What is the behavior of the constructor when a decimal exceeding 34 decimal places is provided

[amoshydra]

Question

What is the expected behavior for the following inputs?

new Decimal("0.1000000000_0000000000_0000000000_1111_4")
new Decimal("0.1000000000_0000000000_0000000000_1111_5")
new Decimal("0.1000000000_0000000000_0000000000_1111_6")
new Decimal("0.1000000000_0000000000_0000000000_1112_4")
new Decimal("0.1000000000_0000000000_0000000000_1112_5")
new Decimal("0.1000000000_0000000000_0000000000_1112_6")

The decimal inputs above has 35 decimals and 35 significant decimals

1. Should the specification define the behavior for such input?
2. If yes, should it be:
   1. undefined, thus up to implementor?
   2. truncate?
   3. round halfEven?
   4. throw error?

From my reading, currently specification only mention ParseText, but ParseText does not provide detail on how such input should be handled.

Ref: https://tc39.es/proposal-decimal/#sec-the-decimal128-constructor-value

Side note

the npm package decimal128 @ 22:

new Decimal("0.00000_0000000000_9999999999_9999999999_9999999999_99915").toString() 

x	v
input	"0.00000_0000000000_9999999999_9999999999_9999999999_99915"
current	"0.00000_0000000001"
expected	"0.00000_0000000000_9999999999_9999999999_9999999999_9992"

^ expectation assuming round halfEven

[jessealama]

The thinking is that the value gets rounded, using half-even. The work happens in step 9.c, below the ParseText call. If you look into that spec function you can see that it involves the RoundToDecimal128Domain abstract operation, which does respect the limit of 34 significant digits, using the 35th if necessary.

[jessealama]

AFAICS this has been clarified. Do you mind if I close the issue?