/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp

Bug Summary

File:	clang/lib/Sema/SemaCoroutine.cpp
Warning:	line 675, column 13 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name SemaCoroutine.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -relaxed-aliasing -fmath-errno -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/build-llvm -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D CLANG_ROUND_TRIP_CC1_ARGS=ON -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I tools/clang/lib/Sema -I /build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema -I /build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/include -I tools/clang/include -I include -I /build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/llvm/include -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-command-line-argument -Wno-unknown-warning-option -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/build-llvm -ferror-limit 19 -fvisibility-inlines-hidden -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-11-10-160236-22541-1 -x c++ /build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/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//===----------------------------------------------------------------------===//

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"

29using namespace clang;
30using namespace sema;

32static LookupResult lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
                               SourceLocation Loc, bool &Res) {
DeclarationName DN = S.PP.getIdentifierInfo(Name);
LookupResult LR(S, DN, Loc, Sema::LookupMemberName);
// Suppress diagnostics when a private member is selected. The same warnings
// will be produced again when building the call.
LR.suppressDiagnostics();
Res = S.LookupQualifiedName(LR, RD);
return LR;
41}

43static bool lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
                       SourceLocation Loc) {
bool Res;
lookupMember(S, Name, RD, Loc, Res);
return Res;
48}

50/// Look up the std::coroutine_traits<...>::promise_type for the given
51/// function type.
52static QualType lookupPromiseType(Sema &S, const FunctionDecl *FD,
                                SourceLocation KwLoc) {
const FunctionProtoType *FnType = FD->getType()->castAs<FunctionProtoType>();
const SourceLocation FuncLoc = FD->getLocation();

NamespaceDecl *CoroNamespace = nullptr;
ClassTemplateDecl *CoroTraits =
    S.lookupCoroutineTraits(KwLoc, FuncLoc, CoroNamespace);
if (!CoroTraits) {
  return QualType();
}

// Form template argument list for coroutine_traits<R, P1, P2, ...> according
// to [dcl.fct.def.coroutine]3
TemplateArgumentListInfo Args(KwLoc, KwLoc);
auto AddArg = [&](QualType T) {
  Args.addArgument(TemplateArgumentLoc(
      TemplateArgument(T), S.Context.getTrivialTypeSourceInfo(T, KwLoc)));
};
AddArg(FnType->getReturnType());
// If the function is a non-static member function, add the type
// of the implicit object parameter before the formal parameters.
if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
  if (MD->isInstance()) {
    // [over.match.funcs]4
    // For non-static member functions, the type of the implicit object
    // parameter is
    //  -- "lvalue reference to cv X" for functions declared without a
    //      ref-qualifier or with the & ref-qualifier
    //  -- "rvalue reference to cv X" for functions declared with the &&
    //      ref-qualifier
    QualType T = MD->getThisType()->castAs<PointerType>()->getPointeeType();
    T = FnType->getRefQualifier() == RQ_RValue
            ? S.Context.getRValueReferenceType(T)
            : S.Context.getLValueReferenceType(T, /*SpelledAsLValue*/ true);
    AddArg(T);
  }
}
for (QualType T : FnType->getParamTypes())
  AddArg(T);

// Build the template-id.
QualType CoroTrait =
    S.CheckTemplateIdType(TemplateName(CoroTraits), KwLoc, Args);
if (CoroTrait.isNull())
  return QualType();
if (S.RequireCompleteType(KwLoc, CoroTrait,
                          diag::err_coroutine_type_missing_specialization))
  return QualType();

auto *RD = CoroTrait->getAsCXXRecordDecl();
assert(RD && "specialization of class template is not a class?")(static_cast <bool> (RD && "specialization of class template is not a class?"
) ? void (0) : __assert_fail ("RD && \"specialization of class template is not a class?\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 103, __extension__ __PRETTY_FUNCTION__));

// Look up the ::promise_type member.
LookupResult R(S, &S.PP.getIdentifierTable().get("promise_type"), KwLoc,
               Sema::LookupOrdinaryName);
S.LookupQualifiedName(R, RD);
auto *Promise = R.getAsSingle<TypeDecl>();
if (!Promise) {
  S.Diag(FuncLoc,
         diag::err_implied_std_coroutine_traits_promise_type_not_found)
      << RD;
  return QualType();
}
// The promise type is required to be a class type.
QualType PromiseType = S.Context.getTypeDeclType(Promise);

auto buildElaboratedType = [&]() {
  auto *NNS = NestedNameSpecifier::Create(S.Context, nullptr, CoroNamespace);
  NNS = NestedNameSpecifier::Create(S.Context, NNS, false,
                                    CoroTrait.getTypePtr());
  return S.Context.getElaboratedType(ETK_None, NNS, PromiseType);
};

if (!PromiseType->getAsCXXRecordDecl()) {
  S.Diag(FuncLoc,
         diag::err_implied_std_coroutine_traits_promise_type_not_class)
      << buildElaboratedType();
  return QualType();
}
if (S.RequireCompleteType(FuncLoc, buildElaboratedType(),
                          diag::err_coroutine_promise_type_incomplete))
  return QualType();

return PromiseType;
137}

139/// Look up the std::coroutine_handle<PromiseType>.
140static QualType lookupCoroutineHandleType(Sema &S, QualType PromiseType,
                                        SourceLocation Loc) {
if (PromiseType.isNull())
  return QualType();

NamespaceDecl *CoroNamespace = S.getCachedCoroNamespace();
assert(CoroNamespace && "Should already be diagnosed")(static_cast <bool> (CoroNamespace && "Should already be diagnosed"
) ? void (0) : __assert_fail ("CoroNamespace && \"Should already be diagnosed\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 146, __extension__ __PRETTY_FUNCTION__));

LookupResult Result(S, &S.PP.getIdentifierTable().get("coroutine_handle"),
                    Loc, Sema::LookupOrdinaryName);
if (!S.LookupQualifiedName(Result, CoroNamespace)) {
  S.Diag(Loc, diag::err_implied_coroutine_type_not_found)
      << "std::coroutine_handle";
  return QualType();
}

ClassTemplateDecl *CoroHandle = Result.getAsSingle<ClassTemplateDecl>();
if (!CoroHandle) {
  Result.suppressDiagnostics();
  // We found something weird. Complain about the first thing we found.
  NamedDecl *Found = *Result.begin();
  S.Diag(Found->getLocation(), diag::err_malformed_std_coroutine_handle);
  return QualType();
}

// Form template argument list for coroutine_handle<Promise>.
TemplateArgumentListInfo Args(Loc, Loc);
Args.addArgument(TemplateArgumentLoc(
    TemplateArgument(PromiseType),
    S.Context.getTrivialTypeSourceInfo(PromiseType, Loc)));

// Build the template-id.
QualType CoroHandleType =
    S.CheckTemplateIdType(TemplateName(CoroHandle), Loc, Args);
if (CoroHandleType.isNull())
  return QualType();
if (S.RequireCompleteType(Loc, CoroHandleType,
                          diag::err_coroutine_type_missing_specialization))
  return QualType();

return CoroHandleType;
181}

183static bool isValidCoroutineContext(Sema &S, SourceLocation Loc,
                                  StringRef Keyword) {
// [expr.await]p2 dictates that 'co_await' and 'co_yield' must be used within
// a function body.
// FIXME: This also covers [expr.await]p2: "An await-expression shall not
// appear in a default argument." But the diagnostic QoI here could be
// improved to inform the user that default arguments specifically are not
// allowed.
auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
if (!FD) {
  S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
                  ? diag::err_coroutine_objc_method
                  : diag::err_coroutine_outside_function) << Keyword;
  return false;
}

// An enumeration for mapping the diagnostic type to the correct diagnostic
// selection index.
enum InvalidFuncDiag {
  DiagCtor = 0,
  DiagDtor,
  DiagMain,
  DiagConstexpr,
  DiagAutoRet,
  DiagVarargs,
  DiagConsteval,
};
bool Diagnosed = false;
auto DiagInvalid = [&](InvalidFuncDiag ID) {
  S.Diag(Loc, diag::err_coroutine_invalid_func_context) << ID << Keyword;
  Diagnosed = true;
  return false;
};

// Diagnose when a constructor, destructor
// or the function 'main' are declared as a coroutine.
auto *MD = dyn_cast<CXXMethodDecl>(FD);
// [class.ctor]p11: "A constructor shall not be a coroutine."
if (MD && isa<CXXConstructorDecl>(MD))
  return DiagInvalid(DiagCtor);
// [class.dtor]p17: "A destructor shall not be a coroutine."
else if (MD && isa<CXXDestructorDecl>(MD))
  return DiagInvalid(DiagDtor);
// [basic.start.main]p3: "The function main shall not be a coroutine."
else if (FD->isMain())
  return DiagInvalid(DiagMain);

