panic: runtime error due to missing Config.Sizes field in go/types.Config

[berkayburakk]

Summary

When running go-mutesting on a Go 1.21+ project, the tool panics with a nil pointer dereference due to an uninitialized Sizes field in go/types.Config.

Steps to Reproduce

1. Use Go 1.21 or 1.22
2. Install and run go-mutesting:

   go-mutesting ./...
   

panic: runtime error: invalid memory address or nil pointer dereference
go/types.(*StdSizes).Sizeof(0x0, ...)

Root Cause

In analyzer/analyzer.go, the types.Config struct is instantiated without setting the Sizes field:

Suggested Fix

Set the Sizes field using the appropriate call:

    Importer: importer,
    Sizes:    types.SizesFor("gc", build.Default.GOARCH),
}