Algorithm 如何在AST中查找标识符的用法？

给定以下AST定义和示例代码，根据标识符在树中的位置，找到其所有用法的最佳算法是什么

AST Definition

type Literal
   = Char  of  char          // character literal
   | String of string        // string literal
   | Integer of  int         // integer literal
   | Float  of  float        // floating point literal   
   | Double of double 
   | Unit

type SrcCol = { startColumn : int; endColumn : int }

type SrcLine = { startLine : int; endLine : int }

type SrcLoc = { srcFilename : string; srcLine : SrcLine; srcColumn : SrcCol }     

type Pat =
    | PVar of 'a
    | PApp of Pat * Pat
    | PLit of Literal    
    | PWithTy of Pat * Type

type Exp 
    = Var      of 'a                           // variable    
    | Lam      of Pat list * Exp       // lambda abstraction
    | App      of Exp * Exp            // application    
    | Let      of Pat * Exp * Exp  // local definition    
    | Lit      of Literal                      // literal 
    | WithTy   of Exp * Type



Sample Code:

let f x = let g x = x                               
          g x 

AST instance of Sample Code
  [Let
                   (PApp
                      (PVar
                         ("f",
                          {srcFilename =
                            "test.fs";
                           srcLine = {startLine = 1;
                                      endLine = 1;};
                           srcColumn = {startColumn = 4;
                                        endColumn = 5;};}),
                       PVar
                         ("x",
                          {srcFilename =
                            "test.fs";
                           srcLine = {startLine = 1;
                                      endLine = 1;};
                           srcColumn = {startColumn = 6;
                                        endColumn = 7;};})),
                    Let
                      (PApp
                         (PVar
                            ("g",
                             {srcFilename =
                               "test.fs";
                              srcLine = {startLine = 1;
                                         endLine = 1;};
                              srcColumn = {startColumn = 14;
                                           endColumn = 15;};}),
                          PVar
                            ("x",
                             {srcFilename =
                               "test.fs";
                              srcLine = {startLine = 1;
                                         endLine = 1;};
                              srcColumn = {startColumn = 16;
                                           endColumn = 17;};})),
                       Var
                         ("x",
                          {srcFilename =
                            "test.fs";
                           srcLine = {startLine = 1;
                                      endLine = 1;};
                           srcColumn = {startColumn = 20;
                                        endColumn = 21;};}),
                       App
                         (Var
                            ("g",
                             {srcFilename =
                               "test.fs";
                              srcLine = {startLine = 2;
                                         endLine = 2;};
                              srcColumn = {startColumn = 10;
                                           endColumn = 11;};}),
                          Var
                            ("x",
                             {srcFilename =
                               "test.fs";
                              srcLine = {startLine = 2;
                                         endLine = 2;};
                              srcColumn = {startColumn = 12;
                                           endColumn = 13;};}))),Lit Unit)]

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在“创建了标识”的节点的子树中，DFS如何？基本上，需要使用所需属性的筛选器对树节点进行任何类型的枚举。深度优先搜索（如另一个答案中所建议的）是枚举节点的一种方法

然而，对于特定树节点中的特定标识符，人们通常想知道它代表什么“声明的实体”？否则，您会找到所有引用，但它们指向不同的实体，这通常是没有帮助的

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这需要为所讨论的应用程序语言构建符号表，然后在标识符节点和符号表条目之间构建映射。一个简单的枚举器无法完成构建符号表的任务。

看看我在周末入侵的实现：

似乎有效：）

Visual Studio Gallery上的FSharpRefactor 0.1（预览版）发行版

干杯；）