19 #include "clang/AST/ExprCXX.h"
  20 #include "clang/AST/StmtCXX.h"
  21 #include "clang/Basic/Builtins.h"
  22 #include "clang/Lex/Preprocessor.h"
  23 #include "clang/Sema/Initialization.h"
  24 #include "clang/Sema/Overload.h"
  25 #include "clang/Sema/ScopeInfo.h"
  26 #include "clang/Sema/SemaInternal.h"
  27 #include "llvm/ADT/SmallSet.h"
  28
  29 using namespace clang;
  30 using namespace sema;
  31
  32 static LookupResult lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
  33                                  SourceLocation Loc, bool &Res) {
  34   DeclarationName DN = S.PP.getIdentifierInfo(Name);
  35   LookupResult LR(S, DN, Loc, Sema::LookupMemberName);
  36   // Suppress diagnostics when a private member is selected. The same warnings
  37   // will be produced again when building the call.
  38   LR.suppressDiagnostics();
  39   Res = S.LookupQualifiedName(LR, RD);
  40   return LR;
  41 }
  42
  43 static bool lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
  44                          SourceLocation Loc) {
  45   bool Res;
  46   lookupMember(S, Name, RD, Loc, Res);
  47   return Res;
  48 }
  49
  50 /// Look up the std::coroutine_traits<...>::promise_type for the given
  51 /// function type.
  52 static QualType lookupPromiseType(Sema &S, const FunctionDecl *FD,
  53                                   SourceLocation KwLoc) {
  54   const FunctionProtoType *FnType = FD->getType()->castAs<FunctionProtoType>();
  55   const SourceLocation FuncLoc = FD->getLocation();
  56
  57   ClassTemplateDecl *CoroTraits =
  58       S.lookupCoroutineTraits(KwLoc, FuncLoc);
  59   if (!CoroTraits)
  60     return QualType();
  61
  62   // Form template argument list for coroutine_traits<R, P1, P2, ...> according
  63   // to [dcl.fct.def.coroutine]3
  64   TemplateArgumentListInfo Args(KwLoc, KwLoc);
  65   auto AddArg = [&](QualType T) {
  66     Args.addArgument(TemplateArgumentLoc(
  67         TemplateArgument(T), S.Context.getTrivialTypeSourceInfo(T, KwLoc)));
  68   };
  69   AddArg(FnType->getReturnType());
  70   // If the function is a non-static member function, add the type
  71   // of the implicit object parameter before the formal parameters.
  72   if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
  73     if (MD->isInstance()) {
  74       // [over.match.funcs]4
  75       // For non-static member functions, the type of the implicit object
  76       // parameter is
  77       //  -- "lvalue reference to cv X" for functions declared without a
  78       //      ref-qualifier or with the & ref-qualifier
  79       //  -- "rvalue reference to cv X" for functions declared with the &&
  80       //      ref-qualifier
  81       QualType T = MD->getThisType()->castAs<PointerType>()->getPointeeType();
  82       T = FnType->getRefQualifier() == RQ_RValue
  83               ? S.Context.getRValueReferenceType(T)
  84               : S.Context.getLValueReferenceType(T, /*SpelledAsLValue*/ true);
  85       AddArg(T);
  86     }
  87   }
  88   for (QualType T : FnType->getParamTypes())
  89     AddArg(T);
  90
  91   // Build the template-id.
  92   QualType CoroTrait =
  93       S.CheckTemplateIdType(TemplateName(CoroTraits), KwLoc, Args);
  94   if (CoroTrait.isNull())
  95     return QualType();
  96   if (S.RequireCompleteType(KwLoc, CoroTrait,
  97                             diag::err_coroutine_type_missing_specialization))
  98     return QualType();
  99
 100   auto *RD = CoroTrait->getAsCXXRecordDecl();
 101   assert(RD && "specialization of class template is not a class?");
 102
 103   // Look up the ::promise_type member.
 104   LookupResult R(S, &S.PP.getIdentifierTable().get("promise_type"), KwLoc,
 105                  Sema::LookupOrdinaryName);
 106   S.LookupQualifiedName(R, RD);
 107   auto *Promise = R.getAsSingle<TypeDecl>();
 108   if (!Promise) {
 109     S.Diag(FuncLoc,
 110            diag::err_implied_std_coroutine_traits_promise_type_not_found)
 111         << RD;
 112     return QualType();
 113   }
 114   // The promise type is required to be a class type.
 115   QualType PromiseType = S.Context.getTypeDeclType(Promise);
 116
 117   auto buildElaboratedType = [&]() {
 118     auto *NNS = NestedNameSpecifier::Create(S.Context, nullptr, S.getStdNamespace());
 119     NNS = NestedNameSpecifier::Create(S.Context, NNS, false,
 120                                       CoroTrait.getTypePtr());
 121     return S.Context.getElaboratedType(ETK_None, NNS, PromiseType);
 122   };
 123
 124   if (!PromiseType->getAsCXXRecordDecl()) {
 125     S.Diag(FuncLoc,
 126            diag::err_implied_std_coroutine_traits_promise_type_not_class)
 127         << buildElaboratedType();
 128     return QualType();
 129   }
 130   if (S.RequireCompleteType(FuncLoc, buildElaboratedType(),
 131                             diag::err_coroutine_promise_type_incomplete))
 132     return QualType();
 133
 134   return PromiseType;
 135 }
 136
 137 /// Look up the std::coroutine_handle<PromiseType>.
 138 static QualType lookupCoroutineHandleType(Sema &S, QualType PromiseType,
 139                                           SourceLocation Loc) {
 140   if (PromiseType.isNull())
 141     return QualType();
 142
 143   NamespaceDecl *CoroNamespace = S.getStdNamespace();
 144   assert(CoroNamespace && "Should already be diagnosed");
 145
 146   LookupResult Result(S, &S.PP.getIdentifierTable().get("coroutine_handle"),
 147                       Loc, Sema::LookupOrdinaryName);
 148   if (!S.LookupQualifiedName(Result, CoroNamespace)) {
 149     S.Diag(Loc, diag::err_implied_coroutine_type_not_found)
 150         << "std::coroutine_handle";
 151     return QualType();
 152   }
 153
 154   ClassTemplateDecl *CoroHandle = Result.getAsSingle<ClassTemplateDecl>();
 155   if (!CoroHandle) {
 156     Result.suppressDiagnostics();
 157     // We found something weird. Complain about the first thing we found.
 158     NamedDecl *Found = *Result.begin();
 159     S.Diag(Found->getLocation(), diag::err_malformed_std_coroutine_handle);
 160     return QualType();
 161   }
 162
 163   // Form template argument list for coroutine_handle<Promise>.
 164   TemplateArgumentListInfo Args(Loc, Loc);
 165   Args.addArgument(TemplateArgumentLoc(
 166       TemplateArgument(PromiseType),
 167       S.Context.getTrivialTypeSourceInfo(PromiseType, Loc)));
 168
 169   // Build the template-id.
 170   QualType CoroHandleType =
 171       S.CheckTemplateIdType(TemplateName(CoroHandle), Loc, Args);
 172   if (CoroHandleType.isNull())
 173     return QualType();
 174   if (S.RequireCompleteType(Loc, CoroHandleType,
 175                             diag::err_coroutine_type_missing_specialization))
 176     return QualType();
 177
 178   return CoroHandleType;
 179 }
 180
 181 static bool isValidCoroutineContext(Sema &S, SourceLocation Loc,
 182                                     StringRef Keyword) {
 183   // [expr.await]p2 dictates that 'co_await' and 'co_yield' must be used within
 184   // a function body.
 185   // FIXME: This also covers [expr.await]p2: "An await-expression shall not
 186   // appear in a default argument." But the diagnostic QoI here could be
 187   // improved to inform the user that default arguments specifically are not
 188   // allowed.
 189   auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
 190   if (!FD) {
 191     S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
 192                     ? diag::err_coroutine_objc_method
 193                     : diag::err_coroutine_outside_function) << Keyword;
 194     return false;
 195   }
 196
 197   // An enumeration for mapping the diagnostic type to the correct diagnostic
 198   // selection index.
 199   enum InvalidFuncDiag {
 200     DiagCtor = 0,
 201     DiagDtor,
 202     DiagMain,
 203     DiagConstexpr,
 204     DiagAutoRet,
 205     DiagVarargs,
 206     DiagConsteval,
 207   };
 208   bool Diagnosed = false;
 209   auto DiagInvalid = [&](InvalidFuncDiag ID) {
 210     S.Diag(Loc, diag::err_coroutine_invalid_func_context) << ID << Keyword;
 211     Diagnosed = true;
 212     return false;
 213   };
 214
 215   // Diagnose when a constructor, destructor
 216   // or the function 'main' are declared as a coroutine.
 217   auto *MD = dyn_cast<CXXMethodDecl>(FD);
 218   // [class.ctor]p11: "A constructor shall not be a coroutine."
 219   if (MD && isa<CXXConstructorDecl>(MD))
 220     return DiagInvalid(DiagCtor);
 221   // [class.dtor]p17: "A destructor shall not be a coroutine."
 222   else if (MD && isa<CXXDestructorDecl>(MD))
 223     return DiagInvalid(DiagDtor);
 224   // [basic.start.main]p3: "The function main shall not be a coroutine."
 225   else if (FD->isMain())
 226     return DiagInvalid(DiagMain);
 227
 228   // Emit a diagnostics for each of the following conditions which is not met.
 229   // [expr.const]p2: "An expression e is a core constant expression unless the
 230   // evaluation of e [...] would evaluate one of the following expressions:
 231   // [...] an await-expression [...] a yield-expression."
 232   if (FD->isConstexpr())
 233     DiagInvalid(FD->isConsteval() ? DiagConsteval : DiagConstexpr);
 234   // [dcl.spec.auto]p15: "A function declared with a return type that uses a
 235   // placeholder type shall not be a coroutine."
 236   if (FD->getReturnType()->isUndeducedType())
 237     DiagInvalid(DiagAutoRet);
 238   // [dcl.fct.def.coroutine]p1
 239   // The parameter-declaration-clause of the coroutine shall not terminate with
 240   // an ellipsis that is not part of a parameter-declaration.
 241   if (FD->isVariadic())
 242     DiagInvalid(DiagVarargs);
 243
 244   return !Diagnosed;
 245 }
 246
 247 /// Build a call to 'operator co_await' if there is a suitable operator for
 248 /// the given expression.
