x/tools/gopls: Completion: failed type assertion in completer.item

[adonovan]

#!stacks
"runtime.typeAssert" && "completion.(*completer).item:+33"

Issue created by stacks.

	if isTypeName(obj) && c.wantTypeParams() {
		// obj is a *types.TypeName, so its type must be Alias|Named.
		tparams := typesinternal.TypeParams(obj.Type().(typesinternal.NamedOrAlias))
		label += typesutil.FormatTypeParams(tparams)
		insert = label // maintain invariant above (label == insert)
	}

This stack kzwYeg was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.getitab:+58
• runtime.typeAssert:+7
• golang.org/x/tools/gopls/internal/golang/completion.(*completer).item:+33
• golang.org/x/tools/gopls/internal/golang/completion.(*completer).addCandidate:+44
• golang.org/x/tools/gopls/internal/golang/completion.(*completer).deepSearch:+71
• golang.org/x/tools/gopls/internal/golang/completion.Completion:+158
• 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@v0.17.1 go1.23.4 darwin/arm64 other,vscode (5)

[gabyhelp]

Related Issues

• x/tools/gopls: completion: failed type assertion in inferExpectedTypeArg #70889 (closed)
• x/tools/gopls: OOB index crash in completion.expectedReturnStmtType #70636 (closed)
• x/tools/gopls: Completion: "ZeroString for unexpected type" panic #70744 (closed)
• x/tools/gopls: nil Signature (?) deref in Completion #70634 (closed)
• x/tools/gopls: automated issue report (crash) - unhandled basic type #40956 (closed)
• x/tools/gopls: crash in Hover (telemetry) #69362
• x/tools/gopls: Rename: crash due to Info.Defs[id]=nil bug in checkStructField #70968
• x/tools/gopls: stubmethods: nil deref of FuncType.Results in fromReturnStmt #70967
• x/tools/gopls: stubmethods: "could not find the enclosing function of the return statement" bug in GetIfaceStubInfo #70666
• x/tools/gopls: panic in completion.enclosingFunction #49397 (closed)

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

[adonovan]

See amap.zip for a repro test case, courtesy of @qiulaidongfeng.

[findleyr]

@qiulaidongfeng do you recall exactly what you were completing when you encountered this crash?