// Emit a diagnostics for each of the following conditions which is not met.
// [expr.const]p2: "An expression e is a core constant expression unless the
// evaluation of e [...] would evaluate one of the following expressions:
// [...] an await-expression [...] a yield-expression."
if (FD->isConstexpr())
  DiagInvalid(FD->isConsteval() ? DiagConsteval : DiagConstexpr);
// [dcl.spec.auto]p15: "A function declared with a return type that uses a
// placeholder type shall not be a coroutine."
if (FD->getReturnType()->isUndeducedType())
  DiagInvalid(DiagAutoRet);
// [dcl.fct.def.coroutine]p1: "The parameter-declaration-clause of the
// coroutine shall not terminate with an ellipsis that is not part of a
// parameter-declaration."
if (FD->isVariadic())
  DiagInvalid(DiagVarargs);

return !Diagnosed;
247}

249static ExprResult buildOperatorCoawaitLookupExpr(Sema &SemaRef, Scope *S,
                                               SourceLocation Loc) {
DeclarationName OpName =
    SemaRef.Context.DeclarationNames.getCXXOperatorName(OO_Coawait);
LookupResult Operators(SemaRef, OpName, SourceLocation(),
                       Sema::LookupOperatorName);
SemaRef.LookupName(Operators, S);

assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous")(static_cast <bool> (!Operators.isAmbiguous() &&
 "Operator lookup cannot be ambiguous") ? void (0) : __assert_fail
 ("!Operators.isAmbiguous() && \"Operator lookup cannot be ambiguous\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 257, __extension__ __PRETTY_FUNCTION__));
const auto &Functions = Operators.asUnresolvedSet();
bool IsOverloaded =
    Functions.size() > 1 ||
    (Functions.size() == 1 && isa<FunctionTemplateDecl>(*Functions.begin()));
Expr *CoawaitOp = UnresolvedLookupExpr::Create(
    SemaRef.Context, /*NamingClass*/ nullptr, NestedNameSpecifierLoc(),
    DeclarationNameInfo(OpName, Loc), /*RequiresADL*/ true, IsOverloaded,
    Functions.begin(), Functions.end());
assert(CoawaitOp)(static_cast <bool> (CoawaitOp) ? void (0) : __assert_fail
 ("CoawaitOp", "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 266, __extension__ __PRETTY_FUNCTION__));
return CoawaitOp;
268}

270/// Build a call to 'operator co_await' if there is a suitable operator for
271/// the given expression.
272static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, SourceLocation Loc,
                                         Expr *E,
                                         UnresolvedLookupExpr *Lookup) {
UnresolvedSet<16> Functions;
Functions.append(Lookup->decls_begin(), Lookup->decls_end());
return SemaRef.CreateOverloadedUnaryOp(Loc, UO_Coawait, Functions, E);
278}

280static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
                                         SourceLocation Loc, Expr *E) {
ExprResult R = buildOperatorCoawaitLookupExpr(SemaRef, S, Loc);
if (R.isInvalid())
  return ExprError();
return buildOperatorCoawaitCall(SemaRef, Loc, E,
                                cast<UnresolvedLookupExpr>(R.get()));
287}

289static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
                                     SourceLocation Loc) {
QualType CoroHandleType = lookupCoroutineHandleType(S, PromiseType, Loc);
if (CoroHandleType.isNull())
  return ExprError();

DeclContext *LookupCtx = S.computeDeclContext(CoroHandleType);
LookupResult Found(S, &S.PP.getIdentifierTable().get("from_address"), Loc,
                   Sema::LookupOrdinaryName);
if (!S.LookupQualifiedName(Found, LookupCtx)) {
  S.Diag(Loc, diag::err_coroutine_handle_missing_member)
      << "from_address";
  return ExprError();
}

Expr *FramePtr =
    S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});

CXXScopeSpec SS;
ExprResult FromAddr =
    S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
if (FromAddr.isInvalid())
  return ExprError();

return S.BuildCallExpr(nullptr, FromAddr.get(), Loc, FramePtr, Loc);
314}

316struct ReadySuspendResumeResult {
enum AwaitCallType { ACT_Ready, ACT_Suspend, ACT_Resume };
Expr *Results[3];
OpaqueValueExpr *OpaqueValue;
bool IsInvalid;
321};

323static ExprResult buildMemberCall(Sema &S, Expr *Base, SourceLocation Loc,
                                StringRef Name, MultiExprArg Args) {
DeclarationNameInfo NameInfo(&S.PP.getIdentifierTable().get(Name), Loc);

// FIXME: Fix BuildMemberReferenceExpr to take a const CXXScopeSpec&.
CXXScopeSpec SS;
ExprResult Result = S.BuildMemberReferenceExpr(
    Base, Base->getType(), Loc, /*IsPtr=*/false, SS,
    SourceLocation(), nullptr, NameInfo, /*TemplateArgs=*/nullptr,
    /*Scope=*/nullptr);
if (Result.isInvalid())
  return ExprError();

// We meant exactly what we asked for. No need for typo correction.
if (auto *TE = dyn_cast<TypoExpr>(Result.get())) {
  S.clearDelayedTypo(TE);
  S.Diag(Loc, diag::err_no_member)
      << NameInfo.getName() << Base->getType()->getAsCXXRecordDecl()
      << Base->getSourceRange();
  return ExprError();
}

return S.BuildCallExpr(nullptr, Result.get(), Loc, Args, Loc, nullptr);
346}

348// See if return type is coroutine-handle and if so, invoke builtin coro-resume
349// on its address. This is to enable experimental support for coroutine-handle
350// returning await_suspend that results in a guaranteed tail call to the target
351// coroutine.
352static Expr *maybeTailCall(Sema &S, QualType RetType, Expr *E,
                         SourceLocation Loc) {
if (RetType->isReferenceType())
  return nullptr;
Type const *T = RetType.getTypePtr();
if (!T->isClassType() && !T->isStructureType())
  return nullptr;

// FIXME: Add convertability check to coroutine_handle<>. Possibly via
// EvaluateBinaryTypeTrait(BTT_IsConvertible, ...) which is at the moment
// a private function in SemaExprCXX.cpp

ExprResult AddressExpr = buildMemberCall(S, E, Loc, "address", None);
if (AddressExpr.isInvalid())
  return nullptr;

Expr *JustAddress = AddressExpr.get();

// Check that the type of AddressExpr is void*
if (!JustAddress->getType().getTypePtr()->isVoidPointerType())
  S.Diag(cast<CallExpr>(JustAddress)->getCalleeDecl()->getLocation(),
         diag::warn_coroutine_handle_address_invalid_return_type)
      << JustAddress->getType();

// Clean up temporary objects so that they don't live across suspension points
// unnecessarily. We choose to clean up before the call to
// __builtin_coro_resume so that the cleanup code are not inserted in-between
// the resume call and return instruction, which would interfere with the
// musttail call contract.
JustAddress = S.MaybeCreateExprWithCleanups(JustAddress);
return S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_resume,
                              JustAddress);
384}

386/// Build calls to await_ready, await_suspend, and await_resume for a co_await
387/// expression.
388/// The generated AST tries to clean up temporary objects as early as
389/// possible so that they don't live across suspension points if possible.
390/// Having temporary objects living across suspension points unnecessarily can
391/// lead to large frame size, and also lead to memory corruptions if the
392/// coroutine frame is destroyed after coming back from suspension. This is done
393/// by wrapping both the await_ready call and the await_suspend call with
394/// ExprWithCleanups. In the end of this function, we also need to explicitly
395/// set cleanup state so that the CoawaitExpr is also wrapped with an
396/// ExprWithCleanups to clean up the awaiter associated with the co_await
397/// expression.
398static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
                                                SourceLocation Loc, Expr *E) {
OpaqueValueExpr *Operand = new (S.Context)
    OpaqueValueExpr(Loc, E->getType(), VK_LValue, E->getObjectKind(), E);

// Assume valid until we see otherwise.
// Further operations are responsible for setting IsInalid to true.
ReadySuspendResumeResult Calls = {{}, Operand, /*IsInvalid=*/false};

using ACT = ReadySuspendResumeResult::AwaitCallType;

auto BuildSubExpr = [&](ACT CallType, StringRef Func,
                        MultiExprArg Arg) -> Expr * {
  ExprResult Result = buildMemberCall(S, Operand, Loc, Func, Arg);
  if (Result.isInvalid()) {
    Calls.IsInvalid = true;
    return nullptr;
  }
  Calls.Results[CallType] = Result.get();
  return Result.get();
};

CallExpr *AwaitReady =
    cast_or_null<CallExpr>(BuildSubExpr(ACT::ACT_Ready, "await_ready", None));
if (!AwaitReady)
  return Calls;
if (!AwaitReady->getType()->isDependentType()) {
  // [expr.await]p3 [...]
  // — await-ready is the expression e.await_ready(), contextually converted
  // to bool.
  ExprResult Conv = S.PerformContextuallyConvertToBool(AwaitReady);
  if (Conv.isInvalid()) {
    S.Diag(AwaitReady->getDirectCallee()->getBeginLoc(),
           diag::note_await_ready_no_bool_conversion);
    S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
        << AwaitReady->getDirectCallee() << E->getSourceRange();
    Calls.IsInvalid = true;
  } else
    Calls.Results[ACT::ACT_Ready] = S.MaybeCreateExprWithCleanups(Conv.get());
}

ExprResult CoroHandleRes =
    buildCoroutineHandle(S, CoroPromise->getType(), Loc);
if (CoroHandleRes.isInvalid()) {
  Calls.IsInvalid = true;
  return Calls;
}
Expr *CoroHandle = CoroHandleRes.get();
CallExpr *AwaitSuspend = cast_or_null<CallExpr>(
    BuildSubExpr(ACT::ACT_Suspend, "await_suspend", CoroHandle));
if (!AwaitSuspend)
  return Calls;
if (!AwaitSuspend->getType()->isDependentType()) {
  // [expr.await]p3 [...]
  //   - await-suspend is the expression e.await_suspend(h), which shall be
  //     a prvalue of type void, bool, or std::coroutine_handle<Z> for some
  //     type Z.
  QualType RetType = AwaitSuspend->getCallReturnType(S.Context);

