Fix null ref in C# expander when adding cast to lambda return statement

[Stabilization] Codefix ordering: Prevent Low Priority fixes from interfering with Medium Priority fix ordering

Put the 'Add Nuget Reference' feature behind a disabled regkey option.

Fix intermittent crash in CompilationWithAnalyzers due to an OjbectDi…

Add a key binding of Ctrl+F12 for Go to Implementation

Handle base keyword for submission class speculation model

Fixes #9576

In the C# expander, we added a step to expand return statement expressions within lambda bodies to aid in conflict resolution for refactoring. However, we failed to account for the fact that lambda return statements can legally have no expression. A simple null-ref is all that's necessary to fix the crash.

Note: This bug was introduced (by me!) in #6432. It was not included in Update 1, so this is a newly-introduced regression in Update 2.

Fixes VSO Bug [199252](https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?_a=edit&id=199252)

Root cause: We were attempting to access the cancellation token for a cancellation token source within a lambda within the using statement for the token source. If client fires a cancellation before the task within the lambda executes, the token source may have been disposed when the task is eventually activated.

Fix: This change saves the cancellation token for the token source upfront for use within the lambda and also checks for cancellation before computing diagnostics.

Justification for ask mode: We are hitting this intermittent crash in perf runs in an internal VSO branch and fix doesn't have any risks.

To enable the feature set the following DWORD regkey to 1:
Key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\VisualStudio\<your hive>\Roslyn\Internal\OnOff\Components
Name: PackageSearch

To disable, set it to 0.

Fixed race in diagnostic tagger

Fixes #9596

To do this, we are relying on the support that Visual Studio provides
that lets us target a keybinding for a specific editor factory. This
has the downside that we must specify the keybinding for each editor
factory and if the user wants to change it they'll have to change it
for each context. It's our belief that to properly define a context
that can be consumed in this case requires either editor support (or
lots of debugging) so until then this is good enough.

Fixes #8226.

Non-Fatal Watson if ReiteratedVersionNumber matches when text does not.

change telemetry reporting for rename

Only log formatting events in telemetry when they are enacted by the …

Fix crash if client completes the event queue before the compiler is finished with it.

Allow null Compilation in SymbolDistinguisher.Description.GetHashCode

Disable diagnostic service for projects that we know we don't have all information to provide good results.

Revert "Revert "Disable diagnostic service for projects that we know we don't have all information to provide good results.""

Port analyzer allocation fixes from master to stabilization

Fix race condition when generating simulated compilation events

Include HasValue check in BoundSwitchStatement

If the switch expression is a  Nullable<T>  a conditional branch is added for the  HasValue  check.
 That check was added as a separate  BoundStatement  outside of the  BoundSwitchStatement .
 If the lambda rewriter subsequently generated any display class instances, the allocations are added
 as a prologue to the rewritten switch statement but since the conditional branch is outside the switch
 statement, the branch skips the prologue, skipping the allocations. The change is to include the
 conditional branch in the  BoundSwitchStatement  so the branch occurs after the prologue.

[AskMode] Put `IOperation` behind a feature flag

don't assume all reference spans in an inline rename session are projected into the current view

Check file checksums to ensure no corruption occurred.

Makes the symbol lookup return no symbols when completing `base.` inside
of a REPL.

Include HasValue check in BoundSwitchStatement so any display class allocation is moved outside of the check

allow cancelation exceptions through the PE stream diagnostic filter

User scenario: Analysis might get skipped in the IDE for a symbol/partial declarations for a partial symbol with more than one definition in a single document.

Cause: When computing symbols declared in the tree to generate symbol declared events, we were adding duplicate entries if a symbol had more than one partial declaration in a tree. This meant that multiple threads might start performing symbol analysis on the same symbol, causing a race condition as driver doesn't expect duplicate events. Though we ensure not to make duplicate callbacks, we might end up missing on making some callbacks at times.

Fix: Compute only unique symbols from declarations in a tree.

Risk: None, it is a trivial fix.

Testing: Before the fix, I was able to repro the race condition and the assert consistently by running the flaky test in a loop for over 10k times. After the fix, it doesn't repro on running the same multiple times. A new unit test has also been added, though it did not fail consistently even before the fix.

Fixes #9462

Revert "Disable diagnostic service for projects that we know we don't have all information to provide good results."

Revert "Disable diagnostic service for projects that we know we don't have all information to provide good results."

only report when visual studio closes.

Disable diagnostic service for projects that we know we don't have all information to provide good results.