disallow from as identifier after export default

packages/babel-parser/src/parser/error-message.js

@@ -42,6 +42,8 @@ export const ErrorMessages = Object.freeze({
   DuplicateRegExpFlags: "Duplicate regular expression flag",
   ElementAfterRest: "Rest element must be last element",
   EscapedCharNotAnIdentifier: "Invalid Unicode escape",
+  ExportDefaultFromAsIdentifier:
+    "'from' is not allowed as an identifier after 'export default'",
   ForInOfLoopInitializer:
     "%0 loop variable declaration may not have an initializer",
   GeneratorInSingleStatementContext:

packages/babel-parser/src/parser/statement.js

@@ -1925,6 +1925,17 @@ export default class StatementParser extends ExpressionParser {
       if (isDefault) {
         // Default exports
         this.checkDuplicateExports(node, "default");
+        if (this.hasPlugin("exportDefaultFrom")) {
+          const declaration = ((node: any): N.ExportDefaultDeclaration)
+            .declaration;
+          if (
+            declaration.type === "Identifier" &&
+            declaration.name === "from" &&
+            declaration.end - declaration.start === 4 // does not contain escape
+          ) {
+            this.raise(declaration.start, Errors.ExportDefaultFromAsIdentifier);
+          }
+        }
       } else if (node.specifiers && node.specifiers.length) {
         // Named exports
         for (const specifier of node.specifiers) {

packages/babel-parser/test/fixtures/experimental/export-extensions/default-default-asi/input.js

@@ -0,0 +1,2 @@
+export default from
+"bar";

packages/babel-parser/test/fixtures/experimental/export-extensions/default-default-asi/options.json

@@ -0,0 +1,4 @@
+{
+  "sourceType": "module",
+  "plugins": ["exportDefaultFrom"]
+}

packages/babel-parser/test/fixtures/experimental/export-extensions/default-default-asi/output.json

@@ -0,0 +1,37 @@
+{
+  "type": "File",
+  "start":0,"end":26,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":6}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":26,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":6}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExportNamedDeclaration",
+        "start":0,"end":26,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":6}},
+        "specifiers": [
+          {
+            "type": "ExportDefaultSpecifier",
+            "start":7,"end":14,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":14}},
+            "exported": {
+              "type": "Identifier",
+              "start":7,"end":14,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":14},"identifierName":"default"},
+              "name": "default"
+            }
+          }
+        ],
+        "source": {
+          "type": "StringLiteral",
+          "start":20,"end":25,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":5}},
+          "extra": {
+            "rawValue": "bar",
+            "raw": "\"bar\""
+          },
+          "value": "bar"
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/export-extensions/default-from/output.json → packages/babel-parser/test/fixtures/experimental/export-extensions/invalid-default-from-identifier/output.json

@@ -1,6 +1,9 @@
 {
   "type": "File",
   "start":0,"end":20,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":20}},
+  "errors": [
+    "SyntaxError: 'from' is not allowed as an identifier after 'export default' (1:15)"
+  ],
   "program": {
     "type": "Program",
     "start":0,"end":20,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":20}},