Updated the status of each feature specification as needed

Change-Id: I23c7e77ac64ce2cad288f42505ccf07257f00abc
Reviewed-on: https://dart-review.googlesource.com/71861
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>

docs/language/informal/README.md

@@ -1,21 +1,29 @@
-This directory contains "informal specifications".
+### This directory contains feature specifications.
 
-**Note**: This directory is no longer where new language proposals are
-discussed. Instead, new language proposals should be submitted to
-[dart-lang/language](https://github.com/dart-lang/language).
+**Note**: This directory contains older feature specifications, new ones
+should be submitted to the language repository
+[here](https://github.com/dart-lang/language).
+
+The existing feature specifications in this directory will have their status
+updated as we proceed, and in particular each of them will become 'background'
+material as it is integrated into the language specification. When all feature
+specifications in this directory (that is, all other files than this one) have
+become background material, this directory will serve only as documentation for
+the process whereby each feature was designed and the associated motivation.
+
+That said, the following section contains a few words about what a feature
+specification is, and how it can be used.
+
+### What is a Feature Specification?
 
 In order to move faster and get better feedback, we implement and iterate on
 language changes before the full official specification has been written. Still,
 the implementers need *something* to go on.
 
-For that, the language team writes "informal specifications". These are
+For that, the language team writes _feature specifications_. These are
 intended to be precise enough for a good faith implementer to correctly
-understand the syntax and semantics of the language, but without all of the
-laborious detail of the complete specification.
-
-Once the feature has been implemented, tested, and we are confident in it, the
-language team will write the real text in the language specification and the
-document here becomes deprecated and no longer canonical.
-
-Until then, while the feature is in progress, a live pull request for the
-informal spec is the source of truth for the feature.
+understand the syntax and semantics of the language, but when the contents
+of a feature specification is integrated into the language specification we
+expect the extra processing to give rise to additional clarifications and
+corrections, which means that a feature specification is expected to be 
+_nearly_ as complete and correct as the language specification.

docs/language/informal/dynamic-members.md

@@ -4,7 +4,7 @@
 
 **Version**: 0.2 (2018-09-04)
 
-**Status**: Under discussion.
+**Status**: Under implementation.
 
 **This document** is a Dart 2 feature specification of the static typing
 of instance members of a receiver whose static type is `dynamic`.

docs/language/informal/extreme-upper-lower-bounds.md

@@ -2,7 +2,7 @@
 
 **Owner**: eernst@
 
-**Status**: Under discussion.
+**Status**: Implemented.
 
 **Version**: 0.2 (2018-05-22)
 

docs/language/informal/generalized-void.md

@@ -4,7 +4,7 @@
 
 **Version**: 0.10 (2018-07-10)
 
-**Status**: Under implementation.
+**Status**: Implemented.
 
 **This document** is a feature specification of the generalized support
 in Dart 2 for the type `void`.

docs/language/informal/generic-function-instantiation.md

@@ -4,7 +4,7 @@ Author: eernst@.
 
 Version: 0.3 (2018-04-05)
 
-Status: Under discussion.
+Status: Under implementation.
 
 **This document** is a Dart 2 feature specification of _generic function
 instantiation_, which is the feature that implicitly coerces a reference to

docs/language/informal/implicit-creation.md

@@ -4,7 +4,7 @@ Author: eernst@.
 
 Version: 0.7 (2018-04-10)
 
-Status: Under implementation.
+Status: Implemented.
 
 **This document** is an informal specification of the *implicit creation*
 feature. **The feature** adds support for omitting some occurrences of the

docs/language/informal/instantiate-to-bound.md

@@ -4,7 +4,7 @@
 
 **Version**: 0.7 (2018-02-26)
 
-**Status**: Under implementation.
+**Status**: Implemented.
 
 Based on [this description](https://github.com/dart-lang/sdk/issues/27526#issuecomment-260021397) by leafp@.
 

docs/language/informal/int64.md

@@ -5,7 +5,7 @@ Dart - Fixed-Size Integers
 
 **Version**: 2017-09-26.
 
-**Status**: Under implementation.
+**Status**: Implemented.
 
 This document discusses Dart's plan to switch the `int` type so that it represents 64-bit integers instead of bigints. It is part of our continued effort of changing the integer type to fixed size ([issue]).
 

docs/language/informal/invalid_returns.md

@@ -1,6 +1,8 @@
 # Dart 2 function return checking
 
-leafp@google.com
+**Owner**: leafp@google.com
+
+**Status**: Implemented.
 
 Status: Ready for implementation
 
@@ -8,6 +10,7 @@ Status: Ready for implementation
 of these rules in terms of which things are errors, rather than which things are
 valid*.*
 
+
 ## Errors for sync and async function return values in Dart 2
 
 ### Expression bodied functions

docs/language/informal/mixin-declaration.md

@@ -1,3 +1,5 @@
 # Dart 2 Mixin Declarations 
 
+**Status**: This is now background material.
+
 ## The canonical version of this document now resides [here](https://github.com/dart-lang/language/blob/master/working/0006.%20Super-invocations%20in%20mixins/0007.%20Mixin%20declarations/lrhn-strawman.md).

docs/language/informal/mixin-inference.md

@@ -1,8 +1,11 @@
 # Dart 2.X super mixin inference proposal
 
-leafp@google.com
+**Owner**: leafp@google.com
 
-Status: Draft
+**Status**: This is now background material.
+
+The current version of this document now resides
+[here](https://github.com/dart-lang/language/blob/master/working/0006.%20Super-invocations%20in%20mixins/0007.%20Mixin%20declarations/mixin-inference.md).
 
 This is intended to define a prototype approach to supporting inference of type
 arguments in super-mixin applications.  This is not an official part of Dart

docs/language/informal/nosuchmethod-forwarding.md

@@ -2,7 +2,7 @@
 
 Author: eernst@
 
-**Status**: Under implementation.
+**Status**: Implemented.
 
 **Version**: 0.7 (2018-07-10)
 

docs/language/informal/subtyping.md

@@ -2,7 +2,7 @@
 
 leafp@google.com
 
-Status: Draft
+**Status**: Implemented.
 
 This is intended to define the core of the Dart 2.0 static and runtime subtyping
 relation.