Enforce like types in type hint positions

Summary: As part of the spec for sound dynamic, we said we want `~T` to enforce as `T`, a departure from our original approach which had it enforce as mixed (but as D40516837 (9e8c173) shows, wasn't happening for reified generics). This way, changing a declaration from `int` to `~int` doesn't cause the code to lose enforcement. The "enforce as mixed" idea came to mind from trying to replace `mixed/dynamic` with like types, but we're introducing TANY_MARKER to deal with those.

Reviewed By: andrewjkennedy

Differential Revision: D40516838

fbshipit-source-id: ec2f0b16edb0398af541ece1f181dd9c4a3ad49b

Author: vassilmladenov

hphp/hack/src/hackc/emitter/emit_type_hint.rs

@@ -210,9 +210,7 @@ fn hint_to_type_constraint<'arena>(
 ) -> Result<Constraint<'arena>> {
     let Hint(_, hint) = h;
     Ok(match &**hint {
-        Hdynamic | Hlike(_) | Hfun(_) | Hunion(_) | Hintersection(_) | Hmixed => {
-            Constraint::default()
-        }
+        Hdynamic | Hfun(_) | Hunion(_) | Hintersection(_) | Hmixed => Constraint::default(),
         Haccess(_, _) => Constraint::make(
             Just("".into()),
             TypeConstraintFlags::ExtendedHint | TypeConstraintFlags::TypeConstant,
@@ -227,6 +225,7 @@ fn hint_to_type_constraint<'arena>(
             t,
             TypeConstraintFlags::Soft | TypeConstraintFlags::ExtendedHint,
         )?,
+        Hlike(h) => hint_to_type_constraint(alloc, kind, tparams, skipawaitable, h)?,
         Herr | Hany => {
             return Err(Error::unrecoverable(
                 "This should be an error caught in naming",

hphp/test/slow/like_types/awaitable1.php

@@ -3,7 +3,7 @@
 /**
  * Error: async functions must return an Awaitable.
  */
-async function f(mixed $x): ~Awaitable<int> {
+async function f(mixed $x): <<__Soft>> ~Awaitable<int> {
   return $x;
 }
 

hphp/test/slow/like_types/awaitable2.php

@@ -1,9 +1,9 @@
 <?hh
 
 /**
- * Like-types are treated as mixed, allowing any return value.
+ * Like-types are enforced at their inner type, so this enforces as Awaitable<int>
  */
-async function f(mixed $x): Awaitable<~int> {
+async function f(mixed $x): Awaitable<<<__Soft>> ~int> {
   return $x;
 }
 

hphp/test/slow/like_types/awaitable2.php.expectf

@@ -1,18 +1,32 @@
 int(1)
+
+Warning: Value returned from async function f() must be of type @int, float given in %s/test/slow/like_types/awaitable2.php on line 7
 float(1.5)
+
+Warning: Value returned from async function f() must be of type @int, string given in %s/test/slow/like_types/awaitable2.php on line 7
 string(3) "foo"
+
+Warning: Value returned from async function f() must be of type @int, bool given in %s/test/slow/like_types/awaitable2.php on line 7
 bool(false)
-resource(%d) of type (stream)
+
+Warning: Value returned from async function f() must be of type @int, File given in %s/test/slow/like_types/awaitable2.php on line 7
+resource(4) of type (stream)
+
+Warning: Value returned from async function f() must be of type @int, stdClass given in %s/test/slow/like_types/awaitable2.php on line 7
 object(stdClass) (0) {
 }
+
+Warning: Value returned from async function f() must be of type @int, HH\vec given in %s/test/slow/like_types/awaitable2.php on line 7
 vec(3) {
   int(1)
   int(2)
   int(3)
 }
+
+Warning: Value returned from async function f() must be of type @int, HH\dict given in %s/test/slow/like_types/awaitable2.php on line 7
 dict(2) {
   ["a"]=>
   int(1)
   ["b"]=>
   int(2)
-}
+}

hphp/test/slow/like_types/awaitable3.php

@@ -1,10 +1,9 @@
 <?hh
 
 /**
- * For non-async functions, a like-Awaitable acts like any other type; it's
- * not enforced.
+ * For non-async functions, a like-Awaitable acts like any other like type, enforced at the inner type.
  */
-function f(mixed $x): ~Awaitable<int> {
+function f(mixed $x): <<__Soft>> ~Awaitable<int> {
   return $x;
 }
 

