Create OngoingRelease status for preview features, set diamond trait reuse to ongoingrelase

Summary:
This diff adds a new OngoingRelease enum in preview features that turns on unstable feature checking in rust_parser_errors for the runtime but not the typechecker.

Once you have a feature in this state, the typechecker will still enforce it. After HHVM is released, you can then remove any use of `check_can_use_feature` for your feature. This will turn off typechecker enforcement.

After that, be warned that there may still be file attributes left in www from previewing. Feature implementers will need to clean those up in www first before removing their feature from the UnstableFeatures enum altogether.

Reviewed By: francesco-zappa-nardelli

Differential Revision: D40182173

fbshipit-source-id: cbdeaa9aefde948d78054d461192ac40712bd25d

Author: jamesjwu

hphp/hack/src/parser/rust_parser_errors.rs

@@ -73,6 +73,7 @@ enum FeatureStatus {
     Preview,
     Migration,
     Deprecated,
+    OngoingRelease,
     // TODO: add other modes like "Advanced" or "Deprecated" if necessary.
     // Those are just variants of "Preview" for the runtime's sake, though,
     // and likely only need to be distinguished in the lint rule rather than here
@@ -121,7 +122,7 @@ impl UnstableFeatures {
             UnstableFeatures::TypeConstSuperBound => Unstable,
             UnstableFeatures::ClassConstDefault => Migration,
             UnstableFeatures::TypeRefinements => Unstable,
-            UnstableFeatures::MethodTraitDiamond => Preview,
+            UnstableFeatures::MethodTraitDiamond => OngoingRelease,
             UnstableFeatures::UpcastExpression => Unstable,
             UnstableFeatures::RequireClass => Preview,
             UnstableFeatures::EnumClassTypeConstants => Unstable,
@@ -1251,7 +1252,12 @@ impl<'a, State: 'a + Clone> ParserErrors<'a, State> {
             }
 
             _ => false,
-        } || self.env.context.active_unstable_features.contains(feature);
+        } || self.env.context.active_unstable_features.contains(feature)
+          // Preview features with an ongoing release should be allowed by the
+          // runtime, but not the typechecker
+          || (feature.get_feature_status() == FeatureStatus::OngoingRelease
+            && self.env.codegen);
+
         if !enabled {
             self.errors.push(make_error_from_node(
                 node,

hphp/test/slow/traits/diamond_use/diamond_use_no_attribute_2.php hphp/hack/test/typecheck/trait_reuse/trait_diamond_no_attribute.php

@@ -0,0 +1,2 @@
+File "trait_diamond_no_attribute.php", line 15, characters 1-30:
+Cannot use unstable feature: `method_trait_diamond` (Parsing[1002])

hphp/hack/test/typecheck/trait_reuse/trait_diamond_no_attribute.php.exp

@@ -0,0 +1,20 @@
+<?hh
+<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
+trait MyTrait1 {
+  public function testFun(): void {}
+}
+trait MyTrait2 {
+  use MyTrait1;
+}
+
+<<__EnableMethodTraitDiamond>>
+class MyClass {
+  use MyTrait1;
+  use MyTrait2;
+}
+
+<<__EntryPoint>>
+function foo(): void {
+  echo "Done!\n";
+}

hphp/test/slow/traits/diamond_use/diamond_trait_with_attribute_good.php

@@ -0,0 +1 @@
+Done!

hphp/test/slow/traits/diamond_use/diamond_trait_with_attribute_good.php.expectf

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use1.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use2.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use3.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use4.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use5.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use6.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use7.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 class C {
   const int X = 1;

hphp/test/slow/traits/diamond_use/diamond_use_const.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public final function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use_final1.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public final function foo() : void {

hphp/test/slow/traits/diamond_use/diamond_use_final2.php

@@ -1,7 +1,7 @@
 <?hh
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 
-<<file:__EnableUnstableFeatures('method_trait_diamond')>>
+
 
 trait T {
   public static function foo() : void {