Implemented rescoping with the do keyword.

lib/grammar.js

@@ -38,7 +38,7 @@
         return new Literal($1);
       })
     ],
-    Expression: [o("Value"), o("Invocation"), o("Code"), o("Operation"), o("Assign"), o("If"), o("Try"), o("While"), o("For"), o("Switch"), o("Extends"), o("Class"), o("Existence"), o("Comment")],
+    Expression: [o("Value"), o("Invocation"), o("Code"), o("Operation"), o("Assign"), o("If"), o("Try"), o("While"), o("For"), o("Switch"), o("Extends"), o("Class"), o("Existence"), o("Comment"), o("Do")],
     Block: [
       o("INDENT Body OUTDENT", function() {
         return $2;
@@ -106,6 +106,11 @@
         return new Existence($1);
       })
     ],
+    Do: [
+      o("DO Code", function() {
+        return new Call($2, $2.params);
+      })
+    ],
     Code: [
       o("PARAM_START ParamList PARAM_END FuncGlyph Block", function() {
         return new Code($2, $5, $4);

lib/lexer.js

@@ -585,7 +585,7 @@
     };
     return Lexer;
   })();
-  JS_KEYWORDS = ['true', 'false', 'null', 'this', 'new', 'delete', 'typeof', 'in', 'instanceof', 'return', 'throw', 'break', 'continue', 'debugger', 'if', 'else', 'switch', 'for', 'while', 'try', 'catch', 'finally', 'class', 'extends', 'super'];
+  JS_KEYWORDS = ['true', 'false', 'null', 'this', 'new', 'delete', 'typeof', 'in', 'instanceof', 'return', 'throw', 'break', 'continue', 'debugger', 'if', 'else', 'switch', 'for', 'while', 'try', 'catch', 'finally', 'class', 'extends', 'super', 'do'];
   COFFEE_KEYWORDS = ['then', 'unless', 'until', 'loop', 'of', 'by', 'when'];
   for (op in COFFEE_ALIASES = {
     and: '&&',
@@ -600,7 +600,7 @@
   }) {
     COFFEE_KEYWORDS.push(op);
   }
-  RESERVED = ['case', 'default', 'do', 'function', 'var', 'void', 'with', 'const', 'let', 'enum', 'export', 'import', 'native', '__hasProp', '__extends', '__slice'];
+  RESERVED = ['case', 'default', 'function', 'var', 'void', 'with', 'const', 'let', 'enum', 'export', 'import', 'native', '__hasProp', '__extends', '__slice'];
   JS_FORBIDDEN = JS_KEYWORDS.concat(RESERVED);
   IDENTIFIER = /^([$A-Za-z_][$\w]*)([^\n\S]*:(?!:))?/;
   NUMBER = /^0x[\da-f]+|^(?:\d+(\.\d+)?|\.\d+)(?:e[+-]?\d+)?/i;

lib/nodes.js

@@ -1728,7 +1728,7 @@
   }).call(this);
   Push = {
     wrap: function(name, expressions) {
-      if (expressions.empty() || (last(expressions.expressions)).containsPureStatement()) {
+      if (expressions.empty() || last(expressions.expressions).containsPureStatement()) {
         return expressions;
       }
       return expressions.push(new Call(new Value(new Literal(name), [new Accessor(new Literal('push'))]), [expressions.pop()]));

src/grammar.coffee

@@ -103,6 +103,7 @@ grammar =
     o "Class"
     o "Existence"
     o "Comment"
+    o "Do"
   ]
 
   # An indented block of expressions. Note that the [Rewriter](rewriter.html)
@@ -169,6 +170,10 @@ grammar =
   Existence: [
     o "Expression ?",                           -> new Existence $1
   ]
+  
+  Do: [
+    o "DO Code",                                  -> new Call $2, $2.params
+  ]
 
   # The **Code** node is the function literal. It's defined by an indented block
   # of **Expressions** preceded by a function arrow, with an optional parameter

src/lexer.coffee

@@ -515,7 +515,7 @@ JS_KEYWORDS = [
   'new', 'delete', 'typeof', 'in', 'instanceof'
   'return', 'throw', 'break', 'continue', 'debugger'
   'if', 'else', 'switch', 'for', 'while', 'try', 'catch', 'finally'
-  'class', 'extends', 'super'
+  'class', 'extends', 'super', 'do'
 ]
 
 # CoffeeScript-only keywords.
@@ -535,7 +535,7 @@ COFFEE_KEYWORDS.push op for all op of COFFEE_ALIASES =
 # used by CoffeeScript internally. We throw an error when these are encountered,
 # to avoid having a JavaScript error at runtime.
 RESERVED = [
-  'case', 'default', 'do', 'function', 'var', 'void', 'with'
+  'case', 'default', 'function', 'var', 'void', 'with'
   'const', 'let', 'enum', 'export', 'import', 'native'
   '__hasProp', '__extends', '__slice'
 ]

test/test_functions.coffee

@@ -345,3 +345,13 @@ eq ok, new ->
   ok
   ### Should `return` implicitly   ###
   ### even with trailing comments. ###
+
+
+# Rescoping with the `do` keyword.
+v1 = 1
+v2 = 2
+do (v1) ->
+  v1 = 3
+  v2 = 4
+ok v1 is 1
+ok v2 is 4