1 //===--- SemaCoroutines.cpp - Semantic Analysis for Coroutines ------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements semantic analysis for C++ Coroutines.
11 //
12 // This file contains references to sections of the Coroutines TS, which
13 // can be found at http://wg21.link/coroutines.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "CoroutineStmtBuilder.h"
18 #include "clang/AST/ASTLambda.h"
19 #include "clang/AST/Decl.h"
20 #include "clang/AST/ExprCXX.h"
21 #include "clang/AST/StmtCXX.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
28 using namespace clang;
29 using namespace sema;
30
lookupMember(Sema & S,const char * Name,CXXRecordDecl * RD,SourceLocation Loc,bool & Res)31 static LookupResult lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
32 SourceLocation Loc, bool &Res) {
33 DeclarationName DN = S.PP.getIdentifierInfo(Name);
34 LookupResult LR(S, DN, Loc, Sema::LookupMemberName);
35 // Suppress diagnostics when a private member is selected. The same warnings
36 // will be produced again when building the call.
37 LR.suppressDiagnostics();
38 Res = S.LookupQualifiedName(LR, RD);
39 return LR;
40 }
41
lookupMember(Sema & S,const char * Name,CXXRecordDecl * RD,SourceLocation Loc)42 static bool lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
43 SourceLocation Loc) {
44 bool Res;
45 lookupMember(S, Name, RD, Loc, Res);
46 return Res;
47 }
48
49 /// Look up the std::coroutine_traits<...>::promise_type for the given
50 /// function type.
lookupPromiseType(Sema & S,const FunctionDecl * FD,SourceLocation KwLoc)51 static QualType lookupPromiseType(Sema &S, const FunctionDecl *FD,
52 SourceLocation KwLoc) {
53 const FunctionProtoType *FnType = FD->getType()->castAs<FunctionProtoType>();
54 const SourceLocation FuncLoc = FD->getLocation();
55 // FIXME: Cache std::coroutine_traits once we've found it.
56 NamespaceDecl *StdExp = S.lookupStdExperimentalNamespace();
57 if (!StdExp) {
58 S.Diag(KwLoc, diag::err_implied_coroutine_type_not_found)
59 << "std::experimental::coroutine_traits";
60 return QualType();
61 }
62
63 ClassTemplateDecl *CoroTraits = S.lookupCoroutineTraits(KwLoc, FuncLoc);
64 if (!CoroTraits) {
65 return QualType();
66 }
67
68 // Form template argument list for coroutine_traits<R, P1, P2, ...> according
69 // to [dcl.fct.def.coroutine]3
70 TemplateArgumentListInfo Args(KwLoc, KwLoc);
71 auto AddArg = [&](QualType T) {
72 Args.addArgument(TemplateArgumentLoc(
73 TemplateArgument(T), S.Context.getTrivialTypeSourceInfo(T, KwLoc)));
74 };
75 AddArg(FnType->getReturnType());
76 // If the function is a non-static member function, add the type
77 // of the implicit object parameter before the formal parameters.
78 if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
79 if (MD->isInstance()) {
80 // [over.match.funcs]4
81 // For non-static member functions, the type of the implicit object
82 // parameter is
83 // -- "lvalue reference to cv X" for functions declared without a
84 // ref-qualifier or with the & ref-qualifier
85 // -- "rvalue reference to cv X" for functions declared with the &&
86 // ref-qualifier
87 QualType T = MD->getThisType()->getAs<PointerType>()->getPointeeType();
88 T = FnType->getRefQualifier() == RQ_RValue
89 ? S.Context.getRValueReferenceType(T)
90 : S.Context.getLValueReferenceType(T, /*SpelledAsLValue*/ true);
91 AddArg(T);
92 }
93 }
94 for (QualType T : FnType->getParamTypes())
95 AddArg(T);
96
97 // Build the template-id.
98 QualType CoroTrait =
99 S.CheckTemplateIdType(TemplateName(CoroTraits), KwLoc, Args);
100 if (CoroTrait.isNull())
101 return QualType();
102 if (S.RequireCompleteType(KwLoc, CoroTrait,
103 diag::err_coroutine_type_missing_specialization))
104 return QualType();
105
106 auto *RD = CoroTrait->getAsCXXRecordDecl();
107 assert(RD && "specialization of class template is not a class?");
108
109 // Look up the ::promise_type member.
110 LookupResult R(S, &S.PP.getIdentifierTable().get("promise_type"), KwLoc,
111 Sema::LookupOrdinaryName);
112 S.LookupQualifiedName(R, RD);
113 auto *Promise = R.getAsSingle<TypeDecl>();
114 if (!Promise) {
115 S.Diag(FuncLoc,
116 diag::err_implied_std_coroutine_traits_promise_type_not_found)
117 << RD;
118 return QualType();
119 }
120 // The promise type is required to be a class type.
121 QualType PromiseType = S.Context.getTypeDeclType(Promise);
122
123 auto buildElaboratedType = [&]() {
124 auto *NNS = NestedNameSpecifier::Create(S.Context, nullptr, StdExp);
125 NNS = NestedNameSpecifier::Create(S.Context, NNS, false,
126 CoroTrait.getTypePtr());
127 return S.Context.getElaboratedType(ETK_None, NNS, PromiseType);
128 };
129
130 if (!PromiseType->getAsCXXRecordDecl()) {
131 S.Diag(FuncLoc,
132 diag::err_implied_std_coroutine_traits_promise_type_not_class)
133 << buildElaboratedType();
134 return QualType();
135 }
136 if (S.RequireCompleteType(FuncLoc, buildElaboratedType(),
137 diag::err_coroutine_promise_type_incomplete))
138 return QualType();
139
140 return PromiseType;
141 }
142
143 /// Look up the std::experimental::coroutine_handle<PromiseType>.
lookupCoroutineHandleType(Sema & S,QualType PromiseType,SourceLocation Loc)144 static QualType lookupCoroutineHandleType(Sema &S, QualType PromiseType,
145 SourceLocation Loc) {
146 if (PromiseType.isNull())
147 return QualType();
148
149 NamespaceDecl *StdExp = S.lookupStdExperimentalNamespace();
150 assert(StdExp && "Should already be diagnosed");
151
152 LookupResult Result(S, &S.PP.getIdentifierTable().get("coroutine_handle"),
153 Loc, Sema::LookupOrdinaryName);
154 if (!S.LookupQualifiedName(Result, StdExp)) {
155 S.Diag(Loc, diag::err_implied_coroutine_type_not_found)
156 << "std::experimental::coroutine_handle";
157 return QualType();
158 }
159
160 ClassTemplateDecl *CoroHandle = Result.getAsSingle<ClassTemplateDecl>();
161 if (!CoroHandle) {
162 Result.suppressDiagnostics();
163 // We found something weird. Complain about the first thing we found.
164 NamedDecl *Found = *Result.begin();
165 S.Diag(Found->getLocation(), diag::err_malformed_std_coroutine_handle);
166 return QualType();
167 }
168
169 // Form template argument list for coroutine_handle<Promise>.
170 TemplateArgumentListInfo Args(Loc, Loc);
171 Args.addArgument(TemplateArgumentLoc(
172 TemplateArgument(PromiseType),
173 S.Context.getTrivialTypeSourceInfo(PromiseType, Loc)));
174
175 // Build the template-id.
176 QualType CoroHandleType =
177 S.CheckTemplateIdType(TemplateName(CoroHandle), Loc, Args);
178 if (CoroHandleType.isNull())
179 return QualType();
180 if (S.RequireCompleteType(Loc, CoroHandleType,
181 diag::err_coroutine_type_missing_specialization))
182 return QualType();
183
184 return CoroHandleType;
185 }
186
isValidCoroutineContext(Sema & S,SourceLocation Loc,StringRef Keyword)187 static bool isValidCoroutineContext(Sema &S, SourceLocation Loc,
188 StringRef Keyword) {
189 // 'co_await' and 'co_yield' are not permitted in unevaluated operands,
190 // such as subexpressions of \c sizeof.
191 //
192 // [expr.await]p2, emphasis added: "An await-expression shall appear only in
193 // a *potentially evaluated* expression within the compound-statement of a
194 // function-body outside of a handler [...] A context within a function where
195 // an await-expression can appear is called a suspension context of the
196 // function." And per [expr.yield]p1: "A yield-expression shall appear only
197 // within a suspension context of a function."
198 if (S.isUnevaluatedContext()) {
199 S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
200 return false;
201 }
202
203 // Per [expr.await]p2, any other usage must be within a function.
204 // FIXME: This also covers [expr.await]p2: "An await-expression shall not
205 // appear in a default argument." But the diagnostic QoI here could be
206 // improved to inform the user that default arguments specifically are not
207 // allowed.
208 auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
209 if (!FD) {
210 S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
211 ? diag::err_coroutine_objc_method
212 : diag::err_coroutine_outside_function) << Keyword;
213 return false;
214 }
215
216 // An enumeration for mapping the diagnostic type to the correct diagnostic
217 // selection index.
