TypeScript Version: 3.2.0-dev.20180929

Search Terms:

• template literal

Code

var invokes = [];
function test(template, _) {
  invokes.push(template); 
}

function update(value) {
  test`some ${value}!`;
}

update(1);
update(2);

document.body.textContent = '' + (invokes[0] === invokes[1]); 

Expected behavior:
After compiling and running the code in a browser console, the body's content should be "true".

The code works as expected when compiled with Babel, or run verbatim in a browser console.

Actual behavior:
The body's content becomes "false". This breaks libraries such as hyperHTML (note: now it contains a workaround that works for me at least WebReflection/hyperHTML@6d3d879)

WebReflection/hyperHTML#270

Playground Link: https://www.typescriptlang.org/play/#src=var%20invokes%20%3D%20%5B%5D%3B%0D%0Afunction%20test(template%2C%20_)%20%7B%0D%0A%20%20invokes.push(template)%3B%20%0D%0A%7D%0D%0A%0D%0Afunction%20update(value)%20%7B%0D%0A%20%20test%60some%20%24%7Bvalue%7D!%60%3B%0D%0A%7D%0D%0A%0D%0Aupdate(1)%3B%0D%0Aupdate(2)%3B%0D%0A%0D%0Adocument.body.textContent%20%3D%20''%20%2B%20(invokes%5B0%5D%20%3D%3D%3D%20invokes%5B1%5D)%3B%20%0D%0A

Related Issues:

• Tagged template literals compiled incorrectly, TemplateStringsArray not cached #17956