Support for matching iota with implicit types

[timkral]

I'm looking to find instances in which we are using the iota feature within golang. There are two general cases that I see available:

1. Explicit Types

type myType int
const (
  ZERO myType = iota
  ONE
)

2. Implicit Types

type myType int
const (
  ZERO = iota
  ONE
)

For the first case, I wrote the following rule and it works, no problem:

	m.Match(`$_ $_ = $iota;`).
		Where(m["iota"].Text == "iota").
		At(m["iota"]).
		Report(`...`)

However, I'm having trouble writing a rule that covers the second case. I've made several attempts:

• $_ $*_ = $iota (I recall that the pattern didn't compile)
• $_ = $iota (I think because the pattern is compiled as an AssignStmt, not a ValueSpec)
• const ( $_ = $iota ) (This works but only if there's a single value in the list, as soon as I add more, the pattern doesn't match)
• const ( $_ = $iota; $*_; ) (this fails the matchNodeList check)

Maybe there's a rule pattern that I haven't considered that would work for that second case. Or maybe it's just not supported by the framework. Any insight here would be greatly appreciated. Thank you!

[quasilyte]

Hello!

This rule should work on tip/recent release:

	m.Match(`const ( $_ = $iota; $*_ )`).
		Where(m["iota"].Text == "iota").
		At(m["iota"]).
		Report(`...`)

If it doesn't work as expected, it needs to be fixed.
But the idea is correct.
I can add tests with that pattern to the analyzer/testdata (or you can do it, contributions are welcome).

[quasilyte]

$_ = $iota (I think because the pattern is compiled as an AssignStmt, not a ValueSpec)

I think this pattern should match both in the future.
But making a const ( $_ = $iota; $*_ ) is more precise I think.
#292