218 enum InvalidFuncDiag {
219 DiagCtor = 0,
220 DiagDtor,
221 DiagCopyAssign,
222 DiagMoveAssign,
223 DiagMain,
224 DiagConstexpr,
225 DiagAutoRet,
226 DiagVarargs,
227 };
228 bool Diagnosed = false;
229 auto DiagInvalid = [&](InvalidFuncDiag ID) {
230 S.Diag(Loc, diag::err_coroutine_invalid_func_context) << ID << Keyword;
231 Diagnosed = true;
232 return false;
233 };
234
235 // Diagnose when a constructor, destructor, copy/move assignment operator,
236 // or the function 'main' are declared as a coroutine.
237 auto *MD = dyn_cast<CXXMethodDecl>(FD);
238 // [class.ctor]p6: "A constructor shall not be a coroutine."
239 if (MD && isa<CXXConstructorDecl>(MD))
240 return DiagInvalid(DiagCtor);
241 // [class.dtor]p17: "A destructor shall not be a coroutine."
242 else if (MD && isa<CXXDestructorDecl>(MD))
243 return DiagInvalid(DiagDtor);
244 // N4499 [special]p6: "A special member function shall not be a coroutine."
245 // Per C++ [special]p1, special member functions are the "default constructor,
246 // copy constructor and copy assignment operator, move constructor and move
247 // assignment operator, and destructor."
248 else if (MD && MD->isCopyAssignmentOperator())
249 return DiagInvalid(DiagCopyAssign);
250 else if (MD && MD->isMoveAssignmentOperator())
251 return DiagInvalid(DiagMoveAssign);
252 // [basic.start.main]p3: "The function main shall not be a coroutine."
253 else if (FD->isMain())
254 return DiagInvalid(DiagMain);
255
256 // Emit a diagnostics for each of the following conditions which is not met.
257 // [expr.const]p2: "An expression e is a core constant expression unless the
258 // evaluation of e [...] would evaluate one of the following expressions:
259 // [...] an await-expression [...] a yield-expression."
260 if (FD->isConstexpr())
261 DiagInvalid(DiagConstexpr);
262 // [dcl.spec.auto]p15: "A function declared with a return type that uses a
263 // placeholder type shall not be a coroutine."
264 if (FD->getReturnType()->isUndeducedType())
265 DiagInvalid(DiagAutoRet);
266 // [dcl.fct.def.coroutine]p1: "The parameter-declaration-clause of the
267 // coroutine shall not terminate with an ellipsis that is not part of a
268 // parameter-declaration."
269 if (FD->isVariadic())
270 DiagInvalid(DiagVarargs);
271
272 return !Diagnosed;
273 }
274
buildOperatorCoawaitLookupExpr(Sema & SemaRef,Scope * S,SourceLocation Loc)275 static ExprResult buildOperatorCoawaitLookupExpr(Sema &SemaRef, Scope *S,
276 SourceLocation Loc) {
277 DeclarationName OpName =
278 SemaRef.Context.DeclarationNames.getCXXOperatorName(OO_Coawait);
279 LookupResult Operators(SemaRef, OpName, SourceLocation(),
280 Sema::LookupOperatorName);
281 SemaRef.LookupName(Operators, S);
282
283 assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous");
284 const auto &Functions = Operators.asUnresolvedSet();
285 bool IsOverloaded =
286 Functions.size() > 1 ||
287 (Functions.size() == 1 && isa<FunctionTemplateDecl>(*Functions.begin()));
288 Expr *CoawaitOp = UnresolvedLookupExpr::Create(
289 SemaRef.Context, /*NamingClass*/ nullptr, NestedNameSpecifierLoc(),
290 DeclarationNameInfo(OpName, Loc), /*RequiresADL*/ true, IsOverloaded,
291 Functions.begin(), Functions.end());
292 assert(CoawaitOp);
293 return CoawaitOp;
294 }
295
296 /// Build a call to 'operator co_await' if there is a suitable operator for
297 /// the given expression.
buildOperatorCoawaitCall(Sema & SemaRef,SourceLocation Loc,Expr * E,UnresolvedLookupExpr * Lookup)298 static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, SourceLocation Loc,
299 Expr *E,
300 UnresolvedLookupExpr *Lookup) {
301 UnresolvedSet<16> Functions;
302 Functions.append(Lookup->decls_begin(), Lookup->decls_end());
303 return SemaRef.CreateOverloadedUnaryOp(Loc, UO_Coawait, Functions, E);
304 }
305
buildOperatorCoawaitCall(Sema & SemaRef,Scope * S,SourceLocation Loc,Expr * E)306 static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
307 SourceLocation Loc, Expr *E) {
308 ExprResult R = buildOperatorCoawaitLookupExpr(SemaRef, S, Loc);
309 if (R.isInvalid())
310 return ExprError();
311 return buildOperatorCoawaitCall(SemaRef, Loc, E,
312 cast<UnresolvedLookupExpr>(R.get()));
313 }
314
buildBuiltinCall(Sema & S,SourceLocation Loc,Builtin::ID Id,MultiExprArg CallArgs)315 static Expr *buildBuiltinCall(Sema &S, SourceLocation Loc, Builtin::ID Id,
316 MultiExprArg CallArgs) {
317 StringRef Name = S.Context.BuiltinInfo.getName(Id);
318 LookupResult R(S, &S.Context.Idents.get(Name), Loc, Sema::LookupOrdinaryName);
319 S.LookupName(R, S.TUScope, /*AllowBuiltinCreation=*/true);
320
321 auto *BuiltInDecl = R.getAsSingle<FunctionDecl>();
322 assert(BuiltInDecl && "failed to find builtin declaration");
323
324 ExprResult DeclRef =
325 S.BuildDeclRefExpr(BuiltInDecl, BuiltInDecl->getType(), VK_LValue, Loc);
326 assert(DeclRef.isUsable() && "Builtin reference cannot fail");
327
328 ExprResult Call =
329 S.ActOnCallExpr(/*Scope=*/nullptr, DeclRef.get(), Loc, CallArgs, Loc);
330
331 assert(!Call.isInvalid() && "Call to builtin cannot fail!");
332 return Call.get();
333 }
334
buildCoroutineHandle(Sema & S,QualType PromiseType,SourceLocation Loc)335 static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
336 SourceLocation Loc) {
337 QualType CoroHandleType = lookupCoroutineHandleType(S, PromiseType, Loc);
338 if (CoroHandleType.isNull())
339 return ExprError();
340
341 DeclContext *LookupCtx = S.computeDeclContext(CoroHandleType);
342 LookupResult Found(S, &S.PP.getIdentifierTable().get("from_address"), Loc,
343 Sema::LookupOrdinaryName);
344 if (!S.LookupQualifiedName(Found, LookupCtx)) {
345 S.Diag(Loc, diag::err_coroutine_handle_missing_member)
346 << "from_address";
347 return ExprError();
348 }
349
350 Expr *FramePtr =
351 buildBuiltinCall(S, Loc, Builtin::BI__builtin_coro_frame, {});
352
353 CXXScopeSpec SS;
354 ExprResult FromAddr =
355 S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
356 if (FromAddr.isInvalid())
357 return ExprError();
358
359 return S.ActOnCallExpr(nullptr, FromAddr.get(), Loc, FramePtr, Loc);
360 }
361
362 struct ReadySuspendResumeResult {
363 enum AwaitCallType { ACT_Ready, ACT_Suspend, ACT_Resume };
364 Expr *Results[3];
365 OpaqueValueExpr *OpaqueValue;
366 bool IsInvalid;
367 };
368
buildMemberCall(Sema & S,Expr * Base,SourceLocation Loc,StringRef Name,MultiExprArg Args)369 static ExprResult buildMemberCall(Sema &S, Expr *Base, SourceLocation Loc,
370 StringRef Name, MultiExprArg Args) {
371 DeclarationNameInfo NameInfo(&S.PP.getIdentifierTable().get(Name), Loc);
372
373 // FIXME: Fix BuildMemberReferenceExpr to take a const CXXScopeSpec&.
374 CXXScopeSpec SS;
375 ExprResult Result = S.BuildMemberReferenceExpr(
376 Base, Base->getType(), Loc, /*IsPtr=*/false, SS,
377 SourceLocation(), nullptr, NameInfo, /*TemplateArgs=*/nullptr,
378 /*Scope=*/nullptr);
379 if (Result.isInvalid())
380 return ExprError();
381
382 // We meant exactly what we asked for. No need for typo correction.