  // Experimental support for coroutine_handle returning await_suspend.
  if (Expr *TailCallSuspend =
          maybeTailCall(S, RetType, AwaitSuspend, Loc))
    // Note that we don't wrap the expression with ExprWithCleanups here
    // because that might interfere with tailcall contract (e.g. inserting
    // clean up instructions in-between tailcall and return). Instead
    // ExprWithCleanups is wrapped within maybeTailCall() prior to the resume
    // call.
    Calls.Results[ACT::ACT_Suspend] = TailCallSuspend;
  else {
    // non-class prvalues always have cv-unqualified types
    if (RetType->isReferenceType() ||
        (!RetType->isBooleanType() && !RetType->isVoidType())) {
      S.Diag(AwaitSuspend->getCalleeDecl()->getLocation(),
             diag::err_await_suspend_invalid_return_type)
          << RetType;
      S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
          << AwaitSuspend->getDirectCallee();
      Calls.IsInvalid = true;
    } else
      Calls.Results[ACT::ACT_Suspend] =
          S.MaybeCreateExprWithCleanups(AwaitSuspend);
  }
}

BuildSubExpr(ACT::ACT_Resume, "await_resume", None);

// Make sure the awaiter object gets a chance to be cleaned up.
S.Cleanup.setExprNeedsCleanups(true);

return Calls;
488}

490static ExprResult buildPromiseCall(Sema &S, VarDecl *Promise,
                                 SourceLocation Loc, StringRef Name,
                                 MultiExprArg Args) {

// Form a reference to the promise.
ExprResult PromiseRef = S.BuildDeclRefExpr(
    Promise, Promise->getType().getNonReferenceType(), VK_LValue, Loc);
if (PromiseRef.isInvalid())
  return ExprError();

return buildMemberCall(S, PromiseRef.get(), Loc, Name, Args);
501}

503VarDecl *Sema::buildCoroutinePromise(SourceLocation Loc) {
assert(isa<FunctionDecl>(CurContext) && "not in a function scope")(static_cast <bool> (isa<FunctionDecl>(CurContext
) && "not in a function scope") ? void (0) : __assert_fail
 ("isa<FunctionDecl>(CurContext) && \"not in a function scope\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 504, __extension__ __PRETTY_FUNCTION__));
auto *FD = cast<FunctionDecl>(CurContext);
bool IsThisDependentType = [&] {
  if (auto *MD = dyn_cast_or_null<CXXMethodDecl>(FD))
    return MD->isInstance() && MD->getThisType()->isDependentType();
  else
    return false;
}();

QualType T = FD->getType()->isDependentType() || IsThisDependentType
                 ? Context.DependentTy
                 : lookupPromiseType(*this, FD, Loc);
if (T.isNull())
  return nullptr;

auto *VD = VarDecl::Create(Context, FD, FD->getLocation(), FD->getLocation(),
                           &PP.getIdentifierTable().get("__promise"), T,
                           Context.getTrivialTypeSourceInfo(T, Loc), SC_None);
VD->setImplicit();
CheckVariableDeclarationType(VD);
if (VD->isInvalidDecl())
  return nullptr;

auto *ScopeInfo = getCurFunction();

// Build a list of arguments, based on the coroutine function's arguments,
// that if present will be passed to the promise type's constructor.
llvm::SmallVector<Expr *, 4> CtorArgExprs;

// Add implicit object parameter.
if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
  if (MD->isInstance() && !isLambdaCallOperator(MD)) {
    ExprResult ThisExpr = ActOnCXXThis(Loc);
    if (ThisExpr.isInvalid())
      return nullptr;
    ThisExpr = CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
    if (ThisExpr.isInvalid())
      return nullptr;
    CtorArgExprs.push_back(ThisExpr.get());
  }
}

// Add the coroutine function's parameters.
auto &Moves = ScopeInfo->CoroutineParameterMoves;
for (auto *PD : FD->parameters()) {
  if (PD->getType()->isDependentType())
    continue;

  auto RefExpr = ExprEmpty();
  auto Move = Moves.find(PD);
  assert(Move != Moves.end() &&(static_cast <bool> (Move != Moves.end() && "Coroutine function parameter not inserted into move map"
) ? void (0) : __assert_fail ("Move != Moves.end() && \"Coroutine function parameter not inserted into move map\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 555, __extension__ __PRETTY_FUNCTION__))
         "Coroutine function parameter not inserted into move map")(static_cast <bool> (Move != Moves.end() && "Coroutine function parameter not inserted into move map"
) ? void (0) : __assert_fail ("Move != Moves.end() && \"Coroutine function parameter not inserted into move map\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 555, __extension__ __PRETTY_FUNCTION__));
  // If a reference to the function parameter exists in the coroutine
  // frame, use that reference.
  auto *MoveDecl =
      cast<VarDecl>(cast<DeclStmt>(Move->second)->getSingleDecl());
  RefExpr =
      BuildDeclRefExpr(MoveDecl, MoveDecl->getType().getNonReferenceType(),
                       ExprValueKind::VK_LValue, FD->getLocation());
  if (RefExpr.isInvalid())
    return nullptr;
  CtorArgExprs.push_back(RefExpr.get());
}

// If we have a non-zero number of constructor arguments, try to use them.
// Otherwise, fall back to the promise type's default constructor.
if (!CtorArgExprs.empty()) {
  // Create an initialization sequence for the promise type using the
  // constructor arguments, wrapped in a parenthesized list expression.
  Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
                                    CtorArgExprs, FD->getLocation());
  InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
  InitializationKind Kind = InitializationKind::CreateForInit(
      VD->getLocation(), /*DirectInit=*/true, PLE);
  InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
                                 /*TopLevelOfInitList=*/false,
                                 /*TreatUnavailableAsInvalid=*/false);

  // Attempt to initialize the promise type with the arguments.
  // If that fails, fall back to the promise type's default constructor.
  if (InitSeq) {
    ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
    if (Result.isInvalid()) {
      VD->setInvalidDecl();
    } else if (Result.get()) {
      VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
      VD->setInitStyle(VarDecl::CallInit);
      CheckCompleteVariableDeclaration(VD);
    }
  } else
    ActOnUninitializedDecl(VD);
} else
  ActOnUninitializedDecl(VD);

FD->addDecl(VD);
return VD;
600}

602/// Check that this is a context in which a coroutine suspension can appear.
603static FunctionScopeInfo *checkCoroutineContext(Sema &S, SourceLocation Loc,
                                              StringRef Keyword,
                                              bool IsImplicit = false) {
if (!isValidCoroutineContext(S, Loc, Keyword))
  return nullptr;

assert(isa<FunctionDecl>(S.CurContext) && "not in a function scope")(static_cast <bool> (isa<FunctionDecl>(S.CurContext
) && "not in a function scope") ? void (0) : __assert_fail
 ("isa<FunctionDecl>(S.CurContext) && \"not in a function scope\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 609, __extension__ __PRETTY_FUNCTION__));

auto *ScopeInfo = S.getCurFunction();
assert(ScopeInfo && "missing function scope for function")(static_cast <bool> (ScopeInfo && "missing function scope for function"
) ? void (0) : __assert_fail ("ScopeInfo && \"missing function scope for function\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 612, __extension__ __PRETTY_FUNCTION__));

if (ScopeInfo->FirstCoroutineStmtLoc.isInvalid() && !IsImplicit)
  ScopeInfo->setFirstCoroutineStmt(Loc, Keyword);

if (ScopeInfo->CoroutinePromise)
  return ScopeInfo;

if (!S.buildCoroutineParameterMoves(Loc))
  return nullptr;

ScopeInfo->CoroutinePromise = S.buildCoroutinePromise(Loc);
if (!ScopeInfo->CoroutinePromise)
  return nullptr;

