x/tools/gopls: "Create variable" declares x := nil or x := 0 where the use needs another type #81808

gopls version

golang.org/x/tools/gopls v0.23.0 (h1:Dn6mf9WXu9iLnTftDDMb9wV0c6Se7PjzEMqP0LEe08Y=), built with go1.27.1.
v0.23.0 is still the newest gopls release (checked 2026-09-28); all five cases reproduce on it again in 3 of 3 runs.
Same results with gopls v0.20.0.

go env

GOARCH=arm64
GOOS=darwin
GOVERSION=go1.27.1
GOFLAGS=-modcacherw
GOTOOLCHAIN=local

(macOS 27 on Apple silicon; path variables left out.)

What did you do?

I drive gopls over LSP from a small script. In five public projects I misspelled one use of a name, which gives undefined: X (UndeclaredName), and applied the quick fix "Create variable X". Each file builds before the typo. Line numbers are 1-based.

1. spf13/cobra at adbc8813901bba65827259daa8e22ff94ec1f30e, command_win.go (a Windows-only file; gopls reports it with [windows,amd64]), MousetrapHelpText misspelled on line 32:

   func preExecHook(c *Command) {
   	if MousetrapHelpText != "" && mousetrap.StartedByExplorer() {
   		c.Print(MousetrappHelpText)

   "Create variable MousetrappHelpText" inserts MousetrappHelpText := nil above line 32.

2. XTLS/Xray-core at d562d8947d3175db86b4fa849742433a9876cb63, common/crypto/io.go, reader misspelled in a struct field of type io.Reader:

   func NewCryptionReader(stream cipher.Stream, reader io.Reader) *CryptionReader {
   	return &CryptionReader{
   		stream: stream,
   		reader: reaer,
   	}
   }

   "Create variable reaer" inserts reaer := 0 as the first line of the function.

3. charmbracelet/bubbletea at 657aaae216e3f87df09b60959a9fe5de7b2ca419, examples/list-default/main.go (module examples), the type name model misspelled in a composite literal:

   	m := moddel{list: list.New(items, list.NewDefaultDelegate(), 0, 0)}

   "Create variable moddel" inserts moddel := 0 above it.

4. caddyserver/caddy at c18099a0af5e88c8d9da0b9d797f6f2c62d60a23, modules/caddyhttp/reverseproxy/selectionpolicies_test.go line 126, poool[1].countRequest(1): the fix inserts poool := 0.

5. nektos/act at 4f411281417e88660bea1c1a1749aa71ae0bd60f, pkg/container/docker_auth.go line 29, strings.ContainsAny(imge[:index], ".:"): the fix inserts imge := 0.

What did you see happen?

In every case the fix removes undefined: X and the file gets a different compile error instead (gopls publishes it right after the edit; the lines below are from go build, or go vet for the test file):

Each case reproduced in 3 of 3 runs.

What did you expect to see?

The docs say the fix inserts "a declaration with a default value inferring its type from the context". So:

• case 1: Print is declared as Print(i ...interface{}), so the context type is interface{}, and x := nil never compiles; something like var MousetrappHelpText interface{} would.
• case 2: the context type is io.Reader (the struct field), so var reaer io.Reader.
• case 3: the name is used as a type, so no variable can fix it; I expected no "Create variable" action there.
• cases 4 and 5: I don't know what type could be inferred, but := 0 cannot be indexed or sliced, so the fix only trades one error for another.

Editor and settings

No editor; a script over stdio (gopls serve). Settings returned for workspace/configuration: {"semanticTokens": true, "hints": {"assignVariableTypes": true, "compositeLiteralFields": true, "compositeLiteralTypes": true, "constantValues": true, "functionTypeParameters": true, "parameterNames": true, "rangeVariableTypes": true}}.

Logs

--> textDocument/didChange {"textDocument":{"uri":F,"version":2},"contentChanges":[{"range":{"start":{"line":31,"character":10},"end":{"line":31,"character":27}},"text":"MousetrappHelpText"}]}
<-- textDocument/publishDiagnostics {"uri":F,"version":2,"diagnostics":[{"range":{"start":{"line":31,"character":10},"end":{"line":31,"character":28}},"severity":1,"code":"UndeclaredName","source":"compiler","message":"undefined: MousetrappHelpText [windows,amd64]"}]}
--> textDocument/codeAction {"textDocument":{"uri":F},"range":{"start":{"line":31,"character":10},"end":{"line":31,"character":28}},"context":{"diagnostics":[(the diagnostic above)],"only":["quickfix"],"triggerKind":1}}
<-- [{"title":"Create variable MousetrappHelpText","kind":"quickfix","data":{"title":"Create variable MousetrappHelpText","command":"gopls.apply_fix",
      "arguments":[{"Fix":"create_undeclared","Location":{"uri":F,"range":{"start":{"line":31,"character":10},"end":{"line":31,"character":28}}},"ResolveEdits":true}]}}]
--> codeAction/resolve (that action)
<-- {"title":"Create variable MousetrappHelpText","kind":"quickfix","edit":{"documentChanges":[{"textDocument":{"version":2,"uri":F},
      "edits":[{"range":{"start":{"line":31,"character":2},"end":{"line":31,"character":2}},"newText":"MousetrappHelpText := nil\n\t\t"}]}]}}
--> textDocument/didChange (the edit above, version 3)
<-- textDocument/publishDiagnostics {"uri":F,"version":3,"diagnostics":[{"range":{"start":{"line":31,"character":24},"end":{"line":31,"character":27}},"severity":1,"code":"UntypedNilUse","source":"compiler","message":"use of untyped nil in assignment [windows,amd64]"}]}