Panic: nil pointer dereference in go/types with Go 1.26

[bsene]

Description

go-mutesting panics with a nil pointer dereference when running against a project using Go 1.26.1.

Steps to Reproduce

1. Install Go 1.26.1
2. Run go-mutesting on any Go source file

go-mutesting myfile.go

Error

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x1010d3a18]

goroutine 4 [running]:
go/types.(*Checker).handleBailout(...)
go/types.(*StdSizes).Sizeof(0x0, ...)
...
golang.org/x/tools/go/packages.(*loader).loadPackage(...)
	golang.org/x/tools@v0.0.0-20191018212557-ed542cd5b28a/go/packages/packages.go:835

Root Cause

The bundled golang.org/x/tools@v0.0.0-20191018212557 dependency predates Go 1.26 and is incompatible with its type system changes, causing the nil pointer in go/types.(*StdSizes).Sizeof.

Environment

• Go version: go1.26.1 darwin/arm64
• OS: macOS (Darwin 25.4.0, arm64)
• go-mutesting: installed via go install github.com/avito-tech/go-mutesting/...@latest