Fixes #17138.

Fixes #16935.

Fixes #16919.

Fixes #14146

Duplicate some existing scoping tests for pattern declarations in declarator arguments, where they are not permitted. (#16804)

* Duplicate some existing scoping tests for pattern declarations in declarator arguments, where they are not permitted.
Fixes #13660

Closes #14113.

Fixes #14202

* add end to end stack depth test

* add comment explaining test

* switch to verify diagnostics

* turn parallel build off

* check pointer size in addition to debug/release

Fixes #16352

The subsumption tree must treat an unconstrained type parameter as possibly null.
Also, if a previous case pattern handles all non-null input, any further case type pattern is subsumed.
Fixes #16688
Fixes #16671

Fixes #16559

Fixes #10765

Attributes will not be permitted on type parameters or parameters of
local functions. This matches the existing behavior for the return type
and symbol itself, neither of which allow attributes to be applied to
them.

Fixes #1640

* Harden compiler against exceptions during stream dispose

It's possible (likely even) for one of the streams the compiler uses for
output files will throw during disposal. Currently this crashes the
compiler. This change adds a wrapper type around stream to catch
exceptions during disposal and report them as diagnostics instead.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems?id=217719

* Add VB tests

* Respond to PR comments

* Respond to PR comments

* Respond to PR comments

* Conform to style guidelines

Fixes #13206.

Fixes:#14600
Fixes:#11013
Fixes:#14116
Fixes:#16168

Fixes #16531

Fixes #16513

Fixes https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=336030
Fixes https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=294570
Fixes https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=363714
Fixes https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=336030
Fixes https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=364165
Fixes #16296
Also adds test for #16559

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems?id=370269.
Releted to #16177.

Expand the lifetime of locals declared within CasePatternSwitchLabelSyntax to the entire switch body.

Fixes #15536.
Fixes #16066.

Fixes #16478.

Fixes #16517 

Extensions methods declared on bases and implemented interfaces are allowed to be applied to receivers that of derived or implementing type.

This change extends this rule to tuple receivers as long as the rule holds for individual elements, recursively.

I.E. valid "this" conversions are:
- identity conversion
- implicit reference conversion
- boxing conversion
- (new)  implicit tuple[literal] conversions as long as all underlying conversions are valid "this" conversions.

Temporarily marks data flow analysis over a region which contains local
functions as "failed." The current implementation is incorrect, so data
flow analysis should mark the result as bad rather than knowingly give
an incorrect result.

This change also causes extract method to emit a warning when extracting
over a region which involves local functions.

Fixes #15532, #16116, #8719, #8718, #8717

* Add regression test for #16399

Closes #16399

Fixes #16167

Fixes #14152.