x/tools/gopls: "file scope is empty" bug in ApplyFix(extract function)

[adonovan]

#!stacks
"gopls/bug" && "collectFreeVars:+3" && "extractFunctionMethod"

Issue created by stacks.

This is a strange one: info.Scopes has no entry for a file, despite the file being non-nil with a valid FileStart (i.e. something produced by the parser), ultimately having come from NarrowestPackageForFile (in ApplyFix), i.e. having been type checked. This points to memory corruption again.

         file := pgf.Cursor.Node().(*ast.File)
        tok := fset.File(file.FileStart)                                        <--- must be non-nil 
        if tok == nil {
                return nil, nil, bug.Errorf("no file for position")             <-- file has valid FileStart
        }
        ...
        variables, err := collectFreeVars(info, file, start, end, path[0])



func collectFreeVars(info *types.Info, file *ast.File, start, end token.Pos, node ast.Node) ([]*variable, error) {
        fileScope := info.Scopes[file]
        if fileScope == nil {
                return nil, bug.Errorf("file scope is empty")  <--------- reached
        }

This stack HG8yiA was reported by telemetry:

• gopls/bug
• golang.org/x/tools/gopls/internal/util/bug.report:+35,+0x412
• golang.org/x/tools/gopls/internal/util/bug.Errorf:+2,+0x34
• golang.org/x/tools/gopls/internal/golang.collectFreeVars:+3,+0x3d2
• golang.org/x/tools/gopls/internal/golang.extractFunctionMethod:+103,+0x42e
• golang.org/x/tools/gopls/internal/golang.extractFunction:+2,+0x4d
• golang.org/x/tools/gopls/internal/golang.ApplyFix.singleFile.func2:+1,+0x23
• golang.org/x/tools/gopls/internal/golang.ApplyFix:+43,+0x702
• golang.org/x/tools/gopls/internal/server.(*commandHandler).ApplyFix.func1:+1,+0x85
• golang.org/x/tools/gopls/internal/server.(*commandHandler).run.func2:+3,+0x86
• golang.org/x/tools/gopls/internal/server.(*commandHandler).run:+81,+0x582
• golang.org/x/tools/gopls/internal/server.(*commandHandler).ApplyFix:+2,+0x19c
• golang.org/x/tools/gopls/internal/protocol/command.Dispatch:+31,+0xac1
• golang.org/x/tools/gopls/internal/server.(*server).ResolveCodeAction:+21,+0x1b8
• golang.org/x/tools/gopls/internal/protocol.serverDispatch:+46,+0xcf9
• golang.org/x/tools/gopls/internal/lsprpc.(*StreamServer).ServeStream.ServerHandler.func4:+5,+0x84
• golang.org/x/tools/gopls/internal/lsprpc.(*StreamServer).ServeStream.handshaker.func5:+52,+0x908

golang.org/x/tools/gopls@v0.20.0 go1.24.7 linux/amd64 vscode (1)

[gabyhelp]

Related Issues

• x/tools/gopls: ApplyFix: createUndeclared calls ZeroExpr(types.Tuple), crashes #74814
• x/tools/gopls: Parse: crash in fixInitStmt #72026 (closed)
• x/tools/gopls: analysisinternal.ZeroValue crash on (presumably) unsafe.Pointer #70585 (closed)
• x/tools/gopls: "invalid selection" bug in ExtractToNewFile #71473 (closed)
• x/tools/gopls: crash in adjustRangeForCommentsAndWhiteSpace #55271 (closed)
• x/tools/gopls: analysis driver spuriously reports invalid suggested fixes due to AST repair #71659 (closed)
• x/tools/gopls: Inline: panic in falcon analysis (unexpected core type) #74393 (closed)
• x/tools/gopls: ApplyFix: "no file for edit position" bug in suggestedFixToDocumentChange (via telemetry) #68818
• x/tools/gopls/internal/golang: inline variable: nil panic in inlineVariableOne #74347
• x/tools/gopls: ChangeSignature: "cannot inline: corrupted reference" bug #73779

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