 249 ExprResult Sema::BuildOperatorCoawaitCall(SourceLocation Loc, Expr *E,
 250                                           UnresolvedLookupExpr *Lookup) {
 251   UnresolvedSet<16> Functions;
 252   Functions.append(Lookup->decls_begin(), Lookup->decls_end());
 253   return CreateOverloadedUnaryOp(Loc, UO_Coawait, Functions, E);
 254 }
 255
 256 static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
 257                                            SourceLocation Loc, Expr *E) {
 258   ExprResult R = SemaRef.BuildOperatorCoawaitLookupExpr(S, Loc);
 259   if (R.isInvalid())
 260     return ExprError();
 261   return SemaRef.BuildOperatorCoawaitCall(Loc, E,
 262                                           cast<UnresolvedLookupExpr>(R.get()));
 263 }
 264
 265 static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
 266                                        SourceLocation Loc) {
 267   QualType CoroHandleType = lookupCoroutineHandleType(S, PromiseType, Loc);
 268   if (CoroHandleType.isNull())
 269     return ExprError();
 270
 271   DeclContext *LookupCtx = S.computeDeclContext(CoroHandleType);
 272   LookupResult Found(S, &S.PP.getIdentifierTable().get("from_address"), Loc,
 273                      Sema::LookupOrdinaryName);
 274   if (!S.LookupQualifiedName(Found, LookupCtx)) {
 275     S.Diag(Loc, diag::err_coroutine_handle_missing_member)
 276         << "from_address";
 277     return ExprError();
 278   }
 279
 280   Expr *FramePtr =
 281       S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});
 282
 283   CXXScopeSpec SS;
 284   ExprResult FromAddr =
 285       S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
 286   if (FromAddr.isInvalid())
 287     return ExprError();
 288
 289   return S.BuildCallExpr(nullptr, FromAddr.get(), Loc, FramePtr, Loc);
 290 }
 291
 292 struct ReadySuspendResumeResult {
 293   enum AwaitCallType { ACT_Ready, ACT_Suspend, ACT_Resume };
 294   Expr *Results[3];
 295   OpaqueValueExpr *OpaqueValue;
 296   bool IsInvalid;
 297 };
 298
 299 static ExprResult buildMemberCall(Sema &S, Expr *Base, SourceLocation Loc,
 300                                   StringRef Name, MultiExprArg Args) {
 301   DeclarationNameInfo NameInfo(&S.PP.getIdentifierTable().get(Name), Loc);
 302
 303   // FIXME: Fix BuildMemberReferenceExpr to take a const CXXScopeSpec&.
 304   CXXScopeSpec SS;
 305   ExprResult Result = S.BuildMemberReferenceExpr(
 306       Base, Base->getType(), Loc, /*IsPtr=*/false, SS,
 307       SourceLocation(), nullptr, NameInfo, /*TemplateArgs=*/nullptr,
 308       /*Scope=*/nullptr);
 309   if (Result.isInvalid())
 310     return ExprError();
 311
 312   // We meant exactly what we asked for. No need for typo correction.
 313   if (auto *TE = dyn_cast<TypoExpr>(Result.get())) {
 314     S.clearDelayedTypo(TE);
 315     S.Diag(Loc, diag::err_no_member)
 316         << NameInfo.getName() << Base->getType()->getAsCXXRecordDecl()
 317         << Base->getSourceRange();
 318     return ExprError();
 319   }
 320
 321   auto EndLoc = Args.empty() ? Loc : Args.back()->getEndLoc();
 322   return S.BuildCallExpr(nullptr, Result.get(), Loc, Args, EndLoc, nullptr);
 323 }
 324
 325 // See if return type is coroutine-handle and if so, invoke builtin coro-resume
 326 // on its address. This is to enable the support for coroutine-handle
 327 // returning await_suspend that results in a guaranteed tail call to the target
 328 // coroutine.
 329 static Expr *maybeTailCall(Sema &S, QualType RetType, Expr *E,
 330                            SourceLocation Loc) {
 331   if (RetType->isReferenceType())
 332     return nullptr;
 333   Type const *T = RetType.getTypePtr();
 334   if (!T->isClassType() && !T->isStructureType())
 335     return nullptr;
 336
 337   // FIXME: Add convertability check to coroutine_handle<>. Possibly via
 338   // EvaluateBinaryTypeTrait(BTT_IsConvertible, ...) which is at the moment
 339   // a private function in SemaExprCXX.cpp
 340
 341   ExprResult AddressExpr = buildMemberCall(S, E, Loc, "address", std::nullopt);
 342   if (AddressExpr.isInvalid())
 343     return nullptr;
 344
 345   Expr *JustAddress = AddressExpr.get();
 346
 347   // Check that the type of AddressExpr is void*
 348   if (!JustAddress->getType().getTypePtr()->isVoidPointerType())
 349     S.Diag(cast<CallExpr>(JustAddress)->getCalleeDecl()->getLocation(),
 350            diag::warn_coroutine_handle_address_invalid_return_type)
 351         << JustAddress->getType();
 352
 353   // Clean up temporary objects so that they don't live across suspension points
 354   // unnecessarily. We choose to clean up before the call to
 355   // __builtin_coro_resume so that the cleanup code are not inserted in-between
 356   // the resume call and return instruction, which would interfere with the
 357   // musttail call contract.
 358   JustAddress = S.MaybeCreateExprWithCleanups(JustAddress);
 359   return S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_resume,
 360                                 JustAddress);
 361 }
 362
 363 /// Build calls to await_ready, await_suspend, and await_resume for a co_await
 364 /// expression.
 365 /// The generated AST tries to clean up temporary objects as early as
 366 /// possible so that they don't live across suspension points if possible.
 367 /// Having temporary objects living across suspension points unnecessarily can
 368 /// lead to large frame size, and also lead to memory corruptions if the
 369 /// coroutine frame is destroyed after coming back from suspension. This is done
 370 /// by wrapping both the await_ready call and the await_suspend call with
 371 /// ExprWithCleanups. In the end of this function, we also need to explicitly
 372 /// set cleanup state so that the CoawaitExpr is also wrapped with an
 373 /// ExprWithCleanups to clean up the awaiter associated with the co_await
 374 /// expression.
 375 static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
 376                                                   SourceLocation Loc, Expr *E) {
 377   OpaqueValueExpr *Operand = new (S.Context)
 378       OpaqueValueExpr(Loc, E->getType(), VK_LValue, E->getObjectKind(), E);
 379
 380   // Assume valid until we see otherwise.
 381   // Further operations are responsible for setting IsInalid to true.
 382   ReadySuspendResumeResult Calls = {{}, Operand, /*IsInvalid=*/false};
 383
 384   using ACT = ReadySuspendResumeResult::AwaitCallType;
 385
 386   auto BuildSubExpr = [&](ACT CallType, StringRef Func,
 387                           MultiExprArg Arg) -> Expr * {
 388     ExprResult Result = buildMemberCall(S, Operand, Loc, Func, Arg);
 389     if (Result.isInvalid()) {
 390       Calls.IsInvalid = true;
 391       return nullptr;
 392     }
 393     Calls.Results[CallType] = Result.get();
 394     return Result.get();
 395   };
 396
 397   CallExpr *AwaitReady = cast_or_null<CallExpr>(
 398       BuildSubExpr(ACT::ACT_Ready, "await_ready", std::nullopt));
 399   if (!AwaitReady)
 400     return Calls;
 401   if (!AwaitReady->getType()->isDependentType()) {
 402     // [expr.await]p3 [...]
 403     // — await-ready is the expression e.await_ready(), contextually converted
 404     // to bool.
 405     ExprResult Conv = S.PerformContextuallyConvertToBool(AwaitReady);
 406     if (Conv.isInvalid()) {
 407       S.Diag(AwaitReady->getDirectCallee()->getBeginLoc(),
 408              diag::note_await_ready_no_bool_conversion);
 409       S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
 410           << AwaitReady->getDirectCallee() << E->getSourceRange();
 411       Calls.IsInvalid = true;
 412     } else
 413       Calls.Results[ACT::ACT_Ready] = S.MaybeCreateExprWithCleanups(Conv.get());
 414   }
 415
 416   ExprResult CoroHandleRes =
 417       buildCoroutineHandle(S, CoroPromise->getType(), Loc);
 418   if (CoroHandleRes.isInvalid()) {
 419     Calls.IsInvalid = true;
 420     return Calls;
 421   }
 422   Expr *CoroHandle = CoroHandleRes.get();
 423   CallExpr *AwaitSuspend = cast_or_null<CallExpr>(
 424       BuildSubExpr(ACT::ACT_Suspend, "await_suspend", CoroHandle));
 425   if (!AwaitSuspend)
 426     return Calls;
 427   if (!AwaitSuspend->getType()->isDependentType()) {
 428     // [expr.await]p3 [...]
 429     //   - await-suspend is the expression e.await_suspend(h), which shall be
 430     //     a prvalue of type void, bool, or std::coroutine_handle<Z> for some
 431     //     type Z.
 432     QualType RetType = AwaitSuspend->getCallReturnType(S.Context);
 433
 434     // Support for coroutine_handle returning await_suspend.
 435     if (Expr *TailCallSuspend =
 436             maybeTailCall(S, RetType, AwaitSuspend, Loc))
 437       // Note that we don't wrap the expression with ExprWithCleanups here
 438       // because that might interfere with tailcall contract (e.g. inserting
 439       // clean up instructions in-between tailcall and return). Instead
 440       // ExprWithCleanups is wrapped within maybeTailCall() prior to the resume
 441       // call.
 442       Calls.Results[ACT::ACT_Suspend] = TailCallSuspend;
 443     else {
 444       // non-class prvalues always have cv-unqualified types
 445       if (RetType->isReferenceType() ||
 446           (!RetType->isBooleanType() && !RetType->isVoidType())) {
 447         S.Diag(AwaitSuspend->getCalleeDecl()->getLocation(),
 448                diag::err_await_suspend_invalid_return_type)
 449             << RetType;
 450         S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
 451             << AwaitSuspend->getDirectCallee();
 452         Calls.IsInvalid = true;
 453       } else
 454         Calls.Results[ACT::ACT_Suspend] =
 455             S.MaybeCreateExprWithCleanups(AwaitSuspend);
 456     }
 457   }
 458
 459   BuildSubExpr(ACT::ACT_Resume, "await_resume", std::nullopt);
 460
 461   // Make sure the awaiter object gets a chance to be cleaned up.
 462   S.Cleanup.setExprNeedsCleanups(true);
 463
 464   return Calls;
 465 }
 466
 467 static ExprResult buildPromiseCall(Sema &S, VarDecl *Promise,
 468                                    SourceLocation Loc, StringRef Name,
 469                                    MultiExprArg Args) {
 470
 471   // Form a reference to the promise.
 472   ExprResult PromiseRef = S.BuildDeclRefExpr(
 473       Promise, Promise->getType().getNonReferenceType(), VK_LValue, Loc);
 474   if (PromiseRef.isInvalid())
 475     return ExprError();
 476
 477   return buildMemberCall(S, PromiseRef.get(), Loc, Name, Args);
 478 }
 479
 480 VarDecl *Sema::buildCoroutinePromise(SourceLocation Loc) {
 481   assert(isa<FunctionDecl>(CurContext) && "not in a function scope");
 482   auto *FD = cast<FunctionDecl>(CurContext);
 483   bool IsThisDependentType = [&] {
 484     if (auto *MD = dyn_cast_or_null<CXXMethodDecl>(FD))
 485       return MD->isInstance() && MD->getThisType()->isDependentType();
 486     else
 487       return false;
 488   }();
 489
 490   QualType T = FD->getType()->isDependentType() || IsThisDependentType
 491                    ? Context.DependentTy
 492                    : lookupPromiseType(*this, FD, Loc);
 493   if (T.isNull())
 494     return nullptr;
 495
 496   auto *VD = VarDecl::Create(Context, FD, FD->getLocation(), FD->getLocation(),
 497                              &PP.getIdentifierTable().get("__promise"), T,
 498                              Context.getTrivialTypeSourceInfo(T, Loc), SC_None);
 499   VD->setImplicit();
 500   CheckVariableDeclarationType(VD);
 501   if (VD->isInvalidDecl())
 502     return nullptr;
 503
 504   auto *ScopeInfo = getCurFunction();
 505
 506   // Build a list of arguments, based on the coroutine function's arguments,
 507   // that if present will be passed to the promise type's constructor.
