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449 lines
16 KiB
449 lines
16 KiB
//===--- SemaCoroutines.cpp - Semantic Analysis for Coroutines ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements semantic analysis for C++ Coroutines.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Sema/SemaInternal.h"
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#include "clang/AST/Decl.h"
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#include "clang/AST/ExprCXX.h"
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#include "clang/AST/StmtCXX.h"
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#include "clang/Lex/Preprocessor.h"
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#include "clang/Sema/Initialization.h"
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#include "clang/Sema/Overload.h"
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using namespace clang;
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using namespace sema;
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/// Look up the std::coroutine_traits<...>::promise_type for the given
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/// function type.
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static QualType lookupPromiseType(Sema &S, const FunctionProtoType *FnType,
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SourceLocation Loc) {
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// FIXME: Cache std::coroutine_traits once we've found it.
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NamespaceDecl *Std = S.getStdNamespace();
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if (!Std) {
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S.Diag(Loc, diag::err_implied_std_coroutine_traits_not_found);
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return QualType();
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}
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LookupResult Result(S, &S.PP.getIdentifierTable().get("coroutine_traits"),
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Loc, Sema::LookupOrdinaryName);
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if (!S.LookupQualifiedName(Result, Std)) {
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S.Diag(Loc, diag::err_implied_std_coroutine_traits_not_found);
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return QualType();
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}
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ClassTemplateDecl *CoroTraits = Result.getAsSingle<ClassTemplateDecl>();
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if (!CoroTraits) {
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Result.suppressDiagnostics();
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// We found something weird. Complain about the first thing we found.
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NamedDecl *Found = *Result.begin();
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S.Diag(Found->getLocation(), diag::err_malformed_std_coroutine_traits);
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return QualType();
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}
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// Form template argument list for coroutine_traits<R, P1, P2, ...>.
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TemplateArgumentListInfo Args(Loc, Loc);
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Args.addArgument(TemplateArgumentLoc(
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TemplateArgument(FnType->getReturnType()),
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S.Context.getTrivialTypeSourceInfo(FnType->getReturnType(), Loc)));
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// FIXME: If the function is a non-static member function, add the type
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// of the implicit object parameter before the formal parameters.
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for (QualType T : FnType->getParamTypes())
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Args.addArgument(TemplateArgumentLoc(
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TemplateArgument(T), S.Context.getTrivialTypeSourceInfo(T, Loc)));
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// Build the template-id.
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QualType CoroTrait =
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S.CheckTemplateIdType(TemplateName(CoroTraits), Loc, Args);
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if (CoroTrait.isNull())
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return QualType();
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if (S.RequireCompleteType(Loc, CoroTrait,
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diag::err_coroutine_traits_missing_specialization))
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return QualType();
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CXXRecordDecl *RD = CoroTrait->getAsCXXRecordDecl();
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assert(RD && "specialization of class template is not a class?");
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// Look up the ::promise_type member.
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LookupResult R(S, &S.PP.getIdentifierTable().get("promise_type"), Loc,
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Sema::LookupOrdinaryName);
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S.LookupQualifiedName(R, RD);
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auto *Promise = R.getAsSingle<TypeDecl>();
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if (!Promise) {
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S.Diag(Loc, diag::err_implied_std_coroutine_traits_promise_type_not_found)
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<< RD;
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return QualType();
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}
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// The promise type is required to be a class type.
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QualType PromiseType = S.Context.getTypeDeclType(Promise);
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if (!PromiseType->getAsCXXRecordDecl()) {
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// Use the fully-qualified name of the type.
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auto *NNS = NestedNameSpecifier::Create(S.Context, nullptr, Std);
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NNS = NestedNameSpecifier::Create(S.Context, NNS, false,
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CoroTrait.getTypePtr());
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PromiseType = S.Context.getElaboratedType(ETK_None, NNS, PromiseType);
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S.Diag(Loc, diag::err_implied_std_coroutine_traits_promise_type_not_class)
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<< PromiseType;
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return QualType();
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}
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return PromiseType;
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}
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/// Check that this is a context in which a coroutine suspension can appear.
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static FunctionScopeInfo *
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checkCoroutineContext(Sema &S, SourceLocation Loc, StringRef Keyword) {
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// 'co_await' and 'co_yield' are not permitted in unevaluated operands.
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if (S.isUnevaluatedContext()) {
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S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
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return nullptr;
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}
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// Any other usage must be within a function.
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// FIXME: Reject a coroutine with a deduced return type.
