istanbul ignore hint misplaced when semi-colons are omitted after literal object

[coreyfarrell]

const obj = {a: 'a'}

/* istanbul ignore if */
if ('b' in obj) {
  console.log('this should not be instrumented')
}

The output of nyc instrument --compact=false for this file is:

/* ...clipped... */
const obj = (cov_2oqccc38jn.s[0]++, {
  a: 'a'
  /* istanbul ignore if */

});
cov_2oqccc38jn.s[1]++;

if ('b' in obj) {
  cov_2oqccc38jn.b[0][0]++;
  cov_2oqccc38jn.s[2]++;
  console.log('this should not be instrumented');
} else {
  cov_2oqccc38jn.b[0][1]++;
}

Somehow the hint is getting moved up. I'm only able to reproduce this issue when the statement before the hint is a literal object assignment with at least one key and no semi-colons are used. Not sure yet if this is a bug in istanbul-lib-instrument or if babel is doing something unexpected.

[coreyfarrell]

Additional detail, the above code results in the istanbul hint being seeing in node.trailingComments for node.type === 'VariableDeclaration'. Adding a semi-colon to the assignment const obj = {a: 'a'}; causes the comment to also be seen in node.leadingComments for node.type === 'IfStatement'.

This issue happens regardless of if the assignment is a variable declaration or not.

[coreyfarrell]

Appears to be the result of a regression in @babel/parser, will be fixed by babel/babel#10445.

[coreyfarrell]

Fixed in @babel/parser@7.6.2