 508   llvm::SmallVector<Expr *, 4> CtorArgExprs;
 509
 510   // Add implicit object parameter.
 511   if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
 512     if (MD->isInstance() && !isLambdaCallOperator(MD)) {
 513       ExprResult ThisExpr = ActOnCXXThis(Loc);
 514       if (ThisExpr.isInvalid())
 515         return nullptr;
 516       ThisExpr = CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
 517       if (ThisExpr.isInvalid())
 518         return nullptr;
 519       CtorArgExprs.push_back(ThisExpr.get());
 520     }
 521   }
 522
 523   // Add the coroutine function's parameters.
 524   auto &Moves = ScopeInfo->CoroutineParameterMoves;
 525   for (auto *PD : FD->parameters()) {
 526     if (PD->getType()->isDependentType())
 527       continue;
 528
 529     auto RefExpr = ExprEmpty();
 530     auto Move = Moves.find(PD);
 531     assert(Move != Moves.end() &&
 532            "Coroutine function parameter not inserted into move map");
 533     // If a reference to the function parameter exists in the coroutine
 534     // frame, use that reference.
 535     auto *MoveDecl =
 536         cast<VarDecl>(cast<DeclStmt>(Move->second)->getSingleDecl());
 537     RefExpr =
 538         BuildDeclRefExpr(MoveDecl, MoveDecl->getType().getNonReferenceType(),
 539                          ExprValueKind::VK_LValue, FD->getLocation());
 540     if (RefExpr.isInvalid())
 541       return nullptr;
 542     CtorArgExprs.push_back(RefExpr.get());
 543   }
 544
 545   // If we have a non-zero number of constructor arguments, try to use them.
 546   // Otherwise, fall back to the promise type's default constructor.
 547   if (!CtorArgExprs.empty()) {
 548     // Create an initialization sequence for the promise type using the
 549     // constructor arguments, wrapped in a parenthesized list expression.
 550     Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
 551                                       CtorArgExprs, FD->getLocation());
 552     InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
 553     InitializationKind Kind = InitializationKind::CreateForInit(
 554         VD->getLocation(), /*DirectInit=*/true, PLE);
 555     InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
 556                                    /*TopLevelOfInitList=*/false,
 557                                    /*TreatUnavailableAsInvalid=*/false);
 558
 559     // [dcl.fct.def.coroutine]5.7
 560     // promise-constructor-arguments is determined as follows: overload
 561     // resolution is performed on a promise constructor call created by
 562     // assembling an argument list  q_1 ... q_n . If a viable constructor is
 563     // found ([over.match.viable]), then promise-constructor-arguments is ( q_1
 564     // , ...,  q_n ), otherwise promise-constructor-arguments is empty.
 565     if (InitSeq) {
 566       ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
 567       if (Result.isInvalid()) {
 568         VD->setInvalidDecl();
 569       } else if (Result.get()) {
 570         VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
 571         VD->setInitStyle(VarDecl::CallInit);
 572         CheckCompleteVariableDeclaration(VD);
 573       }
 574     } else
 575       ActOnUninitializedDecl(VD);
 576   } else
 577     ActOnUninitializedDecl(VD);
 578
 579   FD->addDecl(VD);
 580   return VD;
 581 }
 582
 583 /// Check that this is a context in which a coroutine suspension can appear.
 584 static FunctionScopeInfo *checkCoroutineContext(Sema &S, SourceLocation Loc,
 585                                                 StringRef Keyword,
 586                                                 bool IsImplicit = false) {
 587   if (!isValidCoroutineContext(S, Loc, Keyword))
 588     return nullptr;
 589
 590   assert(isa<FunctionDecl>(S.CurContext) && "not in a function scope");
 591
 592   auto *ScopeInfo = S.getCurFunction();
 593   assert(ScopeInfo && "missing function scope for function");
 594
 595   if (ScopeInfo->FirstCoroutineStmtLoc.isInvalid() && !IsImplicit)
 596     ScopeInfo->setFirstCoroutineStmt(Loc, Keyword);
 597
 598   if (ScopeInfo->CoroutinePromise)
 599     return ScopeInfo;
 600
 601   if (!S.buildCoroutineParameterMoves(Loc))
 602     return nullptr;
 603
 604   ScopeInfo->CoroutinePromise = S.buildCoroutinePromise(Loc);
 605   if (!ScopeInfo->CoroutinePromise)
 606     return nullptr;
 607
 608   return ScopeInfo;
 609 }
 610
 611 /// Recursively check \p E and all its children to see if any call target
 612 /// (including constructor call) is declared noexcept. Also any value returned
 613 /// from the call has a noexcept destructor.
 614 static void checkNoThrow(Sema &S, const Stmt *E,
 615                          llvm::SmallPtrSetImpl<const Decl *> &ThrowingDecls) {
 616   auto checkDeclNoexcept = [&](const Decl *D, bool IsDtor = false) {
 617     // In the case of dtor, the call to dtor is implicit and hence we should
 618     // pass nullptr to canCalleeThrow.
 619     if (Sema::canCalleeThrow(S, IsDtor ? nullptr : cast<Expr>(E), D)) {
 620       if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
 621         // co_await promise.final_suspend() could end up calling
 622         // __builtin_coro_resume for symmetric transfer if await_suspend()
 623         // returns a handle. In that case, even __builtin_coro_resume is not
 624         // declared as noexcept and may throw, it does not throw _into_ the
 625         // coroutine that just suspended, but rather throws back out from
 626         // whoever called coroutine_handle::resume(), hence we claim that
 627         // logically it does not throw.
 628         if (FD->getBuiltinID() == Builtin::BI__builtin_coro_resume)
 629           return;
 630       }
 631       if (ThrowingDecls.empty()) {
 632         // [dcl.fct.def.coroutine]p15
 633         //   The expression co_await promise.final_suspend() shall not be
 634         //   potentially-throwing ([except.spec]).
 635         //
 636         // First time seeing an error, emit the error message.
 637         S.Diag(cast<FunctionDecl>(S.CurContext)->getLocation(),
 638                diag::err_coroutine_promise_final_suspend_requires_nothrow);
 639       }
 640       ThrowingDecls.insert(D);
 641     }
 642   };
 643
 644   if (auto *CE = dyn_cast<CXXConstructExpr>(E)) {
 645     CXXConstructorDecl *Ctor = CE->getConstructor();
 646     checkDeclNoexcept(Ctor);
 647     // Check the corresponding destructor of the constructor.
 648     checkDeclNoexcept(Ctor->getParent()->getDestructor(), /*IsDtor=*/true);
 649   } else if (auto *CE = dyn_cast<CallExpr>(E)) {
 650     if (CE->isTypeDependent())
 651       return;
 652
 653     checkDeclNoexcept(CE->getCalleeDecl());
 654     QualType ReturnType = CE->getCallReturnType(S.getASTContext());
 655     // Check the destructor of the call return type, if any.
 656     if (ReturnType.isDestructedType() ==
 657         QualType::DestructionKind::DK_cxx_destructor) {
 658       const auto *T =
 659           cast<RecordType>(ReturnType.getCanonicalType().getTypePtr());
 660       checkDeclNoexcept(cast<CXXRecordDecl>(T->getDecl())->getDestructor(),
 661                         /*IsDtor=*/true);
 662     }
 663   } else
 664     for (const auto *Child : E->children()) {
 665       if (!Child)
 666         continue;
 667       checkNoThrow(S, Child, ThrowingDecls);
 668     }
 669 }
 670
 671 bool Sema::checkFinalSuspendNoThrow(const Stmt *FinalSuspend) {
 672   llvm::SmallPtrSet<const Decl *, 4> ThrowingDecls;
 673   // We first collect all declarations that should not throw but not declared
 674   // with noexcept. We then sort them based on the location before printing.
 675   // This is to avoid emitting the same note multiple times on the same
 676   // declaration, and also provide a deterministic order for the messages.
 677   checkNoThrow(*this, FinalSuspend, ThrowingDecls);
 678   auto SortedDecls = llvm::SmallVector<const Decl *, 4>{ThrowingDecls.begin(),
 679                                                         ThrowingDecls.end()};
 680   sort(SortedDecls, [](const Decl *A, const Decl *B) {
 681     return A->getEndLoc() < B->getEndLoc();
 682   });
 683   for (const auto *D : SortedDecls) {
 684     Diag(D->getEndLoc(), diag::note_coroutine_function_declare_noexcept);
 685   }
 686   return ThrowingDecls.empty();
 687 }
 688
 689 bool Sema::ActOnCoroutineBodyStart(Scope *SC, SourceLocation KWLoc,
 690                                    StringRef Keyword) {
 691   if (!checkCoroutineContext(*this, KWLoc, Keyword))
 692     return false;
 693   auto *ScopeInfo = getCurFunction();
 694   assert(ScopeInfo->CoroutinePromise);
 695
 696   // If we have existing coroutine statements then we have already built
 697   // the initial and final suspend points.
 698   if (!ScopeInfo->NeedsCoroutineSuspends)
 699     return true;
 700
 701   ScopeInfo->setNeedsCoroutineSuspends(false);
 702
 703   auto *Fn = cast<FunctionDecl>(CurContext);
 704   SourceLocation Loc = Fn->getLocation();
 705   // Build the initial suspend point
 706   auto buildSuspends = [&](StringRef Name) mutable -> StmtResult {
 707     ExprResult Operand = buildPromiseCall(*this, ScopeInfo->CoroutinePromise,
 708                                           Loc, Name, std::nullopt);
 709     if (Operand.isInvalid())
 710       return StmtError();
 711     ExprResult Suspend =
 712         buildOperatorCoawaitCall(*this, SC, Loc, Operand.get());
 713     if (Suspend.isInvalid())
 714       return StmtError();
 715     Suspend = BuildResolvedCoawaitExpr(Loc, Operand.get(), Suspend.get(),
 716                                        /*IsImplicit*/ true);
 717     Suspend = ActOnFinishFullExpr(Suspend.get(), /*DiscardedValue*/ false);
 718     if (Suspend.isInvalid()) {
 719       Diag(Loc, diag::note_coroutine_promise_suspend_implicitly_required)
 720           << ((Name == "initial_suspend") ? 0 : 1);
 721       Diag(KWLoc, diag::note_declared_coroutine_here) << Keyword;
 722       return StmtError();
 723     }
 724     return cast<Stmt>(Suspend.get());
 725   };
 726
 727   StmtResult InitSuspend = buildSuspends("initial_suspend");
 728   if (InitSuspend.isInvalid())
 729     return true;
 730
 731   StmtResult FinalSuspend = buildSuspends("final_suspend");
 732   if (FinalSuspend.isInvalid() || !checkFinalSuspendNoThrow(FinalSuspend.get()))
 733     return true;
 734
 735   ScopeInfo->setCoroutineSuspends(InitSuspend.get(), FinalSuspend.get());
 736
 737   return true;
 738 }
 739
 740 // Recursively walks up the scope hierarchy until either a 'catch' or a function
 741 // scope is found, whichever comes first.