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auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
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if (!FD) {
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S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
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? diag::err_coroutine_objc_method
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: diag::err_coroutine_outside_function) << Keyword;
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} else if (isa<CXXConstructorDecl>(FD) || isa<CXXDestructorDecl>(FD)) {
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// Coroutines TS [special]/6:
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// A special member function shall not be a coroutine.
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//
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// FIXME: We assume that this really means that a coroutine cannot
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// be a constructor or destructor.
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S.Diag(Loc, diag::err_coroutine_ctor_dtor)
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<< isa<CXXDestructorDecl>(FD) << Keyword;
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} else if (FD->isConstexpr()) {
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S.Diag(Loc, diag::err_coroutine_constexpr) << Keyword;
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} else if (FD->isVariadic()) {
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S.Diag(Loc, diag::err_coroutine_varargs) << Keyword;
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} else {
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auto *ScopeInfo = S.getCurFunction();
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assert(ScopeInfo && "missing function scope for function");
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// If we don't have a promise variable, build one now.
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if (!ScopeInfo->CoroutinePromise) {
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QualType T =
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FD->getType()->isDependentType()
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? S.Context.DependentTy
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: lookupPromiseType(S, FD->getType()->castAs<FunctionProtoType>(),
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Loc);
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if (T.isNull())
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return nullptr;
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// Create and default-initialize the promise.
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ScopeInfo->CoroutinePromise =
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VarDecl::Create(S.Context, FD, FD->getLocation(), FD->getLocation(),
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&S.PP.getIdentifierTable().get("__promise"), T,
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S.Context.getTrivialTypeSourceInfo(T, Loc), SC_None);
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S.CheckVariableDeclarationType(ScopeInfo->CoroutinePromise);
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if (!ScopeInfo->CoroutinePromise->isInvalidDecl())
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S.ActOnUninitializedDecl(ScopeInfo->CoroutinePromise, false);
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}
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return ScopeInfo;
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}
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return nullptr;
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}
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/// Build a call to 'operator co_await' if there is a suitable operator for
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/// the given expression.
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static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
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SourceLocation Loc, Expr *E) {
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UnresolvedSet<16> Functions;
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SemaRef.LookupOverloadedOperatorName(OO_Coawait, S, E->getType(), QualType(),
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Functions);
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return SemaRef.CreateOverloadedUnaryOp(Loc, UO_Coawait, Functions, E);
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}
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struct ReadySuspendResumeResult {
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bool IsInvalid;
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Expr *Results[3];
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};
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static ExprResult buildMemberCall(Sema &S, Expr *Base, SourceLocation Loc,
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StringRef Name,
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MutableArrayRef<Expr *> Args) {
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DeclarationNameInfo NameInfo(&S.PP.getIdentifierTable().get(Name), Loc);
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// FIXME: Fix BuildMemberReferenceExpr to take a const CXXScopeSpec&.
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CXXScopeSpec SS;
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ExprResult Result = S.BuildMemberReferenceExpr(
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Base, Base->getType(), Loc, /*IsPtr=*/false, SS,
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SourceLocation(), nullptr, NameInfo, /*TemplateArgs=*/nullptr,
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/*Scope=*/nullptr);
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if (Result.isInvalid())
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return ExprError();
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return S.ActOnCallExpr(nullptr, Result.get(), Loc, Args, Loc, nullptr);
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}
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/// Build calls to await_ready, await_suspend, and await_resume for a co_await
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/// expression.
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static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, SourceLocation Loc,
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Expr *E) {
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// Assume invalid until we see otherwise.
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ReadySuspendResumeResult Calls = {true, {}};
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const StringRef Funcs[] = {"await_ready", "await_suspend", "await_resume"};
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for (size_t I = 0, N = llvm::array_lengthof(Funcs); I != N; ++I) {
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Expr *Operand = new (S.Context) OpaqueValueExpr(
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Loc, E->getType(), VK_LValue, E->getObjectKind(), E);
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// FIXME: Pass coroutine handle to await_suspend.
