JSX: Fix assignment expression parsing in place holders

Fixes #2092

src/syntax/Parser.js

@@ -4409,7 +4409,7 @@ export class Parser {
             case OPEN_CURLY: {
               let start = token.location.start;
               let expression = null;
-              if (peekJsxToken().type !== CLOSE_CURLY) {
+              if (!peek(CLOSE_CURLY)) {
                 expression = this.parseAssignmentExpression_(ALLOW_IN);
               }
               this.eatJsx_(CLOSE_CURLY);

test/feature/JSX/ThisInPlaceHolder.js

@@ -0,0 +1,30 @@
+// Options: --jsx=f
+
+let f = (tag, props, ...children) => {
+  return children;
+};
+
+class C {
+  m() {
+    return <a> x {this} y </a>;
+  }
+  n() {
+    return <a> x {} y </a>;
+  }
+  o() {
+    return <a> x {}{} y </a>;
+  }
+  p() {
+    return <a b={this}/>;
+  }
+}
+
+const c = new C();
+assert.deepEqual([' x ', c, ' y '], c.m());
+assert.deepEqual([' x ', ' y '], c.n());
+assert.deepEqual([' x ', ' y '], c.o());
+
+f = (tag, props, ...children) => {
+  return props;
+};
+assert.deepEqual({b: c}, c.p());