383 if (auto *TE = dyn_cast<TypoExpr>(Result.get())) {
384 S.clearDelayedTypo(TE);
385 S.Diag(Loc, diag::err_no_member)
386 << NameInfo.getName() << Base->getType()->getAsCXXRecordDecl()
387 << Base->getSourceRange();
388 return ExprError();
389 }
390
391 return S.ActOnCallExpr(nullptr, Result.get(), Loc, Args, Loc, nullptr);
392 }
393
394 // See if return type is coroutine-handle and if so, invoke builtin coro-resume
395 // on its address. This is to enable experimental support for coroutine-handle
396 // returning await_suspend that results in a guaranteed tail call to the target
397 // coroutine.
maybeTailCall(Sema & S,QualType RetType,Expr * E,SourceLocation Loc)398 static Expr *maybeTailCall(Sema &S, QualType RetType, Expr *E,
399 SourceLocation Loc) {
400 if (RetType->isReferenceType())
401 return nullptr;
402 Type const *T = RetType.getTypePtr();
403 if (!T->isClassType() && !T->isStructureType())
404 return nullptr;
405
406 // FIXME: Add convertability check to coroutine_handle<>. Possibly via
407 // EvaluateBinaryTypeTrait(BTT_IsConvertible, ...) which is at the moment
408 // a private function in SemaExprCXX.cpp
409
410 ExprResult AddressExpr = buildMemberCall(S, E, Loc, "address", None);
411 if (AddressExpr.isInvalid())
412 return nullptr;
413
414 Expr *JustAddress = AddressExpr.get();
415 // FIXME: Check that the type of AddressExpr is void*
416 return buildBuiltinCall(S, Loc, Builtin::BI__builtin_coro_resume,
417 JustAddress);
418 }
419
420 /// Build calls to await_ready, await_suspend, and await_resume for a co_await
421 /// expression.
buildCoawaitCalls(Sema & S,VarDecl * CoroPromise,SourceLocation Loc,Expr * E)422 static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
423 SourceLocation Loc, Expr *E) {
424 OpaqueValueExpr *Operand = new (S.Context)
425 OpaqueValueExpr(Loc, E->getType(), VK_LValue, E->getObjectKind(), E);
426
427 // Assume invalid until we see otherwise.
428 ReadySuspendResumeResult Calls = {{}, Operand, /*IsInvalid=*/true};
429
430 ExprResult CoroHandleRes = buildCoroutineHandle(S, CoroPromise->getType(), Loc);
431 if (CoroHandleRes.isInvalid())
432 return Calls;
433 Expr *CoroHandle = CoroHandleRes.get();
434
435 const StringRef Funcs[] = {"await_ready", "await_suspend", "await_resume"};
436 MultiExprArg Args[] = {None, CoroHandle, None};
437 for (size_t I = 0, N = llvm::array_lengthof(Funcs); I != N; ++I) {
438 ExprResult Result = buildMemberCall(S, Operand, Loc, Funcs[I], Args[I]);
439 if (Result.isInvalid())
440 return Calls;
441 Calls.Results[I] = Result.get();
442 }
443
444 // Assume the calls are valid; all further checking should make them invalid.
445 Calls.IsInvalid = false;
446
447 using ACT = ReadySuspendResumeResult::AwaitCallType;
448 CallExpr *AwaitReady = cast<CallExpr>(Calls.Results[ACT::ACT_Ready]);
449 if (!AwaitReady->getType()->isDependentType()) {
450 // [expr.await]p3 [...]
451 // — await-ready is the expression e.await_ready(), contextually converted
452 // to bool.
453 ExprResult Conv = S.PerformContextuallyConvertToBool(AwaitReady);
454 if (Conv.isInvalid()) {
455 S.Diag(AwaitReady->getDirectCallee()->getBeginLoc(),
456 diag::note_await_ready_no_bool_conversion);
457 S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
458 << AwaitReady->getDirectCallee() << E->getSourceRange();
459 Calls.IsInvalid = true;
460 }
461 Calls.Results[ACT::ACT_Ready] = Conv.get();
462 }
463 CallExpr *AwaitSuspend = cast<CallExpr>(Calls.Results[ACT::ACT_Suspend]);
464 if (!AwaitSuspend->getType()->isDependentType()) {
465 // [expr.await]p3 [...]
466 // - await-suspend is the expression e.await_suspend(h), which shall be
467 // a prvalue of type void or bool.
468 QualType RetType = AwaitSuspend->getCallReturnType(S.Context);
469
470 // Experimental support for coroutine_handle returning await_suspend.
471 if (Expr *TailCallSuspend = maybeTailCall(S, RetType, AwaitSuspend, Loc))
472 Calls.Results[ACT::ACT_Suspend] = TailCallSuspend;
473 else {
474 // non-class prvalues always have cv-unqualified types
475 if (RetType->isReferenceType() ||
476 (!RetType->isBooleanType() && !RetType->isVoidType())) {
477 S.Diag(AwaitSuspend->getCalleeDecl()->getLocation(),
478 diag::err_await_suspend_invalid_return_type)
479 << RetType;
480 S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
481 << AwaitSuspend->getDirectCallee();
482 Calls.IsInvalid = true;
483 }
484 }
485 }
486
487 return Calls;
488 }
489
buildPromiseCall(Sema & S,VarDecl * Promise,SourceLocation Loc,StringRef Name,MultiExprArg Args)490 static ExprResult buildPromiseCall(Sema &S, VarDecl *Promise,
491 SourceLocation Loc, StringRef Name,
492 MultiExprArg Args) {
493
494 // Form a reference to the promise.
495 ExprResult PromiseRef = S.BuildDeclRefExpr(
496 Promise, Promise->getType().getNonReferenceType(), VK_LValue, Loc);
497 if (PromiseRef.isInvalid())
498 return ExprError();
499
500 return buildMemberCall(S, PromiseRef.get(), Loc, Name, Args);
501 }
502
buildCoroutinePromise(SourceLocation Loc)503 VarDecl *Sema::buildCoroutinePromise(SourceLocation Loc) {
504 assert(isa<FunctionDecl>(CurContext) && "not in a function scope");
505 auto *FD = cast<FunctionDecl>(CurContext);
506 bool IsThisDependentType = [&] {
507 if (auto *MD = dyn_cast_or_null<CXXMethodDecl>(FD))
508 return MD->isInstance() && MD->getThisType()->isDependentType();
509 else
510 return false;
511 }();
512
513 QualType T = FD->getType()->isDependentType() || IsThisDependentType
514 ? Context.DependentTy
515 : lookupPromiseType(*this, FD, Loc);
516 if (T.isNull())
517 return nullptr;
518
519 auto *VD = VarDecl::Create(Context, FD, FD->getLocation(), FD->getLocation(),
520 &PP.getIdentifierTable().get("__promise"), T,
521 Context.getTrivialTypeSourceInfo(T, Loc), SC_None);
522 CheckVariableDeclarationType(VD);
523 if (VD->isInvalidDecl())
524 return nullptr;
525
526 auto *ScopeInfo = getCurFunction();
527 // Build a list of arguments, based on the coroutine functions arguments,
528 // that will be passed to the promise type's constructor.
529 llvm::SmallVector<Expr *, 4> CtorArgExprs;
530
531 // Add implicit object parameter.
532 if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
533 if (MD->isInstance() && !isLambdaCallOperator(MD)) {
534 ExprResult ThisExpr = ActOnCXXThis(Loc);
535 if (ThisExpr.isInvalid())
536 return nullptr;
537 ThisExpr = CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
538 if (ThisExpr.isInvalid())
539 return nullptr;
540 CtorArgExprs.push_back(ThisExpr.get());
541 }
542 }
543
544 auto &Moves = ScopeInfo->CoroutineParameterMoves;
545 for (auto *PD : FD->parameters()) {
546 if (PD->getType()->isDependentType())
547 continue;
548
549 auto RefExpr = ExprEmpty();
550 auto Move = Moves.find(PD);
551 assert(Move != Moves.end() &&
552 "Coroutine function parameter not inserted into move map");
553 // If a reference to the function parameter exists in the coroutine
554 // frame, use that reference.
555 auto *MoveDecl =
556 cast<VarDecl>(cast<DeclStmt>(Move->second)->getSingleDecl());
557 RefExpr =
558 BuildDeclRefExpr(MoveDecl, MoveDecl->getType().getNonReferenceType(),
559 ExprValueKind::VK_LValue, FD->getLocation());
560 if (RefExpr.isInvalid())
561 return nullptr;
562 CtorArgExprs.push_back(RefExpr.get());
563 }
564
565 // Create an initialization sequence for the promise type using the
566 // constructor arguments, wrapped in a parenthesized list expression.
567 Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
568 CtorArgExprs, FD->getLocation());
569 InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
570 InitializationKind Kind = InitializationKind::CreateForInit(
571 VD->getLocation(), /*DirectInit=*/true, PLE);
572 InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
573 /*TopLevelOfInitList=*/false,
574 /*TreatUnavailableAsInvalid=*/false);
575
576 // Attempt to initialize the promise type with the arguments.
577 // If that fails, fall back to the promise type's default constructor.
