92 lines
3.3 KiB
CoffeeScript
92 lines
3.3 KiB
CoffeeScript
# The **Scope** class regulates lexical scoping within CoffeeScript. As you
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# generate code, you create a tree of scopes in the same shape as the nested
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# function bodies. Each scope knows about the variables declared within it,
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# and has a reference to its parent enclosing scope. In this way, we know which
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# variables are new and need to be declared with `var`, and which are shared
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# with the outside.
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# Set up exported variables for both **Node.js** and the browser.
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this.exports: this unless process?
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exports.Scope: class Scope
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# The top-level **Scope** object.
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@root: null
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# Initialize a scope with its parent, for lookups up the chain,
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# as well as a reference to the **Expressions** node is belongs to, which is
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# where it should declare its variables, and a reference to the function that
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# it wraps.
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constructor: (parent, expressions, method) ->
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[@parent, @expressions, @method]: [parent, expressions, method]
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@variables: {}
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if @parent
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@temp_var: @parent.temp_var
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else
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Scope.root: this
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@temp_var: '_a'
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# Look up a variable name in lexical scope, and declare it if it does not
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# already exist.
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find: (name) ->
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return true if @check name
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@variables[name]: 'var'
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false
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# Test variables and return true the first time fn(v, k) returns true
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any: (fn) ->
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for v, k of @variables when fn(v, k)
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return true
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return false
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# Reserve a variable name as originating from a function parameter for this
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# scope. No `var` required for internal references.
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parameter: (name) ->
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@variables[name]: 'param'
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# Just check to see if a variable has already been declared, without reserving.
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check: (name) ->
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return true if @variables[name]
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!!(@parent and @parent.check(name))
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# If we need to store an intermediate result, find an available name for a
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# compiler-generated variable. `_a`, `_b`, and so on...
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free_variable: ->
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while @check @temp_var
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ordinal: 1 + parseInt @temp_var.substr(1), 36
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@temp_var: '_' + ordinal.toString(36).replace(/\d/g, 'a')
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@variables[@temp_var]: 'var'
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@temp_var
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# Ensure that an assignment is made at the top of this scope
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# (or at the top-level scope, if requested).
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assign: (name, value) ->
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@variables[name]: {value: value, assigned: true}
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# Does this scope reference any variables that need to be declared in the
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# given function body?
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has_declarations: (body) ->
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body is @expressions and @any (k, val) -> val is 'var'
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# Does this scope reference any assignments that need to be declared at the
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# top of the given function body?
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has_assignments: (body) ->
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body is @expressions and @any (k, val) -> val.assigned
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# Return the list of variables first declared in this scope.
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declared_variables: ->
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(key for key, val of @variables when val is 'var').sort()
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# Return the list of assignments that are supposed to be made at the top
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# of this scope.
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assigned_variables: ->
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"$key = $val.value" for key, val of @variables when val.assigned
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# Compile the JavaScript for all of the variable declarations in this scope.
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compiled_declarations: ->
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@declared_variables().join ', '
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# Compile the JavaScript for all of the variable assignments in this scope.
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compiled_assignments: ->
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@assigned_variables().join ', '
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