CA2261: Do not use `ConfigureAwaitOptions.SuppressThrowing` with `Task<TResult>`

#Cause

A value of System.Threading.Tasks.ConfigureAwaitOptions.SuppressThrowing is passed to System.Threading.Tasks.Task.ConfigureAwait(System.Threading.Tasks.ConfigureAwaitOptions).

#Rule description

The System.Threading.Tasks.ConfigureAwaitOptions.SuppressThrowing option isn't supported by the generic System.Threading.Tasks.Task, since that might lead to returning an invalid TResult. This rule flags the use of System.Threading.Tasks.ConfigureAwaitOptions.SuppressThrowing with System.Threading.Tasks.Task to surface the error at build time rather than runtime.

#How to fix violations

Cast the System.Threading.Tasks.Task to a non-generic System.Threading.Tasks.Task before calling System.Threading.Tasks.Task.ConfigureAwait(System.Threading.Tasks.ConfigureAwaitOptions).

#Example

The following code snippet shows a violation of CA2261:

Task<int> t = new Task<int>(() => 1);
t.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);

The following code snippet shows the fix:

Task<int> t = new Task<int>(() => 1);
((Task)t).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);

#When to suppress errors

You shouldn't suppress warnings from this rule. If the task is faulted or canceled, TResult will be invalid and cause runtime errors.