Correct update expression Number coercion (#7766)

* Correct update expression Number coercion

You have to `ToNumber` whatever the `UpdateExpression` argument is.

* Fix systemjs update expression

packages/babel-helper-simple-access/src/index.js

@@ -25,27 +25,49 @@ const simpleAssignmentVisitor = {
       }
 
       if (
-        path.node.prefix ||
+        path.parentPath.isExpressionStatement() &&
-        (path.parentPath.isExpressionStatement() && !path.isCompletionRecord())
+        !path.isCompletionRecord()
       ) {
         // ++i => (i += 1);
         const operator = path.node.operator == "++" ? "+=" : "-=";
         path.replaceWith(
           t.assignmentExpression(operator, arg.node, t.numericLiteral(1)),
         );
+      } else if (path.node.prefix) {
+        // ++i => (i = (+i) + 1);
+        path.replaceWith(
+          t.assignmentExpression(
+            "=",
+            t.identifier(localName),
+            t.binaryExpression(
+              path.node.operator[0],
+              t.unaryExpression("+", arg.node),
+              t.numericLiteral(1),
+            ),
+          ),
+        );
       } else {
-        const varName = path.scope.generateDeclaredUidIdentifier("old").name;
+        const old = path.scope.generateUidIdentifierBasedOnNode(
+          arg.node,
+          "old",
+        );
+        const varName = old.name;
+        path.scope.push({ id: old });
 
         const binary = t.binaryExpression(
-          path.node.operator.slice(0, 1),
+          path.node.operator[0],
           t.identifier(varName),
           t.numericLiteral(1),
         );
 
-        // i++ => (_tmp = i, i = _tmp + 1, _tmp)
+        // i++ => (_old = (+i), i = _old + 1, _old)
         path.replaceWith(
           t.sequenceExpression([
-            t.assignmentExpression("=", t.identifier(varName), arg.node),
+            t.assignmentExpression(
+              "=",
+              t.identifier(varName),
+              t.unaryExpression("+", arg.node),
+            ),
             t.assignmentExpression("=", t.cloneNode(arg.node), binary),
             t.identifier(varName),
           ]),

packages/babel-plugin-transform-modules-commonjs/test/fixtures/regression/4462-T7565/output.js

@@ -5,9 +5,9 @@ Object.defineProperty(exports, "__esModule", {
 });
 exports.zz = exports.yy = void 0;
 
-var _old;
+var _yy;
 
 var yy = 0;
 exports.yy = yy;
-var zz = (_old = yy, exports.yy = yy = _old + 1, _old);
+var zz = (_yy = +yy, exports.yy = yy = _yy + 1, _yy);
 exports.zz = zz;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/update-expression/negative-suffix/output.js

@@ -9,7 +9,7 @@ let diffLevel = 0;
 exports.diffLevel = diffLevel;
 
 function diff() {
-  if (!(exports.diffLevel = diffLevel = diffLevel - 1)) {
+  if (!(exports.diffLevel = diffLevel = +diffLevel - 1)) {
     console.log("hey");
   }
 }

packages/babel-plugin-transform-modules-commonjs/test/fixtures/update-expression/positive-suffix/output.js

@@ -9,7 +9,7 @@ let diffLevel = 0;
 exports.diffLevel = diffLevel;
 
 function diff() {
-  if (!(exports.diffLevel = diffLevel = diffLevel + 1)) {
+  if (!(exports.diffLevel = diffLevel = +diffLevel + 1)) {
     console.log("hey");
   }
 }

packages/babel-plugin-transform-modules-systemjs/src/index.js

@@ -50,23 +50,13 @@ export default declare((api, options) => {
       // if it is a non-prefix update expression (x++ etc)
       // then we must replace with the expression (_export('x', x + 1), x++)
       // in order to ensure the same update expression value
-      let isPostUpdateExpression = path.isUpdateExpression() && !node.prefix;
+      const isPostUpdateExpression = path.isUpdateExpression({ prefix: false });
       if (isPostUpdateExpression) {
-        if (node.operator === "++") {
         node = t.binaryExpression(
-            "+",
+          node.operator[0],
-            t.cloneNode(node.argument),
+          t.unaryExpression("+", t.cloneNode(node.argument)),
           t.numericLiteral(1),
         );
-        } else if (node.operator === "--") {
-          node = t.binaryExpression(
-            "-",
-            t.cloneNode(node.argument),
-            t.numericLiteral(1),
-          );
-        } else {
-          isPostUpdateExpression = false;
-        }
       }
 
       for (const exportedName of exportedNames) {

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/hoisting-bindings/output.mjs

@@ -5,7 +5,7 @@ System.register([], function (_export, _context) {
 
   function a() {
     alert("a");
-    _export("c", c + 1), c++;
+    _export("c", +c + 1), c++;
   }
 
   _export("a", a);

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/remap/output.mjs

@@ -11,7 +11,7 @@ System.register([], function (_export, _context) {
 
       _export("test", test = 5);
 
-      _export("test", test + 1), test++;
+      _export("test", +test + 1), test++;
 
       (function () {
         var test = 2;