better string coercion

[mbostock]

For objects that implement both valueOf and toString, we want to favor the toString:

({valueOf: () => 42, toString: () => "foo"}) + "" // returns "42"

`${({valueOf: () => 42, toString: () => "foo"})}` // returns "foo"

This change is particularly critical for APIs such as the proposed Temporal API which will throw an error if you try to concatenate them with a string, even though they implement toString!

Fixes #178.

[Fil]

wow; and the error message about comparisons is quite misleading, since we're not trying to compare.

We'll have to fix that also in all D3 modules I guess?

[mbostock]

We'll have to fix that also in all D3 modules I guess?

Yeah… a pretty pervasive change.