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<h1>scope.litcoffee</h1>
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<p>The <strong>Scope</strong> 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 <code>var</code>, and which are shared
with external scopes.</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-built_in">exports</span>.Scope = <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Scope</span></span></pre></div></div>
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<p>Initialize a scope with its parent, for lookups up the chain,
as well as a reference to the <strong>Block</strong> node it belongs to, which is
where it should declare its variables, a reference to the function that
it belongs to, and a list of variables referenced in the source code
and therefore should be avoided when generating variables.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">constructor</span>: <span class="hljs-function"><span class="hljs-params">(<span class="hljs-property">@parent</span>, <span class="hljs-property">@expressions</span>, <span class="hljs-property">@method</span>, <span class="hljs-property">@referencedVars</span>)</span> -></span>
<span class="hljs-property">@variables</span> = [{<span class="hljs-attribute">name</span>: <span class="hljs-string">'arguments'</span>, <span class="hljs-attribute">type</span>: <span class="hljs-string">'arguments'</span>}]
<span class="hljs-property">@positions</span> = {}
<span class="hljs-property">@utilities</span> = {} <span class="hljs-keyword">unless</span> <span class="hljs-property">@parent</span></pre></div></div>
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<p>The <code>@root</code> is the top-level <strong>Scope</strong> object for a given file.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-property">@root</span> = <span class="hljs-property">@parent</span>?.root ? <span class="hljs-keyword">this</span></pre></div></div>
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<p>Adds a new variable or overrides an existing one.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">add</span>: <span class="hljs-function"><span class="hljs-params">(name, type, immediate)</span> -></span>
<span class="hljs-keyword">return</span> <span class="hljs-property">@parent</span>.add name, type, immediate <span class="hljs-keyword">if</span> <span class="hljs-property">@shared</span> <span class="hljs-keyword">and</span> <span class="hljs-keyword">not</span> immediate
<span class="hljs-keyword">if</span> <span class="hljs-attribute">Object</span>::hasOwnProperty.call <span class="hljs-property">@positions</span>, name
<span class="hljs-property">@variables</span>[<span class="hljs-property">@positions</span>[name]].type = type
<span class="hljs-keyword">else</span>
<span class="hljs-property">@positions</span>[name] = <span class="hljs-property">@variables</span>.push({name, type}) - <span class="hljs-number">1</span></pre></div></div>
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<p>When <code>super</code> is called, we need to find the name of the current method we’re
in, so that we know how to invoke the same method of the parent class. This
can get complicated if super is being called from an inner function.
<code>namedMethod</code> will walk up the scope tree until it either finds the first
function object that has a name filled in, or bottoms out.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">namedMethod</span>:<span class="hljs-function"> -></span>
<span class="hljs-keyword">return</span> <span class="hljs-property">@method</span> <span class="hljs-keyword">if</span> <span class="hljs-property">@method</span>?.name <span class="hljs-keyword">or</span> !<span class="hljs-property">@parent</span>
<span class="hljs-property">@parent</span>.namedMethod()</pre></div></div>
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<p>Look up a variable name in lexical scope, and declare it if it does not
already exist.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">find</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
<span class="hljs-keyword">return</span> <span class="hljs-literal">yes</span> <span class="hljs-keyword">if</span> <span class="hljs-property">@check</span> name
<span class="hljs-property">@add</span> name, <span class="hljs-string">'var'</span>
<span class="hljs-literal">no</span></pre></div></div>
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<p>Reserve a variable name as originating from a function parameter for this
scope. No <code>var</code> required for internal references.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">parameter</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">if</span> <span class="hljs-property">@shared</span> <span class="hljs-keyword">and</span> <span class="hljs-property">@parent</span>.check name, <span class="hljs-literal">yes</span>
<span class="hljs-property">@add</span> name, <span class="hljs-string">'param'</span></pre></div></div>
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<p>Just check to see if a variable has already been declared, without reserving,
walks up to the root scope.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">check</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
!!(<span class="hljs-property">@type</span>(name) <span class="hljs-keyword">or</span> <span class="hljs-property">@parent</span>?.check(name))</pre></div></div>
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<p>Generate a temporary variable name at the given index.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">temporary</span>: <span class="hljs-function"><span class="hljs-params">(name, index, single=<span class="hljs-literal">false</span>)</span> -></span>
<span class="hljs-keyword">if</span> single
(index + parseInt name, <span class="hljs-number">36</span>).toString(<span class="hljs-number">36</span>).replace <span class="hljs-regexp">/\d/g</span>, <span class="hljs-string">'a'</span>
<span class="hljs-keyword">else</span>
name + (index <span class="hljs-keyword">or</span> <span class="hljs-string">''</span>)</pre></div></div>
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<p>Gets the type of a variable.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">type</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
<span class="hljs-keyword">return</span> v.type <span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> <span class="hljs-property">@variables</span> <span class="hljs-keyword">when</span> v.name <span class="hljs-keyword">is</span> name
<span class="hljs-literal">null</span></pre></div></div>
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<p>If we need to store an intermediate result, find an available name for a
compiler-generated variable. <code>_var</code>, <code>_var2</code>, and so on…</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">freeVariable</span>: <span class="hljs-function"><span class="hljs-params">(name, options={})</span> -></span>
index = <span class="hljs-number">0</span>
<span class="hljs-keyword">loop</span>
temp = <span class="hljs-property">@temporary</span> name, index, options.single
<span class="hljs-keyword">break</span> <span class="hljs-keyword">unless</span> <span class="hljs-property">@check</span>(temp) <span class="hljs-keyword">or</span> temp <span class="hljs-keyword">in</span> <span class="hljs-property">@root</span>.referencedVars
index++
<span class="hljs-property">@add</span> temp, <span class="hljs-string">'var'</span>, <span class="hljs-literal">yes</span> <span class="hljs-keyword">if</span> options.reserve ? <span class="hljs-literal">true</span>
temp</pre></div></div>
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<p>Ensure that an assignment is made at the top of this scope
(or at the top-level scope, if requested).</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">assign</span>: <span class="hljs-function"><span class="hljs-params">(name, value)</span> -></span>
<span class="hljs-property">@add</span> name, {value, <span class="hljs-attribute">assigned</span>: <span class="hljs-literal">yes</span>}, <span class="hljs-literal">yes</span>
<span class="hljs-property">@hasAssignments</span> = <span class="hljs-literal">yes</span></pre></div></div>
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<p>Does this scope have any declared variables?</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">hasDeclarations</span>:<span class="hljs-function"> -></span>
!!<span class="hljs-property">@declaredVariables</span>().length</pre></div></div>
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<p>Return the list of variables first declared in this scope.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">declaredVariables</span>:<span class="hljs-function"> -></span>
(v.name <span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> <span class="hljs-property">@variables</span> <span class="hljs-keyword">when</span> v.type <span class="hljs-keyword">is</span> <span class="hljs-string">'var'</span>).sort()</pre></div></div>
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<p>Return the list of assignments that are supposed to be made at the top
of this scope.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">assignedVariables</span>:<span class="hljs-function"> -></span>
<span class="hljs-string">"<span class="hljs-subst">#{v.name}</span> = <span class="hljs-subst">#{v.type.value}</span>"</span> <span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> <span class="hljs-property">@variables</span> <span class="hljs-keyword">when</span> v.type.assigned</pre></div></div>
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