Crash in compiler when trying to use externs to define CommonJS loaded React

[supersteves]

java.lang.RuntimeException: INTERNAL COMPILER ERROR.
Please email js-compiler@google.com with this stack trace and repro steps (a CL# and a build target).

Unexpected variable Symbol
  Node(NAME Symbol):  [synthetic:2] :34:2
  Symbol = $jscomp.global.Symbol || {};
  Parent(ASSIGN):  [synthetic:2] :34:2
  Symbol = $jscomp.global.Symbol || {};

    at com.google.javascript.jscomp.VarCheck.visit(VarCheck.java:202)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:607)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBlockScope(NodeTraversal.java:650)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:595)
    at com.google.javascript.jscomp.NodeTraversal.traverseFunction(NodeTraversal.java:641)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:593)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseRoots(NodeTraversal.java:318)
    at com.google.javascript.jscomp.VarCheck.process(VarCheck.java:142)
    at com.google.javascript.jscomp.PhaseOptimizer$NamedPass.process(PhaseOptimizer.java:285)
    at com.google.javascript.jscomp.PhaseOptimizer.process(PhaseOptimizer.java:217)
    at com.google.javascript.jscomp.Compiler.optimize(Compiler.java:1912)
    at com.google.javascript.jscomp.Compiler.compileInternal(Compiler.java:692)

Test case:
https://closure-compiler-debugger.appspot.com/#input0%3Dgoog.module(%2522test%2522)%253B%250A%250A%250Alet%2520React%2520%253D%2520%252F**%2520%2540type%2520%257BReact%257D%2520*%252F(require(%2522React%2522))%253B%250A%250Aclass%2520MyClass%2520extends%2520React.Component%2520%257B%250A%257D%250A%250Aexports%2520%253D%2520MyClass%253B%250A%26input1%26conformanceConfig%26externs%3D%252F**%250A%2520*%2520%2540type%2520%257BObject%257D%250A%2520*%2520%2540const%250A%2520*%252F%250Avar%2520React%2520%253D%2520%257B%257D%253B%250A%250A%252F**%250A*%2520%2540constructor%250A*%252F%250AReact.Component%2520%253D%2520function()%2520%257B%257D%253B%250A%250A%252F**%250A*%2520%2540param%2520%257Bstring%257D%2520module%250A*%2520%2540return%2520%257B*%257D%250A*%252F%250Avar%2520require%2520%253D%2520function(module)%2520%257B%2520return%2520%257B%257D%253B%2520%257D%253B%250A%26refasterjs-template%26CLOSURE_PASS%3D1%26LANG_IN_IS_ES6%3D1

Externs

/**
 * @type {Object}
 * @const
 */
var React = {};

/**
* @constructor
*/
React.Component = function() {};

/**
* @param {string} module
* @return {*}
*/
var require = function(module) { return {}; };

Code

goog.module("test");

let React = /** @type {React} */(require("React"));

class MyClass extends React.Component {
}

exports = MyClass;

See discussion:
https://groups.google.com/forum/#!topic/closure-compiler-discuss/-r7XK8j5yfA

When I run it locally I don't get this crash, instead I get:

WARNING - Misplaced type annotation. Type annotations are not allowed here. Are you missing parentheses?

[supersteves]

Another simple case which crashes the debugger - related? Externs:

class Y {}

Code:

class X extends Y {}

Crash:

java.lang.RuntimeException: INTERNAL COMPILER ERROR.
Please email js-compiler@google.com with this stack trace and repro steps (a CL# and a build target).

Unexpected variable arguments
  Node(NAME arguments): input0:1:0
class X extends Y {}
  Parent(CALL): input0:1:0
class X extends Y {}

