using 'yield' automatically turns functions into generators

Cakefile

@@ -276,6 +276,12 @@ runTests = (CoffeeScript) ->
 
   # Run every test in the `test` folder, recording failures.
   files = fs.readdirSync 'test'
+
+  # Ignore generators test file if generators are not available
+  generatorsAreAvailable = '--harmony' in process.execArgv or
+    '--harmony-generators' in process.execArgv
+  files.splice files.indexOf('generators.coffee'), 1 if not generatorsAreAvailable
+
   for file in files when helpers.isCoffee file
     literate = helpers.isLiterate file
     currentFile = filename = path.join 'test', file

package.json

@@ -23,7 +23,8 @@
   },
   "preferGlobal": true,
   "scripts": {
-    "test": "node ./bin/cake test"
+    "test":         "node ./bin/cake test",
+    "test-harmony": "node --harmony ./bin/cake test"
   },
   "homepage": "http://coffeescript.org",
   "bugs": "https://github.com/jashkenas/coffeescript/issues",

src/grammar.coffee

@@ -536,6 +536,9 @@ grammar =
     o 'UNARY_MATH Expression',                  -> new Op $1 , $2
     o '-     Expression',                      (-> new Op '-', $2), prec: 'UNARY_MATH'
     o '+     Expression',                      (-> new Op '+', $2), prec: 'UNARY_MATH'
+    o 'YIELD Statement',                        -> new Op $1 , $2
+    o 'YIELD Expression',                       -> new Op $1 , $2
+    o 'YIELD FROM Expression',                  -> new Op $1.concat($2) , $3
 
     o '-- SimpleAssignable',                    -> new Op '--', $2
     o '++ SimpleAssignable',                    -> new Op '++', $2
@@ -586,6 +589,7 @@ operators = [
   ['nonassoc',  '++', '--']
   ['left',      '?']
   ['right',     'UNARY']
+  ['right',     'YIELD']
   ['right',     '**']
   ['right',     'UNARY_MATH']
   ['left',      'MATH']

src/lexer.coffee

@@ -109,6 +109,9 @@ exports.Lexer = class Lexer
     if id is 'own' and @tag() is 'FOR'
       @token 'OWN', id
       return id.length
+    if id is 'from' and @tag() is 'YIELD'
+      @token 'FROM', id
+      return id.length
     forcedIdentifier = colon or
       (prev = last @tokens) and (prev[0] in ['.', '?.', '::', '?::'] or
       not prev.spaced and prev[0] is '@')
@@ -688,7 +691,7 @@ exports.Lexer = class Lexer
   # Are we in the midst of an unfinished expression?
   unfinished: ->
     LINE_CONTINUER.test(@chunk) or
-    @tag() in ['\\', '.', '?.', '?::', 'UNARY', 'MATH', 'UNARY_MATH', '+', '-',
+    @tag() in ['\\', '.', '?.', '?::', 'UNARY', 'MATH', 'UNARY_MATH', '+', '-', 'YIELD',
                '**', 'SHIFT', 'RELATION', 'COMPARE', 'LOGIC', 'THROW', 'EXTENDS']
 
   # Remove newlines from beginning and (non escaped) from end of string literals.
@@ -729,7 +732,7 @@ exports.Lexer = class Lexer
 JS_KEYWORDS = [
   'true', 'false', 'null', 'this'
   'new', 'delete', 'typeof', 'in', 'instanceof'
-  'return', 'throw', 'break', 'continue', 'debugger'
+  'return', 'throw', 'break', 'continue', 'debugger', 'yield'
   'if', 'else', 'switch', 'for', 'while', 'do', 'try', 'catch', 'finally'
   'class', 'extends', 'super'
 ]
@@ -758,10 +761,10 @@ RESERVED = [
   'case', 'default', 'function', 'var', 'void', 'with', 'const', 'let', 'enum'
   'export', 'import', 'native', '__hasProp', '__extends', '__slice', '__bind'
   '__indexOf', 'implements', 'interface', 'package', 'private', 'protected'
-  'public', 'static', 'yield'
+  'public', 'static'
 ]
 
-STRICT_PROSCRIBED = ['arguments', 'eval']
+STRICT_PROSCRIBED = ['arguments', 'eval', 'yield*']
 
