Also reduce cascaded diagnostics in lambdas inside queries.
Fixes #1867

Ensure null pointer is popped if unused

Handle unmatched conditionals in brace matching. Fixes #7534

Trivial fix for 6805.

Revert "Merge pull request #6574 from KevinH-MS/master"

Fixes #7534.

For unmatched conditionals, C# returns null when asked for a matching
conditional directive, whereas VB returns a list with the single
unmatched directive in it. Incorporate checks for those into the
AbstractDirectiveTriviaBraceMatcher and add tests.

Use 'await' instead of 'Wait' in test code.

Make sure we pass cancellation token along to Task.Wait

Don't block threads in a parallel foreach.  Instead just use Tasks with WhenAll

Just fixing the easy-out check that verifies if index conversion is needed at all. Currently the condition is always true - likely a typo.
Otherwise, the part that creates conversion does the right thing regardless, so the end result should be the same.

Fixes #6805