Steps to reproduce

[bool]0n
[bigint]'1n'

Expected behavior

As BigInteger is a number, for all common intents and purposes, a 0 value should cast to $false just like other numbers.

Also, casting from a string to a biginteger should work with a numeric type suffix just like [long]'100L' does.

False
1 # of type System.Numerics.BigInteger

Actual behavior

True
InvalidArgument: Cannot convert value "1n" to type "System.Numerics.BigInteger". Error: "The value could not be parsed."

The behaviour in terms of casting to bool is standard for structs, which always cast to $true. In the case of BigInteger, however, it is simply a slightly more complicated basic value type in function, so it's more appropriate to cast it to $false is the value is 0.

However, casting from an otherwise parseable string should always work for BigInteger; the engine recognises 1n as a biginteger literal -- there's no reason it should fail to see it when casting from a string value as other suffixes work just fine.

Environment data

Name                           Value
----                           -----
PSVersion                      7.1.0-preview.2
PSEdition                      Core
GitCommitId                    7.1.0-preview.2
OS                             Darwin 19.3.0 Darwin Kernel Version 19.3.0: Thu Jan  9 20:58:23 PST 2020; root:xnu-6153.81.5~1/RELEASE_X86_64
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0