* Tests: fix minasync Task<T> to derive from Task

* Tests: provide MinAsyncCorlibRef

This combines the async features of minasync with mincorlib to produce
a minimum unversioned corlib with async stubs.

* Compilation: use System.Object from target corlib

When creating a script compilation without an explicit return type,
System.Object was being resolved via reflection from the host.

This resulted in an implicit dependency of a script compilation on the
host corlib, even if a different corlib was specified as a reference
for the compilation (e.g. Xamarin.iOS).

Fix this by using System.Object as defined in the corlib resovled
for the compilation.

* Tests: fix minasync Task<T> to derive from Task

* Tests: provide MinAsyncCorlibRef

This combines the async features of minasync with mincorlib to produce
a minimum unversioned corlib with async stubs.

* Compilation: use System.Object from target corlib

When creating a script compilation without an explicit return type,
System.Object was being resolved via reflection from the host.

This resulted in an implicit dependency of a script compilation on the
host corlib, even if a different corlib was specified as a reference
for the compilation (e.g. Xamarin.iOS).

Fix this by using System.Object as defined in the corlib resovled
for the compilation.

* Bug 217740: Repro and test harness for C#

* Testing and fixing loading scenario in C# and VB

* Verifying VB case using attribute on field

* Adding more tests

* Adding VB tests

* Adding tests

* More tests on fields with double-attributes

* New test constraint

* Fixing VB side to new test constraints

* Fixing C# side to new test constraints

* Fixing remaining tests

* Adding comments

* Fixing VB field scenario too

Do not report warnings for malformed InformationalVersionAttribute values

- Substitute underlying type with corresponding tuple type at the point of type reference.
- Adjusted implementation of symbol display to account for presence of names in the extension tuples.
- Implemented proper retargeting for tuple types (multi-targeting support).

harden both DetectTypeCircularity and GetDependenceChain

This reverts commit 7debfc47.

This reverts commit a03d8b8e.

Make compiler produce the same Product Build, Major, Minor and Private Parts in VersionInfo as VS2013 compiler when Assembly ProductAssemblyFileVersionAttribute and AssemblyInformationalVersion contain invalid format. Also introduce warning diagnostic for AssemblyInformationalVersion with invalid version string

VB: Always import instance fields for an Enum type in order to be able to infer underlying type of its elements.

Address https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?_a=edit&id=193333.

This reverts commit d43d4780.

This reverts commit d43d4780.

This reverts commit 7bb0b4ea.