From b6d9675d7644c0634222ac6d122b4ed97b1711ce Mon Sep 17 00:00:00 2001
From: Vignesh Shanmugam <vignesh.shanmugam22@gmail.com>
Date: Fri, 11 May 2018 16:14:50 +0200
Subject: [PATCH] handle removed nodes in evaluation phase

---
 .../babel-helper-evaluate-path/src/index.js   | 37 ++++++++++---------
 .../src/index.js                              | 14 ++++---
 .../__tests__/preset-tests.js                 |  1 -
 3 files changed, 27 insertions(+), 25 deletions(-)

diff --git a/packages/babel-helper-evaluate-path/src/index.js b/packages/babel-helper-evaluate-path/src/index.js
index 43c49844c..abb866a70 100644
--- a/packages/babel-helper-evaluate-path/src/index.js
+++ b/packages/babel-helper-evaluate-path/src/index.js
@@ -1,12 +1,14 @@
 "use strict";
 
+const t = require("@babel/types");
+
 module.exports = function evaluate(path, { tdz = false } = {}) {
-  if (path.isReferencedIdentifier()) {
-    return evaluateIdentifier(path);
+  if (!tdz && !path.isReferencedIdentifier()) {
+    return baseEvaluate(path);
   }
 
-  if (!tdz) {
-    return baseEvaluate(path);
+  if (path.isReferencedIdentifier()) {
+    return evaluateIdentifier(path);
   }
 
   const state = {
@@ -119,26 +121,27 @@ function evaluateBasedOnControlFlow(binding, refPath) {
   if (binding.kind === "var") {
     // early-exit
     const declaration = binding.path.parentPath;
+
     if (
-      declaration.parentPath.isIfStatement() ||
-      declaration.parentPath.isLoop() ||
-      declaration.parentPath.isSwitchCase()
+      t.isIfStatement(declaration.parentPath) ||
+      t.isLoop(declaration.parentPath) ||
+      t.isSwitchCase(declaration.parentPath)
     ) {
+      if (declaration.parentPath.removed) {
+        return { confident: true, value: void 0 };
+      }
       return { shouldDeopt: true };
     }
 
-    const fnParent = binding.path.getFunctionParent();
-    if (!fnParent) {
-      return { shouldDeopt: true };
-    }
+    const fnParent = (
+      binding.path.scope.getFunctionParent() ||
+      binding.path.scope.getProgramParent()
+    ).path;
 
     let blockParent = binding.path.scope.getBlockParent().path;
-    if (!blockParent) {
-      return { shouldDeopt: true };
-    }
 
-    if (blockParent === fnParent) {
-      if (!fnParent.isProgram()) blockParent = blockParent.get("body");
+    if (blockParent === fnParent && !fnParent.isProgram()) {
+      blockParent = blockParent.get("body");
     }
 
     // detect Usage Outside Init Scope
@@ -164,8 +167,6 @@ function evaluateBasedOnControlFlow(binding, refPath) {
       ) {
         return { confident: true, value: void 0 };
       }
-
-      return { shouldDeopt: true };
     }
   } else if (binding.kind === "let" || binding.kind === "const") {
     // binding.path is the declarator
diff --git a/packages/babel-plugin-minify-dead-code-elimination/src/index.js b/packages/babel-plugin-minify-dead-code-elimination/src/index.js
index 92ee8f130..a15b14e3f 100644
--- a/packages/babel-plugin-minify-dead-code-elimination/src/index.js
+++ b/packages/babel-plugin-minify-dead-code-elimination/src/index.js
@@ -5,6 +5,11 @@ const { markEvalScopes, hasEval } = require("babel-helper-mark-eval-scopes");
 const removeUseStrict = require("./remove-use-strict");
 const evaluate = require("babel-helper-evaluate-path");
 
+function evaluateTruthy(path) {
+  const res = evaluate(path);
+  if (res.confident) return !!res.value;
+}
+
 function prevSiblings(path) {
   const parentPath = path.parentPath;
   const siblings = [];
@@ -548,7 +553,7 @@ module.exports = ({ types: t, traverse }) => {
 
     ConditionalExpression(path) {
       const { node } = path;
-      const evaluateTest = path.get("test").evaluateTruthy();
+      const evaluateTest = evaluateTruthy(path.get("test"));
       if (evaluateTest === true) {
         path.replaceWith(node.consequent);
       } else if (evaluateTest === false) {
@@ -976,14 +981,11 @@ module.exports = ({ types: t, traverse }) => {
     } else {
       path.traverse({
         VariableDeclaration(varPath) {
-          const { node } = varPath;
+          if (!varPath.isVariableDeclaration({ kind: "var" })) return;
 
-          if (node.kind !== "var") {
-            return;
-          }
           if (!isSameFunctionScope(varPath, path)) return;
 
-          for (const decl of node.declarations) {
+          for (const decl of varPath.node.declarations) {
             const bindingIds = Object.keys(t.getBindingIdentifiers(decl.id));
             declarators.push(
               ...bindingIds.map(name =>
diff --git a/packages/babel-preset-minify/__tests__/preset-tests.js b/packages/babel-preset-minify/__tests__/preset-tests.js
index dd3a6060d..11f016130 100644
--- a/packages/babel-preset-minify/__tests__/preset-tests.js
+++ b/packages/babel-preset-minify/__tests__/preset-tests.js
@@ -190,7 +190,6 @@ describe("preset", () => {
     `,
     `
       var bar;
-      bar && alert('bug!');
     `
   );
 });