hphp/test/slow/like_types/awaitable3.php.expectf

@@ -1,15 +1,30 @@
+Warning: Value returned from function f() must be of type @HH\Awaitable, int given in %s/test/slow/like_types/awaitable3.php on line 7
 int(1)
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, float given in %s/test/slow/like_types/awaitable3.php on line 7
 float(1.5)
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, string given in %s/test/slow/like_types/awaitable3.php on line 7
 string(3) "foo"
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, bool given in %s/test/slow/like_types/awaitable3.php on line 7
 bool(false)
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, File given in %s/test/slow/like_types/awaitable3.php on line 7
 resource(4) of type (stream)
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, stdClass given in %s/test/slow/like_types/awaitable3.php on line 7
 object(stdClass) (0) {
 }
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, HH\vec given in %s/test/slow/like_types/awaitable3.php on line 7
 vec(3) {
   int(1)
   int(2)
   int(3)
 }
+
+Warning: Value returned from function f() must be of type @HH\Awaitable, HH\dict given in %s/test/slow/like_types/awaitable3.php on line 7
 dict(2) {
   ["a"]=>
   int(1)

hphp/test/slow/like_types/parameter.php

@@ -1,9 +1,9 @@
 <?hh
 
 /**
- * Like-types are treated as mixed, allowing any argument value.
+ * Like-types are enforced at their inner type.
  */
-function f(~int $x): void {
+function f(<<__Soft>> ~int $x): void {
   var_dump($x);
 }
 

hphp/test/slow/like_types/parameter.php.expectf

@@ -1,15 +1,29 @@
 int(1)
+
+Warning: Argument 1 to f() must be of type @int, float given in %s/test/slow/like_types/parameter.php on line 13
 float(1.5)
+
+Warning: Argument 1 to f() must be of type @int, string given in %s/test/slow/like_types/parameter.php on line 14
 string(3) "foo"
+
+Warning: Argument 1 to f() must be of type @int, bool given in %s/test/slow/like_types/parameter.php on line 15
 bool(false)
+
+Warning: Argument 1 to f() must be of type @int, File given in %s/test/slow/like_types/parameter.php on line 16
 resource(4) of type (stream)
+
+Warning: Argument 1 to f() must be of type @int, stdClass given in %s/test/slow/like_types/parameter.php on line 17
 object(stdClass) (0) {
 }
+
+Warning: Argument 1 to f() must be of type @int, HH\vec given in %s/test/slow/like_types/parameter.php on line 18
 vec(3) {
   int(1)
   int(2)
   int(3)
 }
+
+Warning: Argument 1 to f() must be of type @int, HH\dict given in %s/test/slow/like_types/parameter.php on line 19
 dict(2) {
   ["a"]=>
   int(1)

hphp/test/slow/like_types/parameter_alias.php

@@ -1,9 +1,9 @@
 <?hh
 
 /**
- * Like-types are treated as mixed, allowing any argument value.
+ * Like-types are enforced at their inner type.
  */
-function f(MyAlias $x): void {
+function f(<<__Soft>> MyAlias $x): void {
   var_dump($x);
 }
 

hphp/test/slow/like_types/parameter_alias.php.expectf

@@ -1,15 +1,29 @@
 int(1)
+
+Warning: Argument 1 to f() must be of type @MyAlias, float given in %s/test/slow/like_types/parameter_alias.php on line 15
 float(1.5)
+
+Warning: Argument 1 to f() must be of type @MyAlias, string given in %s/test/slow/like_types/parameter_alias.php on line 16
 string(3) "foo"
+
+Warning: Argument 1 to f() must be of type @MyAlias, bool given in %s/test/slow/like_types/parameter_alias.php on line 17
 bool(false)
+
+Warning: Argument 1 to f() must be of type @MyAlias, File given in %s/test/slow/like_types/parameter_alias.php on line 18
 resource(4) of type (stream)
+
+Warning: Argument 1 to f() must be of type @MyAlias, stdClass given in %s/test/slow/like_types/parameter_alias.php on line 19
 object(stdClass) (0) {
 }
+
+Warning: Argument 1 to f() must be of type @MyAlias, HH\vec given in %s/test/slow/like_types/parameter_alias.php on line 20
 vec(3) {
   int(1)
   int(2)
   int(3)
 }
+
+Warning: Argument 1 to f() must be of type @MyAlias, HH\dict given in %s/test/slow/like_types/parameter_alias.php on line 21
 dict(2) {
   ["a"]=>
   int(1)