Internal error with let inside while loop

[ochafik]

This simple code:

while (true) {
  let x = null;
  function f() {
    x();
  }
}

Gives the following trace (cmd line args: --language_in=ECMASCRIPT6_STRICT -O SIMPLE):

INTERNAL COMPILER ERROR.
Please report this problem.

Invalid attempt to remove node: NAME $jscomp$loop$0 3 [source_file: bug_closure.js] of CALL 3 [free_call: 1] [source_file: bug_closure.js]
  Node(NAME $jscomp$loop$0): bug_closure.js:3:2
  function f() {
  Parent(CALL): bug_closure.js:3:2
  function f() {

    at com.google.javascript.jscomp.NodeUtil.removeChild(NodeUtil.java:2293)
    at com.google.javascript.jscomp.UnreachableCodeElimination$EliminationPass.removeNode(UnreachableCodeElimination.java:261)
    at com.google.javascript.jscomp.UnreachableCodeElimination$EliminationPass.removeDeadExprStatementSafely(UnreachableCodeElimination.java:251)
    at com.google.javascript.jscomp.UnreachableCodeElimination$EliminationPass.visit(UnreachableCodeElimination.java:104)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:609)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:603)
    at com.google.javascript.jscomp.NodeTraversal.traverseBlockScope(NodeTraversal.java:652)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:597)
    at com.google.javascript.jscomp.NodeTraversal.traverseBlockScope(NodeTraversal.java:652)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:597)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:603)
    at com.google.javascript.jscomp.NodeTraversal.traverseBranch(NodeTraversal.java:603)
    at com.google.javascript.jscomp.NodeTraversal.traverse(NodeTraversal.java:295)
    at com.google.javascript.jscomp.NodeTraversal.traverseEs6(NodeTraversal.java:560)
    at com.google.javascript.jscomp.UnreachableCodeElimination$1.enterFunction(UnreachableCodeElimination.java:81)

Note that it works fine with var instead of let.

[MatrixFrog]

This might be another one that will be fixed with --language_out=ES5?

[Dominator008]

@MatrixFrog Seems like it's a bug in Es6ToEs3RewriteBlockScopedDeclaration

[ochafik]

(neither --language_out=ES5 nor --language_out=ECMASCRIPT5_STRICT help here, unfortunately)

[ochafik]

Thanks a lot guys!