util.inspect not checking for loops in {,Weak}Map data

[rdeforest]

• Version: v8.2.1
• Platform: Darwin a0999b0cf96f.ant.amazon.com 16.6.0 Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64 x86_64
• Subsystem: util

Expected behavior:

coffee> m = new Map
Map {}
coffee> m.set m, m
ref1 = Map {
  ref1 => ref1
}
coffee>

Actual behavior:

coffee> m = new Map
Map {}
coffee> m.set m, m
Map {
  Map {
  Map { [Object] => [Object] } => Map { [Object] => [Object] } } => Map {
  Map { [Object] => [Object] } => Map { [Object] => [Object] } } }
coffee>

I know this is a non-trivial problem to solve but it seems worth at least documenting if not solving.

[TimothyGu]

Can reproduce on Node.js' REPL:

> var m = new Map()
undefined
> m.set('m', m)
Map { 'm' => Map { 'm' => Map { 'm' => [Object] } } }

Note, this works fine with a normal object:

> var o = {}
undefined
> o.o = o
{ o: [Circular] }
> o
{ o: [Circular] }