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?

[findleyr]

Nevermind: I can construct a simple repro based on this stack.

[gopherbot]

Change https://go.dev/cl/643016 mentions this issue: gopls/internal/golang/completion: fix crash adding receiver type params

[qiulaidongfeng]

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

Yes, I was writing a method declaration at the time when writing the receiver type, line 41 of amap.zip

I can reproduce it.

[Error - 08:07:57] 2025/01/16 08:07:57 imports fixes: allImportsFixes: D:\file\gofile\amap2\amap\uint64.go:41:18: expected '(', found newline (and 2 more errors)
file="D:\file\gofile\amap2\amap\uint64.go"

panic: interface conversion: *types.Basic is not typesinternal.NamedOrAlias: missing method Obj

goroutine 12912 gp=0xc00654fc00 m=0 mp=0x25a5100 [running]:
panic({0x1a03ee0?, 0xc0072fec60?})
C:/Users/26454/.go/gotip/src/runtime/panic.go:806 +0x168 fp=0xc006efc870 sp=0xc006efc7c0 pc=0xed06c8
runtime.getitab(0x1a37f60, 0x1a92ea0, 0x0)
C:/Users/26454/.go/gotip/src/runtime/iface.go:102 +0x1c5 fp=0xc006efc8b8 sp=0xc006efc870 pc=0xecde45
runtime.typeAssert(0x2566be0, 0x1a92ea0)
C:/Users/26454/.go/gotip/src/runtime/iface.go:474 +0x3f fp=0xc006efc8f8 sp=0xc006efc8b8 pc=0xe6e99f
golang.org/x/tools/gopls/internal/golang/completion.(*completer).item(, {, _}, {{0x1e6b178, 0xc00012a640}, 0x4012333333333333, {0xc00b8bc7d0, 0xe}, {0x0, 0x0}, ...})
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/golang/completion/format.go:65 +0x373 fp=0xc006efcd30 sp=0xc006efc8f8 pc=0x1891bd3
golang.org/x/tools/gopls/internal/golang/completion.(*completer).addCandidate(0xc00030a008, {0x1e5d028, 0xc006efed70}, 0xc006efd058)
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/golang/completion/deep_completion.go:294 +0x3d3 fp=0xc006efcfe0 sp=0xc006efcd30 pc=0x188f633
golang.org/x/tools/gopls/internal/golang/completion.(*completer).deepSearch(0xc00030a008, {0x1e5d028, 0xc006efed70}, 0x0?, 0xc00b8bc680?)
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/golang/completion/deep_completion.go:180 +0x4df fp=0xc006efd220 sp=0xc006efcfe0 pc=0x188e6ff
golang.org/x/tools/gopls/internal/golang/completion.Completion({0x1e5cff0?, 0xc0072c6c30?}, 0xc0072590e0, {0x1e5fdc0, 0xc00721fda0}, {0x0?, 0x0?}, {0x1, {0x0, 0x0}})
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/golang/completion/completion.go:659 +0x12fb fp=0xc006efd6f8 sp=0xc006efd220 pc=0x187cf5b
golang.org/x/tools/gopls/internal/server.(*server).Completion(0xc0000fa900, {0x1e5cff0, 0xc0072c6c30}, 0xc006efeb40)
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/server/completion.go:43 +0x358 fp=0xc006efd900 sp=0xc006efd6f8 pc=0x18c9518
golang.org/x/tools/gopls/internal/protocol.serverDispatch({0x1e5cff0, 0xc0070e3b90}, {0x1e7c780, 0xc0000fa900}, 0xc0072c6b40, {0x1e5d1e8, 0xc006bafac0})
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/protocol/tsserver.go:363 +0x2547 fp=0xc006efdbe0 sp=0xc006efd900 pc=0x126af27
golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.ServerHandler.func3({0x1e5cff0, 0xc0070e3b90}, 0xc0072c6b40, {0x1e5d1e8, 0xc006bafac0})
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/protocol/protocol.go:160 +0x85 fp=0xc006efdc40 sp=0xc006efdbe0 pc=0x18eba65
golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.handshaker.func4({0x1e5cff0, 0xc0070e3b90}, 0xc0072c6b40, {0x1e5d1e8, 0xc006bafac0})
D:/file/gofile/pkg/mod/golang.org/x/tools/gopls@v0.17.1/internal/lsprpc/lsprpc.go:509 +0x90b fp=0xc006efdef8 sp=0xc006efdc40 pc=0x18eb7cb
golang.org/x/tools/gopls/internal/protocol.Handlers.MustReplyHandler.func1({0x1e5cff0, 0xc0070e3b90}, 0xc0070bb4b8, {0x1e5d1e8, 0xc006bafac0})
D:/file/gofile/pkg/mod/golang.org/x/tools@v0.27.1-0.20241219162658-575221bfbda3/internal/jsonrpc2/handler.go:35 +0xc6 fp=0xc006efdf50 sp=0xc006efdef8 pc=0x125a466
golang.org/x/tools/gopls/internal/protocol.Handlers.AsyncHandler.func2.2()
D:/file/gofile/pkg/mod/golang.org/x/tools@v0.27.1-0.20241219162658-575221bfbda3/internal/jsonrpc2/handler.go:104 +0x96 fp=0xc006efdfe0 sp=0xc006efdf50 pc=0x125a296
runtime.goexit({})
C:/Users/26454/.go/gotip/src/runtime/asm_amd64.s:1700 +0x1 fp=0xc006efdfe8 sp=0xc006efdfe0 pc=0xed8681
created by golang.org/x/tools/gopls/internal/protocol.Handlers.AsyncHandler.func2 in goroutine 120
D:/file/gofile/pkg/mod/golang.org/x/tools@v0.27.1-0.20241219162658-575221bfbda3/internal/jsonrpc2/handler.go:101 +0x22f