return ScopeInfo;
628}

630/// Recursively check \p E and all its children to see if any call target
631/// (including constructor call) is declared noexcept. Also any value returned
632/// from the call has a noexcept destructor.
633static void checkNoThrow(Sema &S, const Stmt *E,
                       llvm::SmallPtrSetImpl<const Decl *> &ThrowingDecls) {
auto checkDeclNoexcept = [&](const Decl *D, bool IsDtor = false) {
  // In the case of dtor, the call to dtor is implicit and hence we should
  // pass nullptr to canCalleeThrow.
  if (Sema::canCalleeThrow(S, IsDtor ? nullptr : cast<Expr>(E), D)) {
    if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
      // co_await promise.final_suspend() could end up calling
      // __builtin_coro_resume for symmetric transfer if await_suspend()
      // returns a handle. In that case, even __builtin_coro_resume is not
      // declared as noexcept and may throw, it does not throw _into_ the
      // coroutine that just suspended, but rather throws back out from
      // whoever called coroutine_handle::resume(), hence we claim that
      // logically it does not throw.
      if (FD->getBuiltinID() == Builtin::BI__builtin_coro_resume)
        return;
    }
    if (ThrowingDecls.empty()) {
      // First time seeing an error, emit the error message.
      S.Diag(cast<FunctionDecl>(S.CurContext)->getLocation(),
             diag::err_coroutine_promise_final_suspend_requires_nothrow);
    }
    ThrowingDecls.insert(D);
  }
};
auto SC = E->getStmtClass();
if (SC == Expr::CXXConstructExprClass) {
13
←
Assuming 'SC' is not equal to CXXConstructExprClass→
21
←
Assuming 'SC' is not equal to CXXConstructExprClass→
  auto const *Ctor = cast<CXXConstructExpr>(E)->getConstructor();
  checkDeclNoexcept(Ctor);
  // Check the corresponding destructor of the constructor.
  checkDeclNoexcept(Ctor->getParent()->getDestructor(), true);
} else if (SC == Expr::CallExprClass || SC == Expr::CXXMemberCallExprClass ||
14
←
Assuming 'SC' is not equal to CallExprClass→
15
←
Assuming 'SC' is not equal to CXXMemberCallExprClass→
17
←
Taking false branch→
22
←
Assuming 'SC' is equal to CallExprClass→
           SC == Expr::CXXOperatorCallExprClass) {
16
←
Assuming 'SC' is not equal to CXXOperatorCallExprClass→
  if (!cast<CallExpr>(E)->isTypeDependent()) {
23
←
'E' is a 'CallExpr'→
24
←
Assuming the condition is true→
25
←
Taking true branch→
    checkDeclNoexcept(cast<CallExpr>(E)->getCalleeDecl());
26
←
'E' is a 'CallExpr'→
    auto ReturnType = cast<CallExpr>(E)->getCallReturnType(S.getASTContext());
27
←
'E' is a 'CallExpr'→
    // Check the destructor of the call return type, if any.
    if (ReturnType.isDestructedType() ==
28
←
Assuming the condition is true→
29
←
Taking true branch→
        QualType::DestructionKind::DK_cxx_destructor) {
      const auto *T =
          cast<RecordType>(ReturnType.getCanonicalType().getTypePtr());
30
←
The object is a 'RecordType'→
      checkDeclNoexcept(
          dyn_cast<CXXRecordDecl>(T->getDecl())->getDestructor(), true);
31
←
Assuming the object is not a 'CXXRecordDecl'→
32
←
Called C++ object pointer is null
    }
  }
}
for (const auto *Child : E->children()) {
  if (!Child)
18
←
Assuming 'Child' is non-null→
19
←
Taking false branch→
    continue;
  checkNoThrow(S, Child, ThrowingDecls);
20
←
Calling 'checkNoThrow'→
}
684}

686bool Sema::checkFinalSuspendNoThrow(const Stmt *FinalSuspend) {
llvm::SmallPtrSet<const Decl *, 4> ThrowingDecls;
// We first collect all declarations that should not throw but not declared
// with noexcept. We then sort them based on the location before printing.
// This is to avoid emitting the same note multiple times on the same
// declaration, and also provide a deterministic order for the messages.
checkNoThrow(*this, FinalSuspend, ThrowingDecls);
12
←
Calling 'checkNoThrow'→
auto SortedDecls = llvm::SmallVector<const Decl *, 4>{ThrowingDecls.begin(),
                                                      ThrowingDecls.end()};
sort(SortedDecls, [](const Decl *A, const Decl *B) {
  return A->getEndLoc() < B->getEndLoc();
});
for (const auto *D : SortedDecls) {
  Diag(D->getEndLoc(), diag::note_coroutine_function_declare_noexcept);
}
return ThrowingDecls.empty();
702}

704bool Sema::ActOnCoroutineBodyStart(Scope *SC, SourceLocation KWLoc,
                                 StringRef Keyword) {
if (!checkCoroutineContext(*this, KWLoc, Keyword))
2
←
Taking false branch→
  return false;
auto *ScopeInfo = getCurFunction();
assert(ScopeInfo->CoroutinePromise)(static_cast <bool> (ScopeInfo->CoroutinePromise) ? void
 (0) : __assert_fail ("ScopeInfo->CoroutinePromise", "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 709, __extension__ __PRETTY_FUNCTION__));
3
←
Assuming field 'CoroutinePromise' is non-null→
4
←
'?' condition is true→

// If we have existing coroutine statements then we have already built
// the initial and final suspend points.
if (!ScopeInfo->NeedsCoroutineSuspends)
5
←
Assuming field 'NeedsCoroutineSuspends' is true→
6
←
Taking false branch→
  return true;

ScopeInfo->setNeedsCoroutineSuspends(false);

auto *Fn = cast<FunctionDecl>(CurContext);
7
←
Field 'CurContext' is a 'FunctionDecl'→
SourceLocation Loc = Fn->getLocation();
// Build the initial suspend point
auto buildSuspends = [&](StringRef Name) mutable -> StmtResult {
  ExprResult Suspend =
      buildPromiseCall(*this, ScopeInfo->CoroutinePromise, Loc, Name, None);
  if (Suspend.isInvalid())
    return StmtError();
  Suspend = buildOperatorCoawaitCall(*this, SC, Loc, Suspend.get());
  if (Suspend.isInvalid())
    return StmtError();
  Suspend = BuildResolvedCoawaitExpr(Loc, Suspend.get(),
                                     /*IsImplicit*/ true);
  Suspend = ActOnFinishFullExpr(Suspend.get(), /*DiscardedValue*/ false);
  if (Suspend.isInvalid()) {
    Diag(Loc, diag::note_coroutine_promise_suspend_implicitly_required)
        << ((Name == "initial_suspend") ? 0 : 1);
    Diag(KWLoc, diag::note_declared_coroutine_here) << Keyword;
    return StmtError();
  }
  return cast<Stmt>(Suspend.get());
};

StmtResult InitSuspend = buildSuspends("initial_suspend");
if (InitSuspend.isInvalid())
8
←
Assuming the condition is false→
9
←
Taking false branch→
  return true;

StmtResult FinalSuspend = buildSuspends("final_suspend");
if (FinalSuspend.isInvalid() || !checkFinalSuspendNoThrow(FinalSuspend.get()))
10
←
Assuming the condition is false→
11
←
Calling 'Sema::checkFinalSuspendNoThrow'→
  return true;

ScopeInfo->setCoroutineSuspends(InitSuspend.get(), FinalSuspend.get());

return true;
752}

754// Recursively walks up the scope hierarchy until either a 'catch' or a function
755// scope is found, whichever comes first.
756static bool isWithinCatchScope(Scope *S) {
// 'co_await' and 'co_yield' keywords are disallowed within catch blocks, but
// lambdas that use 'co_await' are allowed. The loop below ends when a
// function scope is found in order to ensure the following behavior:
//
// void foo() {      // <- function scope
//   try {           //
//     co_await x;   // <- 'co_await' is OK within a function scope
//   } catch {       // <- catch scope
//     co_await x;   // <- 'co_await' is not OK within a catch scope
//     []() {        // <- function scope
//       co_await x; // <- 'co_await' is OK within a function scope
//     }();
//   }
// }
while (S && !(S->getFlags() & Scope::FnScope)) {
  if (S->getFlags() & Scope::CatchScope)
    return true;
  S = S->getParent();
}
return false;
777}

779// [expr.await]p2, emphasis added: "An await-expression shall appear only in
780// a *potentially evaluated* expression within the compound-statement of a
781// function-body *outside of a handler* [...] A context within a function
782// where an await-expression can appear is called a suspension context of the
783// function."
784static void checkSuspensionContext(Sema &S, SourceLocation Loc,
                                 StringRef Keyword) {
// First emphasis of [expr.await]p2: must be a potentially evaluated context.
// That is, 'co_await' and 'co_yield' cannot appear in subexpressions of
// \c sizeof.
if (S.isUnevaluatedContext())
  S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;

// Second emphasis of [expr.await]p2: must be outside of an exception handler.
if (isWithinCatchScope(S.getCurScope()))
  S.Diag(Loc, diag::err_coroutine_within_handler) << Keyword;
795}

797ExprResult Sema::ActOnCoawaitExpr(Scope *S, SourceLocation Loc, Expr *E) {
if (!ActOnCoroutineBodyStart(S, Loc, "co_await")) {
  CorrectDelayedTyposInExpr(E);
  return ExprError();
}

checkSuspensionContext(*this, Loc, "co_await");

if (E->getType()->isPlaceholderType()) {
  ExprResult R = CheckPlaceholderExpr(E);
  if (R.isInvalid()) return ExprError();
  E = R.get();
}
ExprResult Lookup = buildOperatorCoawaitLookupExpr(*this, S, Loc);
if (Lookup.isInvalid())
  return ExprError();
return BuildUnresolvedCoawaitExpr(Loc, E,
                                 cast<UnresolvedLookupExpr>(Lookup.get()));
815}

817ExprResult Sema::BuildUnresolvedCoawaitExpr(SourceLocation Loc, Expr *E,
                                          UnresolvedLookupExpr *Lookup) {
auto *FSI = checkCoroutineContext(*this, Loc, "co_await");
if (!FSI)
  return ExprError();

if (E->getType()->isPlaceholderType()) {
  ExprResult R = CheckPlaceholderExpr(E);
  if (R.isInvalid())
    return ExprError();
  E = R.get();
}

auto *Promise = FSI->CoroutinePromise;
if (Promise->getType()->isDependentType()) {
  Expr *Res =
      new (Context) DependentCoawaitExpr(Loc, Context.DependentTy, E, Lookup);
  return Res;
}

auto *RD = Promise->getType()->getAsCXXRecordDecl();
if (lookupMember(*this, "await_transform", RD, Loc)) {
  ExprResult R = buildPromiseCall(*this, Promise, Loc, "await_transform", E);
  if (R.isInvalid()) {
    Diag(Loc,
         diag::note_coroutine_promise_implicit_await_transform_required_here)
        << E->getSourceRange();
    return ExprError();
  }
  E = R.get();
}
ExprResult Awaitable = buildOperatorCoawaitCall(*this, Loc, E, Lookup);
if (Awaitable.isInvalid())
  return ExprError();

return BuildResolvedCoawaitExpr(Loc, Awaitable.get());
853}

855ExprResult Sema::BuildResolvedCoawaitExpr(SourceLocation Loc, Expr *E,
                                bool IsImplicit) {
auto *Coroutine = checkCoroutineContext(*this, Loc, "co_await", IsImplicit);
if (!Coroutine)
  return ExprError();

if (E->getType()->isPlaceholderType()) {
  ExprResult R = CheckPlaceholderExpr(E);
  if (R.isInvalid()) return ExprError();
  E = R.get();
}

if (E->getType()->isDependentType()) {
  Expr *Res = new (Context)
      CoawaitExpr(Loc, Context.DependentTy, E, IsImplicit);
  return Res;
}