 742 static bool isWithinCatchScope(Scope *S) {
 743   // 'co_await' and 'co_yield' keywords are disallowed within catch blocks, but
 744   // lambdas that use 'co_await' are allowed. The loop below ends when a
 745   // function scope is found in order to ensure the following behavior:
 746   //
 747   // void foo() {      // <- function scope
 748   //   try {           //
 749   //     co_await x;   // <- 'co_await' is OK within a function scope
 750   //   } catch {       // <- catch scope
 751   //     co_await x;   // <- 'co_await' is not OK within a catch scope
 752   //     []() {        // <- function scope
 753   //       co_await x; // <- 'co_await' is OK within a function scope
 754   //     }();
 755   //   }
 756   // }
 757   while (S && !S->isFunctionScope()) {
 758     if (S->isCatchScope())
 759       return true;
 760     S = S->getParent();
 761   }
 762   return false;
 763 }
 764
 765 // [expr.await]p2, emphasis added: "An await-expression shall appear only in
 766 // a *potentially evaluated* expression within the compound-statement of a
 767 // function-body *outside of a handler* [...] A context within a function
 768 // where an await-expression can appear is called a suspension context of the
 769 // function."
 770 static bool checkSuspensionContext(Sema &S, SourceLocation Loc,
 771                                    StringRef Keyword) {
 772   // First emphasis of [expr.await]p2: must be a potentially evaluated context.
 773   // That is, 'co_await' and 'co_yield' cannot appear in subexpressions of
 774   // \c sizeof.
 775   if (S.isUnevaluatedContext()) {
 776     S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
 777     return false;
 778   }
 779
 780   // Second emphasis of [expr.await]p2: must be outside of an exception handler.
 781   if (isWithinCatchScope(S.getCurScope())) {
 782     S.Diag(Loc, diag::err_coroutine_within_handler) << Keyword;
 783     return false;
 784   }
 785
 786   return true;
 787 }
 788
 789 ExprResult Sema::ActOnCoawaitExpr(Scope *S, SourceLocation Loc, Expr *E) {
 790   if (!checkSuspensionContext(*this, Loc, "co_await"))
 791     return ExprError();
 792
 793   if (!ActOnCoroutineBodyStart(S, Loc, "co_await")) {
 794     CorrectDelayedTyposInExpr(E);
 795     return ExprError();
 796   }
 797
 798   if (E->hasPlaceholderType()) {
 799     ExprResult R = CheckPlaceholderExpr(E);
 800     if (R.isInvalid()) return ExprError();
 801     E = R.get();
 802   }
 803   ExprResult Lookup = BuildOperatorCoawaitLookupExpr(S, Loc);
 804   if (Lookup.isInvalid())
 805     return ExprError();
 806   return BuildUnresolvedCoawaitExpr(Loc, E,
 807                                    cast<UnresolvedLookupExpr>(Lookup.get()));
 808 }
 809
 810 ExprResult Sema::BuildOperatorCoawaitLookupExpr(Scope *S, SourceLocation Loc) {
 811   DeclarationName OpName =
 812       Context.DeclarationNames.getCXXOperatorName(OO_Coawait);
 813   LookupResult Operators(*this, OpName, SourceLocation(),
 814                          Sema::LookupOperatorName);
 815   LookupName(Operators, S);
 816
 817   assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous");
 818   const auto &Functions = Operators.asUnresolvedSet();
 819   bool IsOverloaded =
 820       Functions.size() > 1 ||
 821       (Functions.size() == 1 && isa<FunctionTemplateDecl>(*Functions.begin()));
 822   Expr *CoawaitOp = UnresolvedLookupExpr::Create(
 823       Context, /*NamingClass*/ nullptr, NestedNameSpecifierLoc(),
 824       DeclarationNameInfo(OpName, Loc), /*RequiresADL*/ true, IsOverloaded,
 825       Functions.begin(), Functions.end());
 826   assert(CoawaitOp);
 827   return CoawaitOp;
 828 }
 829
 830 // Attempts to resolve and build a CoawaitExpr from "raw" inputs, bailing out to
 831 // DependentCoawaitExpr if needed.
 832 ExprResult Sema::BuildUnresolvedCoawaitExpr(SourceLocation Loc, Expr *Operand,
 833                                             UnresolvedLookupExpr *Lookup) {
 834   auto *FSI = checkCoroutineContext(*this, Loc, "co_await");
 835   if (!FSI)
 836     return ExprError();
 837
 838   if (Operand->hasPlaceholderType()) {
 839     ExprResult R = CheckPlaceholderExpr(Operand);
 840     if (R.isInvalid())
 841       return ExprError();
 842     Operand = R.get();
 843   }
 844
 845   auto *Promise = FSI->CoroutinePromise;
 846   if (Promise->getType()->isDependentType()) {
 847     Expr *Res = new (Context)
 848         DependentCoawaitExpr(Loc, Context.DependentTy, Operand, Lookup);
 849     return Res;
 850   }
 851
 852   auto *RD = Promise->getType()->getAsCXXRecordDecl();
 853   auto *Transformed = Operand;
 854   if (lookupMember(*this, "await_transform", RD, Loc)) {
 855     ExprResult R =
 856         buildPromiseCall(*this, Promise, Loc, "await_transform", Operand);
 857     if (R.isInvalid()) {
 858       Diag(Loc,
 859            diag::note_coroutine_promise_implicit_await_transform_required_here)
 860           << Operand->getSourceRange();
 861       return ExprError();
 862     }
 863     Transformed = R.get();
 864   }
 865   ExprResult Awaiter = BuildOperatorCoawaitCall(Loc, Transformed, Lookup);
 866   if (Awaiter.isInvalid())
 867     return ExprError();
 868
 869   return BuildResolvedCoawaitExpr(Loc, Operand, Awaiter.get());
 870 }
 871
 872 ExprResult Sema::BuildResolvedCoawaitExpr(SourceLocation Loc, Expr *Operand,
 873                                           Expr *Awaiter, bool IsImplicit) {
 874   auto *Coroutine = checkCoroutineContext(*this, Loc, "co_await", IsImplicit);
 875   if (!Coroutine)
 876     return ExprError();
 877
 878   if (Awaiter->hasPlaceholderType()) {
 879     ExprResult R = CheckPlaceholderExpr(Awaiter);
 880     if (R.isInvalid()) return ExprError();
 881     Awaiter = R.get();
 882   }
 883
 884   if (Awaiter->getType()->isDependentType()) {
 885     Expr *Res = new (Context)
 886         CoawaitExpr(Loc, Context.DependentTy, Operand, Awaiter, IsImplicit);
 887     return Res;
 888   }
 889
 890   // If the expression is a temporary, materialize it as an lvalue so that we
 891   // can use it multiple times.
 892   if (Awaiter->isPRValue())
 893     Awaiter = CreateMaterializeTemporaryExpr(Awaiter->getType(), Awaiter, true);
 894
 895   // The location of the `co_await` token cannot be used when constructing
 896   // the member call expressions since it's before the location of `Expr`, which
 897   // is used as the start of the member call expression.
 898   SourceLocation CallLoc = Awaiter->getExprLoc();
 899
 900   // Build the await_ready, await_suspend, await_resume calls.
 901   ReadySuspendResumeResult RSS =
 902       buildCoawaitCalls(*this, Coroutine->CoroutinePromise, CallLoc, Awaiter);
 903   if (RSS.IsInvalid)
 904     return ExprError();
 905
 906   Expr *Res = new (Context)
 907       CoawaitExpr(Loc, Operand, Awaiter, RSS.Results[0], RSS.Results[1],
 908                   RSS.Results[2], RSS.OpaqueValue, IsImplicit);
 909
 910   return Res;
 911 }
 912
 913 ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) {
 914   if (!checkSuspensionContext(*this, Loc, "co_yield"))
 915     return ExprError();
 916
 917   if (!ActOnCoroutineBodyStart(S, Loc, "co_yield")) {
 918     CorrectDelayedTyposInExpr(E);
 919     return ExprError();
 920   }
 921
 922   // Build yield_value call.
 923   ExprResult Awaitable = buildPromiseCall(
 924       *this, getCurFunction()->CoroutinePromise, Loc, "yield_value", E);
 925   if (Awaitable.isInvalid())
 926     return ExprError();
 927
 928   // Build 'operator co_await' call.
 929   Awaitable = buildOperatorCoawaitCall(*this, S, Loc, Awaitable.get());
 930   if (Awaitable.isInvalid())
 931     return ExprError();
 932
 933   return BuildCoyieldExpr(Loc, Awaitable.get());
 934 }
 935 ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
 936   auto *Coroutine = checkCoroutineContext(*this, Loc, "co_yield");
 937   if (!Coroutine)
 938     return ExprError();
 939
 940   if (E->hasPlaceholderType()) {
 941     ExprResult R = CheckPlaceholderExpr(E);
 942     if (R.isInvalid()) return ExprError();
 943     E = R.get();
 944   }
 945
 946   Expr *Operand = E;
 947
 948   if (E->getType()->isDependentType()) {
 949     Expr *Res = new (Context) CoyieldExpr(Loc, Context.DependentTy, Operand, E);
 950     return Res;
 951   }
 952
 953   // If the expression is a temporary, materialize it as an lvalue so that we
 954   // can use it multiple times.
 955   if (E->isPRValue())
 956     E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
 957
 958   // Build the await_ready, await_suspend, await_resume calls.
