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scope.coffee

The Scope class regulates lexical scoping within CoffeeScript. As you generate code, you create a tree of scopes in the same shape as the nested function bodies. Each scope knows about the variables declared within it, and has a reference to its parent enclosing scope. In this way, we know which variables are new and need to be declared with var, and which are shared with the outside.

 
             		           
                               
                            
                                
               
Import the helpers we plan to use.
             		                            
{extend, last} = require './helpers'

exports.Scope = class Scope
             		           
                               
                            
                                
               
The top-level Scope object.
             		                            
  @root: null
             		           
                               
                            
                                
               
Initialize a scope with its parent, for lookups up the chain,
as well as a reference to the Block node is belongs to, which is
where it should declare its variables, and a reference to the function that
it wraps.
             		                            
  constructor: (@parent, @expressions, @method) ->
    @variables = [{name: 'arguments', type: 'arguments'}]
    @positions = {}
    Scope.root = this unless @parent
             		           
                               
                            
                                
               
Adds a new variable or overrides an existing one.
             		                            
  add: (name, type, immediate) ->
    return @parent.add name, type, immediate if @shared and not immediate
    if typeof (pos = @positions[name]) is 'number'
      @variables[pos].type = type
    else
      @positions[name] = @variables.push({name, type}) - 1
             		           
                               
                            
                                
               
Look up a variable name in lexical scope, and declare it if it does not
already exist.
             		                            
  find: (name, options) ->
    return yes if @check name, options
    @add name, 'var'
    no
             		           
                               
                            
                                
               
Reserve a variable name as originating from a function parameter for this
scope. No var required for internal references.
             		                            
  parameter: (name) ->
    return if @shared and @parent.check name, yes
    @add name, 'param'
             		           
                               
                            
                                
               
Just check to see if a variable has already been declared, without reserving,
walks up to the root scope.
             		                            
  check: (name, immediate) ->
    found = !!@type(name)
    return found if found or immediate
    !!@parent?.check name
             		           
                               
                            
                                
               
Generate a temporary variable name at the given index.
             		                            
  temporary: (name, index) ->
    if name.length > 1
      '_' + name + if index > 1 then index else ''
    else
      '_' + (index + parseInt name, 36).toString(36).replace /\d/g, 'a'
             		           
                               
                            
                                
               
Gets the type of a variable.
             		                            
  type: (name) ->
    return v.type for v in @variables when v.name is name
    null
             		           
                               
                            
                                
               
If we need to store an intermediate result, find an available name for a
compiler-generated variable. _var, _var2, and so on...
             		                            
  freeVariable: (type) ->
    index = 0
    index++ while @check((temp = @temporary type, index))
    @add temp, 'var', yes
    temp
             		           
                               
                            
                                
               
Ensure that an assignment is made at the top of this scope
(or at the top-level scope, if requested).
             		                            
  assign: (name, value) ->
    @add name, value: value, assigned: true
    @hasAssignments = yes
             		           
                               
                            
                                
               
Does this scope have any declared variables?
             		                            
  hasDeclarations: ->
    !!@declaredVariables().length
             		           
                               
                            
                                
               
Return the list of variables first declared in this scope.
             		                            
  declaredVariables: ->
    realVars = []
    tempVars = []
    for v in @variables when v.type is 'var'
      (if v.name.charAt(0) is '_' then tempVars else realVars).push v.name
    realVars.sort().concat tempVars.sort()
             		           
                               
                            
                                
               
Return the list of assignments that are supposed to be made at the top
of this scope.
             		                            
  assignedVariables: ->
    "#{v.name} = #{v.type.value}" for v in @variables when v.type.assigned