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ExprResult Result = buildMemberCall(S, Operand, Loc, Funcs[I], None);
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if (Result.isInvalid())
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return Calls;
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Calls.Results[I] = Result.get();
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}
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Calls.IsInvalid = false;
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return Calls;
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}
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ExprResult Sema::ActOnCoawaitExpr(Scope *S, SourceLocation Loc, Expr *E) {
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if (E->getType()->isPlaceholderType()) {
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ExprResult R = CheckPlaceholderExpr(E);
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if (R.isInvalid()) return ExprError();
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E = R.get();
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}
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ExprResult Awaitable = buildOperatorCoawaitCall(*this, S, Loc, E);
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if (Awaitable.isInvalid())
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return ExprError();
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return BuildCoawaitExpr(Loc, Awaitable.get());
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}
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ExprResult Sema::BuildCoawaitExpr(SourceLocation Loc, Expr *E) {
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auto *Coroutine = checkCoroutineContext(*this, Loc, "co_await");
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if (!Coroutine)
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return ExprError();
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if (E->getType()->isPlaceholderType()) {
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ExprResult R = CheckPlaceholderExpr(E);
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if (R.isInvalid()) return ExprError();
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E = R.get();
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}
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if (E->getType()->isDependentType()) {
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Expr *Res = new (Context) CoawaitExpr(Loc, Context.DependentTy, E);
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Coroutine->CoroutineStmts.push_back(Res);
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return Res;
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}
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// If the expression is a temporary, materialize it as an lvalue so that we
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// can use it multiple times.
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if (E->getValueKind() == VK_RValue)
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E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
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// Build the await_ready, await_suspend, await_resume calls.
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ReadySuspendResumeResult RSS = buildCoawaitCalls(*this, Loc, E);
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if (RSS.IsInvalid)
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return ExprError();
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Expr *Res = new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
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RSS.Results[2]);
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Coroutine->CoroutineStmts.push_back(Res);
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return Res;
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}
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static ExprResult buildPromiseCall(Sema &S, FunctionScopeInfo *Coroutine,
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SourceLocation Loc, StringRef Name,
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MutableArrayRef<Expr *> Args) {
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assert(Coroutine->CoroutinePromise && "no promise for coroutine");
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// Form a reference to the promise.
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auto *Promise = Coroutine->CoroutinePromise;
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ExprResult PromiseRef = S.BuildDeclRefExpr(
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Promise, Promise->getType().getNonReferenceType(), VK_LValue, Loc);
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if (PromiseRef.isInvalid())
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return ExprError();
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// Call 'yield_value', passing in E.
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return buildMemberCall(S, PromiseRef.get(), Loc, Name, Args);
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}
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ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) {
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auto *Coroutine = checkCoroutineContext(*this, Loc, "co_yield");
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if (!Coroutine)
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return ExprError();
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// Build yield_value call.
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ExprResult Awaitable =
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buildPromiseCall(*this, Coroutine, Loc, "yield_value", E);
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if (Awaitable.isInvalid())
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return ExprError();
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// Build 'operator co_await' call.
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Awaitable = buildOperatorCoawaitCall(*this, S, Loc, Awaitable.get());
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if (Awaitable.isInvalid())
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return ExprError();
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return BuildCoyieldExpr(Loc, Awaitable.get());
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}
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ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
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auto *Coroutine = checkCoroutineContext(*this, Loc, "co_yield");
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if (!Coroutine)
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return ExprError();
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if (E->getType()->isPlaceholderType()) {
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ExprResult R = CheckPlaceholderExpr(E);
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if (R.isInvalid()) return ExprError();
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E = R.get();
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}
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if (E->getType()->isDependentType()) {
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Expr *Res = new (Context) CoyieldExpr(Loc, Context.DependentTy, E);
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Coroutine->CoroutineStmts.push_back(Res);
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return Res;
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}
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// If the expression is a temporary, materialize it as an lvalue so that we
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// can use it multiple times.
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if (E->getValueKind() == VK_RValue)
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E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
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// Build the await_ready, await_suspend, await_resume calls.
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ReadySuspendResumeResult RSS = buildCoawaitCalls(*this, Loc, E);
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if (RSS.IsInvalid)
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return ExprError();
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Expr *Res = new (Context) CoyieldExpr(Loc, E, RSS.Results[0], RSS.Results[1],
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RSS.Results[2]);
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Coroutine->CoroutineStmts.push_back(Res);
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return Res;
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}
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StmtResult Sema::ActOnCoreturnStmt(SourceLocation Loc, Expr *E) {
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return BuildCoreturnStmt(Loc, E);
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}
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StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E) {
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auto *Coroutine = checkCoroutineContext(*this, Loc, "co_return");
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if (!Coroutine)
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return StmtError();
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if (E && E->getType()->isPlaceholderType() &&
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!E->getType()->isSpecificPlaceholderType(BuiltinType::Overload)) {
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ExprResult R = CheckPlaceholderExpr(E);
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if (R.isInvalid()) return StmtError();
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E = R.get();
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}
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// FIXME: If the operand is a reference to a variable that's about to go out
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// of scope, we should treat the operand as an xvalue for this overload
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// resolution.
