r335420 - [Sema] isValidCoroutineContext FIXME and citations
Brian Gesiak via cfe-commits
cfe-commits at lists.llvm.org
Sat Jun 23 11:01:03 PDT 2018
Author: modocache
Date: Sat Jun 23 11:01:02 2018
New Revision: 335420
URL: http://llvm.org/viewvc/llvm-project?rev=335420&view=rev
Log:
[Sema] isValidCoroutineContext FIXME and citations
Summary:
Add citations to the Coroutines TS to the `isValidCoroutineContext`
function, as well as a FIXME and test for [expr.await]p2, which states
a co_await expression cannot be used in a default argument.
Test Plan: check-clang
Reviewers: GorNishanov, EricWF
Reviewed By: GorNishanov
Subscribers: rsmith, cfe-commits
Differential Revision: https://reviews.llvm.org/D48519
Modified:
cfe/trunk/lib/Sema/SemaCoroutine.cpp
cfe/trunk/test/SemaCXX/coroutines.cpp
Modified: cfe/trunk/lib/Sema/SemaCoroutine.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCoroutine.cpp?rev=335420&r1=335419&r2=335420&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaCoroutine.cpp (original)
+++ cfe/trunk/lib/Sema/SemaCoroutine.cpp Sat Jun 23 11:01:02 2018
@@ -9,6 +9,9 @@
//
// This file implements semantic analysis for C++ Coroutines.
//
+// This file contains references to sections of the Coroutines TS, which
+// can be found at http://wg21.link/coroutines.
+//
//===----------------------------------------------------------------------===//
#include "CoroutineStmtBuilder.h"
@@ -196,13 +199,25 @@ static QualType lookupCoroutineHandleTyp
static bool isValidCoroutineContext(Sema &S, SourceLocation Loc,
StringRef Keyword) {
- // 'co_await' and 'co_yield' are not permitted in unevaluated operands.
+ // 'co_await' and 'co_yield' are not permitted in unevaluated operands,
+ // such as subexpressions of \c sizeof.
+ //
+ // [expr.await]p2, emphasis added: "An await-expression shall appear only in
+ // a *potentially evaluated* expression within the compound-statement of a
+ // function-body outside of a handler [...] A context within a function where
+ // an await-expression can appear is called a suspension context of the
+ // function." And per [expr.yield]p1: "A yield-expression shall appear only
+ // within a suspension context of a function."
if (S.isUnevaluatedContext()) {
S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
return false;
}
- // Any other usage must be within a function.
+ // Per [expr.await]p2, any other usage must be within a function.
+ // FIXME: This also covers [expr.await]p2: "An await-expression shall not
+ // appear in a default argument." But the diagnostic QoI here could be
+ // improved to inform the user that default arguments specifically are not
+ // allowed.
auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
if (!FD) {
S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
@@ -233,22 +248,37 @@ static bool isValidCoroutineContext(Sema
// Diagnose when a constructor, destructor, copy/move assignment operator,
// or the function 'main' are declared as a coroutine.
auto *MD = dyn_cast<CXXMethodDecl>(FD);
+ // [class.ctor]p6: "A constructor shall not be a coroutine."
if (MD && isa<CXXConstructorDecl>(MD))
return DiagInvalid(DiagCtor);
+ // [class.dtor]p17: "A destructor shall not be a coroutine."
else if (MD && isa<CXXDestructorDecl>(MD))
return DiagInvalid(DiagDtor);
+ // N4499 [special]p6: "A special member function shall not be a coroutine."
+ // Per C++ [special]p1, special member functions are the "default constructor,
+ // copy constructor and copy assignment operator, move constructor and move
+ // assignment operator, and destructor."
else if (MD && MD->isCopyAssignmentOperator())
return DiagInvalid(DiagCopyAssign);
else if (MD && MD->isMoveAssignmentOperator())
return DiagInvalid(DiagMoveAssign);
+ // [basic.start.main]p3: "The function main shall not be a coroutine."
else if (FD->isMain())
return DiagInvalid(DiagMain);
// Emit a diagnostics for each of the following conditions which is not met.
+ // [expr.const]p2: "An expression e is a core constant expression unless the
+ // evaluation of e [...] would evaluate one of the following expressions:
+ // [...] an await-expression [...] a yield-expression."
if (FD->isConstexpr())
DiagInvalid(DiagConstexpr);
+ // [dcl.spec.auto]p15: "A function declared with a return type that uses a
+ // placeholder type shall not be a coroutine."
if (FD->getReturnType()->isUndeducedType())
DiagInvalid(DiagAutoRet);
+ // [dcl.fct.def.coroutine]p1: "The parameter-declaration-clause of the
+ // coroutine shall not terminate with an ellipsis that is not part of a
+ // parameter-declaration."
if (FD->isVariadic())
DiagInvalid(DiagVarargs);
Modified: cfe/trunk/test/SemaCXX/coroutines.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/coroutines.cpp?rev=335420&r1=335419&r2=335420&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/coroutines.cpp (original)
+++ cfe/trunk/test/SemaCXX/coroutines.cpp Sat Jun 23 11:01:02 2018
@@ -1,3 +1,6 @@
+// This file contains references to sections of the Coroutines TS, which can be
+// found at http://wg21.link/coroutines.
+
// RUN: %clang_cc1 -std=c++14 -fcoroutines-ts -verify %s -fcxx-exceptions -fexceptions -Wunused-result
void no_coroutine_traits_bad_arg_await() {
@@ -320,6 +323,11 @@ void unevaluated() {
typeid(co_yield a); // expected-error {{cannot be used in an unevaluated context}}
}
+// [expr.await]p2: "An await-expression shall not appear in a default argument."
+// FIXME: A better diagnostic would explicitly state that default arguments are
+// not allowed. A user may not understand that this is "outside a function."
+void default_argument(int arg = co_await 0) {} // expected-error {{'co_await' cannot be used outside a function}}
+
constexpr auto constexpr_deduced_return_coroutine() {
co_yield 0; // expected-error {{'co_yield' cannot be used in a constexpr function}}
// expected-error at -1 {{'co_yield' cannot be used in a function with a deduced return type}}
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