Using multiple operators in INumber-constrained generic functions leads to compiler error

Please provide a succinct description of the issue.

```fsharp
// ok
let numericOpsPlus<'T when INumber<'T>>(num: 'T) =
num + num

// FS0670 - code is not sufficiently generic
let numericOpsPlusPlus<'T when INumber<'T>>(num: 'T) =
num + num + num

// ok again
let inline numericOpsPlusPlusInlined<'T when INumber<'T>>(num: 'T) =
num + num + num
```