578 if (InitSeq) {
579 ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
580 if (Result.isInvalid()) {
581 VD->setInvalidDecl();
582 } else if (Result.get()) {
583 VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
584 VD->setInitStyle(VarDecl::CallInit);
585 CheckCompleteVariableDeclaration(VD);
586 }
587 } else
588 ActOnUninitializedDecl(VD);
589
590 FD->addDecl(VD);
591 return VD;
592 }
593
594 /// Check that this is a context in which a coroutine suspension can appear.
checkCoroutineContext(Sema & S,SourceLocation Loc,StringRef Keyword,bool IsImplicit=false)595 static FunctionScopeInfo *checkCoroutineContext(Sema &S, SourceLocation Loc,
596 StringRef Keyword,
597 bool IsImplicit = false) {
598 if (!isValidCoroutineContext(S, Loc, Keyword))
599 return nullptr;
600
601 assert(isa<FunctionDecl>(S.CurContext) && "not in a function scope");
602
603 auto *ScopeInfo = S.getCurFunction();
604 assert(ScopeInfo && "missing function scope for function");
605
606 if (ScopeInfo->FirstCoroutineStmtLoc.isInvalid() && !IsImplicit)
607 ScopeInfo->setFirstCoroutineStmt(Loc, Keyword);
608
609 if (ScopeInfo->CoroutinePromise)
610 return ScopeInfo;
611
612 if (!S.buildCoroutineParameterMoves(Loc))
613 return nullptr;
614
615 ScopeInfo->CoroutinePromise = S.buildCoroutinePromise(Loc);
616 if (!ScopeInfo->CoroutinePromise)
617 return nullptr;
618
619 return ScopeInfo;
620 }
621
ActOnCoroutineBodyStart(Scope * SC,SourceLocation KWLoc,StringRef Keyword)622 bool Sema::ActOnCoroutineBodyStart(Scope *SC, SourceLocation KWLoc,
623 StringRef Keyword) {
624 if (!checkCoroutineContext(*this, KWLoc, Keyword))
625 return false;
626 auto *ScopeInfo = getCurFunction();
627 assert(ScopeInfo->CoroutinePromise);
628
629 // If we have existing coroutine statements then we have already built
630 // the initial and final suspend points.
631 if (!ScopeInfo->NeedsCoroutineSuspends)
632 return true;
633
634 ScopeInfo->setNeedsCoroutineSuspends(false);
635
636 auto *Fn = cast<FunctionDecl>(CurContext);
637 SourceLocation Loc = Fn->getLocation();
638 // Build the initial suspend point
639 auto buildSuspends = [&](StringRef Name) mutable -> StmtResult {
640 ExprResult Suspend =
641 buildPromiseCall(*this, ScopeInfo->CoroutinePromise, Loc, Name, None);
642 if (Suspend.isInvalid())
643 return StmtError();
644 Suspend = buildOperatorCoawaitCall(*this, SC, Loc, Suspend.get());
645 if (Suspend.isInvalid())
646 return StmtError();
647 Suspend = BuildResolvedCoawaitExpr(Loc, Suspend.get(),
648 /*IsImplicit*/ true);
649 Suspend = ActOnFinishFullExpr(Suspend.get());
650 if (Suspend.isInvalid()) {
651 Diag(Loc, diag::note_coroutine_promise_suspend_implicitly_required)
652 << ((Name == "initial_suspend") ? 0 : 1);
653 Diag(KWLoc, diag::note_declared_coroutine_here) << Keyword;
654 return StmtError();
655 }
656 return cast<Stmt>(Suspend.get());
657 };
658
659 StmtResult InitSuspend = buildSuspends("initial_suspend");
660 if (InitSuspend.isInvalid())
661 return true;
662
663 StmtResult FinalSuspend = buildSuspends("final_suspend");
664 if (FinalSuspend.isInvalid())
665 return true;
666
667 ScopeInfo->setCoroutineSuspends(InitSuspend.get(), FinalSuspend.get());
668
669 return true;
670 }
671
ActOnCoawaitExpr(Scope * S,SourceLocation Loc,Expr * E)672 ExprResult Sema::ActOnCoawaitExpr(Scope *S, SourceLocation Loc, Expr *E) {
673 if (!ActOnCoroutineBodyStart(S, Loc, "co_await")) {
674 CorrectDelayedTyposInExpr(E);
675 return ExprError();
676 }
677
678 if (E->getType()->isPlaceholderType()) {
679 ExprResult R = CheckPlaceholderExpr(E);
680 if (R.isInvalid()) return ExprError();
681 E = R.get();
682 }
683 ExprResult Lookup = buildOperatorCoawaitLookupExpr(*this, S, Loc);
684 if (Lookup.isInvalid())
685 return ExprError();
686 return BuildUnresolvedCoawaitExpr(Loc, E,
687 cast<UnresolvedLookupExpr>(Lookup.get()));
688 }
689
BuildUnresolvedCoawaitExpr(SourceLocation Loc,Expr * E,UnresolvedLookupExpr * Lookup)690 ExprResult Sema::BuildUnresolvedCoawaitExpr(SourceLocation Loc, Expr *E,
691 UnresolvedLookupExpr *Lookup) {
692 auto *FSI = checkCoroutineContext(*this, Loc, "co_await");
693 if (!FSI)
694 return ExprError();
695
696 if (E->getType()->isPlaceholderType()) {
697 ExprResult R = CheckPlaceholderExpr(E);
698 if (R.isInvalid())
699 return ExprError();
700 E = R.get();
701 }
702
703 auto *Promise = FSI->CoroutinePromise;
704 if (Promise->getType()->isDependentType()) {
705 Expr *Res =
706 new (Context) DependentCoawaitExpr(Loc, Context.DependentTy, E, Lookup);
707 return Res;
708 }
709
710 auto *RD = Promise->getType()->getAsCXXRecordDecl();
711 if (lookupMember(*this, "await_transform", RD, Loc)) {
712 ExprResult R = buildPromiseCall(*this, Promise, Loc, "await_transform", E);
713 if (R.isInvalid()) {
714 Diag(Loc,
715 diag::note_coroutine_promise_implicit_await_transform_required_here)
716 << E->getSourceRange();
717 return ExprError();
718 }
719 E = R.get();
720 }
721 ExprResult Awaitable = buildOperatorCoawaitCall(*this, Loc, E, Lookup);
722 if (Awaitable.isInvalid())
723 return ExprError();
724
725 return BuildResolvedCoawaitExpr(Loc, Awaitable.get());
726 }
727
BuildResolvedCoawaitExpr(SourceLocation Loc,Expr * E,bool IsImplicit)728 ExprResult Sema::BuildResolvedCoawaitExpr(SourceLocation Loc, Expr *E,
729 bool IsImplicit) {
730 auto *Coroutine = checkCoroutineContext(*this, Loc, "co_await", IsImplicit);
731 if (!Coroutine)
732 return ExprError();
733
734 if (E->getType()->isPlaceholderType()) {
735 ExprResult R = CheckPlaceholderExpr(E);
736 if (R.isInvalid()) return ExprError();
737 E = R.get();
738 }
739
740 if (E->getType()->isDependentType()) {
741 Expr *Res = new (Context)
742 CoawaitExpr(Loc, Context.DependentTy, E, IsImplicit);
743 return Res;
744 }
745
746 // If the expression is a temporary, materialize it as an lvalue so that we
747 // can use it multiple times.
748 if (E->getValueKind() == VK_RValue)
749 E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
750
751 // The location of the `co_await` token cannot be used when constructing
752 // the member call expressions since it's before the location of `Expr`, which
753 // is used as the start of the member call expression.
754 SourceLocation CallLoc = E->getExprLoc();
755
756 // Build the await_ready, await_suspend, await_resume calls.
757 ReadySuspendResumeResult RSS =
758 buildCoawaitCalls(*this, Coroutine->CoroutinePromise, CallLoc, E);
759 if (RSS.IsInvalid)
760 return ExprError();
761
762 Expr *Res =
763 new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
764 RSS.Results[2], RSS.OpaqueValue, IsImplicit);
765
766 return Res;
767 }
768
ActOnCoyieldExpr(Scope * S,SourceLocation Loc,Expr * E)769 ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) {
770 if (!ActOnCoroutineBodyStart(S, Loc, "co_yield")) {
771 CorrectDelayedTyposInExpr(E);
772 return ExprError();
773 }
774
775 // Build yield_value call.
776 ExprResult Awaitable = buildPromiseCall(
777 *this, getCurFunction()->CoroutinePromise, Loc, "yield_value", E);
778 if (Awaitable.isInvalid())
779 return ExprError();
780
781 // Build 'operator co_await' call.
