From 11d17fcf928608520634a79c8de97a4c0d4d1cf6 Mon Sep 17 00:00:00 2001
From: summivox <summivox@gmail.com>
Date: Sun, 31 Jan 2016 23:40:06 -0500
Subject: [PATCH] ES7 async await impl with concise syntax

see http://wiki.ecmascript.org/doku.php?id=strawman:async_functions

async function: `->>`, `~>>`, `-->>`, `~~>>`, `async (arglist) ->...`, `async function name (arglist)`
await: `await` => `await`; `await all` => `await*` (proposed to translate to `Promise.all`, not final)

backcall does NOT work, but this should be fine because they were invented to create the illusion of async function anyway
---
 src/ast.ls     | 32 +++++++++++++++++++-------------
 src/grammar.ls |  8 ++++++--
 src/lexer.ls   | 14 +++++++++++---
 3 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/src/ast.ls b/src/ast.ls
index 794baf368..9cf9eb1ee 100644
--- a/src/ast.ls
+++ b/src/ast.ls
@@ -1122,21 +1122,23 @@ class exports.Yield extends Node
 
     children: <[ it ]>
 
-    show: -> if @op is 'yieldfrom' then 'from' else ''
+    show: -> switch @op
+    | 'yield' => ''
+    | 'yieldfrom' => 'from'
+    | 'await' => 'await'
+    | 'awaitall' => 'await all'
+    | _ => ''
 
     ::delegate <[ isCallable ]> -> yes
 
     compile-node: (o) ->
-        code = []
-
-        if @op is \yieldfrom
-            code.push 'yield*'
-        else
-            code.push 'yield'
-
-        if @it
-            code.push " #{@it.compile o, LEVEL_OP + PREC.unary}"
-
+        code = [(switch @op
+        | 'yield' => 'yield'
+        | 'yieldfrom' => 'yield*'
+        | 'await' => 'await'
+        | 'awaitall' => 'await*'
+        )]
+        if @it then code.push " #{@it.compile o, LEVEL_OP + PREC.unary}"
         sn(this, "(", ...code, ")")
 
 #### Unary operators
@@ -1797,7 +1799,7 @@ class exports.Existence extends Node implements Negatable
 #### Fun
 # A function definition. This is the only node that creates a `new Scope`.
 class exports.Fun extends Node
-    (@params or [], @body or Block!, @bound and \this$, @curried or false, @hushed = false, @generator = false) ~>
+    (@params or [], @body or Block!, @bound and \this$, @curried or false, @hushed = false, @generator = false, @async = false) ~>
 
     children: <[ params body ]>
 
@@ -1829,7 +1831,11 @@ class exports.Fun extends Node
         o.indent += TAB
         {body, name, tab} = this
         code = [\function]
-        if @generator
+        if @async
+            @ctor and @carp "a constructor can't be async"
+            o.in-generator = true
+            code.unshift 'async '
+        else if @generator
             @ctor and @carp "a constructor can't be a generator"
             o.in-generator = true
             code.push \*
diff --git a/src/grammar.ls b/src/grammar.ls
index dc4e8f2a0..a0b2714e9 100644
--- a/src/grammar.ls
+++ b/src/grammar.ls
@@ -257,11 +257,15 @@ bnf =
 
         # The function literal can be either anonymous with `->`,
         o 'PARAM( ArgList OptComma )PARAM -> Block'
-        , -> Fun $2, $6, /~/.test($5), /--|~~/.test($5), /!/.test($5), /\*/.test($5)
+        , -> Fun $2, $6, /~/.test($5), /--|~~/.test($5), /!/.test($5), /\*/.test($5), />>/.test($5)
+        o 'ASYNC PARAM( ArgList OptComma )PARAM -> Block'
+        , -> Fun $3, $7, /~/.test($6), /--|~~/.test($6), /!/.test($6), false, true
         # or named with `function`.
         o 'FUNCTION CALL( ArgList OptComma )CALL Block' -> (Fun $3, $6).named $1
         o 'GENERATOR CALL( ArgList OptComma )CALL Block'
-        , -> (Fun $3, $6, false, false, false, true).named $1
+        , -> (Fun $3, $6, false, false, false, true, false).named $1
+        o 'ASYNC FUNCTION CALL( ArgList OptComma )CALL Block'
+        , -> (Fun $4, $7, false, false, false, false, true).named $2
 
         # The full complement of `if` and `unless` expressions
         o 'IF Expression Block Else'      -> L 1 2 If $2, $3, $1 is 'unless' .add-else $4
diff --git a/src/lexer.ls b/src/lexer.ls
index bc8c4e823..6a4d283ce 100644
--- a/src/lexer.ls
+++ b/src/lexer.ls
@@ -143,7 +143,7 @@ exports <<<
             tag = 'LITERAL'
         case <[ new do typeof delete ]>
             tag = 'UNARY'
-        case 'yield'
+        case 'yield' 'await'
             tag = 'YIELD'
         case 'return' 'throw'
             tag = 'HURL'
@@ -239,6 +239,9 @@ exports <<<
                 or last.1 is 'import' and 'All'
                     last.1 += that
                     return 3
+                if last.0 is 'yield' and last.1 is 'await'
+                    last.1 += 'all'
+                    return 3
             case 'from'
                 if last.1 is 'yield'
                     last.1 += 'from'
@@ -657,7 +660,7 @@ exports <<<
             @fset 'for' false
             tag = 'THEN'
         default
-            if /^!?(?:--?|~~?)>\*?$/.test val # function arrow
+            if /^!?(?:--?|~~?)>(?:>|\*)?$/.test val # function arrow
                 @parameters tag = '->'
             else if /^\*?<(?:--?|~~?)!?$/.test val # backcall
                 @parameters tag = '<-'
@@ -1022,6 +1025,11 @@ character = if not JSON? then uxxxx else ->
                                 [')PARAM' ')'  line, column]
                                 ['->'     '~>' line, column]
                             break LOOP
+        case tag is 'ID' and val is 'async'
+            next = tokens[i + 1]
+            switch next.0
+            | 'PARAM(', 'FUNCTION' => token.0 = 'ASYNC'
+            | 'GENERATOR' => carp 'named generator cannot be async' line
         prev = token
         continue
 
@@ -1336,7 +1344,7 @@ SYMBOL = //
 | \.{1,3}                       # dot / cascade / splat/placeholder/yada*3
 | \^\^                          # clone
 | \*?<(?:--?|~~?)!?             # backcall
-| !?(?:--?|~~?)>\*?             # function, bound function
+| !?(?:--?|~~?)>(?:>|\*)?       # function, bound function
 | ([-+&|:])\1                   # crement / logic / `prototype`
 | %%                            # mod
 | &                             # arguments