 959   ReadySuspendResumeResult RSS = buildCoawaitCalls(
 960       *this, Coroutine->CoroutinePromise, Loc, E);
 961   if (RSS.IsInvalid)
 962     return ExprError();
 963
 964   Expr *Res =
 965       new (Context) CoyieldExpr(Loc, Operand, E, RSS.Results[0], RSS.Results[1],
 966                                 RSS.Results[2], RSS.OpaqueValue);
 967
 968   return Res;
 969 }
 970
 971 StmtResult Sema::ActOnCoreturnStmt(Scope *S, SourceLocation Loc, Expr *E) {
 972   if (!ActOnCoroutineBodyStart(S, Loc, "co_return")) {
 973     CorrectDelayedTyposInExpr(E);
 974     return StmtError();
 975   }
 976   return BuildCoreturnStmt(Loc, E);
 977 }
 978
 979 StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E,
 980                                    bool IsImplicit) {
 981   auto *FSI = checkCoroutineContext(*this, Loc, "co_return", IsImplicit);
 982   if (!FSI)
 983     return StmtError();
 984
 985   if (E && E->hasPlaceholderType() &&
 986       !E->hasPlaceholderType(BuiltinType::Overload)) {
 987     ExprResult R = CheckPlaceholderExpr(E);
 988     if (R.isInvalid()) return StmtError();
 989     E = R.get();
 990   }
 991
 992   VarDecl *Promise = FSI->CoroutinePromise;
 993   ExprResult PC;
 994   if (E && (isa<InitListExpr>(E) || !E->getType()->isVoidType())) {
 995     getNamedReturnInfo(E, SimplerImplicitMoveMode::ForceOn);
 996     PC = buildPromiseCall(*this, Promise, Loc, "return_value", E);
 997   } else {
 998     E = MakeFullDiscardedValueExpr(E).get();
 999     PC = buildPromiseCall(*this, Promise, Loc, "return_void", std::nullopt);
1000   }
1001   if (PC.isInvalid())
1002     return StmtError();
1003
1004   Expr *PCE = ActOnFinishFullExpr(PC.get(), /*DiscardedValue*/ false).get();
1005
1006   Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE, IsImplicit);
1007   return Res;
1008 }
1009
1010 /// Look up the std::nothrow object.
1011 static Expr *buildStdNoThrowDeclRef(Sema &S, SourceLocation Loc) {
1012   NamespaceDecl *Std = S.getStdNamespace();
1013   assert(Std && "Should already be diagnosed");
1014
1015   LookupResult Result(S, &S.PP.getIdentifierTable().get("nothrow"), Loc,
1016                       Sema::LookupOrdinaryName);
1017   if (!S.LookupQualifiedName(Result, Std)) {
1018     // <coroutine> is not requred to include <new>, so we couldn't omit
1019     // the check here.
1020     S.Diag(Loc, diag::err_implicit_coroutine_std_nothrow_type_not_found);
1021     return nullptr;
1022   }
1023
1024   auto *VD = Result.getAsSingle<VarDecl>();
1025   if (!VD) {
1026     Result.suppressDiagnostics();
1027     // We found something weird. Complain about the first thing we found.
1028     NamedDecl *Found = *Result.begin();
1029     S.Diag(Found->getLocation(), diag::err_malformed_std_nothrow);
1030     return nullptr;
1031   }
1032
1033   ExprResult DR = S.BuildDeclRefExpr(VD, VD->getType(), VK_LValue, Loc);
1034   if (DR.isInvalid())
1035     return nullptr;
1036
1037   return DR.get();
1038 }
1039
1040 static TypeSourceInfo *getTypeSourceInfoForStdAlignValT(Sema &S,
1041                                                         SourceLocation Loc) {
1042   EnumDecl *StdAlignValT = S.getStdAlignValT();
1043   QualType StdAlignValDecl = S.Context.getTypeDeclType(StdAlignValT);
1044   return S.Context.getTrivialTypeSourceInfo(StdAlignValDecl);
1045 }
1046
1047 // Find an appropriate delete for the promise.
1048 static bool findDeleteForPromise(Sema &S, SourceLocation Loc, QualType PromiseType,
1049                                  FunctionDecl *&OperatorDelete) {
1050   DeclarationName DeleteName =
1051       S.Context.DeclarationNames.getCXXOperatorName(OO_Delete);
1052
1053   auto *PointeeRD = PromiseType->getAsCXXRecordDecl();
1054   assert(PointeeRD && "PromiseType must be a CxxRecordDecl type");
1055
1056   const bool Overaligned = S.getLangOpts().CoroAlignedAllocation;
1057
1058   // [dcl.fct.def.coroutine]p12
1059   // The deallocation function's name is looked up by searching for it in the
1060   // scope of the promise type. If nothing is found, a search is performed in
1061   // the global scope.
1062   if (S.FindDeallocationFunction(Loc, PointeeRD, DeleteName, OperatorDelete,
1063                                  /*Diagnose*/ true, /*WantSize*/ true,
1064                                  /*WantAligned*/ Overaligned))
1065     return false;
1066
1067   // [dcl.fct.def.coroutine]p12
1068   //   If both a usual deallocation function with only a pointer parameter and a
1069   //   usual deallocation function with both a pointer parameter and a size
1070   //   parameter are found, then the selected deallocation function shall be the
1071   //   one with two parameters. Otherwise, the selected deallocation function
1072   //   shall be the function with one parameter.
1073   if (!OperatorDelete) {
1074     // Look for a global declaration.
1075     // Coroutines can always provide their required size.
1076     const bool CanProvideSize = true;
1077     // Sema::FindUsualDeallocationFunction will try to find the one with two
1078     // parameters first. It will return the deallocation function with one
1079     // parameter if failed.
1080     OperatorDelete = S.FindUsualDeallocationFunction(Loc, CanProvideSize,
1081                                                      Overaligned, DeleteName);
1082
1083     if (!OperatorDelete)
1084       return false;
1085   }
1086
1087   S.MarkFunctionReferenced(Loc, OperatorDelete);
1088   return true;
1089 }
1090
1091
1092 void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
1093   FunctionScopeInfo *Fn = getCurFunction();
1094   assert(Fn && Fn->isCoroutine() && "not a coroutine");
1095   if (!Body) {
1096     assert(FD->isInvalidDecl() &&
1097            "a null body is only allowed for invalid declarations");
1098     return;
1099   }
1100   // We have a function that uses coroutine keywords, but we failed to build
1101   // the promise type.
1102   if (!Fn->CoroutinePromise)
1103     return FD->setInvalidDecl();
1104
1105   if (isa<CoroutineBodyStmt>(Body)) {
1106     // Nothing todo. the body is already a transformed coroutine body statement.
1107     return;
1108   }
1109
1110   // The always_inline attribute doesn't reliably apply to a coroutine,
1111   // because the coroutine will be split into pieces and some pieces
1112   // might be called indirectly, as in a virtual call. Even the ramp
1113   // function cannot be inlined at -O0, due to pipeline ordering
1114   // problems (see https://llvm.org/PR53413). Tell the user about it.
1115   if (FD->hasAttr<AlwaysInlineAttr>())
1116     Diag(FD->getLocation(), diag::warn_always_inline_coroutine);
1117
1118   // [stmt.return.coroutine]p1:
1119   //   A coroutine shall not enclose a return statement ([stmt.return]).
1120   if (Fn->FirstReturnLoc.isValid()) {
1121     assert(Fn->FirstCoroutineStmtLoc.isValid() &&
1122                    "first coroutine location not set");
1123     Diag(Fn->FirstReturnLoc, diag::err_return_in_coroutine);
1124     Diag(Fn->FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1125             << Fn->getFirstCoroutineStmtKeyword();
1126   }
1127
1128   // Coroutines will get splitted into pieces. The GNU address of label
1129   // extension wouldn't be meaningful in coroutines.
1130   for (AddrLabelExpr *ALE : Fn->AddrLabels)
1131     Diag(ALE->getBeginLoc(), diag::err_coro_invalid_addr_of_label);
1132
1133   CoroutineStmtBuilder Builder(*this, *FD, *Fn, Body);
1134   if (Builder.isInvalid() || !Builder.buildStatements())
1135     return FD->setInvalidDecl();
1136
1137   // Build body for the coroutine wrapper statement.
1138   Body = CoroutineBodyStmt::Create(Context, Builder);
1139 }
1140
1141 static CompoundStmt *buildCoroutineBody(Stmt *Body, ASTContext &Context) {
1142   if (auto *CS = dyn_cast<CompoundStmt>(Body))
1143     return CS;
1144
1145   // The body of the coroutine may be a try statement if it is in
1146   // 'function-try-block' syntax. Here we wrap it into a compound
1147   // statement for consistency.
1148   assert(isa<CXXTryStmt>(Body) && "Unimaged coroutine body type");
1149   return CompoundStmt::Create(Context, {Body}, FPOptionsOverride(),
1150                               SourceLocation(), SourceLocation());
1151 }
1152
1153 CoroutineStmtBuilder::CoroutineStmtBuilder(Sema &S, FunctionDecl &FD,
1154                                            sema::FunctionScopeInfo &Fn,
1155                                            Stmt *Body)
1156     : S(S), FD(FD), Fn(Fn), Loc(FD.getLocation()),
1157       IsPromiseDependentType(
1158           !Fn.CoroutinePromise ||
1159           Fn.CoroutinePromise->getType()->isDependentType()) {
1160   this->Body = buildCoroutineBody(Body, S.getASTContext());
1161
1162   for (auto KV : Fn.CoroutineParameterMoves)
1163     this->ParamMovesVector.push_back(KV.second);
1164   this->ParamMoves = this->ParamMovesVector;
1165
1166   if (!IsPromiseDependentType) {
1167     PromiseRecordDecl = Fn.CoroutinePromise->getType()->getAsCXXRecordDecl();
1168     assert(PromiseRecordDecl && "Type should have already been checked");
1169   }
1170   this->IsValid = makePromiseStmt() && makeInitialAndFinalSuspend();
1171 }
1172
1173 bool CoroutineStmtBuilder::buildStatements() {
1174   assert(this->IsValid && "coroutine already invalid");
1175   this->IsValid = makeReturnObject();
1176   if (this->IsValid && !IsPromiseDependentType)
1177     buildDependentStatements();
1178   return this->IsValid;
1179 }
1180
1181 bool CoroutineStmtBuilder::buildDependentStatements() {
1182   assert(this->IsValid && "coroutine already invalid");
1183   assert(!this->IsPromiseDependentType &&
1184          "coroutine cannot have a dependent promise type");
1185   this->IsValid = makeOnException() && makeOnFallthrough() &&
1186                   makeGroDeclAndReturnStmt() && makeReturnOnAllocFailure() &&
1187                   makeNewAndDeleteExpr();
1188   return this->IsValid;
1189 }
1190
1191 bool CoroutineStmtBuilder::makePromiseStmt() {
1192   // Form a declaration statement for the promise declaration, so that AST
1193   // visitors can more easily find it.