782 Awaitable = buildOperatorCoawaitCall(*this, S, Loc, Awaitable.get());
783 if (Awaitable.isInvalid())
784 return ExprError();
785
786 return BuildCoyieldExpr(Loc, Awaitable.get());
787 }
BuildCoyieldExpr(SourceLocation Loc,Expr * E)788 ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
789 auto *Coroutine = checkCoroutineContext(*this, Loc, "co_yield");
790 if (!Coroutine)
791 return ExprError();
792
793 if (E->getType()->isPlaceholderType()) {
794 ExprResult R = CheckPlaceholderExpr(E);
795 if (R.isInvalid()) return ExprError();
796 E = R.get();
797 }
798
799 if (E->getType()->isDependentType()) {
800 Expr *Res = new (Context) CoyieldExpr(Loc, Context.DependentTy, E);
801 return Res;
802 }
803
804 // If the expression is a temporary, materialize it as an lvalue so that we
805 // can use it multiple times.
806 if (E->getValueKind() == VK_RValue)
807 E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
808
809 // Build the await_ready, await_suspend, await_resume calls.
810 ReadySuspendResumeResult RSS =
811 buildCoawaitCalls(*this, Coroutine->CoroutinePromise, Loc, E);
812 if (RSS.IsInvalid)
813 return ExprError();
814
815 Expr *Res =
816 new (Context) CoyieldExpr(Loc, E, RSS.Results[0], RSS.Results[1],
817 RSS.Results[2], RSS.OpaqueValue);
818
819 return Res;
820 }
821
ActOnCoreturnStmt(Scope * S,SourceLocation Loc,Expr * E)822 StmtResult Sema::ActOnCoreturnStmt(Scope *S, SourceLocation Loc, Expr *E) {
823 if (!ActOnCoroutineBodyStart(S, Loc, "co_return")) {
824 CorrectDelayedTyposInExpr(E);
825 return StmtError();
826 }
827 return BuildCoreturnStmt(Loc, E);
828 }
829
BuildCoreturnStmt(SourceLocation Loc,Expr * E,bool IsImplicit)830 StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E,
831 bool IsImplicit) {
832 auto *FSI = checkCoroutineContext(*this, Loc, "co_return", IsImplicit);
833 if (!FSI)
834 return StmtError();
835
836 if (E && E->getType()->isPlaceholderType() &&
837 !E->getType()->isSpecificPlaceholderType(BuiltinType::Overload)) {
838 ExprResult R = CheckPlaceholderExpr(E);
839 if (R.isInvalid()) return StmtError();
840 E = R.get();
841 }
842
843 // Move the return value if we can
844 if (E) {
845 auto NRVOCandidate = this->getCopyElisionCandidate(E->getType(), E, CES_AsIfByStdMove);
846 if (NRVOCandidate) {
847 InitializedEntity Entity =
848 InitializedEntity::InitializeResult(Loc, E->getType(), NRVOCandidate);
849 ExprResult MoveResult = this->PerformMoveOrCopyInitialization(
850 Entity, NRVOCandidate, E->getType(), E);
851 if (MoveResult.get())
852 E = MoveResult.get();
853 }
854 }
855
856 // FIXME: If the operand is a reference to a variable that's about to go out
857 // of scope, we should treat the operand as an xvalue for this overload
858 // resolution.
859 VarDecl *Promise = FSI->CoroutinePromise;
860 ExprResult PC;
861 if (E && (isa<InitListExpr>(E) || !E->getType()->isVoidType())) {
862 PC = buildPromiseCall(*this, Promise, Loc, "return_value", E);
863 } else {
864 E = MakeFullDiscardedValueExpr(E).get();
865 PC = buildPromiseCall(*this, Promise, Loc, "return_void", None);
866 }
867 if (PC.isInvalid())
868 return StmtError();
869
870 Expr *PCE = ActOnFinishFullExpr(PC.get()).get();
871
872 Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE, IsImplicit);
873 return Res;
874 }
875
876 /// Look up the std::nothrow object.
buildStdNoThrowDeclRef(Sema & S,SourceLocation Loc)877 static Expr *buildStdNoThrowDeclRef(Sema &S, SourceLocation Loc) {
878 NamespaceDecl *Std = S.getStdNamespace();
879 assert(Std && "Should already be diagnosed");
880
881 LookupResult Result(S, &S.PP.getIdentifierTable().get("nothrow"), Loc,
882 Sema::LookupOrdinaryName);
883 if (!S.LookupQualifiedName(Result, Std)) {
884 // FIXME: <experimental/coroutine> should have been included already.
885 // If we require it to include <new> then this diagnostic is no longer
886 // needed.
887 S.Diag(Loc, diag::err_implicit_coroutine_std_nothrow_type_not_found);
888 return nullptr;
889 }
890
891 auto *VD = Result.getAsSingle<VarDecl>();
892 if (!VD) {
893 Result.suppressDiagnostics();
894 // We found something weird. Complain about the first thing we found.
895 NamedDecl *Found = *Result.begin();
896 S.Diag(Found->getLocation(), diag::err_malformed_std_nothrow);
897 return nullptr;
898 }
899
900 ExprResult DR = S.BuildDeclRefExpr(VD, VD->getType(), VK_LValue, Loc);
901 if (DR.isInvalid())
902 return nullptr;
903
904 return DR.get();
905 }
906
907 // Find an appropriate delete for the promise.
findDeleteForPromise(Sema & S,SourceLocation Loc,QualType PromiseType)908 static FunctionDecl *findDeleteForPromise(Sema &S, SourceLocation Loc,
909 QualType PromiseType) {
910 FunctionDecl *OperatorDelete = nullptr;
911
912 DeclarationName DeleteName =
913 S.Context.DeclarationNames.getCXXOperatorName(OO_Delete);
914
915 auto *PointeeRD = PromiseType->getAsCXXRecordDecl();
916 assert(PointeeRD && "PromiseType must be a CxxRecordDecl type");
917
918 if (S.FindDeallocationFunction(Loc, PointeeRD, DeleteName, OperatorDelete))
919 return nullptr;
920
921 if (!OperatorDelete) {
922 // Look for a global declaration.
923 const bool CanProvideSize = S.isCompleteType(Loc, PromiseType);
924 const bool Overaligned = false;
925 OperatorDelete = S.FindUsualDeallocationFunction(Loc, CanProvideSize,
926 Overaligned, DeleteName);
927 }
928 S.MarkFunctionReferenced(Loc, OperatorDelete);
929 return OperatorDelete;
930 }
931
932
CheckCompletedCoroutineBody(FunctionDecl * FD,Stmt * & Body)933 void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
934 FunctionScopeInfo *Fn = getCurFunction();
935 assert(Fn && Fn->isCoroutine() && "not a coroutine");
936 if (!Body) {
937 assert(FD->isInvalidDecl() &&
938 "a null body is only allowed for invalid declarations");
939 return;
940 }
941 // We have a function that uses coroutine keywords, but we failed to build
942 // the promise type.
943 if (!Fn->CoroutinePromise)
944 return FD->setInvalidDecl();
945
946 if (isa<CoroutineBodyStmt>(Body)) {
947 // Nothing todo. the body is already a transformed coroutine body statement.
948 return;
949 }
950
951 // Coroutines [stmt.return]p1:
952 // A return statement shall not appear in a coroutine.
953 if (Fn->FirstReturnLoc.isValid()) {
954 assert(Fn->FirstCoroutineStmtLoc.isValid() &&
955 "first coroutine location not set");
956 Diag(Fn->FirstReturnLoc, diag::err_return_in_coroutine);
957 Diag(Fn->FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
958 << Fn->getFirstCoroutineStmtKeyword();
959 }
960 CoroutineStmtBuilder Builder(*this, *FD, *Fn, Body);
961 if (Builder.isInvalid() || !Builder.buildStatements())
962 return FD->setInvalidDecl();
963
964 // Build body for the coroutine wrapper statement.
965 Body = CoroutineBodyStmt::Create(Context, Builder);
966 }
967
CoroutineStmtBuilder(Sema & S,FunctionDecl & FD,sema::FunctionScopeInfo & Fn,Stmt * Body)968 CoroutineStmtBuilder::CoroutineStmtBuilder(Sema &S, FunctionDecl &FD,
969 sema::FunctionScopeInfo &Fn,
970 Stmt *Body)
971 : S(S), FD(FD), Fn(Fn), Loc(FD.getLocation()),
972 IsPromiseDependentType(
973 !Fn.CoroutinePromise ||
974 Fn.CoroutinePromise->getType()->isDependentType()) {
975 this->Body = Body;
976
977 for (auto KV : Fn.CoroutineParameterMoves)
978 this->ParamMovesVector.push_back(KV.second);
979 this->ParamMoves = this->ParamMovesVector;
980
981 if (!IsPromiseDependentType) {
982 PromiseRecordDecl = Fn.CoroutinePromise->getType()->getAsCXXRecordDecl();
983 assert(PromiseRecordDecl && "Type should have already been checked");
984 }
985 this->IsValid = makePromiseStmt() && makeInitialAndFinalSuspend();
986 }
987
buildStatements()988 bool CoroutineStmtBuilder::buildStatements() {
989 assert(this->IsValid && "coroutine already invalid");
990 this->IsValid = makeReturnObject();
991 if (this->IsValid && !IsPromiseDependentType)
992 buildDependentStatements();
993 return this->IsValid;
994 }
995
buildDependentStatements()996 bool CoroutineStmtBuilder::buildDependentStatements() {
997 assert(this->IsValid && "coroutine already invalid");
998 assert(!this->IsPromiseDependentType &&
999 "coroutine cannot have a dependent promise type");
1000 this->IsValid = makeOnException() && makeOnFallthrough() &&
1001 makeGroDeclAndReturnStmt() && makeReturnOnAllocFailure() &&
1002 makeNewAndDeleteExpr();
1003 return this->IsValid;
1004 }
1005
makePromiseStmt()1006 bool CoroutineStmtBuilder::makePromiseStmt() {
1007 // Form a declaration statement for the promise declaration, so that AST
1008 // visitors can more easily find it.