// If the expression is a temporary, materialize it as an lvalue so that we
// can use it multiple times.
if (E->isPRValue())
  E = CreateMaterializeTemporaryExpr(E->getType(), E, true);

// The location of the `co_await` token cannot be used when constructing
// the member call expressions since it's before the location of `Expr`, which
// is used as the start of the member call expression.
SourceLocation CallLoc = E->getExprLoc();

// Build the await_ready, await_suspend, await_resume calls.
ReadySuspendResumeResult RSS = buildCoawaitCalls(
    *this, Coroutine->CoroutinePromise, CallLoc, E);
if (RSS.IsInvalid)
  return ExprError();

Expr *Res =
    new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
                              RSS.Results[2], RSS.OpaqueValue, IsImplicit);

return Res;
894}

896ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) {
if (!ActOnCoroutineBodyStart(S, Loc, "co_yield")) {
  CorrectDelayedTyposInExpr(E);
  return ExprError();
}

checkSuspensionContext(*this, Loc, "co_yield");

// Build yield_value call.
ExprResult Awaitable = buildPromiseCall(
    *this, getCurFunction()->CoroutinePromise, Loc, "yield_value", E);
if (Awaitable.isInvalid())
  return ExprError();

// Build 'operator co_await' call.
Awaitable = buildOperatorCoawaitCall(*this, S, Loc, Awaitable.get());
if (Awaitable.isInvalid())
  return ExprError();

return BuildCoyieldExpr(Loc, Awaitable.get());
916}
917ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
auto *Coroutine = checkCoroutineContext(*this, Loc, "co_yield");
if (!Coroutine)
  return ExprError();

if (E->getType()->isPlaceholderType()) {
  ExprResult R = CheckPlaceholderExpr(E);
  if (R.isInvalid()) return ExprError();
  E = R.get();
}

if (E->getType()->isDependentType()) {
  Expr *Res = new (Context) CoyieldExpr(Loc, Context.DependentTy, E);
  return Res;
}

// If the expression is a temporary, materialize it as an lvalue so that we
// can use it multiple times.
if (E->isPRValue())
  E = CreateMaterializeTemporaryExpr(E->getType(), E, true);

// Build the await_ready, await_suspend, await_resume calls.
ReadySuspendResumeResult RSS = buildCoawaitCalls(
    *this, Coroutine->CoroutinePromise, Loc, E);
if (RSS.IsInvalid)
  return ExprError();

Expr *Res =
    new (Context) CoyieldExpr(Loc, E, RSS.Results[0], RSS.Results[1],
                              RSS.Results[2], RSS.OpaqueValue);

return Res;
949}

951StmtResult Sema::ActOnCoreturnStmt(Scope *S, SourceLocation Loc, Expr *E) {
if (!ActOnCoroutineBodyStart(S, Loc, "co_return")) {
1
Calling 'Sema::ActOnCoroutineBodyStart'→
  CorrectDelayedTyposInExpr(E);
  return StmtError();
}
return BuildCoreturnStmt(Loc, E);
957}

959StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E,
                                 bool IsImplicit) {
auto *FSI = checkCoroutineContext(*this, Loc, "co_return", IsImplicit);
if (!FSI)
  return StmtError();

if (E && E->getType()->isPlaceholderType() &&
    !E->getType()->isSpecificPlaceholderType(BuiltinType::Overload)) {
  ExprResult R = CheckPlaceholderExpr(E);
  if (R.isInvalid()) return StmtError();
  E = R.get();
}

VarDecl *Promise = FSI->CoroutinePromise;
ExprResult PC;
if (E && (isa<InitListExpr>(E) || !E->getType()->isVoidType())) {
  getNamedReturnInfo(E, SimplerImplicitMoveMode::ForceOn);
  PC = buildPromiseCall(*this, Promise, Loc, "return_value", E);
} else {
  E = MakeFullDiscardedValueExpr(E).get();
  PC = buildPromiseCall(*this, Promise, Loc, "return_void", None);
}
if (PC.isInvalid())
  return StmtError();

Expr *PCE = ActOnFinishFullExpr(PC.get(), /*DiscardedValue*/ false).get();

Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE, IsImplicit);
return Res;
988}

990/// Look up the std::nothrow object.
991static Expr *buildStdNoThrowDeclRef(Sema &S, SourceLocation Loc) {
NamespaceDecl *Std = S.getStdNamespace();
assert(Std && "Should already be diagnosed")(static_cast <bool> (Std && "Should already be diagnosed"
) ? void (0) : __assert_fail ("Std && \"Should already be diagnosed\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 993, __extension__ __PRETTY_FUNCTION__));

LookupResult Result(S, &S.PP.getIdentifierTable().get("nothrow"), Loc,
                    Sema::LookupOrdinaryName);
if (!S.LookupQualifiedName(Result, Std)) {
  // FIXME: <coroutine> should have been included already.
  // If we require it to include <new> then this diagnostic is no longer
  // needed.
  S.Diag(Loc, diag::err_implicit_coroutine_std_nothrow_type_not_found);
  return nullptr;
}

auto *VD = Result.getAsSingle<VarDecl>();
if (!VD) {
  Result.suppressDiagnostics();
  // We found something weird. Complain about the first thing we found.
  NamedDecl *Found = *Result.begin();
  S.Diag(Found->getLocation(), diag::err_malformed_std_nothrow);
  return nullptr;
}

ExprResult DR = S.BuildDeclRefExpr(VD, VD->getType(), VK_LValue, Loc);
if (DR.isInvalid())
  return nullptr;

return DR.get();
1019}

1021// Find an appropriate delete for the promise.
1022static FunctionDecl *findDeleteForPromise(Sema &S, SourceLocation Loc,
                                        QualType PromiseType) {
FunctionDecl *OperatorDelete = nullptr;

DeclarationName DeleteName =
    S.Context.DeclarationNames.getCXXOperatorName(OO_Delete);

auto *PointeeRD = PromiseType->getAsCXXRecordDecl();
assert(PointeeRD && "PromiseType must be a CxxRecordDecl type")(static_cast <bool> (PointeeRD && "PromiseType must be a CxxRecordDecl type"
) ? void (0) : __assert_fail ("PointeeRD && \"PromiseType must be a CxxRecordDecl type\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1030, __extension__ __PRETTY_FUNCTION__));

if (S.FindDeallocationFunction(Loc, PointeeRD, DeleteName, OperatorDelete))
  return nullptr;

if (!OperatorDelete) {
  // Look for a global declaration.
  const bool CanProvideSize = S.isCompleteType(Loc, PromiseType);
  const bool Overaligned = false;
  OperatorDelete = S.FindUsualDeallocationFunction(Loc, CanProvideSize,
                                                   Overaligned, DeleteName);
}
S.MarkFunctionReferenced(Loc, OperatorDelete);
return OperatorDelete;
1044}


1047void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
FunctionScopeInfo *Fn = getCurFunction();
assert(Fn && Fn->isCoroutine() && "not a coroutine")(static_cast <bool> (Fn && Fn->isCoroutine()
 && "not a coroutine") ? void (0) : __assert_fail ("Fn && Fn->isCoroutine() && \"not a coroutine\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1049, __extension__ __PRETTY_FUNCTION__));
if (!Body) {
  assert(FD->isInvalidDecl() &&(static_cast <bool> (FD->isInvalidDecl() && "a null body is only allowed for invalid declarations"
) ? void (0) : __assert_fail ("FD->isInvalidDecl() && \"a null body is only allowed for invalid declarations\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1052, __extension__ __PRETTY_FUNCTION__))
         "a null body is only allowed for invalid declarations")(static_cast <bool> (FD->isInvalidDecl() && "a null body is only allowed for invalid declarations"
) ? void (0) : __assert_fail ("FD->isInvalidDecl() && \"a null body is only allowed for invalid declarations\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1052, __extension__ __PRETTY_FUNCTION__));
  return;
}
// We have a function that uses coroutine keywords, but we failed to build
// the promise type.
if (!Fn->CoroutinePromise)
  return FD->setInvalidDecl();

if (isa<CoroutineBodyStmt>(Body)) {
  // Nothing todo. the body is already a transformed coroutine body statement.
  return;
}

// Coroutines [stmt.return]p1:
//   A return statement shall not appear in a coroutine.
if (Fn->FirstReturnLoc.isValid()) {
  assert(Fn->FirstCoroutineStmtLoc.isValid() &&(static_cast <bool> (Fn->FirstCoroutineStmtLoc.isValid
() && "first coroutine location not set") ? void (0) :
 __assert_fail ("Fn->FirstCoroutineStmtLoc.isValid() && \"first coroutine location not set\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1069, __extension__ __PRETTY_FUNCTION__))
                 "first coroutine location not set")(static_cast <bool> (Fn->FirstCoroutineStmtLoc.isValid
() && "first coroutine location not set") ? void (0) :
 __assert_fail ("Fn->FirstCoroutineStmtLoc.isValid() && \"first coroutine location not set\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1069, __extension__ __PRETTY_FUNCTION__));
  Diag(Fn->FirstReturnLoc, diag::err_return_in_coroutine);
  Diag(Fn->FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
          << Fn->getFirstCoroutineStmtKeyword();
}
CoroutineStmtBuilder Builder(*this, *FD, *Fn, Body);
if (Builder.isInvalid() || !Builder.buildStatements())
  return FD->setInvalidDecl();

