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+/**
+ ** \file escapes/escapes-visitor.hh
+ ** \brief Compute the escapes.
+ **
+ ** Variables and formals of a function may escape, i.e., be accessed
+ ** by an inner function.
+ **
+ ** When the semantic analysis finds a declaration of variable or
+ ** formal FOO, it needs to know whether it escapes or not.  This
+ ** requires an additional pass, before the semantic analysis, just to
+ ** spot the potential escapes of FOO.
+ **
+ ** In order to pass the result to the semantic analysis which walks
+ ** across the ast, the most natural and easy solution consists in
+ ** tagging the various VarDec and Field.
+ **
+ ** Now, how shall we compute the escapes?
+ ** The answer is obvious: we need to walk the ast, searching for variables
+ ** declared then accessed by an inner function.
+ **
+ ** If a variable is accessed from a nested function
+ **
+ ** 2è possibilité :
+ **  - Aucune n'échappe
+ **  - Echappe si accessed dans une fonction nestée
+ ** Attention
+ */
+
+#pragma once
+
+#include <map>
+
+#include <ast/default-visitor.hh>
+#include <ast/non-assert-visitor.hh>
+#include <ast/non-object-visitor.hh>
+
+namespace escapes
+{
+  /** \brief Compute the escapes.
+   **
+   ** The EscapeVisitor is extremely similar to type::TypeChecker:
+   ** in its course of operation it must relate uses to
+   ** definitions.  Therefore it will be run after the bind::Binder.
+   ** It also needs auxiliary information about the definitions (their
+   ** depth): a simple map suffices, since scoping issues were handled
+   ** by the bind::Binder.
+   **
+   ** Note that this EscapesVisitor is mainly doing nothing: it is just
+   ** interested in declaration and uses of variables/formals (and, of
+   ** course, function declaration...).  It would be somewhat stupid to
+   ** write all the methods that `do nothing but walk'.  This is why we
+   ** will inherit from the non const ast::DefaultVisitor.
+   **/
+  class EscapesVisitor
+    : public ast::DefaultVisitor
+    , public ast::NonObjectVisitor
+    , public ast::NonAssertVisitor
+  {
+  public:
+    /// Super class type.
+    using super_type = ast::DefaultVisitor;
+    /// Import all the overloaded visit methods.
+    using super_type::operator();
+
+    // FIXME DONE: Some code was deleted here.
+    void operator()(ast::SimpleVar& e) override;
+    void operator()(ast::VarDec& e) override;
+    void operator()(ast::FunctionDec& e) override;
+  protected:
+    std::map<ast::VarDec*, size_t> depth_map_;
+  private:
+    size_t current_depth_ = 0;
+  };
+
+} // namespace escapes