1009 StmtResult PromiseStmt =
1010 S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(Fn.CoroutinePromise), Loc, Loc);
1011 if (PromiseStmt.isInvalid())
1012 return false;
1013
1014 this->Promise = PromiseStmt.get();
1015 return true;
1016 }
1017
makeInitialAndFinalSuspend()1018 bool CoroutineStmtBuilder::makeInitialAndFinalSuspend() {
1019 if (Fn.hasInvalidCoroutineSuspends())
1020 return false;
1021 this->InitialSuspend = cast<Expr>(Fn.CoroutineSuspends.first);
1022 this->FinalSuspend = cast<Expr>(Fn.CoroutineSuspends.second);
1023 return true;
1024 }
1025
diagReturnOnAllocFailure(Sema & S,Expr * E,CXXRecordDecl * PromiseRecordDecl,FunctionScopeInfo & Fn)1026 static bool diagReturnOnAllocFailure(Sema &S, Expr *E,
1027 CXXRecordDecl *PromiseRecordDecl,
1028 FunctionScopeInfo &Fn) {
1029 auto Loc = E->getExprLoc();
1030 if (auto *DeclRef = dyn_cast_or_null<DeclRefExpr>(E)) {
1031 auto *Decl = DeclRef->getDecl();
1032 if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(Decl)) {
1033 if (Method->isStatic())
1034 return true;
1035 else
1036 Loc = Decl->getLocation();
1037 }
1038 }
1039
1040 S.Diag(
1041 Loc,
1042 diag::err_coroutine_promise_get_return_object_on_allocation_failure)
1043 << PromiseRecordDecl;
1044 S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1045 << Fn.getFirstCoroutineStmtKeyword();
1046 return false;
1047 }
1048
makeReturnOnAllocFailure()1049 bool CoroutineStmtBuilder::makeReturnOnAllocFailure() {
1050 assert(!IsPromiseDependentType &&
1051 "cannot make statement while the promise type is dependent");
1052
1053 // [dcl.fct.def.coroutine]/8
1054 // The unqualified-id get_return_object_on_allocation_failure is looked up in
1055 // the scope of class P by class member access lookup (3.4.5). ...
1056 // If an allocation function returns nullptr, ... the coroutine return value
1057 // is obtained by a call to ... get_return_object_on_allocation_failure().
1058
1059 DeclarationName DN =
1060 S.PP.getIdentifierInfo("get_return_object_on_allocation_failure");
1061 LookupResult Found(S, DN, Loc, Sema::LookupMemberName);
1062 if (!S.LookupQualifiedName(Found, PromiseRecordDecl))
1063 return true;
1064
1065 CXXScopeSpec SS;
1066 ExprResult DeclNameExpr =
1067 S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
1068 if (DeclNameExpr.isInvalid())
1069 return false;
1070
1071 if (!diagReturnOnAllocFailure(S, DeclNameExpr.get(), PromiseRecordDecl, Fn))
1072 return false;
1073
1074 ExprResult ReturnObjectOnAllocationFailure =
1075 S.ActOnCallExpr(nullptr, DeclNameExpr.get(), Loc, {}, Loc);
1076 if (ReturnObjectOnAllocationFailure.isInvalid())
1077 return false;
1078
1079 StmtResult ReturnStmt =
1080 S.BuildReturnStmt(Loc, ReturnObjectOnAllocationFailure.get());
1081 if (ReturnStmt.isInvalid()) {
1082 S.Diag(Found.getFoundDecl()->getLocation(), diag::note_member_declared_here)
1083 << DN;
1084 S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1085 << Fn.getFirstCoroutineStmtKeyword();
1086 return false;
1087 }
1088
1089 this->ReturnStmtOnAllocFailure = ReturnStmt.get();
1090 return true;
1091 }
1092
makeNewAndDeleteExpr()1093 bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
1094 // Form and check allocation and deallocation calls.
1095 assert(!IsPromiseDependentType &&
1096 "cannot make statement while the promise type is dependent");
1097 QualType PromiseType = Fn.CoroutinePromise->getType();
1098
1099 if (S.RequireCompleteType(Loc, PromiseType, diag::err_incomplete_type))
1100 return false;
1101
1102 const bool RequiresNoThrowAlloc = ReturnStmtOnAllocFailure != nullptr;
1103
1104 // [dcl.fct.def.coroutine]/7
1105 // Lookup allocation functions using a parameter list composed of the
1106 // requested size of the coroutine state being allocated, followed by
1107 // the coroutine function's arguments. If a matching allocation function
1108 // exists, use it. Otherwise, use an allocation function that just takes
1109 // the requested size.
1110
1111 FunctionDecl *OperatorNew = nullptr;
1112 FunctionDecl *OperatorDelete = nullptr;
1113 FunctionDecl *UnusedResult = nullptr;
1114 bool PassAlignment = false;
1115 SmallVector<Expr *, 1> PlacementArgs;
1116
1117 // [dcl.fct.def.coroutine]/7
1118 // "The allocation function’s name is looked up in the scope of P.
1119 // [...] If the lookup finds an allocation function in the scope of P,
1120 // overload resolution is performed on a function call created by assembling
1121 // an argument list. The first argument is the amount of space requested,
1122 // and has type std::size_t. The lvalues p1 ... pn are the succeeding
1123 // arguments."
1124 //
1125 // ...where "p1 ... pn" are defined earlier as:
1126 //
1127 // [dcl.fct.def.coroutine]/3
1128 // "For a coroutine f that is a non-static member function, let P1 denote the
1129 // type of the implicit object parameter (13.3.1) and P2 ... Pn be the types
1130 // of the function parameters; otherwise let P1 ... Pn be the types of the
1131 // function parameters. Let p1 ... pn be lvalues denoting those objects."
1132 if (auto *MD = dyn_cast<CXXMethodDecl>(&FD)) {
1133 if (MD->isInstance() && !isLambdaCallOperator(MD)) {
1134 ExprResult ThisExpr = S.ActOnCXXThis(Loc);
1135 if (ThisExpr.isInvalid())
1136 return false;
1137 ThisExpr = S.CreateBuiltinUnaryOp(Loc, UO_Deref, ThisExpr.get());
1138 if (ThisExpr.isInvalid())
1139 return false;
1140 PlacementArgs.push_back(ThisExpr.get());
1141 }
1142 }
1143 for (auto *PD : FD.parameters()) {
1144 if (PD->getType()->isDependentType())
1145 continue;
1146
1147 // Build a reference to the parameter.
1148 auto PDLoc = PD->getLocation();
1149 ExprResult PDRefExpr =
1150 S.BuildDeclRefExpr(PD, PD->getOriginalType().getNonReferenceType(),
1151 ExprValueKind::VK_LValue, PDLoc);
1152 if (PDRefExpr.isInvalid())
1153 return false;
1154
1155 PlacementArgs.push_back(PDRefExpr.get());
1156 }
1157 S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Class,
1158 /*DeleteScope*/ Sema::AFS_Both, PromiseType,
1159 /*isArray*/ false, PassAlignment, PlacementArgs,
1160 OperatorNew, UnusedResult, /*Diagnose*/ false);
1161
1162 // [dcl.fct.def.coroutine]/7
1163 // "If no matching function is found, overload resolution is performed again
1164 // on a function call created by passing just the amount of space required as
1165 // an argument of type std::size_t."
1166 if (!OperatorNew && !PlacementArgs.empty()) {
1167 PlacementArgs.clear();
1168 S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Class,
1169 /*DeleteScope*/ Sema::AFS_Both, PromiseType,
1170 /*isArray*/ false, PassAlignment, PlacementArgs,
1171 OperatorNew, UnusedResult, /*Diagnose*/ false);
1172 }
1173
1174 // [dcl.fct.def.coroutine]/7
1175 // "The allocation function’s name is looked up in the scope of P. If this
1176 // lookup fails, the allocation function’s name is looked up in the global
1177 // scope."
