cmd/doc: does not generate docs for generic functions that return []T

[ahxxm]

What version of Go are you using (go version)?

$ gotip version
`devel go1.18-a83a558 Mon Sep 20 00:13:47 2021 +0000`

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

linux amd64

What did you do?

I wrote a generic function(inside package), run gotip doc -all -c -u [package-name]

What did you expect to see?

expect to see the function signature in output, like func Intersection[T comparable](slices... []T) []T

What did you see instead?

functions that return []T are not printed, others like func Some[T any](slice []T, pred func(T) bool) bool are printed

I tried dig into the doc generator, found that

• these functions are now considered to be factory functions of T, their associations go typ.funcs.set branch instead of r.funcs.set
• cleanupTypes() deleted T from r.types because it has no definition
• then T is not included in docPkg.Types, thus no results are printed

with following immature hack diff those functions will be printed:

@@ -429,8 +436,9 @@ func (r *reader) readFunc(fun *ast.FuncDecl) {
                 }
                 // If there is exactly one result type,
                 // associate the function with that type.
-                if numResultTypes == 1 {
+                if numResultTypes == 1 && typ.decl != nil {

[dr2chase]

@mvdan, @mdempsky this seems to have your name on it, seems relevant to getting generics into 1.18.

[mvdan]

With the suggested change, is the result that the generic function isn't considered a constructor, and is thus rendered as a regular top-level function?

That seems fine to me - if it returns a generic slice type, it's not like we can attach it to any specific type.

Want to send a PR? It should include a test.

[ahxxm]

@mvdan yup, they are rendered as regular top-level functions

I submitted a PR, is this test case ok..?

[gopherbot]

Change https://golang.org/cl/352389 mentions this issue: cmd/doc: generate docs for generic functions that return []T

[mvdan]

Thanks! I've left you a review on Gerrit. See https://github.com/golang/go/wiki/GerritBot.

[jba]

Duplicate of #49477, which was fixed.