Fix nulls in AnalyzerDependencyChecker.

Currently we use a `Task.FromResult(null)` as a sentinel task before a
real dependency check has been queued up. This works fine until we try
to access the results of this task, and things blow up.

Instead, we should create an AnalyzerDependecyResults.Empty singleton,
and create a task from that.

Also, this change catches all exceptions coming out of
`AnalyzerDependencyChecker`, to avoid bringing down VS.

Disable Deterministic PDB GUID generation for RTM

Only return a fix if the assembly identity matches the diagnostic mes…

Don't leak Workspace objects from AnalyzerAndOptions

Add tests for #976. The actual fix for this was in the compiler #2540.

Introduce local on interpolated string expressions should not generate a
constant, but a variable.

Add tests for #976. The actual fix for this was in the compiler #2540.

Introduce local on interpolated string expressions should not generate a
constant, but a variable.

Guard visitors against stack overflow exceptions

Currently we use a `Task.FromResult(null)` as a sentinel task before a
real dependency check has been queued up. This works fine until we try
to access the results of this task, and things blow up.

Instead, we should create an AnalyzerDependecyResults.Empty singleton,
and create a task from that.

Also, this change catches all exceptions coming out of
`AnalyzerDependencyChecker`, to avoid bringing down VS.

Handle BoundSequence as an assignment target in CodeGenerator.EmitAssignmentExpression.

Dont offer cast simplification fixes for explicit reference conversions

For code snippets such as below: "Base M(Base b) => (Derived)b;", we currently offer cast removal for cast to derived. However, this involves an explicit/narrowing conversion and hence can lead to an exception or data loss. The only way to detect such redundant casts is via flow analysis, which is not currently in our scope.

Fix is to bail out early for such cast expressions. I have also fixed incorrect tests that were added to ensure the current behavior.

Fixes #2761 

Improve the documentation comments on CodeFixContext constructors and CodeFixProvider.RegisterCodeFixesAsync methods.

Fixes #2643 

Improve the documentation comments on CodeFixContext constructors and CodeFixProvider.RegisterCodeFixesAsync methods.

Fix breakpoint handling and EnC of queries containing Select and GroupBy clauses that don't translate their select/group-by expression to lambda

Add regression tests for #2441

Fixes #2878.

For code snippets such as below: "Base M(Base b) => (Derived)b;", we currently offer cast removal for cast to derived. However, this involves an explicit/narrowing conversion and hence can lead to an exception or data loss. The only way to detect such redundant casts is via flow analysis, which is not currently in our scope.

Fix is to bail out early for such cast expressions. I have also fixed incorrect tests that were added to ensure the current behavior.

Fixes #2761

Make ICompilationFactoryService internal

After discussing the matter, @agocke, @tmat and I have concluded that the
implementation in EETypeNameDecoder will never be affected by the bug the
compiler was seeing.  However, we still felt it would be worthwhile to
make the implementations consistent.  There is, however, no test, since
the behavior is unchanged.

I added some using/import tests since they use the compiler implementation
(which has already been fixed).

Fixes #2441

Do not hoist ByRef locals used within iterator methods, even when building debug.

Fix breakpoint handling and EnC of queries containing Select and GroupBy clauses that don't translate their select/group-by expression to lambda

made hostanalyzermanager to use object as id type

Apply spacing rules to fixed, default, sizeof

Switch MSBuildWorkspace to use UTF-8 without BOM

CodeLens Object allocations

Added missing copyright headers

Fixes #2862.

Test for nullref while formatting properties

Fixes a couple of issues around import scope compilation

Update the VS AnalyzerDependencyChecker.

This commit updates the `AnalyzerDependencyChecker` type to reflect the
recent changes to require all analyzers and dependencies to be
specified, and the changes in how we load analyzer assemblies.

Now that we require all analyzers and dependencies to be specified, we
no longer look next to the specified analyzers to optimistically locate
dependencies. Instead, we only consider the list of passed-in analyzers
*plus* the assemblies already loaded into the `AppDomain`. The latter
avoids unhelpful warnings in the event that the analyzer assembly
includes a code fix that take a dependency on a Visual Studio assembly,
which of course can't be included in the list of analyzers. We now
create a warning when we identify a missing dependency.

We now also check analyzers themselves for conflicts (i.e., assemblies
at different paths with the same identity but different contents)
instead of just their dependencies.

Fixes #2684.
Fixes #2728.
Fixes #2738.

Minor cleanup of C#'s Syntax.xml