Support static & return-typed arrow functions (#1362)

* Support static arrow functions

* Support arrow function return types

Author: adamaveray

src/printer.js

@@ -1721,8 +1721,12 @@ function printNode(path, options, print) {
       return printFunction(path, options, print);
     case "arrowfunc":
       return concat([
+        node.isStatic ? "static " : "",
         "fn",
         printArgumentsList(path, options, print),
+        node.type
+          ? concat([": ", node.nullable ? "?" : "", path.call(print, "type")])
+          : "",
         " => ",
         path.call(print, "body"),
       ]);

tests/arrowfunc/__snapshots__/jsfmt.spec.js.snap

@@ -11,6 +11,9 @@ $var = fn() => "something";
 $var = fn($arg) =>  "something";
 $var = fn(&$arg) => "something";
 $var = fn($arg, $arg, $arg) => "something";
+$var = fn($arg, $arg, $arg): string => "something";
+$var = fn($arg, $arg, $arg): ?string => "something";
+$var = static fn($arg, $arg, $arg) => "something";
 // $var = fn(): ?string => "something";
 
 call(fn($arg) => $arg);
@@ -21,6 +24,9 @@ $var = fn() => "something";
 $var = fn($arg) => "something";
 $var = fn(&$arg) => "something";
 $var = fn($arg, $arg, $arg) => "something";
+$var = fn($arg, $arg, $arg): string => "something";
+$var = fn($arg, $arg, $arg): ?string => "something";
+$var = static fn($arg, $arg, $arg) => "something";
 // $var = fn(): ?string => "something";
 
 call(fn($arg) => $arg);

tests/arrowfunc/arrowfunc.php

@@ -3,6 +3,9 @@
 $var = fn($arg) =>  "something";
 $var = fn(&$arg) => "something";
 $var = fn($arg, $arg, $arg) => "something";
+$var = fn($arg, $arg, $arg): string => "something";
+$var = fn($arg, $arg, $arg): ?string => "something";
+$var = static fn($arg, $arg, $arg) => "something";
 // $var = fn(): ?string => "something";
 
 call(fn($arg) => $arg);