Add syntactic space for block params

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

@@ -206,6 +206,7 @@ export default class ExpressionParser extends LValParser {
     const startPos = this.state.start;
     const startLoc = this.state.startLoc;
     const expr = this.parseMaybeAssign(refExpressionErrors);
+
     if (this.match(tt.comma)) {
       const node = this.startNodeAt(startPos, startLoc);
       node.expressions = [expr];
@@ -884,6 +885,12 @@ export default class ExpressionParser extends LValParser {
         }
       }
     }
+    // throw new Error(node);
+    if (this.match(tt.braceL)) {
+      const param = this.parseBlockParam();
+      node.arguments.push(param);
+      // console.log(node);
+    }
     return this.finishNode(
       node,
       optional ? "OptionalCallExpression" : "CallExpression",
@@ -2081,6 +2088,23 @@ export default class ExpressionParser extends LValParser {
     );
   }
 
+  // Parse block params as arrow function expressions.
+  parseBlockParam(): N.ArrowFunctionExpression {
+    const node = this.startNode();
+    const isAsync = false;
+    this.scope.enter(SCOPE_FUNCTION | SCOPE_ARROW);
+    const flags = functionFlags(isAsync, false);
+    this.prodParam.enter(flags);
+    this.initFunction(node, isAsync);
+    this.setArrowFunctionParameters(node, []);
+    this.state.maybeInArrowParameters = false;
+    this.parseFunctionBody(node, false, false);
+    this.prodParam.exit();
+    this.scope.exit();
+
+    return this.finishNode(node, "ArrowFunctionExpression");
+  }
+
   // Parse arrow function expression.
   // If the parameters are provided, they will be converted to an
   // assignable list.

packages/babel-parser/test/block-params.js

@@ -0,0 +1,11 @@
+import { parse } from "../lib";
+
+function getParser(code) {
+  return () => parse(code, { sourceType: "module" });
+}
+
+describe("block params syntax", () => {
+  it("should parse", () => {
+    expect(getParser(`foo() {}`)()).toMatchSnapshot();
+  });
+});