fix: incorrect conciseBody lookahead (#14194)

JLHwung · web-flow · commit e5d29f6e402e · 2022-01-21T18:27:34.000-05:00
diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
@@ -2373,8 +2373,10 @@ export default class ExpressionParser extends LValParser {
   ): N.ArrowFunctionExpression {
     this.scope.enter(SCOPE_FUNCTION | SCOPE_ARROW);
     let flags = functionFlags(isAsync, false);
-    // ConciseBody and AsyncConciseBody inherit [In]
-    if (!this.match(tt.bracketL) && this.prodParam.hasIn) {
+    // ConciseBody[In] :
+    //   [lookahead ≠ {] ExpressionBody[?In, ~Await]
+    //   { FunctionBody[~Yield, ~Await] }
+    if (!this.match(tt.braceL) && this.prodParam.hasIn) {
       flags |= PARAM_IN;
     }
     this.prodParam.enter(flags);
diff --git a/packages/babel-parser/test/fixtures/es2015/arrow-functions/concise-body-binary-in-regression-14193/input.js b/packages/babel-parser/test/fixtures/es2015/arrow-functions/concise-body-binary-in-regression-14193/input.js
@@ -0,0 +1 @@
+() => [] in x
diff --git a/packages/babel-parser/test/fixtures/es2015/arrow-functions/concise-body-binary-in-regression-14193/output.json b/packages/babel-parser/test/fixtures/es2015/arrow-functions/concise-body-binary-in-regression-14193/output.json
@@ -0,0 +1,40 @@
+{
+  "type": "File",
+  "start":0,"end":13,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":13}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":13,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":13}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":13,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":13}},
+        "expression": {
+          "type": "ArrowFunctionExpression",
+          "start":0,"end":13,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":13}},
+          "id": null,
+          "generator": false,
+          "async": false,
+          "params": [],
+          "body": {
+            "type": "BinaryExpression",
+            "start":6,"end":13,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":13}},
+            "left": {
+              "type": "ArrayExpression",
+              "start":6,"end":8,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":8}},
+              "elements": []
+            },
+            "operator": "in",
+            "right": {
+              "type": "Identifier",
+              "start":12,"end":13,"loc":{"start":{"line":1,"column":12},"end":{"line":1,"column":13},"identifierName":"x"},
+              "name": "x"
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
diff --git a/packages/babel-parser/test/fixtures/es2015/arrow-functions/invalid-arrow-before-in/input.js b/packages/babel-parser/test/fixtures/es2015/arrow-functions/invalid-arrow-before-in/input.js
@@ -0,0 +1 @@
+() => {} in x
diff --git a/packages/babel-parser/test/fixtures/es2015/arrow-functions/invalid-arrow-before-in/options.json b/packages/babel-parser/test/fixtures/es2015/arrow-functions/invalid-arrow-before-in/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token (1:9)"
+}

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+{`
	`2`	`+ "throws": "Unexpected token (1:9)"`
	`3`	`+}`