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cmd/go: check that test funcs have no type parameters #48953

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findleyr opened this issue Oct 13, 2021 · 2 comments
Closed

cmd/go: check that test funcs have no type parameters #48953

findleyr opened this issue Oct 13, 2021 · 2 comments

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@findleyr
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@findleyr findleyr commented Oct 13, 2021

Currently, when writing a test function with type parameters, cmd/go produces an error like this:

package p

import "testing"

func TestP[P any](t *testing.T) {
        t.Error("bad")
}
/tmp/go-build4080445357/b001/_testmain.go:21:12: cannot use generic function _test.TestP without instantiation

Presumably because the generated code tries to call the generic test func without type arguments.

We should provide a more helpful error message, to the effect of "test functions cannot have type parameters". It looks like it would suffice to add this check here:
https://cs.opensource.google/go/go/+/master:src/cmd/go/internal/load/test.go;l=680;drc=5abfd2379b2e7319d3f08f496c12acdb50e1065a
(note that we probably want to continue matching these funcs in isTestFunc, specifically so that we can provide a useful error)

@bcmills @matloob does this make sense? Did you have a different behavior in mind? Shall I send a CL?

@bcmills
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@bcmills bcmills commented Oct 13, 2021

I agree that load.checkTestFunc is probably the right place for this fix.

(It's a bit unfortunate that isTestFunc is analyzing syntax rather than, say, extracting the actual function signatures — such as from the compiler's export data — but that seems like a separate cleanup.)

@gopherbot
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@gopherbot gopherbot commented Oct 14, 2021

Change https://golang.org/cl/355889 mentions this issue: cmd/go: produce a better error for generic test functions

@gopherbot gopherbot closed this in 4cbc0a5 Oct 14, 2021
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