 # The superset of both JavaScript keywords and reserved words, none of which may
 # be used as identifiers or properties.

src/nodes.coffee

@@ -455,7 +455,6 @@ exports.Return = class Return extends Base
     answer.push @makeCode ";"
     return answer
 
-
 #### Value
 
 # A value, variable or literal or parenthesized, indexed or dotted into,
@@ -1315,9 +1314,11 @@ exports.Assign = class Assign extends Base
 # has no *children* -- they're within the inner scope.
 exports.Code = class Code extends Base
   constructor: (params, body, tag) ->
-    @params  = params or []
-    @body    = body or new Block
-    @bound   = tag is 'boundfunc'
+    @params      = params or []
+    @body        = body or new Block
+    @bound       = tag is 'boundfunc'
+    @isGenerator = @body.contains (node) ->
+      node instanceof Op and node.operator in ['yield', 'yield*']
 
   children: ['params', 'body']
 
@@ -1384,9 +1385,10 @@ exports.Code = class Code extends Base
       node.error "multiple parameters named '#{name}'" if name in uniqs
       uniqs.push name
     @body.makeReturn() unless wasEmpty or @noReturn
-    code  = 'function'
-    code  += ' ' + @name if @ctor
-    code  += '('
+    code = 'function'
+    code += '*' if @isGenerator
+    code += ' ' + @name if @ctor
+    code += '('
     answer = [@makeCode(code)]
     for p, i in params
       if i then answer.push @makeCode ", "
@@ -1612,9 +1614,10 @@ exports.Op = class Op extends Base
 
   # The map of conversions from CoffeeScript to JavaScript symbols.
   CONVERSIONS =
-    '==': '==='
-    '!=': '!=='
-    'of': 'in'
+    '==':        '==='
+    '!=':        '!=='
+    'of':        'in'
+    'yieldfrom': 'yield*'
 
   # The map of invertible operators.
   INVERSIONS =
@@ -1625,6 +1628,9 @@ exports.Op = class Op extends Base
 
   isSimpleNumber: NO
 
+  isYield: ->
+    @operator in ['yield', 'yield*']
+
   isUnary: ->
     not @second
 
@@ -1691,6 +1697,7 @@ exports.Op = class Op extends Base
       @error 'delete operand may not be argument or var'
     if @operator in ['--', '++'] and @first.unwrapAll().value in STRICT_PROSCRIBED
       @error "cannot increment/decrement \"#{@first.unwrapAll().value}\""
+    return @compileYield     o if @isYield()
     return @compileUnary     o if @isUnary()
     return @compileChain     o if isChain
     switch @operator
@@ -1745,6 +1752,19 @@ exports.Op = class Op extends Base
     parts.reverse() if @flip
     @joinFragmentArrays parts, ''
 
+  compileYield: (o) ->
+    parts = []
+    op = @operator
+    if not o.scope.parent?
+      @error 'yield statements must occur within a function generator.'
+    if 'expression' in Object.keys @first
+      parts.push @first.expression.compileToFragments o, LEVEL_OP if @first.expression?
+    else 
+      parts.push [@makeCode "(#{op} "] 
+      parts.push @first.compileToFragments o, LEVEL_OP
+      parts.push [@makeCode ")"] 
+    @joinFragmentArrays parts, ''
+
   compilePower: (o) ->
     # Make a Math.pow call
     pow = new Value new Literal('Math'), [new Access new Literal 'pow']

src/rewriter.coffee

@@ -467,7 +467,7 @@ IMPLICIT_FUNC    = ['IDENTIFIER', 'SUPER', ')', 'CALL_END', ']', 'INDEX_END', '@
 # If preceded by an `IMPLICIT_FUNC`, indicates a function invocation.
 IMPLICIT_CALL    = [
   'IDENTIFIER', 'NUMBER', 'STRING', 'JS', 'REGEX', 'NEW', 'PARAM_START', 'CLASS'
-  'IF', 'TRY', 'SWITCH', 'THIS', 'BOOL', 'NULL', 'UNDEFINED', 'UNARY',
+  'IF', 'TRY', 'SWITCH', 'THIS', 'BOOL', 'NULL', 'UNDEFINED', 'UNARY', 'YIELD'
   'UNARY_MATH', 'SUPER', 'THROW', '@', '->', '=>', '[', '(', '{', '--', '++'
 ]