1178 if (!OperatorNew) {
1179 S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Global,
1180 /*DeleteScope*/ Sema::AFS_Both, PromiseType,
1181 /*isArray*/ false, PassAlignment, PlacementArgs,
1182 OperatorNew, UnusedResult);
1183 }
1184
1185 bool IsGlobalOverload =
1186 OperatorNew && !isa<CXXRecordDecl>(OperatorNew->getDeclContext());
1187 // If we didn't find a class-local new declaration and non-throwing new
1188 // was is required then we need to lookup the non-throwing global operator
1189 // instead.
1190 if (RequiresNoThrowAlloc && (!OperatorNew || IsGlobalOverload)) {
1191 auto *StdNoThrow = buildStdNoThrowDeclRef(S, Loc);
1192 if (!StdNoThrow)
1193 return false;
1194 PlacementArgs = {StdNoThrow};
1195 OperatorNew = nullptr;
1196 S.FindAllocationFunctions(Loc, SourceRange(), /*NewScope*/ Sema::AFS_Both,
1197 /*DeleteScope*/ Sema::AFS_Both, PromiseType,
1198 /*isArray*/ false, PassAlignment, PlacementArgs,
1199 OperatorNew, UnusedResult);
1200 }
1201
1202 if (!OperatorNew)
1203 return false;
1204
1205 if (RequiresNoThrowAlloc) {
1206 const auto *FT = OperatorNew->getType()->getAs<FunctionProtoType>();
1207 if (!FT->isNothrow(/*ResultIfDependent*/ false)) {
1208 S.Diag(OperatorNew->getLocation(),
1209 diag::err_coroutine_promise_new_requires_nothrow)
1210 << OperatorNew;
1211 S.Diag(Loc, diag::note_coroutine_promise_call_implicitly_required)
1212 << OperatorNew;
1213 return false;
1214 }
1215 }
1216
1217 if ((OperatorDelete = findDeleteForPromise(S, Loc, PromiseType)) == nullptr)
1218 return false;
1219
1220 Expr *FramePtr =
1221 buildBuiltinCall(S, Loc, Builtin::BI__builtin_coro_frame, {});
1222
1223 Expr *FrameSize =
1224 buildBuiltinCall(S, Loc, Builtin::BI__builtin_coro_size, {});
1225
1226 // Make new call.
1227
1228 ExprResult NewRef =
1229 S.BuildDeclRefExpr(OperatorNew, OperatorNew->getType(), VK_LValue, Loc);
1230 if (NewRef.isInvalid())
1231 return false;
1232
1233 SmallVector<Expr *, 2> NewArgs(1, FrameSize);
1234 for (auto Arg : PlacementArgs)
1235 NewArgs.push_back(Arg);
1236
1237 ExprResult NewExpr =
1238 S.ActOnCallExpr(S.getCurScope(), NewRef.get(), Loc, NewArgs, Loc);
1239 NewExpr = S.ActOnFinishFullExpr(NewExpr.get());
1240 if (NewExpr.isInvalid())
1241 return false;
1242
1243 // Make delete call.
1244
1245 QualType OpDeleteQualType = OperatorDelete->getType();
1246
1247 ExprResult DeleteRef =
1248 S.BuildDeclRefExpr(OperatorDelete, OpDeleteQualType, VK_LValue, Loc);
1249 if (DeleteRef.isInvalid())
1250 return false;
1251
1252 Expr *CoroFree =
1253 buildBuiltinCall(S, Loc, Builtin::BI__builtin_coro_free, {FramePtr});
1254
1255 SmallVector<Expr *, 2> DeleteArgs{CoroFree};
1256
1257 // Check if we need to pass the size.
1258 const auto *OpDeleteType =
1259 OpDeleteQualType.getTypePtr()->getAs<FunctionProtoType>();
1260 if (OpDeleteType->getNumParams() > 1)
1261 DeleteArgs.push_back(FrameSize);
1262
1263 ExprResult DeleteExpr =
1264 S.ActOnCallExpr(S.getCurScope(), DeleteRef.get(), Loc, DeleteArgs, Loc);
1265 DeleteExpr = S.ActOnFinishFullExpr(DeleteExpr.get());
1266 if (DeleteExpr.isInvalid())
1267 return false;
1268
1269 this->Allocate = NewExpr.get();
1270 this->Deallocate = DeleteExpr.get();
1271
1272 return true;
1273 }
1274
makeOnFallthrough()1275 bool CoroutineStmtBuilder::makeOnFallthrough() {
1276 assert(!IsPromiseDependentType &&
1277 "cannot make statement while the promise type is dependent");
1278
1279 // [dcl.fct.def.coroutine]/4
1280 // The unqualified-ids 'return_void' and 'return_value' are looked up in
1281 // the scope of class P. If both are found, the program is ill-formed.
1282 bool HasRVoid, HasRValue;
1283 LookupResult LRVoid =
1284 lookupMember(S, "return_void", PromiseRecordDecl, Loc, HasRVoid);
1285 LookupResult LRValue =
1286 lookupMember(S, "return_value", PromiseRecordDecl, Loc, HasRValue);
1287
1288 StmtResult Fallthrough;
1289 if (HasRVoid && HasRValue) {
1290 // FIXME Improve this diagnostic
1291 S.Diag(FD.getLocation(),
1292 diag::err_coroutine_promise_incompatible_return_functions)
1293 << PromiseRecordDecl;
1294 S.Diag(LRVoid.getRepresentativeDecl()->getLocation(),
1295 diag::note_member_first_declared_here)
1296 << LRVoid.getLookupName();
1297 S.Diag(LRValue.getRepresentativeDecl()->getLocation(),
1298 diag::note_member_first_declared_here)
1299 << LRValue.getLookupName();
1300 return false;
1301 } else if (!HasRVoid && !HasRValue) {
1302 // FIXME: The PDTS currently specifies this case as UB, not ill-formed.
1303 // However we still diagnose this as an error since until the PDTS is fixed.
1304 S.Diag(FD.getLocation(),
1305 diag::err_coroutine_promise_requires_return_function)
1306 << PromiseRecordDecl;
1307 S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
1308 << PromiseRecordDecl;
1309 return false;
1310 } else if (HasRVoid) {
1311 // If the unqualified-id return_void is found, flowing off the end of a
1312 // coroutine is equivalent to a co_return with no operand. Otherwise,
1313 // flowing off the end of a coroutine results in undefined behavior.
1314 Fallthrough = S.BuildCoreturnStmt(FD.getLocation(), nullptr,
1315 /*IsImplicit*/false);
1316 Fallthrough = S.ActOnFinishFullStmt(Fallthrough.get());
1317 if (Fallthrough.isInvalid())
1318 return false;
1319 }
1320
1321 this->OnFallthrough = Fallthrough.get();
1322 return true;
1323 }
1324
makeOnException()1325 bool CoroutineStmtBuilder::makeOnException() {
1326 // Try to form 'p.unhandled_exception();'
1327 assert(!IsPromiseDependentType &&
1328 "cannot make statement while the promise type is dependent");
1329
1330 const bool RequireUnhandledException = S.getLangOpts().CXXExceptions;
1331
1332 if (!lookupMember(S, "unhandled_exception", PromiseRecordDecl, Loc)) {
1333 auto DiagID =
1334 RequireUnhandledException
1335 ? diag::err_coroutine_promise_unhandled_exception_required
1336 : diag::
1337 warn_coroutine_promise_unhandled_exception_required_with_exceptions;
1338 S.Diag(Loc, DiagID) << PromiseRecordDecl;
1339 S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
1340 << PromiseRecordDecl;
1341 return !RequireUnhandledException;
1342 }
1343
1344 // If exceptions are disabled, don't try to build OnException.
1345 if (!S.getLangOpts().CXXExceptions)
1346 return true;
1347
1348 ExprResult UnhandledException = buildPromiseCall(S, Fn.CoroutinePromise, Loc,
1349 "unhandled_exception", None);
1350 UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(), Loc);
1351 if (UnhandledException.isInvalid())
1352 return false;
1353
1354 // Since the body of the coroutine will be wrapped in try-catch, it will
1355 // be incompatible with SEH __try if present in a function.
1356 if (!S.getLangOpts().Borland && Fn.FirstSEHTryLoc.isValid()) {
1357 S.Diag(Fn.FirstSEHTryLoc, diag::err_seh_in_a_coroutine_with_cxx_exceptions);
1358 S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1359 << Fn.getFirstCoroutineStmtKeyword();
1360 return false;
1361 }
1362
1363 this->OnException = UnhandledException.get();
1364 return true;
1365 }
1366
makeReturnObject()1367 bool CoroutineStmtBuilder::makeReturnObject() {
1368 // Build implicit 'p.get_return_object()' expression and form initialization
1369 // of return type from it.
