x/tools/gopls: stubmethods: SEGV after failed Cursor.FindByPos fails in GetIfaceStubInfo

#!stacks
"Cursor.Enclosing.func1:+1" && "sigpanic"

Issue created by stacks.

func GetIfaceStubInfo(fset *token.FileSet, info *types.Info, pgf *parsego.File, pos, end token.Pos) *IfaceStubInfo {
	cur, _ := pgf.Cursor().FindByPos(pos, end)
	for cur := range cur.Enclosing() {

This stack ilWB9Q was reported by telemetry:

• crash/crash
• runtime.gopanic:+69,+0x158
• runtime.panicmem:=336,+0x194
• runtime.sigpanic:+9,+0x167
• golang.org/x/tools/go/ast/inspector.Cursor.Enclosing.func1:+1,+0x2c
• golang.org/x/tools/gopls/internal/golang/stubmethods.GetIfaceStubInfo:+2,+0x13b
• golang.org/x/tools/gopls/internal/golang.quickFix:+43,+0x609
• golang.org/x/tools/gopls/internal/golang.CodeActions:+64,+0x6cd
• golang.org/x/tools/gopls/internal/server.(*server).CodeAction:+154,+0x5b6
• golang.org/x/tools/gopls/internal/protocol.ServerDispatchCall:+181,+0x2ba8
• golang.org/x/tools/gopls/internal/protocol.serverDispatch:+1,+0x98
• golang.org/x/tools/gopls/internal/protocol.ServerHandler.func1:+5,+0x84
• golang.org/x/tools/gopls/internal/lsprpc.handshaker.func1:+52,+0x8ea
• golang.org/x/tools/internal/jsonrpc2.MustReplyHandler.func1:+2,+0xd4
• golang.org/x/tools/internal/jsonrpc2.AsyncHandler.func1.2:+3,+0x95
• runtime.goexit:+0,+0x0

golang.org/x/tools/[email protected] go1.27.0 windows/amd64 gopls.client=vscode (1)

Use this command to reproduce the executable: (HOME=$(mktemp -d); GOOS=windows GOARCH=amd64 GOTOOLCHAIN=go1.27.0 go install golang.org/x/tools/[email protected] && find $HOME/go/bin -type f) To disassemble: go tool objdump exe | less