1194   StmtResult PromiseStmt =
1195       S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(Fn.CoroutinePromise), Loc, Loc);
1196   if (PromiseStmt.isInvalid())
1197     return false;
1198
1199   this->Promise = PromiseStmt.get();
1200   return true;
1201 }
1202
1203 bool CoroutineStmtBuilder::makeInitialAndFinalSuspend() {
1204   if (Fn.hasInvalidCoroutineSuspends())
1205     return false;
1206   this->InitialSuspend = cast<Expr>(Fn.CoroutineSuspends.first);
1207   this->FinalSuspend = cast<Expr>(Fn.CoroutineSuspends.second);
1208   return true;
1209 }
1210
1211 static bool diagReturnOnAllocFailure(Sema &S, Expr *E,
1212                                      CXXRecordDecl *PromiseRecordDecl,
1213                                      FunctionScopeInfo &Fn) {
1214   auto Loc = E->getExprLoc();
1215   if (auto *DeclRef = dyn_cast_or_null<DeclRefExpr>(E)) {
1216     auto *Decl = DeclRef->getDecl();
1217     if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(Decl)) {
1218       if (Method->isStatic())
1219         return true;
1220       else
1221         Loc = Decl->getLocation();
1222     }
1223   }
1224
1225   S.Diag(
1226       Loc,
1227       diag::err_coroutine_promise_get_return_object_on_allocation_failure)
1228       << PromiseRecordDecl;
1229   S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1230       << Fn.getFirstCoroutineStmtKeyword();
1231   return false;
1232 }
1233
1234 bool CoroutineStmtBuilder::makeReturnOnAllocFailure() {
1235   assert(!IsPromiseDependentType &&
1236          "cannot make statement while the promise type is dependent");
1237
1238   // [dcl.fct.def.coroutine]p10
1239   //   If a search for the name get_return_object_on_allocation_failure in
1240   // the scope of the promise type ([class.member.lookup]) finds any
1241   // declarations, then the result of a call to an allocation function used to
1242   // obtain storage for the coroutine state is assumed to return nullptr if it
1243   // fails to obtain storage, ... If the allocation function returns nullptr,
1244   // ... and the return value is obtained by a call to
1245   // T::get_return_object_on_allocation_failure(), where T is the
1246   // promise type.
1247   DeclarationName DN =
1248       S.PP.getIdentifierInfo("get_return_object_on_allocation_failure");
1249   LookupResult Found(S, DN, Loc, Sema::LookupMemberName);
1250   if (!S.LookupQualifiedName(Found, PromiseRecordDecl))
1251     return true;
1252
1253   CXXScopeSpec SS;
1254   ExprResult DeclNameExpr =
1255       S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
1256   if (DeclNameExpr.isInvalid())
1257     return false;
1258
1259   if (!diagReturnOnAllocFailure(S, DeclNameExpr.get(), PromiseRecordDecl, Fn))
1260     return false;
1261
1262   ExprResult ReturnObjectOnAllocationFailure =
1263       S.BuildCallExpr(nullptr, DeclNameExpr.get(), Loc, {}, Loc);
1264   if (ReturnObjectOnAllocationFailure.isInvalid())
1265     return false;
1266
1267   StmtResult ReturnStmt =
1268       S.BuildReturnStmt(Loc, ReturnObjectOnAllocationFailure.get());
1269   if (ReturnStmt.isInvalid()) {
1270     S.Diag(Found.getFoundDecl()->getLocation(), diag::note_member_declared_here)
1271         << DN;
1272     S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1273         << Fn.getFirstCoroutineStmtKeyword();
1274     return false;
1275   }
1276
1277   this->ReturnStmtOnAllocFailure = ReturnStmt.get();
1278   return true;
1279 }
1280
1281 // Collect placement arguments for allocation function of coroutine FD.
1282 // Return true if we collect placement arguments succesfully. Return false,
1283 // otherwise.
1284 static bool collectPlacementArgs(Sema &S, FunctionDecl &FD, SourceLocation Loc,
1285                                  SmallVectorImpl<Expr *> &PlacementArgs) {
1286   if (auto *MD = dyn_cast<CXXMethodDecl>(&FD)) {
1287     if (MD->isInstance() && !isLambdaCallOperator(MD)) {
1288       ExprResult ThisExpr = S.ActOnCXXThis(Loc);
1289       if (ThisExpr.isInvalid())
1290         return false;
1291       ThisExpr = S.CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
1292       if (ThisExpr.isInvalid())
1293         return false;
1294       PlacementArgs.push_back(ThisExpr.get());
1295     }
1296   }
1297
1298   for (auto *PD : FD.parameters()) {
1299     if (PD->getType()->isDependentType())
1300       continue;
1301
1302     // Build a reference to the parameter.
1303     auto PDLoc = PD->getLocation();
1304     ExprResult PDRefExpr =
1305         S.BuildDeclRefExpr(PD, PD->getOriginalType().getNonReferenceType(),
1306                            ExprValueKind::VK_LValue, PDLoc);
1307     if (PDRefExpr.isInvalid())
1308       return false;
1309
1310     PlacementArgs.push_back(PDRefExpr.get());
1311   }
1312
1313   return true;
1314 }
1315
1316 bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
1317   // Form and check allocation and deallocation calls.
1318   assert(!IsPromiseDependentType &&
1319          "cannot make statement while the promise type is dependent");
1320   QualType PromiseType = Fn.CoroutinePromise->getType();
1321
1322   if (S.RequireCompleteType(Loc, PromiseType, diag::err_incomplete_type))
1323     return false;
1324
1325   const bool RequiresNoThrowAlloc = ReturnStmtOnAllocFailure != nullptr;
1326
1327   // According to [dcl.fct.def.coroutine]p9, Lookup allocation functions using a
1328   // parameter list composed of the requested size of the coroutine state being
1329   // allocated, followed by the coroutine function's arguments. If a matching
1330   // allocation function exists, use it. Otherwise, use an allocation function
1331   // that just takes the requested size.
1332   //
1333   // [dcl.fct.def.coroutine]p9
1334   //   An implementation may need to allocate additional storage for a
1335   //   coroutine.
1336   // This storage is known as the coroutine state and is obtained by calling a
1337   // non-array allocation function ([basic.stc.dynamic.allocation]). The
1338   // allocation function's name is looked up by searching for it in the scope of
1339   // the promise type.
1340   // - If any declarations are found, overload resolution is performed on a
1341   // function call created by assembling an argument list. The first argument is
1342   // the amount of space requested, and has type std::size_t. The
1343   // lvalues p1 ... pn are the succeeding arguments.
1344   //
1345   // ...where "p1 ... pn" are defined earlier as:
1346   //
1347   // [dcl.fct.def.coroutine]p3
1348   //   The promise type of a coroutine is `std::coroutine_traits<R, P1, ...,
1349   //   Pn>`
1350   // , where R is the return type of the function, and `P1, ..., Pn` are the
1351   // sequence of types of the non-object function parameters, preceded by the
1352   // type of the object parameter ([dcl.fct]) if the coroutine is a non-static
1353   // member function. [dcl.fct.def.coroutine]p4 In the following, p_i is an
1354   // lvalue of type P_i, where p1 denotes the object parameter and p_i+1 denotes
1355   // the i-th non-object function parameter for a non-static member function,
1356   // and p_i denotes the i-th function parameter otherwise. For a non-static
1357   // member function, q_1 is an lvalue that denotes *this; any other q_i is an
1358   // lvalue that denotes the parameter copy corresponding to p_i.
1359
1360   FunctionDecl *OperatorNew = nullptr;
1361   SmallVector<Expr *, 1> PlacementArgs;
1362
1363   const bool PromiseContainsNew = [this, &PromiseType]() -> bool {
1364     DeclarationName NewName =
1365         S.getASTContext().DeclarationNames.getCXXOperatorName(OO_New);
1366     LookupResult R(S, NewName, Loc, Sema::LookupOrdinaryName);
1367
1368     if (PromiseType->isRecordType())
1369       S.LookupQualifiedName(R, PromiseType->getAsCXXRecordDecl());
1370
1371     return !R.empty() && !R.isAmbiguous();
1372   }();
1373
1374   // Helper function to indicate whether the last lookup found the aligned
1375   // allocation function.
1376   bool PassAlignment = S.getLangOpts().CoroAlignedAllocation;
1377   auto LookupAllocationFunction = [&](Sema::AllocationFunctionScope NewScope =
1378                                           Sema::AFS_Both,
1379                                       bool WithoutPlacementArgs = false,
1380                                       bool ForceNonAligned = false) {
1381     // [dcl.fct.def.coroutine]p9
1382     //   The allocation function's name is looked up by searching for it in the
1383     // scope of the promise type.
1384     // - If any declarations are found, ...
1385     // - If no declarations are found in the scope of the promise type, a search
1386     // is performed in the global scope.
1387     if (NewScope == Sema::AFS_Both)
1388       NewScope = PromiseContainsNew ? Sema::AFS_Class : Sema::AFS_Global;
1389
1390     PassAlignment = !ForceNonAligned && S.getLangOpts().CoroAlignedAllocation;
1391     FunctionDecl *UnusedResult = nullptr;
1392     S.FindAllocationFunctions(Loc, SourceRange(), NewScope,
1393                               /*DeleteScope*/ Sema::AFS_Both, PromiseType,
1394                               /*isArray*/ false, PassAlignment,
1395                               WithoutPlacementArgs ? MultiExprArg{}
1396                                                    : PlacementArgs,
1397                               OperatorNew, UnusedResult, /*Diagnose*/ false);
1398   };
1399
1400   // We don't expect to call to global operator new with (size, p0, …, pn).
1401   // So if we choose to lookup the allocation function in global scope, we
1402   // shouldn't lookup placement arguments.
1403   if (PromiseContainsNew && !collectPlacementArgs(S, FD, Loc, PlacementArgs))
1404     return false;
1405
1406   LookupAllocationFunction();
1407
1408   if (PromiseContainsNew && !PlacementArgs.empty()) {
1409     // [dcl.fct.def.coroutine]p9
1410     //   If no viable function is found ([over.match.viable]), overload
1411     //   resolution
1412     // is performed again on a function call created by passing just the amount
1413     // of space required as an argument of type std::size_t.
1414     //
1415     // Proposed Change of [dcl.fct.def.coroutine]p9 in P2014R0:
1416     //   Otherwise, overload resolution is performed again on a function call
1417     //   created
1418     // by passing the amount of space requested as an argument of type
1419     // std::size_t as the first argument, and the requested alignment as
1420     // an argument of type std:align_val_t as the second argument.
1421     if (!OperatorNew ||
1422         (S.getLangOpts().CoroAlignedAllocation && !PassAlignment))
1423       LookupAllocationFunction(/*NewScope*/ Sema::AFS_Class,
1424                                /*WithoutPlacementArgs*/ true);
1425   }
1426
1427   // Proposed Change of [dcl.fct.def.coroutine]p12 in P2014R0:
1428   //   Otherwise, overload resolution is performed again on a function call
1429   //   created
1430   // by passing the amount of space requested as an argument of type
1431   // std::size_t as the first argument, and the lvalues p1 ... pn as the
1432   // succeeding arguments. Otherwise, overload resolution is performed again
1433   // on a function call created by passing just the amount of space required as
1434   // an argument of type std::size_t.
1435   //
1436   // So within the proposed change in P2014RO, the priority order of aligned
1437   // allocation functions wiht promise_type is:
1438   //
1439   //    void* operator new( std::size_t, std::align_val_t, placement_args... );
1440   //    void* operator new( std::size_t, std::align_val_t);
1441   //    void* operator new( std::size_t, placement_args... );
1442   //    void* operator new( std::size_t);
1443
1444   // Helper variable to emit warnings.