1370 ExprResult ReturnObject =
1371 buildPromiseCall(S, Fn.CoroutinePromise, Loc, "get_return_object", None);
1372 if (ReturnObject.isInvalid())
1373 return false;
1374
1375 this->ReturnValue = ReturnObject.get();
1376 return true;
1377 }
1378
noteMemberDeclaredHere(Sema & S,Expr * E,FunctionScopeInfo & Fn)1379 static void noteMemberDeclaredHere(Sema &S, Expr *E, FunctionScopeInfo &Fn) {
1380 if (auto *MbrRef = dyn_cast<CXXMemberCallExpr>(E)) {
1381 auto *MethodDecl = MbrRef->getMethodDecl();
1382 S.Diag(MethodDecl->getLocation(), diag::note_member_declared_here)
1383 << MethodDecl;
1384 }
1385 S.Diag(Fn.FirstCoroutineStmtLoc, diag::note_declared_coroutine_here)
1386 << Fn.getFirstCoroutineStmtKeyword();
1387 }
1388
makeGroDeclAndReturnStmt()1389 bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
1390 assert(!IsPromiseDependentType &&
1391 "cannot make statement while the promise type is dependent");
1392 assert(this->ReturnValue && "ReturnValue must be already formed");
1393
1394 QualType const GroType = this->ReturnValue->getType();
1395 assert(!GroType->isDependentType() &&
1396 "get_return_object type must no longer be dependent");
1397
1398 QualType const FnRetType = FD.getReturnType();
1399 assert(!FnRetType->isDependentType() &&
1400 "get_return_object type must no longer be dependent");
1401
1402 if (FnRetType->isVoidType()) {
1403 ExprResult Res = S.ActOnFinishFullExpr(this->ReturnValue, Loc);
1404 if (Res.isInvalid())
1405 return false;
1406
1407 this->ResultDecl = Res.get();
1408 return true;
1409 }
1410
1411 if (GroType->isVoidType()) {
1412 // Trigger a nice error message.
1413 InitializedEntity Entity =
1414 InitializedEntity::InitializeResult(Loc, FnRetType, false);
1415 S.PerformMoveOrCopyInitialization(Entity, nullptr, FnRetType, ReturnValue);
1416 noteMemberDeclaredHere(S, ReturnValue, Fn);
1417 return false;
1418 }
1419
1420 auto *GroDecl = VarDecl::Create(
1421 S.Context, &FD, FD.getLocation(), FD.getLocation(),
1422 &S.PP.getIdentifierTable().get("__coro_gro"), GroType,
1423 S.Context.getTrivialTypeSourceInfo(GroType, Loc), SC_None);
1424
1425 S.CheckVariableDeclarationType(GroDecl);
1426 if (GroDecl->isInvalidDecl())
1427 return false;
1428
1429 InitializedEntity Entity = InitializedEntity::InitializeVariable(GroDecl);
1430 ExprResult Res = S.PerformMoveOrCopyInitialization(Entity, nullptr, GroType,
1431 this->ReturnValue);
1432 if (Res.isInvalid())
1433 return false;
1434
1435 Res = S.ActOnFinishFullExpr(Res.get());
1436 if (Res.isInvalid())
1437 return false;
1438
1439 S.AddInitializerToDecl(GroDecl, Res.get(),
1440 /*DirectInit=*/false);
1441
1442 S.FinalizeDeclaration(GroDecl);
1443
1444 // Form a declaration statement for the return declaration, so that AST
1445 // visitors can more easily find it.
1446 StmtResult GroDeclStmt =
1447 S.ActOnDeclStmt(S.ConvertDeclToDeclGroup(GroDecl), Loc, Loc);
1448 if (GroDeclStmt.isInvalid())
1449 return false;
1450
1451 this->ResultDecl = GroDeclStmt.get();
1452
1453 ExprResult declRef = S.BuildDeclRefExpr(GroDecl, GroType, VK_LValue, Loc);
1454 if (declRef.isInvalid())
1455 return false;
1456
1457 StmtResult ReturnStmt = S.BuildReturnStmt(Loc, declRef.get());
1458 if (ReturnStmt.isInvalid()) {
1459 noteMemberDeclaredHere(S, ReturnValue, Fn);
1460 return false;
1461 }
1462 if (cast<clang::ReturnStmt>(ReturnStmt.get())->getNRVOCandidate() == GroDecl)
1463 GroDecl->setNRVOVariable(true);
1464
1465 this->ReturnStmt = ReturnStmt.get();
1466 return true;
1467 }
1468
1469 // Create a static_cast\<T&&>(expr).
castForMoving(Sema & S,Expr * E,QualType T=QualType ())1470 static Expr *castForMoving(Sema &S, Expr *E, QualType T = QualType()) {
1471 if (T.isNull())
1472 T = E->getType();
1473 QualType TargetType = S.BuildReferenceType(
1474 T, /*SpelledAsLValue*/ false, SourceLocation(), DeclarationName());
1475 SourceLocation ExprLoc = E->getBeginLoc();
1476 TypeSourceInfo *TargetLoc =
1477 S.Context.getTrivialTypeSourceInfo(TargetType, ExprLoc);
1478
1479 return S
1480 .BuildCXXNamedCast(ExprLoc, tok::kw_static_cast, TargetLoc, E,
1481 SourceRange(ExprLoc, ExprLoc), E->getSourceRange())
1482 .get();
1483 }
1484
1485 /// Build a variable declaration for move parameter.
buildVarDecl(Sema & S,SourceLocation Loc,QualType Type,IdentifierInfo * II)1486 static VarDecl *buildVarDecl(Sema &S, SourceLocation Loc, QualType Type,
1487 IdentifierInfo *II) {
1488 TypeSourceInfo *TInfo = S.Context.getTrivialTypeSourceInfo(Type, Loc);
1489 VarDecl *Decl = VarDecl::Create(S.Context, S.CurContext, Loc, Loc, II, Type,
1490 TInfo, SC_None);
1491 Decl->setImplicit();
1492 return Decl;
1493 }
1494
1495 // Build statements that move coroutine function parameters to the coroutine
1496 // frame, and store them on the function scope info.
buildCoroutineParameterMoves(SourceLocation Loc)1497 bool Sema::buildCoroutineParameterMoves(SourceLocation Loc) {
1498 assert(isa<FunctionDecl>(CurContext) && "not in a function scope");
1499 auto *FD = cast<FunctionDecl>(CurContext);
1500
1501 auto *ScopeInfo = getCurFunction();
1502 assert(ScopeInfo->CoroutineParameterMoves.empty() &&
1503 "Should not build parameter moves twice");
1504
1505 for (auto *PD : FD->parameters()) {
1506 if (PD->getType()->isDependentType())
1507 continue;
1508
1509 ExprResult PDRefExpr =
1510 BuildDeclRefExpr(PD, PD->getType().getNonReferenceType(),
1511 ExprValueKind::VK_LValue, Loc); // FIXME: scope?
1512 if (PDRefExpr.isInvalid())
1513 return false;
1514
1515 Expr *CExpr = nullptr;
1516 if (PD->getType()->getAsCXXRecordDecl() ||
1517 PD->getType()->isRValueReferenceType())
1518 CExpr = castForMoving(*this, PDRefExpr.get());
1519 else
1520 CExpr = PDRefExpr.get();
1521
1522 auto D = buildVarDecl(*this, Loc, PD->getType(), PD->getIdentifier());
1523 AddInitializerToDecl(D, CExpr, /*DirectInit=*/true);
1524
1525 // Convert decl to a statement.
1526 StmtResult Stmt = ActOnDeclStmt(ConvertDeclToDeclGroup(D), Loc, Loc);
1527 if (Stmt.isInvalid())
1528 return false;
1529
1530 ScopeInfo->CoroutineParameterMoves.insert(std::make_pair(PD, Stmt.get()));
1531 }
1532 return true;
1533 }
1534
BuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs Args)1535 StmtResult Sema::BuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs Args) {
1536 CoroutineBodyStmt *Res = CoroutineBodyStmt::Create(Context, Args);
1537 if (!Res)
1538 return StmtError();
1539 return Res;
1540 }
1541
lookupCoroutineTraits(SourceLocation KwLoc,SourceLocation FuncLoc)1542 ClassTemplateDecl *Sema::lookupCoroutineTraits(SourceLocation KwLoc,
1543 SourceLocation FuncLoc) {
1544 if (!StdCoroutineTraitsCache) {
1545 if (auto StdExp = lookupStdExperimentalNamespace()) {
1546 LookupResult Result(*this,
1547 &PP.getIdentifierTable().get("coroutine_traits"),
1548 FuncLoc, LookupOrdinaryName);
1549 if (!LookupQualifiedName(Result, StdExp)) {
1550 Diag(KwLoc, diag::err_implied_coroutine_type_not_found)
1551 << "std::experimental::coroutine_traits";
1552 return nullptr;
1553 }
1554 if (!(StdCoroutineTraitsCache =
1555 Result.getAsSingle<ClassTemplateDecl>())) {
1556 Result.suppressDiagnostics();
1557 NamedDecl *Found = *Result.begin();
1558 Diag(Found->getLocation(), diag::err_malformed_std_coroutine_traits);
1559 return nullptr;
1560 }
1561 }
1562 }
1563 return StdCoroutineTraitsCache;
1564 }
1565