x/tools/gopls: Parse: crash in fixInitStmt

[adonovan]

#!stacks
"goPanicSliceAcap" && "fixInitStmt:+10"

Issue created by stacks.

This is not how to use safetoken:

	// Try to extract a statement from the BadExpr.
	start, end, err := safetoken.Offsets(tok, bad.Pos(), bad.End()-1)
	if err != nil {
		return false
	}
	stmtBytes := src[start : end+1]
	stmt, err := parseStmt(tok, bad.Pos(), stmtBytes)
	if err != nil {
		return false
	}

This stack LKUsng was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.goPanicSliceAcap:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixInitStmt:+10
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST.func1:+27
• golang.org/x/tools/gopls/internal/cache/parsego.walkASTWithParent.func1:+17
• go/ast.inspector.Visit:+1
• go/ast.Walk:+1
• go/ast.Walk:+224
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+239
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+299
• go/ast.walkList[...]:=21
• go/ast.Walk:+308
• go/ast.Inspect:=372
• golang.org/x/tools/gopls/internal/cache/parsego.walkASTWithParent:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST:+2
• golang.org/x/tools/gopls/internal/cache/parsego.Parse:+57

golang.org/x/tools/gopls@v0.18.0 go1.24.0 linux/amd64 vscode (2)

Dups: Dyo-dQ Cys7zA

[gopherbot]

Change https://go.dev/cl/653596 mentions this issue: gopls/internal/cache/parsego: fix OOB crash in fixInitStmt

[gabyhelp]

Related Issues

• x/tools/gopls: slice OOB panic in fixAST on array type #70745 (closed)
• x/tools/gopls: illegal line number panic #37226 (closed)
• x/tools/gopls: automated issue report (crash) #48763 (closed)
• x/tools/gopls: "internal error converting diagnostic" (bug reported by telemetry) #64547
• x/tools/gopls: xrefs.Index panics after "can't fail" pgf.PosRange #70446 (closed)
• x/tools/gopls: analysisinternal.ZeroValue crash on (presumably) unsafe.Pointer #70585 (closed)
• x/tools/gopls: sigpanic in persistent.(*mapNode).forEach #71115
• x/tools/gopls: panic in aeshashbody on behalf of mapaccess2_faststr: string memory corrupted #71367
• x/tools/gopls: panic in token.File.Name within PackageDocHTML (telemetry) #70149 (closed)
• x/tools/gopls: crash due to panic: invalid Pos value (go/token/position.go:281) #47231 (closed)

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

[gopherbot]

Change https://go.dev/cl/654336 mentions this issue: gopls/internal/cache: reproduce and fix crash on if cond overflow

[adonovan]

This stack Dyo-dQ was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.goPanicSliceAcap:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixInitStmt:+10
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST.func1:+27
• golang.org/x/tools/gopls/internal/cache/parsego.walkASTWithParent.func1:+17
• go/ast.inspector.Visit:+1
• go/ast.Walk:+1
• go/ast.Walk:+184
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+239
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+299
• go/ast.walkList[...]:=21
• go/ast.Walk:+308
• go/ast.Inspect:=372
• golang.org/x/tools/gopls/internal/cache/parsego.walkASTWithParent:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST:+2
• golang.org/x/tools/gopls/internal/cache/parsego.Parse:+57

golang.org/x/tools/gopls@v0.18.1 go1.24.0 darwin/arm64 vscode (4)

[adonovan]

This stack Cys7zA was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.goPanicSliceAcap:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixInitStmt:+10
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST.func1:+27
• golang.org/x/tools/gopls/internal/cache/parsego.walkASTWithParent.func1:+17
• go/ast.inspector.Visit:+1
• go/ast.Walk:+1
• go/ast.Walk:+224
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+299
• go/ast.walkList[...]:=21
• go/ast.Walk:+308
• go/ast.Inspect:=372
• golang.org/x/tools/gopls/internal/cache/parsego.walkASTWithParent:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST:+2
• golang.org/x/tools/gopls/internal/cache/parsego.Parse:+57
• golang.org/x/tools/gopls/internal/cache.(*parseCache).startParse.func1:+5
• golang.org/x/tools/internal/memoize.(*Promise).run.func2.1:+7

golang.org/x/tools/gopls@v0.18.1 go1.23.6 linux/amd64 vscode (2)