1445   bool FoundNonAlignedInPromise = false;
1446   if (PromiseContainsNew && S.getLangOpts().CoroAlignedAllocation)
1447     if (!OperatorNew || !PassAlignment) {
1448       FoundNonAlignedInPromise = OperatorNew;
1449
1450       LookupAllocationFunction(/*NewScope*/ Sema::AFS_Class,
1451                                /*WithoutPlacementArgs*/ false,
1452                                /*ForceNonAligned*/ true);
1453
1454       if (!OperatorNew && !PlacementArgs.empty())
1455         LookupAllocationFunction(/*NewScope*/ Sema::AFS_Class,
1456                                  /*WithoutPlacementArgs*/ true,
1457                                  /*ForceNonAligned*/ true);
1458     }
1459
1460   bool IsGlobalOverload =
1461       OperatorNew && !isa<CXXRecordDecl>(OperatorNew->getDeclContext());
1462   // If we didn't find a class-local new declaration and non-throwing new
1463   // was is required then we need to lookup the non-throwing global operator
1464   // instead.
1465   if (RequiresNoThrowAlloc && (!OperatorNew || IsGlobalOverload)) {
1466     auto *StdNoThrow = buildStdNoThrowDeclRef(S, Loc);
1467     if (!StdNoThrow)
1468       return false;
1469     PlacementArgs = {StdNoThrow};
1470     OperatorNew = nullptr;
1471     LookupAllocationFunction(Sema::AFS_Global);
1472   }
1473
1474   // If we found a non-aligned allocation function in the promise_type,
1475   // it indicates the user forgot to update the allocation function. Let's emit
1476   // a warning here.
1477   if (FoundNonAlignedInPromise) {
1478     S.Diag(OperatorNew->getLocation(),
1479            diag::warn_non_aligned_allocation_function)
1480         << &FD;
1481   }
1482
1483   if (!OperatorNew) {
1484     if (PromiseContainsNew)
1485       S.Diag(Loc, diag::err_coroutine_unusable_new) << PromiseType << &FD;
1486     else if (RequiresNoThrowAlloc)
1487       S.Diag(Loc, diag::err_coroutine_unfound_nothrow_new)
1488           << &FD << S.getLangOpts().CoroAlignedAllocation;
1489
1490     return false;
1491   }
1492
1493   if (RequiresNoThrowAlloc) {
1494     const auto *FT = OperatorNew->getType()->castAs<FunctionProtoType>();
1495     if (!FT->isNothrow(/*ResultIfDependent*/ false)) {
1496       S.Diag(OperatorNew->getLocation(),
1497              diag::err_coroutine_promise_new_requires_nothrow)
1498           << OperatorNew;
1499       S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
1500           << OperatorNew;
1501       return false;
1502     }
1503   }
1504
1505   FunctionDecl *OperatorDelete = nullptr;
1506   if (!findDeleteForPromise(S, Loc, PromiseType, OperatorDelete)) {
1507     // FIXME: We should add an error here. According to:
1508     // [dcl.fct.def.coroutine]p12
1509     //   If no usual deallocation function is found, the program is ill-formed.
1510     return false;
1511   }
1512
1513   Expr *FramePtr =
1514       S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});
1515
1516   Expr *FrameSize =
1517       S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_size, {});
1518
1519   Expr *FrameAlignment = nullptr;
1520
1521   if (S.getLangOpts().CoroAlignedAllocation) {
1522     FrameAlignment =
1523         S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_align, {});
1524
1525     TypeSourceInfo *AlignValTy = getTypeSourceInfoForStdAlignValT(S, Loc);
1526     if (!AlignValTy)
1527       return false;
1528
1529     FrameAlignment = S.BuildCXXNamedCast(Loc, tok::kw_static_cast, AlignValTy,
1530                                          FrameAlignment, SourceRange(Loc, Loc),
1531                                          SourceRange(Loc, Loc))
1532                          .get();
1533   }
1534
1535   // Make new call.
1536   ExprResult NewRef =
1537       S.BuildDeclRefExpr(OperatorNew, OperatorNew->getType(), VK_LValue, Loc);
1538   if (NewRef.isInvalid())
1539     return false;
1540
1541   SmallVector<Expr *, 2> NewArgs(1, FrameSize);
1542   if (S.getLangOpts().CoroAlignedAllocation && PassAlignment)
1543     NewArgs.push_back(FrameAlignment);
1544
1545   if (OperatorNew->getNumParams() > NewArgs.size())
1546     llvm::append_range(NewArgs, PlacementArgs);
1547
1548   ExprResult NewExpr =
1549       S.BuildCallExpr(S.getCurScope(), NewRef.get(), Loc, NewArgs, Loc);
1550   NewExpr = S.ActOnFinishFullExpr(NewExpr.get(), /*DiscardedValue*/ false);
1551   if (NewExpr.isInvalid())
1552     return false;
1553
1554   // Make delete call.
1555
1556   QualType OpDeleteQualType = OperatorDelete->getType();
1557
1558   ExprResult DeleteRef =
1559       S.BuildDeclRefExpr(OperatorDelete, OpDeleteQualType, VK_LValue, Loc);
1560   if (DeleteRef.isInvalid())
1561     return false;
1562
1563   Expr *CoroFree =
1564       S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_free, {FramePtr});
1565
1566   SmallVector<Expr *, 2> DeleteArgs{CoroFree};
1567
1568   // [dcl.fct.def.coroutine]p12
1569   //   The selected deallocation function shall be called with the address of
1570   //   the block of storage to be reclaimed as its first argument. If a
1571   //   deallocation function with a parameter of type std::size_t is
1572   //   used, the size of the block is passed as the corresponding argument.
1573   const auto *OpDeleteType =
1574       OpDeleteQualType.getTypePtr()->castAs<FunctionProtoType>();
1575   if (OpDeleteType->getNumParams() > DeleteArgs.size() &&
1576       S.getASTContext().hasSameUnqualifiedType(
1577           OpDeleteType->getParamType(DeleteArgs.size()), FrameSize->getType()))
1578     DeleteArgs.push_back(FrameSize);
1579
1580   // Proposed Change of [dcl.fct.def.coroutine]p12 in P2014R0:
1581   //   If deallocation function lookup finds a usual deallocation function with
1582   //   a pointer parameter, size parameter and alignment parameter then this
1583   //   will be the selected deallocation function, otherwise if lookup finds a
1584   //   usual deallocation function with both a pointer parameter and a size
1585   //   parameter, then this will be the selected deallocation function.
1586   //   Otherwise, if lookup finds a usual deallocation function with only a
1587   //   pointer parameter, then this will be the selected deallocation
1588   //   function.
1589   //
1590   // So we are not forced to pass alignment to the deallocation function.
1591   if (S.getLangOpts().CoroAlignedAllocation &&
1592       OpDeleteType->getNumParams() > DeleteArgs.size() &&
1593       S.getASTContext().hasSameUnqualifiedType(
1594           OpDeleteType->getParamType(DeleteArgs.size()),
1595           FrameAlignment->getType()))
1596     DeleteArgs.push_back(FrameAlignment);
1597
1598   ExprResult DeleteExpr =
1599       S.BuildCallExpr(S.getCurScope(), DeleteRef.get(), Loc, DeleteArgs, Loc);
1600   DeleteExpr =
1601       S.ActOnFinishFullExpr(DeleteExpr.get(), /*DiscardedValue*/ false);
1602   if (DeleteExpr.isInvalid())
1603     return false;
1604
1605   this->Allocate = NewExpr.get();
1606   this->Deallocate = DeleteExpr.get();
1607
1608   return true;
1609 }
1610
1611 bool CoroutineStmtBuilder::makeOnFallthrough() {
1612   assert(!IsPromiseDependentType &&
1613          "cannot make statement while the promise type is dependent");
1614
1615   // [dcl.fct.def.coroutine]/p6
1616   // If searches for the names return_void and return_value in the scope of
1617   // the promise type each find any declarations, the program is ill-formed.
1618   // [Note 1: If return_void is found, flowing off the end of a coroutine is
1619   // equivalent to a co_return with no operand. Otherwise, flowing off the end
1620   // of a coroutine results in undefined behavior ([stmt.return.coroutine]). —
1621   // end note]
1622   bool HasRVoid, HasRValue;
1623   LookupResult LRVoid =
1624       lookupMember(S, "return_void", PromiseRecordDecl, Loc, HasRVoid);
1625   LookupResult LRValue =
1626       lookupMember(S, "return_value", PromiseRecordDecl, Loc, HasRValue);
1627
1628   StmtResult Fallthrough;
1629   if (HasRVoid && HasRValue) {
1630     // FIXME Improve this diagnostic
1631     S.Diag(FD.getLocation(),
1632            diag::err_coroutine_promise_incompatible_return_functions)
1633         << PromiseRecordDecl;
1634     S.Diag(LRVoid.getRepresentativeDecl()->getLocation(),
1635            diag::note_member_first_declared_here)
1636         << LRVoid.getLookupName();
1637     S.Diag(LRValue.getRepresentativeDecl()->getLocation(),
1638            diag::note_member_first_declared_here)
1639         << LRValue.getLookupName();
1640     return false;
1641   } else if (!HasRVoid && !HasRValue) {
1642     // We need to set 'Fallthrough'. Otherwise the other analysis part might
1643     // think the coroutine has defined a return_value method. So it might emit
1644     // **false** positive warning. e.g.,
1645     //
1646     //    promise_without_return_func foo() {
1647     //        co_await something();
1648     //    }
1649     //
1650     // Then AnalysisBasedWarning would emit a warning about `foo()` lacking a
1651     // co_return statements, which isn't correct.
1652     Fallthrough = S.ActOnNullStmt(PromiseRecordDecl->getLocation());
1653     if (Fallthrough.isInvalid())
1654       return false;
1655   } else if (HasRVoid) {
1656     Fallthrough = S.BuildCoreturnStmt(FD.getLocation(), nullptr,
1657                                       /*IsImplicit*/false);
1658     Fallthrough = S.ActOnFinishFullStmt(Fallthrough.get());
1659     if (Fallthrough.isInvalid())
1660       return false;
1661   }
1662
1663   this->OnFallthrough = Fallthrough.get();
1664   return true;
1665 }
1666
1667 bool CoroutineStmtBuilder::makeOnException() {
1668   // Try to form 'p.unhandled_exception();'
1669   assert(!IsPromiseDependentType &&
1670          "cannot make statement while the promise type is dependent");
1671
1672   const bool RequireUnhandledException = S.getLangOpts().CXXExceptions;
1673
1674   if (!lookupMember(S, "unhandled_exception", PromiseRecordDecl, Loc)) {
1675     auto DiagID =
1676         RequireUnhandledException
1677             ? diag::err_coroutine_promise_unhandled_exception_required
1678             : diag::
1679                   warn_coroutine_promise_unhandled_exception_required_with_exceptions;
1680     S.Diag(Loc, DiagID) << PromiseRecordDecl;
1681     S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
1682         << PromiseRecordDecl;
1683     return !RequireUnhandledException;
1684   }
1685
1686   // If exceptions are disabled, don't try to build OnException.
