Function getExpandoInitializer

test/fixtures/snapshot/typescript.js:16465–16478

* Recognized expando initializers are: * 1. (function() {})() -- IIFEs * 2. function() { } -- Function expressions * 3. class { } -- Class expressions * 4. {} -- Empty object literals * 5. { ... } -- Non-empty object literals, when used to initialize a prototype, like `C.pro

(initializer, isPrototypeAssignment)

     * This function returns the provided initializer, or undefined if it is not valid.
     */
    function getExpandoInitializer(initializer, isPrototypeAssignment) {
        if (ts.isCallExpression(initializer)) {
            var e = skipParentheses(initializer.expression);
            return e.kind === 213 /* SyntaxKind.FunctionExpression */ || e.kind === 214 /* SyntaxKind.ArrowFunction */ ? initializer : undefined;
        }
        if (initializer.kind === 213 /* SyntaxKind.FunctionExpression */ ||
            initializer.kind === 226 /* SyntaxKind.ClassExpression */ ||
            initializer.kind === 214 /* SyntaxKind.ArrowFunction */) {
            return initializer;
        }
        if (ts.isObjectLiteralExpression(initializer) && (initializer.properties.length === 0 || isPrototypeAssignment)) {
            return initializer;
        }
    }
    ts.getExpandoInitializer = getExpandoInitializer;
    /**
     * A defaulted expando initializer matches the pattern