diff options
Diffstat (limited to 'lib/Sema/SemaCoroutine.cpp')
-rw-r--r-- | lib/Sema/SemaCoroutine.cpp | 73 |
1 files changed, 53 insertions, 20 deletions
diff --git a/lib/Sema/SemaCoroutine.cpp b/lib/Sema/SemaCoroutine.cpp index 181efa6d3d..9d328f4926 100644 --- a/lib/Sema/SemaCoroutine.cpp +++ b/lib/Sema/SemaCoroutine.cpp @@ -1,9 +1,8 @@ -//===--- SemaCoroutines.cpp - Semantic Analysis for Coroutines ------------===// +//===-- SemaCoroutine.cpp - Semantic Analysis for Coroutines --------------===// // -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // @@ -186,21 +185,8 @@ static QualType lookupCoroutineHandleType(Sema &S, QualType PromiseType, static bool isValidCoroutineContext(Sema &S, SourceLocation Loc, StringRef Keyword) { - // '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; - } - - // Per [expr.await]p2, any other usage must be within a function. + // [expr.await]p2 dictates that 'co_await' and 'co_yield' must be used within + // a function body. // FIXME: This also covers [expr.await]p2: "An await-expression shall not // appear in a default argument." But the diagnostic QoI here could be // improved to inform the user that default arguments specifically are not @@ -669,12 +655,57 @@ bool Sema::ActOnCoroutineBodyStart(Scope *SC, SourceLocation KWLoc, return true; } +// Recursively walks up the scope hierarchy until either a 'catch' or a function +// scope is found, whichever comes first. +static bool isWithinCatchScope(Scope *S) { + // 'co_await' and 'co_yield' keywords are disallowed within catch blocks, but + // lambdas that use 'co_await' are allowed. The loop below ends when a + // function scope is found in order to ensure the following behavior: + // + // void foo() { // <- function scope + // try { // + // co_await x; // <- 'co_await' is OK within a function scope + // } catch { // <- catch scope + // co_await x; // <- 'co_await' is not OK within a catch scope + // []() { // <- function scope + // co_await x; // <- 'co_await' is OK within a function scope + // }(); + // } + // } + while (S && !(S->getFlags() & Scope::FnScope)) { + if (S->getFlags() & Scope::CatchScope) + return true; + S = S->getParent(); + } + return false; +} + +// [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." +static void checkSuspensionContext(Sema &S, SourceLocation Loc, + StringRef Keyword) { + // First emphasis of [expr.await]p2: must be a potentially evaluated context. + // That is, 'co_await' and 'co_yield' cannot appear in subexpressions of + // \c sizeof. + if (S.isUnevaluatedContext()) + S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword; + + // Second emphasis of [expr.await]p2: must be outside of an exception handler. + if (isWithinCatchScope(S.getCurScope())) + S.Diag(Loc, diag::err_coroutine_within_handler) << Keyword; +} + ExprResult Sema::ActOnCoawaitExpr(Scope *S, SourceLocation Loc, Expr *E) { if (!ActOnCoroutineBodyStart(S, Loc, "co_await")) { CorrectDelayedTyposInExpr(E); return ExprError(); } + checkSuspensionContext(*this, Loc, "co_await"); + if (E->getType()->isPlaceholderType()) { ExprResult R = CheckPlaceholderExpr(E); if (R.isInvalid()) return ExprError(); @@ -772,6 +803,8 @@ ExprResult Sema::ActOnCoyieldExpr(Scope *S, SourceLocation Loc, Expr *E) { return ExprError(); } + checkSuspensionContext(*this, Loc, "co_yield"); + // Build yield_value call. ExprResult Awaitable = buildPromiseCall( *this, getCurFunction()->CoroutinePromise, Loc, "yield_value", E); |