[coroutines][PR40978] Emit error for co_yield within catch block

Summary:
As reported in https://bugs.llvm.org/show_bug.cgi?id=40978, it's an
error to use the `co_yield` or `co_await` keywords outside of a valid
"suspension context" as defined by [expr.await]p2 of
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/n4775.pdf.

Whether or not the current scope was in a function-try-block's
(https://en.cppreference.com/w/cpp/language/function-try-block) handler
could be determined using scope flag `Scope::FnTryCatchScope`. No
such flag existed for a simple C++ catch statement, so this commit adds
one.

Reviewers: GorNishanov, tks2103, rsmith

Reviewed By: GorNishanov

Subscribers: EricWF, jdoerfert, cfe-commits, lewissbaker

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59076

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@356296 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/Parse/ParseStmt.cpp b/lib/Parse/ParseStmt.cpp
index 267003b518..fde19b9ad8 100644
--- a/lib/Parse/ParseStmt.cpp
+++ b/lib/Parse/ParseStmt.cpp
@@ -2260,8 +2260,10 @@ StmtResult Parser::ParseCXXCatchBlock(bool FnCatch) {
   // C++ 3.3.2p3:
   // The name in a catch exception-declaration is local to the handler and
   // shall not be redeclared in the outermost block of the handler.
-  ParseScope CatchScope(this, Scope::DeclScope | Scope::ControlScope |
-                          (FnCatch ? Scope::FnTryCatchScope : 0));
+  unsigned ScopeFlags = Scope::DeclScope | Scope::ControlScope |
+                        Scope::CatchScope |
+                        (FnCatch ? Scope::FnTryCatchScope : 0);
+  ParseScope CatchScope(this, ScopeFlags);
 
   // exception-declaration is equivalent to '...' or a parameter-declaration
   // without default arguments.
@@ -2290,7 +2292,7 @@ StmtResult Parser::ParseCXXCatchBlock(bool FnCatch) {
     return StmtError(Diag(Tok, diag::err_expected) << tok::l_brace);
 
   // FIXME: Possible draft standard bug: attribute-specifier should be allowed?
-  StmtResult Block(ParseCompoundStatement());
+  StmtResult Block(ParseCompoundStatement(/*isStmtExpr=*/false, ScopeFlags));
   if (Block.isInvalid())
     return Block;