From 4ec5d8f644c46518ce984c36712437aa211f8cf2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?F=C3=A1bio=20Santos?= <fabiosantosart@gmail.com>
Date: Sun, 6 Sep 2015 21:33:17 +0100
Subject: [PATCH] parse, output the let statement

---
 lib/ast.js                   |  4 ++++
 lib/output.js                |  3 +++
 lib/parse.js                 | 23 ++++++++++++++++++-----
 test/compress/block-scope.js |  8 ++++++++
 4 files changed, 33 insertions(+), 5 deletions(-)
 create mode 100644 test/compress/block-scope.js

diff --git a/lib/ast.js b/lib/ast.js
index 756b1c69..94a96a64 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -682,6 +682,10 @@ var AST_Var = DEFNODE("Var", null, {
     $documentation: "A `var` statement"
 }, AST_Definitions);
 
+var AST_Let = DEFNODE("Let", null, {
+    $documentation: "A `let` statement"
+}, AST_Definitions);
+
 var AST_Const = DEFNODE("Const", null, {
     $documentation: "A `const` statement"
 }, AST_Definitions);
diff --git a/lib/output.js b/lib/output.js
index da4bb540..463ca6ba 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -1017,6 +1017,9 @@ function OutputStream(options) {
         if (!avoid_semicolon)
             output.semicolon();
     });
+    DEFPRINT(AST_Let, function(self, output){
+        self._do_print(output, "let");
+    });
     DEFPRINT(AST_Var, function(self, output){
         self._do_print(output, "var");
     });
diff --git a/lib/parse.js b/lib/parse.js
index e1de45c3..dbfa9f08 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -44,7 +44,7 @@
 
 "use strict";
 
-var KEYWORDS = 'break case catch const continue debugger default delete do else finally for function if in of instanceof new return switch throw try typeof var void while with';
+var KEYWORDS = 'break case catch const continue debugger default delete do else finally for function if in of instanceof new return switch throw try typeof var let void while with';
 var KEYWORDS_ATOM = 'false null true';
 var RESERVED_WORDS = 'abstract boolean byte char class double enum export extends final float goto implements import int interface long native package private protected public short static super synchronized this throws transient volatile yield'
     + " " + KEYWORDS_ATOM + " " + KEYWORDS;
@@ -891,6 +891,9 @@ function parse($TEXT, options) {
               case "var":
                 return tmp = var_(), semicolon(), tmp;
 
+              case "let":
+                return tmp = let_(), semicolon(), tmp;
+
               case "const":
                 return tmp = const_(), semicolon(), tmp;
 
@@ -961,13 +964,15 @@ function parse($TEXT, options) {
         expect("(");
         var init = null;
         if (!is("punc", ";")) {
-            init = is("keyword", "var")
-                ? (next(), var_(true))
-                : expression(true, true);
+            init =
+                is("keyword", "var") ? (next(), var_(true)) :
+                is("keyword", "let") ? (next(), let_(true)) :
+                                       expression(true, true);
             var is_in = is("operator", "in");
             var is_of = is("keyword", "of");
             if (is_in || is_of) {
-                if (init instanceof AST_Var && init.definitions.length > 1)
+                if ((init instanceof AST_Var || init instanceof AST_Let) &&
+                        init.definitions.length > 1)
                     croak("Only one variable declaration allowed in for..in loop");
                 next();
                 if (is_in) {
@@ -1265,6 +1270,14 @@ function parse($TEXT, options) {
         });
     };
 
+    var let_ = function(no_in) {
+        return new AST_Let({
+            start       : prev(),
+            definitions : vardefs(no_in, false),
+            end         : prev()
+        });
+    };
+
     var const_ = function() {
         return new AST_Const({
             start       : prev(),
diff --git a/test/compress/block-scope.js b/test/compress/block-scope.js
new file mode 100644
index 00000000..d0cdf75e
--- /dev/null
+++ b/test/compress/block-scope.js
@@ -0,0 +1,8 @@
+
+let_statement: {
+    input: {
+        let x = 6;
+    }
+    expect_exact: "let x=6;"
+}
+