Duplicated object key in const not detected when the key is a number preceded by - or +

[rigwild]

TypeScript Version: 3.9.0-dev.20200422

Search Terms:

• Signed numbers
• Object keys negative
• readonly negative key
• object key negative
• object key duplicate
• as const negative
• object key operand
• others...

Code

export const rotate = {
  "-45": "test",
  [-45]: "test" // Duplicate NOT detected
};

export const rotate2 = {
  "45": "test",
  [+45]: "test" // Duplicate NOT detected
};

export const rotate4 = {
  "45": "test",
  [45]: "test" // Duplicate detected
};

Expected behavior:
TypeScript should alert the user that there's a duplicated key.

Actual behavior:
Key duplication is not detected when the key is a number preceded by - or +.

Playground Link

Related Issues:
#37866 #38133 #37292

The bug seems to be there for a very long time (it has the same behavior on v2.4.1 on the playground).

[lissein]

After some investigations, I found that the expression between the square brackets is not evaluated but just used as text.

I would like to fix this issue but I don't really know where to put the stuff. The fix could be something similar to how typescript handles constant enum values (computeConstantValue in checker.ts).

This looks a little bit more complicated for such cases:

let b = 10

const a = {
  "46": 123,
  [b + 46]: 1234,
};

I think we can make it work by updating getPropertyNameForPropertyNameNode in utilities.ts but I'm not sure if it is the right place.