// Build body for the coroutine wrapper statement.
Body = CoroutineBodyStmt::Create(Context, Builder);
1080}

1082CoroutineStmtBuilder::CoroutineStmtBuilder(Sema &S, FunctionDecl &FD,
                                         sema::FunctionScopeInfo &Fn,
                                         Stmt *Body)
  : S(S), FD(FD), Fn(Fn), Loc(FD.getLocation()),
    IsPromiseDependentType(
        !Fn.CoroutinePromise ||
        Fn.CoroutinePromise->getType()->isDependentType()) {
this->Body = Body;

for (auto KV : Fn.CoroutineParameterMoves)
  this->ParamMovesVector.push_back(KV.second);
this->ParamMoves = this->ParamMovesVector;

if (!IsPromiseDependentType) {
  PromiseRecordDecl = Fn.CoroutinePromise->getType()->getAsCXXRecordDecl();
  assert(PromiseRecordDecl && "Type should have already been checked")(static_cast <bool> (PromiseRecordDecl && "Type should have already been checked"
) ? void (0) : __assert_fail ("PromiseRecordDecl && \"Type should have already been checked\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1097, __extension__ __PRETTY_FUNCTION__));
}
this->IsValid = makePromiseStmt() && makeInitialAndFinalSuspend();
1100}

1102bool CoroutineStmtBuilder::buildStatements() {
assert(this->IsValid && "coroutine already invalid")(static_cast <bool> (this->IsValid && "coroutine already invalid"
) ? void (0) : __assert_fail ("this->IsValid && \"coroutine already invalid\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1103, __extension__ __PRETTY_FUNCTION__));
this->IsValid = makeReturnObject();
if (this->IsValid && !IsPromiseDependentType)
  buildDependentStatements();
return this->IsValid;
1108}

1110bool CoroutineStmtBuilder::buildDependentStatements() {
assert(this->IsValid && "coroutine already invalid")(static_cast <bool> (this->IsValid && "coroutine already invalid"
) ? void (0) : __assert_fail ("this->IsValid && \"coroutine already invalid\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1111, __extension__ __PRETTY_FUNCTION__));
assert(!this->IsPromiseDependentType &&(static_cast <bool> (!this->IsPromiseDependentType &&
 "coroutine cannot have a dependent promise type") ? void (0)
 : __assert_fail ("!this->IsPromiseDependentType && \"coroutine cannot have a dependent promise type\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1113, __extension__ __PRETTY_FUNCTION__))
       "coroutine cannot have a dependent promise type")(static_cast <bool> (!this->IsPromiseDependentType &&
 "coroutine cannot have a dependent promise type") ? void (0)
 : __assert_fail ("!this->IsPromiseDependentType && \"coroutine cannot have a dependent promise type\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1113, __extension__ __PRETTY_FUNCTION__));
this->IsValid = makeOnException() && makeOnFallthrough() &&
                makeGroDeclAndReturnStmt() && makeReturnOnAllocFailure() &&
                makeNewAndDeleteExpr();
return this->IsValid;
1118}

1120bool CoroutineStmtBuilder::makePromiseStmt() {
// Form a declaration statement for the promise declaration, so that AST
// visitors can more easily find it.
StmtResult PromiseStmt =
    S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(Fn.CoroutinePromise), Loc, Loc);
if (PromiseStmt.isInvalid())
  return false;

this->Promise = PromiseStmt.get();
return true;
1130}

1132bool CoroutineStmtBuilder::makeInitialAndFinalSuspend() {
if (Fn.hasInvalidCoroutineSuspends())
  return false;
this->InitialSuspend = cast<Expr>(Fn.CoroutineSuspends.first);
this->FinalSuspend = cast<Expr>(Fn.CoroutineSuspends.second);
return true;
1138}

1140static bool diagReturnOnAllocFailure(Sema &S, Expr *E,
                                   CXXRecordDecl *PromiseRecordDecl,
                                   FunctionScopeInfo &Fn) {
auto Loc = E->getExprLoc();
if (auto *DeclRef = dyn_cast_or_null<DeclRefExpr>(E)) {
  auto *Decl = DeclRef->getDecl();
  if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(Decl)) {
    if (Method->isStatic())
      return true;
    else
      Loc = Decl->getLocation();
  }
}

S.Diag(
    Loc,
    diag::err_coroutine_promise_get_return_object_on_allocation_failure)
    << PromiseRecordDecl;
S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
    << Fn.getFirstCoroutineStmtKeyword();
return false;
1161}

1163bool CoroutineStmtBuilder::makeReturnOnAllocFailure() {
assert(!IsPromiseDependentType &&(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1165, __extension__ __PRETTY_FUNCTION__))
       "cannot make statement while the promise type is dependent")(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1165, __extension__ __PRETTY_FUNCTION__));

// [dcl.fct.def.coroutine]/8
// The unqualified-id get_return_object_on_allocation_failure is looked up in
// the scope of class P by class member access lookup (3.4.5). ...
// If an allocation function returns nullptr, ... the coroutine return value
// is obtained by a call to ... get_return_object_on_allocation_failure().

DeclarationName DN =
    S.PP.getIdentifierInfo("get_return_object_on_allocation_failure");
LookupResult Found(S, DN, Loc, Sema::LookupMemberName);
if (!S.LookupQualifiedName(Found, PromiseRecordDecl))
  return true;

CXXScopeSpec SS;
ExprResult DeclNameExpr =
    S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
if (DeclNameExpr.isInvalid())
  return false;

if (!diagReturnOnAllocFailure(S, DeclNameExpr.get(), PromiseRecordDecl, Fn))
  return false;

ExprResult ReturnObjectOnAllocationFailure =
    S.BuildCallExpr(nullptr, DeclNameExpr.get(), Loc, {}, Loc);
if (ReturnObjectOnAllocationFailure.isInvalid())
  return false;

StmtResult ReturnStmt =
    S.BuildReturnStmt(Loc, ReturnObjectOnAllocationFailure.get());
if (ReturnStmt.isInvalid()) {
  S.Diag(Found.getFoundDecl()->getLocation(), diag::note_member_declared_here)
      << DN;
  S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
      << Fn.getFirstCoroutineStmtKeyword();
  return false;
}

this->ReturnStmtOnAllocFailure = ReturnStmt.get();
return true;
1205}

1207bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
// Form and check allocation and deallocation calls.
assert(!IsPromiseDependentType &&(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1210, __extension__ __PRETTY_FUNCTION__))
       "cannot make statement while the promise type is dependent")(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1210, __extension__ __PRETTY_FUNCTION__));
QualType PromiseType = Fn.CoroutinePromise->getType();

if (S.RequireCompleteType(Loc, PromiseType, diag::err_incomplete_type))
  return false;

const bool RequiresNoThrowAlloc = ReturnStmtOnAllocFailure != nullptr;

// [dcl.fct.def.coroutine]/7
// Lookup allocation functions using a parameter list composed of the
// requested size of the coroutine state being allocated, followed by
// the coroutine function's arguments. If a matching allocation function
// exists, use it. Otherwise, use an allocation function that just takes
// the requested size.

FunctionDecl *OperatorNew = nullptr;
FunctionDecl *OperatorDelete = nullptr;
FunctionDecl *UnusedResult = nullptr;
bool PassAlignment = false;
SmallVector<Expr *, 1> PlacementArgs;

// [dcl.fct.def.coroutine]/7
// "The allocation function’s name is looked up in the scope of P.
// [...] If the lookup finds an allocation function in the scope of P,
// overload resolution is performed on a function call created by assembling
// an argument list. The first argument is the amount of space requested,
// and has type std::size_t. The lvalues p1 ... pn are the succeeding
// arguments."
//
// ...where "p1 ... pn" are defined earlier as:
//
// [dcl.fct.def.coroutine]/3
// "For a coroutine f that is a non-static member function, let P1 denote the
// type of the implicit object parameter (13.3.1) and P2 ... Pn be the types
// of the function parameters; otherwise let P1 ... Pn be the types of the
// function parameters. Let p1 ... pn be lvalues denoting those objects."
if (auto *MD = dyn_cast<CXXMethodDecl>(&FD)) {
  if (MD->isInstance() && !isLambdaCallOperator(MD)) {
    ExprResult ThisExpr = S.ActOnCXXThis(Loc);
    if (ThisExpr.isInvalid())
      return false;
    ThisExpr = S.CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
    if (ThisExpr.isInvalid())
      return false;
    PlacementArgs.push_back(ThisExpr.get());
  }
}
for (auto *PD : FD.parameters()) {
  if (PD->getType()->isDependentType())
    continue;

  // Build a reference to the parameter.
  auto PDLoc = PD->getLocation();
  ExprResult PDRefExpr =
      S.BuildDeclRefExpr(PD, PD->getOriginalType().getNonReferenceType(),
                         ExprValueKind::VK_LValue, PDLoc);
  if (PDRefExpr.isInvalid())
    return false;