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ExprResult PC;
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if (E && !E->getType()->isVoidType()) {
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PC = buildPromiseCall(*this, Coroutine, Loc, "return_value", E);
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} else {
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E = MakeFullDiscardedValueExpr(E).get();
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PC = buildPromiseCall(*this, Coroutine, Loc, "return_void", None);
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}
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if (PC.isInvalid())
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return StmtError();
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Expr *PCE = ActOnFinishFullExpr(PC.get()).get();
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Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE);
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Coroutine->CoroutineStmts.push_back(Res);
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return Res;
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}
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void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
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FunctionScopeInfo *Fn = getCurFunction();
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assert(Fn && !Fn->CoroutineStmts.empty() && "not a coroutine");
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// Coroutines [stmt.return]p1:
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// A return statement shall not appear in a coroutine.
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if (Fn->FirstReturnLoc.isValid()) {
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Diag(Fn->FirstReturnLoc, diag::err_return_in_coroutine);
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auto *First = Fn->CoroutineStmts[0];
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Diag(First->getLocStart(), diag::note_declared_coroutine_here)
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<< (isa<CoawaitExpr>(First) ? 0 :
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isa<CoyieldExpr>(First) ? 1 : 2);
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}
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bool AnyCoawaits = false;
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bool AnyCoyields = false;
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for (auto *CoroutineStmt : Fn->CoroutineStmts) {
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AnyCoawaits |= isa<CoawaitExpr>(CoroutineStmt);
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AnyCoyields |= isa<CoyieldExpr>(CoroutineStmt);
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}
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if (!AnyCoawaits && !AnyCoyields)
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Diag(Fn->CoroutineStmts.front()->getLocStart(),
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diag::ext_coroutine_without_co_await_co_yield);
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SourceLocation Loc = FD->getLocation();
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// Form a declaration statement for the promise declaration, so that AST
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// visitors can more easily find it.
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StmtResult PromiseStmt =
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ActOnDeclStmt(ConvertDeclToDeclGroup(Fn->CoroutinePromise), Loc, Loc);
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if (PromiseStmt.isInvalid())
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return FD->setInvalidDecl();
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// Form and check implicit 'co_await p.initial_suspend();' statement.
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ExprResult InitialSuspend =
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buildPromiseCall(*this, Fn, Loc, "initial_suspend", None);
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// FIXME: Support operator co_await here.
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if (!InitialSuspend.isInvalid())
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InitialSuspend = BuildCoawaitExpr(Loc, InitialSuspend.get());
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InitialSuspend = ActOnFinishFullExpr(InitialSuspend.get());
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if (InitialSuspend.isInvalid())
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return FD->setInvalidDecl();
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// Form and check implicit 'co_await p.final_suspend();' statement.
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ExprResult FinalSuspend =
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buildPromiseCall(*this, Fn, Loc, "final_suspend", None);
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// FIXME: Support operator co_await here.
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if (!FinalSuspend.isInvalid())
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FinalSuspend = BuildCoawaitExpr(Loc, FinalSuspend.get());
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FinalSuspend = ActOnFinishFullExpr(FinalSuspend.get());
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if (FinalSuspend.isInvalid())
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return FD->setInvalidDecl();
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// FIXME: Perform analysis of set_exception call.
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// FIXME: Try to form 'p.return_void();' expression statement to handle
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// control flowing off the end of the coroutine.
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// Build implicit 'p.get_return_object()' expression and form initialization
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// of return type from it.
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ExprResult ReturnObject =
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buildPromiseCall(*this, Fn, Loc, "get_return_object", None);
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if (ReturnObject.isInvalid())
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return FD->setInvalidDecl();
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QualType RetType = FD->getReturnType();
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if (!RetType->isDependentType()) {
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InitializedEntity Entity =
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InitializedEntity::InitializeResult(Loc, RetType, false);
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ReturnObject = PerformMoveOrCopyInitialization(Entity, nullptr, RetType,
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ReturnObject.get());
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if (ReturnObject.isInvalid())
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return FD->setInvalidDecl();
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}
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ReturnObject = ActOnFinishFullExpr(ReturnObject.get(), Loc);
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if (ReturnObject.isInvalid())
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return FD->setInvalidDecl();
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// FIXME: Perform move-initialization of parameters into frame-local copies.
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SmallVector<Expr*, 16> ParamMoves;
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// Build body for the coroutine wrapper statement.
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Body = new (Context) CoroutineBodyStmt(
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Body, PromiseStmt.get(), InitialSuspend.get(), FinalSuspend.get(),
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/*SetException*/nullptr, /*Fallthrough*/nullptr,
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ReturnObject.get(), ParamMoves);
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}
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