Add TypedFormatString to typedefs in HH

Summary: The newtype `TypedFormatString` was added to `hhi` file but omitted from the corresponding `php` file for HHVM. This diff fixes that, and adds an HHVM test.

Differential Revision: D90947026

fbshipit-source-id: 752a649c936e33c85ba257624a9feef1f85abe60

Author: Andrew Kennedy

hphp/runtime/ext/string/ext_string.php

@@ -2,6 +2,7 @@
 
 namespace HH {
 newtype FormatString<T> = string;
+newtype TypedFormatString<T,Targs as (mixed...)> = string;
 }
 
 namespace {

hphp/test/slow/printf-user.php

@@ -0,0 +1,12 @@
+<?hh
+
+function myprintf<Targs as (mixed...)>(string $test, HH\TypedFormatString<PlainSprintf,Targs> $fmt, ...Targs $args):void {
+  printf("test = %s\n", $test);
+  printf($fmt, ...$args);
+}
+<<__EntryPoint>>
+function main():void {
+  myprintf("one", "int %d float %f\n", 32, 12.3);
+  myprintf("two", "simple\n");
+  myprintf("three", "string %s\n", "test");
+}

hphp/test/slow/printf-user.php.expect

@@ -0,0 +1,6 @@
+test = one
+int 32 float 12.300000
+test = two
+simple
+test = three
+string test