Un-revert "[coroutines][PR40978] Emit error for co_yield within catch block"

Summary:
https://reviews.llvm.org/D59076 added a new coroutine error that
prevented users from using 'co_await' or 'co_yield' within a exception
handler. However, it was reverted in https://reviews.llvm.org/rC356774
because it caused a regression in nested scopes in C++ catch statements,
as documented by https://bugs.llvm.org/show_bug.cgi?id=41171.

The issue was due to an incorrect use of a `clang::ParseScope`. To fix:

1. Add a regression test for catch statement parsing that mimics the bug
   report from https://bugs.llvm.org/show_bug.cgi?id=41171.
2. Re-apply the coroutines error patch from
   https://reviews.llvm.org/D59076, but this time with the correct
   ParseScope behavior.

Reviewers: GorNishanov, tks2103, rsmith, riccibruno, jbulow

Reviewed By: riccibruno

Subscribers: EricWF, jdoerfert, lewissbaker, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59752

llvm-svn: 356865
diff --git a/clang/lib/Parse/ParseStmt.cpp b/clang/lib/Parse/ParseStmt.cpp
index 267003b..2db3132 100644
--- a/clang/lib/Parse/ParseStmt.cpp
+++ b/clang/lib/Parse/ParseStmt.cpp
@@ -2261,7 +2261,8 @@
   // 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));
+                                  Scope::CatchScope |
+                                  (FnCatch ? Scope::FnTryCatchScope : 0));
 
   // exception-declaration is equivalent to '...' or a parameter-declaration
   // without default arguments.