x/tools/gopls: nil panic in types.Package.Path while writing export data (internal/gcimporter)

[adonovan]

#!stacks
"go/types.(*Package).Path:=34" && "gcimporter.(*exportWriter).exportPath"

Issue created by stacks.

If you walk all the way up the stack, you get to this line, which writes the value of a constant. It passes pkg=nil (meaning "the current package"), yet somehow the nil pkg is plumbed all the way down to exportPath, which assumes it is non-nil.

func (w *exportWriter) value(typ types.Type, v constant.Value) {
	w.typ(typ, nil)

This stack 0BaS9w was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• golang.org/x/tools/internal/gcimporter.iexportCommon.func1:+7
• runtime.gopanic:+50
• runtime.panicmem:=262
• runtime.sigpanic:+19
• go/types.(*Package).Path:=34
• golang.org/x/tools/internal/gcimporter.(*exportWriter).exportPath:=688
• golang.org/x/tools/internal/gcimporter.(*exportWriter).pkg:+4
• golang.org/x/tools/internal/gcimporter.(*exportWriter).doTyp:+119
• golang.org/x/tools/internal/gcimporter.(*iexporter).typOff:+4
• golang.org/x/tools/internal/gcimporter.(*exportWriter).typ:+1
• golang.org/x/tools/internal/gcimporter.(*exportWriter).typeList:+3
• golang.org/x/tools/internal/gcimporter.(*exportWriter).doTyp:+27
• golang.org/x/tools/internal/gcimporter.(*iexporter).typOff:+4
• golang.org/x/tools/internal/gcimporter.(*exportWriter).typ:+1
• golang.org/x/tools/internal/gcimporter.(*exportWriter).value:+1
• golang.org/x/tools/internal/gcimporter.(*iexporter).doDecl:+51
• golang.org/x/tools/internal/gcimporter.iexportCommon:+55
• golang.org/x/tools/internal/gcimporter.IExportShallow:+8

golang.org/x/tools/gopls@v0.18.1 go1.23.8 darwin/arm64 other,vscode (25)

[gabyhelp]

Related Issues

• x/tools/gopls: crash exporting constant with partially defined type #60891 (closed)
• x/tools/gopls: SEGV in gcimporter.iexportCommon (bad SP) #72135
• x/tools/gopls: nil deref in Exporter.ProcessEvent #71928
• x/tools/gopls: Package.Path called on nil Package in AddTestForFunc #73687 (closed)
• x/tools/gopls: nil *types.Package panic in testKind #73096 (closed)
• runtime: SEGV in mapaccess2 (go1.23.2 darwin/amd64) #71123
• x/tools/gopls: "failed to find object for objectPath" bug in gcimporter #73588
• x/tools/gopls: nil deref panic in go.test code action #72907 (closed)
• x/tools/gopls: Rename: type assertion panics in renameImports #71656 (closed)
• x/tools/gopls: "package name is %q, want %q" bug in typeCheckBatch.importPackage #64235

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