  PlacementArgs.push_back(PDRefExpr.get());
}
S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Class,
                          /*DeleteScope*/ Sema::AFS_Both, PromiseType,
                          /*isArray*/ false, PassAlignment, PlacementArgs,
                          OperatorNew, UnusedResult, /*Diagnose*/ false);

// [dcl.fct.def.coroutine]/7
// "If no matching function is found, overload resolution is performed again
// on a function call created by passing just the amount of space required as
// an argument of type std::size_t."
if (!OperatorNew && !PlacementArgs.empty()) {
  PlacementArgs.clear();
  S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Class,
                            /*DeleteScope*/ Sema::AFS_Both, PromiseType,
                            /*isArray*/ false, PassAlignment, PlacementArgs,
                            OperatorNew, UnusedResult, /*Diagnose*/ false);
}

// [dcl.fct.def.coroutine]/7
// "The allocation function’s name is looked up in the scope of P. If this
// lookup fails, the allocation function’s name is looked up in the global
// scope."
if (!OperatorNew) {
  S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Global,
                            /*DeleteScope*/ Sema::AFS_Both, PromiseType,
                            /*isArray*/ false, PassAlignment, PlacementArgs,
                            OperatorNew, UnusedResult);
}

bool IsGlobalOverload =
    OperatorNew && !isa<CXXRecordDecl>(OperatorNew->getDeclContext());
// If we didn't find a class-local new declaration and non-throwing new
// was is required then we need to lookup the non-throwing global operator
// instead.
if (RequiresNoThrowAlloc && (!OperatorNew || IsGlobalOverload)) {
  auto *StdNoThrow = buildStdNoThrowDeclRef(S, Loc);
  if (!StdNoThrow)
    return false;
  PlacementArgs = {StdNoThrow};
  OperatorNew = nullptr;
  S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Both,
                            /*DeleteScope*/ Sema::AFS_Both, PromiseType,
                            /*isArray*/ false, PassAlignment, PlacementArgs,
                            OperatorNew, UnusedResult);
}

if (!OperatorNew)
  return false;

if (RequiresNoThrowAlloc) {
  const auto *FT = OperatorNew->getType()->castAs<FunctionProtoType>();
  if (!FT->isNothrow(/*ResultIfDependent*/ false)) {
    S.Diag(OperatorNew->getLocation(),
           diag::err_coroutine_promise_new_requires_nothrow)
        << OperatorNew;
    S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
        << OperatorNew;
    return false;
  }
}

if ((OperatorDelete = findDeleteForPromise(S, Loc, PromiseType)) == nullptr)
  return false;

Expr *FramePtr =
    S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});

Expr *FrameSize =
    S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_size, {});

// Make new call.

ExprResult NewRef =
    S.BuildDeclRefExpr(OperatorNew, OperatorNew->getType(), VK_LValue, Loc);
if (NewRef.isInvalid())
  return false;

SmallVector<Expr *, 2> NewArgs(1, FrameSize);
for (auto Arg : PlacementArgs)
  NewArgs.push_back(Arg);

ExprResult NewExpr =
    S.BuildCallExpr(S.getCurScope(), NewRef.get(), Loc, NewArgs, Loc);
NewExpr = S.ActOnFinishFullExpr(NewExpr.get(), /*DiscardedValue*/ false);
if (NewExpr.isInvalid())
  return false;

// Make delete call.

QualType OpDeleteQualType = OperatorDelete->getType();

ExprResult DeleteRef =
    S.BuildDeclRefExpr(OperatorDelete, OpDeleteQualType, VK_LValue, Loc);
if (DeleteRef.isInvalid())
  return false;

Expr *CoroFree =
    S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_free, {FramePtr});

SmallVector<Expr *, 2> DeleteArgs{CoroFree};

// Check if we need to pass the size.
const auto *OpDeleteType =
    OpDeleteQualType.getTypePtr()->castAs<FunctionProtoType>();
if (OpDeleteType->getNumParams() > 1)
  DeleteArgs.push_back(FrameSize);

ExprResult DeleteExpr =
    S.BuildCallExpr(S.getCurScope(), DeleteRef.get(), Loc, DeleteArgs, Loc);
DeleteExpr =
    S.ActOnFinishFullExpr(DeleteExpr.get(), /*DiscardedValue*/ false);
if (DeleteExpr.isInvalid())
  return false;

this->Allocate = NewExpr.get();
this->Deallocate = DeleteExpr.get();

return true;
1388}

1390bool CoroutineStmtBuilder::makeOnFallthrough() {
assert(!IsPromiseDependentType &&(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1392, __extension__ __PRETTY_FUNCTION__))
       "cannot make statement while the promise type is dependent")(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1392, __extension__ __PRETTY_FUNCTION__));

// [dcl.fct.def.coroutine]/4
// The unqualified-ids 'return_void' and 'return_value' are looked up in
// the scope of class P. If both are found, the program is ill-formed.
bool HasRVoid, HasRValue;
LookupResult LRVoid =
    lookupMember(S, "return_void", PromiseRecordDecl, Loc, HasRVoid);
LookupResult LRValue =
    lookupMember(S, "return_value", PromiseRecordDecl, Loc, HasRValue);

StmtResult Fallthrough;
if (HasRVoid && HasRValue) {
  // FIXME Improve this diagnostic
  S.Diag(FD.getLocation(),
         diag::err_coroutine_promise_incompatible_return_functions)
      << PromiseRecordDecl;
  S.Diag(LRVoid.getRepresentativeDecl()->getLocation(),
         diag::note_member_first_declared_here)
      << LRVoid.getLookupName();
  S.Diag(LRValue.getRepresentativeDecl()->getLocation(),
         diag::note_member_first_declared_here)
      << LRValue.getLookupName();
  return false;
} else if (!HasRVoid && !HasRValue) {
  // FIXME: The PDTS currently specifies this case as UB, not ill-formed.
  // However we still diagnose this as an error since until the PDTS is fixed.
  S.Diag(FD.getLocation(),
         diag::err_coroutine_promise_requires_return_function)
      << PromiseRecordDecl;
  S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
      << PromiseRecordDecl;
  return false;
} else if (HasRVoid) {
  // If the unqualified-id return_void is found, flowing off the end of a
  // coroutine is equivalent to a co_return with no operand. Otherwise,
  // flowing off the end of a coroutine results in undefined behavior.
  Fallthrough = S.BuildCoreturnStmt(FD.getLocation(), nullptr,
                                    /*IsImplicit*/false);
  Fallthrough = S.ActOnFinishFullStmt(Fallthrough.get());
  if (Fallthrough.isInvalid())
    return false;
}

this->OnFallthrough = Fallthrough.get();
return true;
1438}

1440bool CoroutineStmtBuilder::makeOnException() {
// Try to form 'p.unhandled_exception();'
assert(!IsPromiseDependentType &&(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1443, __extension__ __PRETTY_FUNCTION__))
       "cannot make statement while the promise type is dependent")(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1443, __extension__ __PRETTY_FUNCTION__));

const bool RequireUnhandledException = S.getLangOpts().CXXExceptions;

if (!lookupMember(S, "unhandled_exception", PromiseRecordDecl, Loc)) {
  auto DiagID =
      RequireUnhandledException
          ? diag::err_coroutine_promise_unhandled_exception_required
          : diag::
                warn_coroutine_promise_unhandled_exception_required_with_exceptions;
  S.Diag(Loc, DiagID) << PromiseRecordDecl;
  S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
      << PromiseRecordDecl;
  return !RequireUnhandledException;
}

// If exceptions are disabled, don't try to build OnException.
if (!S.getLangOpts().CXXExceptions)
  return true;

ExprResult UnhandledException = buildPromiseCall(S, Fn.CoroutinePromise, Loc,
                                                 "unhandled_exception", None);
UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(), Loc,
                                           /*DiscardedValue*/ false);
if (UnhandledException.isInvalid())
  return false;

// Since the body of the coroutine will be wrapped in try-catch, it will
// be incompatible with SEH __try if present in a function.
if (!S.getLangOpts().Borland && Fn.FirstSEHTryLoc.isValid()) {
  S.Diag(Fn.FirstSEHTryLoc, diag::err_seh_in_a_coroutine_with_cxx_exceptions);
  S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
      << Fn.getFirstCoroutineStmtKeyword();
  return false;
}

this->OnException = UnhandledException.get();
return true;
1481}

1483bool CoroutineStmtBuilder::makeReturnObject() {
// Build implicit 'p.get_return_object()' expression and form initialization
// of return type from it.
ExprResult ReturnObject =
    buildPromiseCall(S, Fn.CoroutinePromise, Loc, "get_return_object", None);
if (ReturnObject.isInvalid())
  return false;

this->ReturnValue = ReturnObject.get();
return true;
1493}

1495static void noteMemberDeclaredHere(Sema &S, Expr *E, FunctionScopeInfo &Fn) {
if (auto *MbrRef = dyn_cast<CXXMemberCallExpr>(E)) {
  auto *MethodDecl = MbrRef->getMethodDecl();
  S.Diag(MethodDecl->getLocation(), diag::note_member_declared_here)
      << MethodDecl;
}
S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
    << Fn.getFirstCoroutineStmtKeyword();
1503}

1505bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
assert(!IsPromiseDependentType &&(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1507, __extension__ __PRETTY_FUNCTION__))
       "cannot make statement while the promise type is dependent")(static_cast <bool> (!IsPromiseDependentType &&
 "cannot make statement while the promise type is dependent")
 ? void (0) : __assert_fail ("!IsPromiseDependentType && \"cannot make statement while the promise type is dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1507, __extension__ __PRETTY_FUNCTION__));
assert(this->ReturnValue && "ReturnValue must be already formed")(static_cast <bool> (this->ReturnValue && "ReturnValue must be already formed"
) ? void (0) : __assert_fail ("this->ReturnValue && \"ReturnValue must be already formed\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1508, __extension__ __PRETTY_FUNCTION__));

