x/tools/gopls: missing function name in signature when hovering over built-in function

[katsusan]

gopls version

 ~/go/bin  gopls -v version                                                           
Build info
----------
golang.org/x/tools/gopls v0.8.1
    golang.org/x/tools/[email protected] h1:q5nDpRopYrnF4DN/1o8ZQ7Oar4Yd4I5OtGMx5RyV2/8=
    github.com/BurntSushi/[email protected] h1:dtDWrepsVPfW9H/4y7dDgFc2MBUSeJhlaDtK13CxFlU=
    github.com/google/[email protected] h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
    github.com/sergi/[email protected] h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
    golang.org/x/[email protected] h1:kQgndtyPBW/JIYERgdxfwMYh3AVStj88WQTlNDi2a+o=
    golang.org/x/[email protected] h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
    golang.org/x/[email protected] h1:rm+CHSpPEEW2IsXUib1ThaHIjuBVZjxNgSKmBLFfD4c=
    golang.org/x/[email protected] h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
    golang.org/x/[email protected] h1:AOqgMGxa5hFduIlFkKEX87HoRPO9wjyfhqf1yqwybeg=
    golang.org/x/[email protected] h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
    honnef.co/go/[email protected] h1:MNh1AVMyVX23VUHE2O27jm6lNj3vjO5DexS4A1xvnzk=
    mvdan.cc/[email protected] h1:kTojdZo9AcEYbQYhGuLf/zszYthRdhDNDUi2JKTxas4=
    mvdan.cc/xurls/[email protected] h1:tzxjVAj+wSBmDcF6zBB7/myTy3gX9xvi8Tyr28AuQgc=
go: go1.18

go env

 ~/go/bin  go env                                                                           
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/root/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/root/go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="/usr/local/bin/gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1830292990=/tmp/go-build -gno-record-gcc-switches"

What did you do?

1. create a x.go and use built-in function like panic/recover/make/...
2. hover on the built-in function.

What did you expect to see?

func(v any) → func panic(v any)

What did you see instead?

Editor and settings

It doesn't seem to be related to editor setting.

Logs

trace logs:

[Trace - 19:18:15.658 PM] Sending request 'textDocument/hover - (7)'.
Params: {"textDocument":{"uri":"file:///root/trygo/x.go"},"position":{"line":13,"character":3}}


[Trace - 19:18:15.663 PM] Received response 'textDocument/hover - (7)' in 4ms.
Result: {"contents":{"kind":"markdown","value":"```go\nfunc(v any)\n```\n\n[`panic` on pkg.go.dev](https://pkg.go.dev/builtin?utm_source=gopls#panic)\n\nThe panic built\\-in function stops normal execution of the current\ngoroutine\\. When a function F calls panic, normal execution of F stops\nimmediately\\. Any functions whose execution was deferred by F are run in\nthe usual way, and then F returns to its caller\\. To the caller G, the\ninvocation of F then behaves like a call to panic, terminating G\\'s\nexecution and running any deferred functions\\. This continues until all\nfunctions in the executing goroutine have stopped, in reverse order\\. At\nthat point, the program is terminated with a non\\-zero exit code\\. This\ntermination sequence is called panicking and can be controlled by the\nbuilt\\-in function recover\\.\n"},"range":{"start":{"line":13,"character":1},"end":{"line":13,"character":6}}}

Possible reason

//https://github.com/golang/tools/blob/5ea13d0d89f92d5ca5468e282dd4ba2ad7503564/internal/lsp/source/hover.go#L576-L581

func FindHoverContext(ctx context.Context, s Snapshot, pkg Package, obj types.Object, pkgNode ast.Node, fullDecl ast.Decl) (*HoverContext, error) {
        ...
	case *ast.FuncDecl:
		switch obj.(type) {
		case *types.Func:
			info = &HoverContext{signatureSource: obj, Comment: node.Doc}
		case *types.Builtin:
			info = &HoverContext{signatureSource: node.Type, Comment: node.Doc}

In the case of *types.Builtin only node.Type (ast.FuncDecl.Type) is reserved while ast.FuncDecl.Name
info is discarded. I tried following change and the function name can be shown correctly.

  info = &HoverContext{signatureSource: node.Type, Comment: node.Doc}
    ↓
  info = &HoverContext{
      signatureSource: &ast.FuncDecl{
	  Name: node.Name,
	  Type: node.Type,
      },
      Comment: node.Doc,
  }

[gopherbot]

Change https://go.dev/cl/395294 mentions this issue: internal/lsp/source: include builtin name in hovered signature