Panic on array parsing if length is externally defined

[jmaeso]

Actual behavior

generating code for the following interface makes the tool to panic.

(Note: math constant used just for convenience. Can be any other package-defined constant, not a hardcoded value)

type Fooer interface {
    Foo([math.MaxInt8]string)
}

Output: panic: interface conversion: ast.Expr is *ast.SelectorExpr, not *ast.BasicLit

Expected behavior

Generate a mocked struct with a method that takes a [127]string{} (or [math.MaxInt8]string{}) array

To Reproduce Steps to reproduce the behavior
Explained in the "Actual behaviour" section

Additional Information

• gomock mode (reflect or source): source
• gomock version or git ref: v1.5.0
• golang version: go version go1.15.8 darwin/amd64

Triage Notes for the Maintainers

[codyoss]

Thanks for the report. It looks like more work needs to be done onto the changes that were made in #520. I think those changes assume that the const is defined locally. I would be willing to accept a PR for this issue.