QualType const GroType = this->ReturnValue->getType();
assert(!GroType->isDependentType() &&(static_cast <bool> (!GroType->isDependentType() &&
 "get_return_object type must no longer be dependent") ? void
 (0) : __assert_fail ("!GroType->isDependentType() && \"get_return_object type must no longer be dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1512, __extension__ __PRETTY_FUNCTION__))
       "get_return_object type must no longer be dependent")(static_cast <bool> (!GroType->isDependentType() &&
 "get_return_object type must no longer be dependent") ? void
 (0) : __assert_fail ("!GroType->isDependentType() && \"get_return_object type must no longer be dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1512, __extension__ __PRETTY_FUNCTION__));

QualType const FnRetType = FD.getReturnType();
assert(!FnRetType->isDependentType() &&(static_cast <bool> (!FnRetType->isDependentType() &&
 "get_return_object type must no longer be dependent") ? void
 (0) : __assert_fail ("!FnRetType->isDependentType() && \"get_return_object type must no longer be dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1516, __extension__ __PRETTY_FUNCTION__))
       "get_return_object type must no longer be dependent")(static_cast <bool> (!FnRetType->isDependentType() &&
 "get_return_object type must no longer be dependent") ? void
 (0) : __assert_fail ("!FnRetType->isDependentType() && \"get_return_object type must no longer be dependent\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1516, __extension__ __PRETTY_FUNCTION__));

if (FnRetType->isVoidType()) {
  ExprResult Res =
      S.ActOnFinishFullExpr(this->ReturnValue, Loc, /*DiscardedValue*/ false);
  if (Res.isInvalid())
    return false;

  this->ResultDecl = Res.get();
  return true;
}

if (GroType->isVoidType()) {
  // Trigger a nice error message.
  InitializedEntity Entity =
      InitializedEntity::InitializeResult(Loc, FnRetType);
  S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
  noteMemberDeclaredHere(S, ReturnValue, Fn);
  return false;
}

auto *GroDecl = VarDecl::Create(
    S.Context, &FD, FD.getLocation(), FD.getLocation(),
    &S.PP.getIdentifierTable().get("__coro_gro"), GroType,
    S.Context.getTrivialTypeSourceInfo(GroType, Loc), SC_None);
GroDecl->setImplicit();

S.CheckVariableDeclarationType(GroDecl);
if (GroDecl->isInvalidDecl())
  return false;

InitializedEntity Entity = InitializedEntity::InitializeVariable(GroDecl);
ExprResult Res =
    S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
if (Res.isInvalid())
  return false;

Res = S.ActOnFinishFullExpr(Res.get(), /*DiscardedValue*/ false);
if (Res.isInvalid())
  return false;

S.AddInitializerToDecl(GroDecl, Res.get(),
                       /*DirectInit=*/false);

S.FinalizeDeclaration(GroDecl);

// Form a declaration statement for the return declaration, so that AST
// visitors can more easily find it.
StmtResult GroDeclStmt =
    S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(GroDecl), Loc, Loc);
if (GroDeclStmt.isInvalid())
  return false;

this->ResultDecl = GroDeclStmt.get();

ExprResult declRef = S.BuildDeclRefExpr(GroDecl, GroType, VK_LValue, Loc);
if (declRef.isInvalid())
  return false;

StmtResult ReturnStmt = S.BuildReturnStmt(Loc, declRef.get());
if (ReturnStmt.isInvalid()) {
  noteMemberDeclaredHere(S, ReturnValue, Fn);
  return false;
}
if (cast<clang::ReturnStmt>(ReturnStmt.get())->getNRVOCandidate() == GroDecl)
  GroDecl->setNRVOVariable(true);

this->ReturnStmt = ReturnStmt.get();
return true;
1585}

1587// Create a static_cast\<T&&>(expr).
1588static Expr *castForMoving(Sema &S, Expr *E, QualType T = QualType()) {
if (T.isNull())
  T = E->getType();
QualType TargetType = S.BuildReferenceType(
    T, /*SpelledAsLValue*/ false, SourceLocation(), DeclarationName());
SourceLocation ExprLoc = E->getBeginLoc();
TypeSourceInfo *TargetLoc =
    S.Context.getTrivialTypeSourceInfo(TargetType, ExprLoc);

return S
    .BuildCXXNamedCast(ExprLoc, tok::kw_static_cast, TargetLoc, E,
                       SourceRange(ExprLoc, ExprLoc), E->getSourceRange())
    .get();
1601}

1603/// Build a variable declaration for move parameter.
1604static VarDecl *buildVarDecl(Sema &S, SourceLocation Loc, QualType Type,
                           IdentifierInfo *II) {
TypeSourceInfo *TInfo = S.Context.getTrivialTypeSourceInfo(Type, Loc);
VarDecl *Decl = VarDecl::Create(S.Context, S.CurContext, Loc, Loc, II, Type,
                                TInfo, SC_None);
Decl->setImplicit();
return Decl;
1611}

1613// Build statements that move coroutine function parameters to the coroutine
1614// frame, and store them on the function scope info.
1615bool Sema::buildCoroutineParameterMoves(SourceLocation Loc) {
assert(isa<FunctionDecl>(CurContext) && "not in a function scope")(static_cast <bool> (isa<FunctionDecl>(CurContext
) && "not in a function scope") ? void (0) : __assert_fail
 ("isa<FunctionDecl>(CurContext) && \"not in a function scope\""
, "/build/llvm-toolchain-snapshot-14~++20211110111138+cffbfd01e37b/clang/lib/Sema/SemaCoroutine.cpp"
, 1616, __extension__ __PRETTY_FUNCTION__));
auto *FD = cast<FunctionDecl>(CurContext);

auto *ScopeInfo = getCurFunction();
if (!ScopeInfo->CoroutineParameterMoves.empty())
  return false;

for (auto *PD : FD->parameters()) {
  if (PD->getType()->isDependentType())
    continue;

  ExprResult PDRefExpr =
      BuildDeclRefExpr(PD, PD->getType().getNonReferenceType(),
                       ExprValueKind::VK_LValue, Loc); // FIXME: scope?
  if (PDRefExpr.isInvalid())
    return false;

  Expr *CExpr = nullptr;
  if (PD->getType()->getAsCXXRecordDecl() ||
      PD->getType()->isRValueReferenceType())
    CExpr = castForMoving(*this, PDRefExpr.get());
  else
    CExpr = PDRefExpr.get();

  auto D = buildVarDecl(*this, Loc, PD->getType(), PD->getIdentifier());
  AddInitializerToDecl(D, CExpr, /*DirectInit=*/true);

  // Convert decl to a statement.
  StmtResult Stmt = ActOnDeclStmt(ConvertDeclToDeclGroup(D), Loc, Loc);
  if (Stmt.isInvalid())
    return false;

  ScopeInfo->CoroutineParameterMoves.insert(std::make_pair(PD, Stmt.get()));
}
return true;
1651}

1653StmtResult Sema::BuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs Args) {
CoroutineBodyStmt *Res = CoroutineBodyStmt::Create(Context, Args);
if (!Res)
  return StmtError();
return Res;
1658}

1660ClassTemplateDecl *Sema::lookupCoroutineTraits(SourceLocation KwLoc,
                                             SourceLocation FuncLoc,
                                             NamespaceDecl *&Namespace) {
if (!StdCoroutineTraitsCache) {
  NamespaceDecl *CoroNamespace = getStdNamespace();
  LookupResult Result(*this, &PP.getIdentifierTable().get("coroutine_traits"),
                      FuncLoc, LookupOrdinaryName);

  if (!CoroNamespace || !LookupQualifiedName(Result, CoroNamespace)) {
    /// Look up in namespace std::experimental, for compatibility.
    /// TODO: Remove this extra lookup when <experimental/coroutine> is
    /// removed.
    CoroNamespace = lookupStdExperimentalNamespace();
    if (!CoroNamespace || !LookupQualifiedName(Result, CoroNamespace)) {
      Diag(KwLoc, diag::err_implied_coroutine_type_not_found)
          << "std::coroutine_traits";
      return nullptr;
    }
    /// TODO: Add a warning about not including <experimental/coroutine>
    /// once we update libcxx.
  } else {
    /// When we found coroutine_traits in std namespace. Make sure there is no
    /// misleading definition in std::experimental namespace.
    NamespaceDecl *ExpNamespace = lookupStdExperimentalNamespace();
    LookupResult ExpResult(*this,
                           &PP.getIdentifierTable().get("coroutine_traits"),
                           FuncLoc, LookupOrdinaryName);
    if (ExpNamespace && LookupQualifiedName(ExpResult, ExpNamespace)) {
      Diag(KwLoc,
           diag::err_mixed_use_std_and_experimental_namespace_for_coroutine);
      return nullptr;
    }
  }

  if (!(StdCoroutineTraitsCache = Result.getAsSingle<ClassTemplateDecl>())) {
    Result.suppressDiagnostics();
    NamedDecl *Found = *Result.begin();
    Diag(Found->getLocation(), diag::err_malformed_std_coroutine_traits);
    return nullptr;
  }
  CoroTraitsNamespaceCache = CoroNamespace;
}
Namespace = CoroTraitsNamespaceCache;
return StdCoroutineTraitsCache;
1704}