1687   if (!S.getLangOpts().CXXExceptions)
1688     return true;
1689
1690   ExprResult UnhandledException = buildPromiseCall(
1691       S, Fn.CoroutinePromise, Loc, "unhandled_exception", std::nullopt);
1692   UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(), Loc,
1693                                              /*DiscardedValue*/ false);
1694   if (UnhandledException.isInvalid())
1695     return false;
1696
1697   // Since the body of the coroutine will be wrapped in try-catch, it will
1698   // be incompatible with SEH __try if present in a function.
1699   if (!S.getLangOpts().Borland && Fn.FirstSEHTryLoc.isValid()) {
1700     S.Diag(Fn.FirstSEHTryLoc, diag::err_seh_in_a_coroutine_with_cxx_exceptions);
1701     S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1702         << Fn.getFirstCoroutineStmtKeyword();
1703     return false;
1704   }
1705
1706   this->OnException = UnhandledException.get();
1707   return true;
1708 }
1709
1710 bool CoroutineStmtBuilder::makeReturnObject() {
1711   // [dcl.fct.def.coroutine]p7
1712   // The expression promise.get_return_object() is used to initialize the
1713   // returned reference or prvalue result object of a call to a coroutine.
1714   ExprResult ReturnObject = buildPromiseCall(S, Fn.CoroutinePromise, Loc,
1715                                              "get_return_object", std::nullopt);
1716   if (ReturnObject.isInvalid())
1717     return false;
1718
1719   this->ReturnValue = ReturnObject.get();
1720   return true;
1721 }
1722
1723 static void noteMemberDeclaredHere(Sema &S, Expr *E, FunctionScopeInfo &Fn) {
1724   if (auto *MbrRef = dyn_cast<CXXMemberCallExpr>(E)) {
1725     auto *MethodDecl = MbrRef->getMethodDecl();
1726     S.Diag(MethodDecl->getLocation(), diag::note_member_declared_here)
1727         << MethodDecl;
1728   }
1729   S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1730       << Fn.getFirstCoroutineStmtKeyword();
1731 }
1732
1733 bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
1734   assert(!IsPromiseDependentType &&
1735          "cannot make statement while the promise type is dependent");
1736   assert(this->ReturnValue && "ReturnValue must be already formed");
1737
1738   QualType const GroType = this->ReturnValue->getType();
1739   assert(!GroType->isDependentType() &&
1740          "get_return_object type must no longer be dependent");
1741
1742   QualType const FnRetType = FD.getReturnType();
1743   assert(!FnRetType->isDependentType() &&
1744          "get_return_object type must no longer be dependent");
1745
1746   // The call to get_return_object is sequenced before the call to
1747   // initial_suspend and is invoked at most once, but there are caveats
1748   // regarding on whether the prvalue result object may be initialized
1749   // directly/eager or delayed, depending on the types involved.
1750   //
1751   // More info at https://github.com/cplusplus/papers/issues/1414
1752   bool GroMatchesRetType = S.getASTContext().hasSameType(GroType, FnRetType);
1753
1754   if (FnRetType->isVoidType()) {
1755     ExprResult Res =
1756         S.ActOnFinishFullExpr(this->ReturnValue, Loc, /*DiscardedValue*/ false);
1757     if (Res.isInvalid())
1758       return false;
1759
1760     if (!GroMatchesRetType)
1761       this->ResultDecl = Res.get();
1762     return true;
1763   }
1764
1765   if (GroType->isVoidType()) {
1766     // Trigger a nice error message.
1767     InitializedEntity Entity =
1768         InitializedEntity::InitializeResult(Loc, FnRetType);
1769     S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
1770     noteMemberDeclaredHere(S, ReturnValue, Fn);
1771     return false;
1772   }
1773
1774   StmtResult ReturnStmt;
1775   clang::VarDecl *GroDecl = nullptr;
1776   if (GroMatchesRetType) {
1777     ReturnStmt = S.BuildReturnStmt(Loc, ReturnValue);
1778   } else {
1779     GroDecl = VarDecl::Create(
1780         S.Context, &FD, FD.getLocation(), FD.getLocation(),
1781         &S.PP.getIdentifierTable().get("__coro_gro"), GroType,
1782         S.Context.getTrivialTypeSourceInfo(GroType, Loc), SC_None);
1783     GroDecl->setImplicit();
1784
1785     S.CheckVariableDeclarationType(GroDecl);
1786     if (GroDecl->isInvalidDecl())
1787       return false;
1788
1789     InitializedEntity Entity = InitializedEntity::InitializeVariable(GroDecl);
1790     ExprResult Res =
1791         S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
1792     if (Res.isInvalid())
1793       return false;
1794
1795     Res = S.ActOnFinishFullExpr(Res.get(), /*DiscardedValue*/ false);
1796     if (Res.isInvalid())
1797       return false;
1798
1799     S.AddInitializerToDecl(GroDecl, Res.get(),
1800                            /*DirectInit=*/false);
1801
1802     S.FinalizeDeclaration(GroDecl);
1803
1804     // Form a declaration statement for the return declaration, so that AST
1805     // visitors can more easily find it.
1806     StmtResult GroDeclStmt =
1807         S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(GroDecl), Loc, Loc);
1808     if (GroDeclStmt.isInvalid())
1809       return false;
1810
1811     this->ResultDecl = GroDeclStmt.get();
1812
1813     ExprResult declRef = S.BuildDeclRefExpr(GroDecl, GroType, VK_LValue, Loc);
1814     if (declRef.isInvalid())
1815       return false;
1816
1817     ReturnStmt = S.BuildReturnStmt(Loc, declRef.get());
1818   }
1819
1820   if (ReturnStmt.isInvalid()) {
1821     noteMemberDeclaredHere(S, ReturnValue, Fn);
1822     return false;
1823   }
1824
1825   if (!GroMatchesRetType &&
1826       cast<clang::ReturnStmt>(ReturnStmt.get())->getNRVOCandidate() == GroDecl)
1827     GroDecl->setNRVOVariable(true);
1828
1829   this->ReturnStmt = ReturnStmt.get();
1830   return true;
1831 }
1832
1833 // Create a static_cast\<T&&>(expr).
1834 static Expr *castForMoving(Sema &S, Expr *E, QualType T = QualType()) {
1835   if (T.isNull())
1836     T = E->getType();
1837   QualType TargetType = S.BuildReferenceType(
1838       T, /*SpelledAsLValue*/ false, SourceLocation(), DeclarationName());
1839   SourceLocation ExprLoc = E->getBeginLoc();
1840   TypeSourceInfo *TargetLoc =
1841       S.Context.getTrivialTypeSourceInfo(TargetType, ExprLoc);
1842
1843   return S
1844       .BuildCXXNamedCast(ExprLoc, tok::kw_static_cast, TargetLoc, E,
1845                          SourceRange(ExprLoc, ExprLoc), E->getSourceRange())
1846       .get();
1847 }
1848
1849 /// Build a variable declaration for move parameter.
1850 static VarDecl *buildVarDecl(Sema &S, SourceLocation Loc, QualType Type,
1851                              IdentifierInfo *II) {
1852   TypeSourceInfo *TInfo = S.Context.getTrivialTypeSourceInfo(Type, Loc);
1853   VarDecl *Decl = VarDecl::Create(S.Context, S.CurContext, Loc, Loc, II, Type,
1854                                   TInfo, SC_None);
1855   Decl->setImplicit();
1856   return Decl;
1857 }
1858
1859 // Build statements that move coroutine function parameters to the coroutine
1860 // frame, and store them on the function scope info.
1861 bool Sema::buildCoroutineParameterMoves(SourceLocation Loc) {
1862   assert(isa<FunctionDecl>(CurContext) && "not in a function scope");
1863   auto *FD = cast<FunctionDecl>(CurContext);
1864
1865   auto *ScopeInfo = getCurFunction();
1866   if (!ScopeInfo->CoroutineParameterMoves.empty())
1867     return false;
1868
1869   // [dcl.fct.def.coroutine]p13
1870   //   When a coroutine is invoked, after initializing its parameters
1871   //   ([expr.call]), a copy is created for each coroutine parameter. For a
1872   //   parameter of type cv T, the copy is a variable of type cv T with
1873   //   automatic storage duration that is direct-initialized from an xvalue of
1874   //   type T referring to the parameter.
1875   for (auto *PD : FD->parameters()) {
1876     if (PD->getType()->isDependentType())
1877       continue;
1878
1879     ExprResult PDRefExpr =
1880         BuildDeclRefExpr(PD, PD->getType().getNonReferenceType(),
1881                          ExprValueKind::VK_LValue, Loc); // FIXME: scope?
1882     if (PDRefExpr.isInvalid())
1883       return false;
1884
1885     Expr *CExpr = nullptr;
1886     if (PD->getType()->getAsCXXRecordDecl() ||
1887         PD->getType()->isRValueReferenceType())
1888       CExpr = castForMoving(*this, PDRefExpr.get());
1889     else
1890       CExpr = PDRefExpr.get();
1891     // [dcl.fct.def.coroutine]p13
1892     //   The initialization and destruction of each parameter copy occurs in the
1893     //   context of the called coroutine.
1894     auto *D = buildVarDecl(*this, Loc, PD->getType(), PD->getIdentifier());
1895     AddInitializerToDecl(D, CExpr, /*DirectInit=*/true);
1896
1897     // Convert decl to a statement.
1898     StmtResult Stmt = ActOnDeclStmt(ConvertDeclToDeclGroup(D), Loc, Loc);
1899     if (Stmt.isInvalid())
1900       return false;
1901
1902     ScopeInfo->CoroutineParameterMoves.insert(std::make_pair(PD, Stmt.get()));
1903   }
1904   return true;
1905 }
1906
1907 StmtResult Sema::BuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs Args) {
1908   CoroutineBodyStmt *Res = CoroutineBodyStmt::Create(Context, Args);
1909   if (!Res)
1910     return StmtError();
1911   return Res;
1912 }
1913
1914 ClassTemplateDecl *Sema::lookupCoroutineTraits(SourceLocation KwLoc,
1915                                                SourceLocation FuncLoc) {
1916   if (StdCoroutineTraitsCache)
1917     return StdCoroutineTraitsCache;
1918
1919   IdentifierInfo const &TraitIdent =
1920       PP.getIdentifierTable().get("coroutine_traits");
1921
1922   NamespaceDecl *StdSpace = getStdNamespace();
1923   LookupResult Result(*this, &TraitIdent, FuncLoc, LookupOrdinaryName);
1924   bool Found = StdSpace && LookupQualifiedName(Result, StdSpace);
1925
1926   if (!Found) {
1927     // The goggles, we found nothing!
1928     Diag(KwLoc, diag::err_implied_coroutine_type_not_found)
1929         << "std::coroutine_traits";
1930     return nullptr;
1931   }
1932
1933   // coroutine_traits is required to be a class template.
1934   StdCoroutineTraitsCache = Result.getAsSingle<ClassTemplateDecl>();
1935   if (!StdCoroutineTraitsCache) {
1936     Result.suppressDiagnostics();
1937     NamedDecl *Found = *Result.begin();
1938     Diag(Found->getLocation(), diag::err_malformed_std_coroutine_traits);
1939     return nullptr;
1940   }
1941
1942   return StdCoroutineTraitsCache;
1943 }