x/tools/gopls: ast.StructType has type other than types.StructType (no type?)

[adonovan]

This stack iWGuoA was reported by telemetry:

xtools/gopls/internal/golang/hover.go:

	if v, ok := obj.(*types.Var); ok && v.IsField() {
		// Find enclosing struct type.
		var tStruct *types.Struct
		for _, n := range path {
			if n, ok := n.(*ast.StructType); ok {
				tStruct = pkg.TypesInfo().TypeOf(n).(*types.Struct) // type assertion failed
				break
			}
		}

I think this must mean TypeOf returned nil (some other type for ast.StructType seems unlikely). If so, the underlying bug is in the type checker.

crash/crash
runtime.gopanic:+69
runtime.panicdottypeE:=275
runtime.panicdottypeI:+5
golang.org/x/tools/gopls/internal/golang.computeSizeOffsetInfo:+40
golang.org/x/tools/gopls/internal/golang.hover:+186
golang.org/x/tools/gopls/internal/golang.Hover:+4
golang.org/x/tools/gopls/internal/server.(*server).Hover:+30
golang.org/x/tools/gopls/internal/protocol.serverDispatch:+335
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@v0.16.1 go1.23.0 darwin/arm64 vscode (1)

Issue created by golang.org/x/tools/gopls/internal/telemetry/cmd/stacks.

[gabyhelp]

Related Issues and Documentation

• x/tools/gopls: "type name %q without type spec" bug in Hover(reported by telemetry) #66314 (closed)
• x/tools/gopls: "type name %q without type spec" bug in Hover (via telemetry) #64241
• x/tools/gopls: Hover bug reported by telemetry [PE4R3g] #64244 (closed)
• x/tools/gopls: Definition bug reported by telemetry [kkvfqw] #64242 (closed)
• x/tools/gopls: bug reported by telemetry [qoVPwQ] #64243 (closed)
• x/tools/gopls: Hover bug reported by telemetry #66857 (closed)
• x/tools/gopls: Hover bug reported by telemetry #64237 (closed)
• x/tools/gopls: toGobDiagnostic bug reported by telemetry #65695 (closed)
• x/tools/gopls: Definition bug "no object for %s" (reported by telemetry) #64604 (closed)
• x/tools/gopls: crash in typeparams.Free.Has (empty type set) #68213 (closed)

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

[adonovan]

@timothy-king @griesemer

[adonovan]

@findleyr points out that this is likely a consequence of #69092, which doesn't set the types for the inside of a CompositeLit. If the StructType happens to be within it, then we get the above crash.

See #68918 (comment), which anticipates the likely need for adding a number of workarounds for crashes from the same underlying cause as they show up.

[findleyr]

I'm not sure that's the only way to reach this crash, but it does seem like we can the known bug in CompositeLit type checking to write a test, and fix by making gopls more defensive.

[gopherbot]

Change https://go.dev/cl/627135 mentions this issue: gopls/internal/golang: avoid crash in hover on field of non-struct