feat: use syntax plugin

README.md

@@ -139,6 +139,7 @@ require("babylon").parse("code", {
  - `functionSent`
  - `dynamicImport` ([proposal](https://github.com/tc39/proposal-dynamic-import))
  - `numericSeparator` ([proposal](https://github.com/samuelgoto/proposal-numeric-separator))
+ - `optionalChaining` ([proposal](https://github.com/tc39/proposal-optional-chaining))
 
 ### FAQ
 

src/parser/expression.js

@@ -303,8 +303,13 @@ export default class ExpressionParser extends LValParser {
         return this.parseSubscripts(this.finishNode(node, "BindExpression"), startPos, startLoc, noCalls);
 
       } else if (this.eat(tt.questionDot)) {
-        if (this.eat(tt.bracketL)) {
         const node = this.startNodeAt(startPos, startLoc);
+
+        if (!this.hasPlugin("optionalChaining")) {
+          this.raise(node.start, "You can only use optional-chaining when the 'optionalChaining' plugin is enabled.");
+        }
+
+        if (this.eat(tt.bracketL)) {
           node.object = base;
           node.optional = true;
           node.property = this.parseExpression();
@@ -312,7 +317,6 @@ export default class ExpressionParser extends LValParser {
           this.expect(tt.bracketR);
           base = this.finishNode(node, "MemberExpression");
         } else {
-          const node = this.startNodeAt(startPos, startLoc);
           node.object = base;
           node.property = this.parseIdentifier(true);
           node.optional = true;

test/fixtures/experimental/optional-chaining/class-contructor-call/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalChaining"]
+}

test/fixtures/experimental/optional-chaining/function-call/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalChaining"]
+}

test/fixtures/experimental/optional-chaining/member-access-bracket/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalChaining"]
+}

test/fixtures/experimental/optional-chaining/member-access/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalChaining"]
+}

test/fixtures/experimental/optional-chaining/missing-plugin/actual.js

@@ -0,0 +1 @@
+a?.b

test/fixtures/experimental/optional-chaining/missing-plugin/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "You can only use optional-chaining when the 'optionalChaining' plugin is enabled. (1:0)"
+}