x/tools/gopls: Completion: "ZeroString for unexpected type" panic

[adonovan]

#!stacks
"runtime.gopanic" && "ZeroString:+15"

Issue created by stacks.

Looks like an untyped or invalid BasicType:

func ZeroString(t types.Type, qf types.Qualifier) string {
	switch t := t.(type) {
	case *types.Basic:
		switch {
		case t.Info()&types.IsBoolean != 0:
			return "false"
		case t.Info()&types.IsNumeric != 0:
			return "0"
		case t.Info()&types.IsString != 0:
			return `""`
		case t.Kind() == types.UnsafePointer:
			fallthrough
		case t.Kind() == types.UntypedNil:
			return "nil"
		default:
			panic(fmt.Sprint("ZeroString for unexpected type:", t))
		}

This stack A4anUg was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• golang.org/x/tools/internal/typesinternal.ZeroString:+15
• golang.org/x/tools/gopls/internal/golang/completion.(*completer).addReturnZeroValues:+35
• golang.org/x/tools/gopls/internal/golang/completion.(*completer).addStatementCandidates:+3
• golang.org/x/tools/gopls/internal/golang/completion.Completion:+186
• golang.org/x/tools/gopls/internal/server.(*server).Completion:+19
• golang.org/x/tools/gopls/internal/protocol.serverDispatch:+193
• golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.ServerHandler.func3:+5
• golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.handshaker.func4:+52
• golang.org/x/tools/gopls/internal/protocol.Handlers.MustReplyHandler.func1:+2
• golang.org/x/tools/gopls/internal/protocol.Handlers.AsyncHandler.func2.2:+3
• runtime.goexit:+0

golang.org/x/tools/gopls@v0.17.0-pre.3 go1.23.3 linux/amd64 other,vscode (3)

[gabyhelp]

Related Issues

• x/tools/gopls: OOB index crash in completion.expectedReturnStmtType #70636 (closed)
• x/tools/gopls: nil Signature (?) deref in Completion #70634 (closed)
• x/tools/gopls: analysisinternal.ZeroValue crash on (presumably) unsafe.Pointer #70585 (closed)
• x/tools/gopls: automated issue report (crash) - unhandled basic type #40956 (closed)
• x/tools/gopls: panic in completion.enclosingFunction #49397 (closed)
• x/tools/gopls: crash in Hover (telemetry) #69362
• x/tools/gopls: Hover: nil deref in parseDocLink #70635 (closed)
• x/tools/gopls: Hover: panic in lookup{ObjectByName,DocLinkSymbol} #69616
• x/tools/gopls: bug report in GetIfaceStubInfo #70666
• x/tools/gopls: panic in completion on variables of type *error #56505 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[gopherbot]

Change https://go.dev/cl/634923 mentions this issue: internal/typesinternal: rollback of Zero{Value,Expr} for gopls

[gopherbot]

Change https://go.dev/cl/635215 mentions this issue: [gopls-release-branch.0.17] internal/typesinternal: rollback of Zero{Value,Expr} for gopls