2nd/10_Wiki/Topics/Programming & Language/AST(Abstract Syntax Tree).md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-20260508-ast-abstract-syntax-tree--redir	AST (Abstract Syntax Tree)	10_Wiki/Topics	verified	self	AST Abstract Syntax Tree 추상 구문 트리	none	A	0.92	applied	compiler parser ast language		2026-05-10	pending	language framework typescript babel-parser, ts-morph, tree-sitter

AST (Abstract Syntax Tree)

매 한 줄

"매 source code 의 tree-shaped semantic skeleton". 매 lexer 의 token stream 을 parser 가 grammar rule 따라 nested node 의 tree 로 변환 — comment/whitespace/parens 의 trivia 를 제거하고 매 program 의 structural meaning 만 보존. 매 2026 의 Babel·SWC·TypeScript Compiler·Tree-sitter·Rust analyzer 의 모든 modern toolchain 의 핵심 IR.

매 핵심

매 AST vs CST

• CST (Concrete Syntax Tree): 매 source 의 every char 보존 — formatter, linter용.
• AST: 매 semantic structure 만 — compiler, transpiler, type checker용.
• 매 trade-off: lossless ↔ analysis-friendly.

매 Node 의 구조

• 매 type field (e.g. BinaryExpression, Identifier).
• 매 children (positional or named).
• 매 loc/range (source position).
• 매 ESTree spec — JS 의 standard AST shape.

매 응용

1. Compiler: AST → IR → bytecode/machine code.
2. Transpiler (Babel, SWC): AST → transformed AST → code.
3. Linter (ESLint): AST traversal + rule matching.
4. Formatter (Prettier): AST → printer.
5. IDE: hover, refactor, go-to-def 의 AST query.
6. Codemod (jscodeshift, ts-morph): bulk refactor.

💻 패턴

Babel parse

import { parse } from "@babel/parser";

const code = `const x = 1 + 2;`;
const ast = parse(code, { sourceType: "module" });
console.log(ast.program.body[0]);
// VariableDeclaration { kind: "const", declarations: [...] }

Visitor (transform)

import traverse from "@babel/traverse";

traverse(ast, {
  BinaryExpression(path) {
    if (path.node.operator === "+") {
      // 매 constant folding
      const { left, right } = path.node;
      if (left.type === "NumericLiteral" && right.type === "NumericLiteral") {
        path.replaceWith({ type: "NumericLiteral", value: left.value + right.value });
      }
    }
  },
});

TypeScript Compiler API

import * as ts from "typescript";

const source = ts.createSourceFile("x.ts", "const x: number = 1;", ts.ScriptTarget.Latest);
function visit(node: ts.Node) {
  if (ts.isVariableDeclaration(node)) {
    console.log(node.name.getText(source));
  }
  ts.forEachChild(node, visit);
}
visit(source);

Tree-sitter (incremental)

const Parser = require("tree-sitter");
const TS = require("tree-sitter-typescript").typescript;
const parser = new Parser();
parser.setLanguage(TS);
const tree = parser.parse("const x = 1;");
// 매 incremental: tree.edit(...) 로 partial reparse

ts-morph (codemod)

import { Project } from "ts-morph";
const proj = new Project();
const sf = proj.addSourceFileAtPath("src/foo.ts");
sf.getFunctions().forEach((fn) => fn.setIsAsync(true));
sf.saveSync();

매 결정 기준

상황	Approach
Compile / transpile JS/TS	Babel (@babel/parser) or SWC
IDE / editor highlighting	Tree-sitter (incremental, fast)
TypeScript-specific 의 type-aware refactor	TypeScript Compiler API or ts-morph
Linting	ESLint (espree/typescript-eslint)
1-off codemod	jscodeshift or ts-morph
Native speed (Rust/Go)	SWC, Rome, Biome

기본값: 매 TS 의 type-aware 작업 → ts-morph. 매 perf-critical 의 transpile → SWC. 매 editor → Tree-sitter.

🔗 Graph

• 부모: Parser
• 응용: ESLint · Prettier

🤖 LLM 활용

언제: 매 codemod 의 generation, AST node type 의 explanation, visitor pattern 의 boilerplate. 언제 X: 매 large-scale 의 type-aware refactor — ts-morph 의 deterministic 가 더 안전.

❌ 안티패턴

• Regex 의 code 의 transform: 매 nested syntax 의 break — AST 의 use.
• Mutate AST 의 children array 의 직접: 매 visitor 의 path API 의 use.
• Source map 의 무시: 매 transform 후 의 debug 의 broken — retainLines/sourcemap 의 emit.

🧪 검증 / 중복

• Verified (Babel docs, TS Compiler API, ESTree spec).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — full AST treatment with Babel/TS/Tree-sitter patterns