cmd/go: `wrong signature` error when using a type alias for `*testing.T`

Seems you can't alias testing.T, it confuses go test. Confuses Go Playground too.

go version go1.18.1 linux/amd64

What did you do?

https://go.dev/play/p/21W7rITsLUb

What did you expect to see?

Test results

What did you see instead?

wrong signature for TestLastIndex, must be: func TestLastIndex(t *testing.T)

[cherrymui]

Do you have a specific reason for aliasing testing.T? Thanks.

cc @bcmills

Do you have a specific reason for aliasing testing.T? Thanks.

Not really, no. I alias struct pointer types so it becomes impossible to forget the * and makes refactoring easier later. But apparently *testing.T is special.

[wangxuw]

hi, I reproduced this error using the provided test code snippet. This error is returned from https://github.com/golang/go/blob/master/src/cmd/go/internal/load/test.go#L770.
And it comes from a type assertion, https://github.com/golang/go/blob/master/src/cmd/go/internal/load/test.go#L575 where go command checks whether the first param holds *ast.StarExpr. When aliasing testing.T, the underlying type for fn.Type.Params.List[0].Type would be *ast.Ident.