x/tools/gopls: slice OOB panic in fixAST on array type

[adonovan]

#!stacks
"goPanicSliceAcap" && "parsego.fixArrayType:+18"

Issue created by stacks.

Looks like the indices that were sliced were not what was checked with safetoken:

func fixArrayType(bad *ast.BadExpr, parent ast.Node, tok *token.File, src []byte) bool {
...
	// Avoid doing tok.Offset(to) since that panics if badExpr ends at EOF.
	// It also panics if the position is not in the range of the file, and
	// badExprs may not necessarily have good positions, so check first.
	fromOffset, toOffset, err := safetoken.Offsets(tok, from, to-1)
	if err != nil {
		return false
	}
	exprBytes = append(exprBytes, src[fromOffset:toOffset+1]...) // <------ goPanicSliceAcap

This stack N2S9sg was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.goPanicSliceAcap:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixArrayType:+18
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST.func1:+13
• 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:+185
• go/ast.walkList[...]:=21
• go/ast.Walk:+192
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+201
• go/ast.walkList[...]:=21
• go/ast.Walk:+178
• go/ast.Walk:+229
• go/ast.walkList[...]:=21

golang.org/x/tools/gopls@v0.16.1 go1.23.0 darwin/arm64 other (1)

Dups: P6TRhg

[gabyhelp]

Related Issues

• x/tools/gopls: xrefs.Index panics after "can't fail" pgf.PosRange #70446 (closed)
• x/tools/gopls: illegal line number panic #37226 (closed)
• x/tools/gopls: "internal error converting diagnostic" (bug reported by telemetry) #64547 (closed)
• x/tools/gopls: slice bounds out of range - internal/lsp/cache.fixArrayType #58943 (closed)
• x/tools/gopls: "slice bounds out of range" crash in ExtractToNewFile #70553
• x/tools/gopls: Highlight: nil deref panic on CompositeLiteral with no type #68918 (closed)
• x/tools/gopls: automated issue report (crash) #48763 (closed)
• x/tools/gopls: crash due to panic: invalid Pos value (go/token/position.go:281) #47231 (closed)
• x/tools/gopls: OOB index panic after parsing go list error from file with //line directives #67360 (closed)
• x/tools/gopls: automated issue report (crash) #40819 (closed)

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

[adonovan]

This stack P6TRhg was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.goPanicSliceAcap:+2
• golang.org/x/tools/gopls/internal/cache/parsego.fixArrayType:+18
• golang.org/x/tools/gopls/internal/cache/parsego.fixAST.func1:+13
• 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@v0.17.0-pre.3 go1.23.3 darwin/arm64 sublimetext (2)