    at com.google.javascript.jscomp.VarCheck.visit(VarCheck.java:202)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:607)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBlockScope(NodeTraversal.java:650)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:595)
    at com.google.javascript.jscomp.NodeTraversal.traverseFunction(NodeTraversal.java:641)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:593)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:601)
    at com.google.javascript.jscomp.NodeTraversal.traverseRoots(NodeTraversal.java:318)
    at com.google.javascript.jscomp.VarCheck.process(VarCheck.java:142)
    at com.google.javascript.jscomp.PhaseOptimizer$NamedPass.process(PhaseOptimizer.java:285)
    at com.google.javascript.jscomp.PhaseOptimizer.process(PhaseOptimizer.java:217)
    at com.google.javascript.jscomp.Compiler.optimize(Compiler.java:1912)
    at com.google.javascript.jscomp.Compiler.compileInternal(Compiler.java:692)
    at com.google.javascript.jscomp.Compiler.access$000(Compiler.java:91)
    at com.google.javascript.jscomp.Compiler$2.call(Compiler.java:643)
    at com.google.javascript.jscomp.Compiler$2.call(Compiler.java:640)
    at com.google.javascript.jscomp.CompilerExecutor.runInCompilerThread(CompilerExecutor.java:118)
    at com.google.javascript.jscomp.Compiler.runInCompilerThread(Compiler.java:666)
    at com.google.javascript.jscomp.Compiler.compile(Compiler.java:640)

https://closure-compiler-debugger.appspot.com/#input0%3Dclass%2520X%2520extends%2520Y%2520%257B%250A%257D%250A%26input1%26conformanceConfig%26externs%3Dclass%2520Y%2520%257B%257D%250A%26refasterjs-template%26includeDefaultExterns%3D1%26CHECK_SYMBOLS%3D1%26CHECK_TYPES%3D1%26CLOSURE_PASS%3D1%26LANG_IN_IS_ES6%3D1%26MISSING_PROPERTIES%3D1

[blickly]

The second case is a dup of #1125, which I'll be pushing a fix out for today.

[supersteves]

@blickly Second case indeed fixed in debugger

[supersteves]

First case still open, here's the updated test case with the (new?) TRANSPILE checkbox ticked:

https://closure-compiler-debugger.appspot.com/#input0%3Dgoog.module(%2522test%2522)%253B%250A%250A%250Alet%2520React%2520%253D%2520%252F**%2520%2540type%2520%257BReact%257D%2520*%252F(require(%2522React%2522))%253B%250A%250Aclass%2520MyClass%2520extends%2520React.Component%2520%257B%250A%257D%250A%250Aexports%2520%253D%2520MyClass%253B%250A%26input1%26conformanceConfig%26externs%3D%252F**%250A%2520*%2520%2540type%2520%257BObject%257D%250A%2520*%2520%2540const%250A%2520*%252F%250Avar%2520React%2520%253D%2520%257B%257D%253B%250A%250A%252F**%250A*%2520%2540constructor%250A*%252F%250AReact.Component%2520%253D%2520function()%2520%257B%257D%253B%250A%250A%252F**%250A*%2520%2540param%2520%257Bstring%257D%2520module%250A*%2520%2540return%2520%257B*%257D%250A*%252F%250Avar%2520require%2520%253D%2520function(module)%2520%257B%2520return%2520%257B%257D%253B%2520%257D%253B%250A%26refasterjs-template%26CLOSURE_PASS%3D1%26LANG_IN_IS_ES6%3D1%26TRANSPILE%3D1

[MatrixFrog]

You need the default externs (or rather, there are a few core externs you need, like Array and Symbol, otherwise nothing will work). I have it on my TODO list to make sure the error here is much clearer rather than a crash.

[MatrixFrog]

I believe it's now fairly difficult to forget the default externs when using the command-line, so this should only happen if you go out of your way to pass unusual flags, or specifically uncheck the default externs box on the debugger. I also don't see a good way to fix this (hard-coding checks for built-ins like Array is pretty hacky) so marking these crashes as P3.

[supersteves]

@MatrixFrog My bad, I was trying to isolate the problem by unchecking that. In practice I do use default externs so I don't need a fix.

Also I've dropped the original ambition of using runtime CommonJS "require()" to load React because I couldn't get it to work (WARNING - Misplaced type annotation. Type annotations are not allowed here. Are you missing parentheses?) and now I can't figure out how to reproduce this in the debugger (perhaps it's fixed).

[supersteves]

Update: having revisited this with ES6 modules I now realise it was my JSX transformation that was stripping the () needed in a cast. This probably helps identify the original crash, and entirely explains the misplaced type annotation error. See #1782