createSourceFile build wrong AST in some cases.

[dkulyk]

Bug Report

🕗 Version & Regression Information

• This is a parsing error on 4.5(maybe lower), 4.6-dev

⏯ Playground Link

AST Tree

💻 Code

Parsed JS

!a
    ? (a = (function () {})())
    : (function(a){})(a);

Workbench Repro

import { createPrinter, createSourceFile, ScriptTarget } from "typescript";

const source = `!a
    ? (a = (function () {})())
    : (function(a){return !0})(a);`

console.log(
    createPrinter().printFile(
        createSourceFile(`test.js`, source, ScriptTarget.Latest)
    )
);

Workbench Repro

🙁 Actual behavior

Wrong JS/TS.

!a
    ? (a = (function () { })()): (function(: a):) => { } : ;
(a);

Local tsc for example.ts code make

"use strict";
!a
    ? (a = (function () { })()) => { } : ;
(a);

🙂 Expected behavior

!a
    ? (a = (function () { })()): (function (a) { })(a); ;
(a);

[jakebailey]

Some more reduced examples:

1 ? (a) : (function() {})         // not OK
1 ? (undefined) : (function() {}) // not OK
1 ? (null) : (function() {})      // OK
1 ? () : (function() {})          // recovers 

This appears to be a parser bug (not a printer bug, darn); when the conditional expression gets past the ?, it tries to parse the first part of (a) : (function() {}) and the (a): tricks it into trying to parse an arrow expression with a missing => (thanks to recovery), rather than just (a) alone.

[jakebailey]

My fix for this was incomplete; #46962 is a full fix. I didn't consider something like 1 ? (a) : ((((function() {})))).