Behavior change in Go 1.24 causes internal/method/resolver_test.go's `TestNewResolveReferences` to fail

[ulucinar]

What happened?

If you bump the module's Go version to 1.24, the TestNewResolveReferences test in internal/method/resolver_test.go starts to fail as follows:

=== RUN   TestNewResolveReferences
    invoke.go:205: starting GOROOT= GOPATH=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modcache GO111MODULE=on GOPROXY=file:///var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modproxy PWD=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake go list -f "{{context.GOARCH}} {{context.Compiler}}" -- unsafe
    invoke.go:205: starting GOROOT= GOPATH=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modcache GO111MODULE=off GOPROXY=file:///var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modproxy PWD=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake go list -e -f {{context.ReleaseTags}} -- unsafe
    invoke.go:205: 5.566833ms for GOROOT= GOPATH=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modcache GO111MODULE=off GOPROXY=file:///var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modproxy PWD=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake go list -e -f {{context.ReleaseTags}} -- unsafe
    invoke.go:205: starting GOROOT= GOPATH=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modcache GO111MODULE=on GOPROXY=file:///var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modproxy PWD=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake go list -e -json=Name,ImportPath,Error,Dir,GoFiles,IgnoredGoFiles,IgnoredOtherFiles,CFiles,CgoFiles,CXXFiles,MFiles,HFiles,FFiles,SFiles,SwigFiles,SwigCXXFiles,SysoFiles,TestGoFiles,XTestGoFiles,CompiledGoFiles,DepOnly,Imports,ImportMap,TestImports,XTestImports,Module -compiled=true -test=true -export=false -deps=true -find=false -pgo=off -- /var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake/v1alpha1
    invoke.go:205: 6.188875ms for GOROOT= GOPATH=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modcache GO111MODULE=on GOPROXY=file:///var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modproxy PWD=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake go list -f "{{context.GOARCH}} {{context.Compiler}}" -- unsafe
    invoke.go:205: 12.165708ms for GOROOT= GOPATH=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modcache GO111MODULE=on GOPROXY=file:///var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/modproxy PWD=/var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake go list -e -json=Name,ImportPath,Error,Dir,GoFiles,IgnoredGoFiles,IgnoredOtherFiles,CFiles,CgoFiles,CXXFiles,MFiles,HFiles,FFiles,SFiles,SwigFiles,SwigCXXFiles,SysoFiles,TestGoFiles,XTestGoFiles,CompiledGoFiles,DepOnly,Imports,ImportMap,TestImports,XTestImports,Module -compiled=true -test=true -export=false -deps=true -find=false -pgo=off -- /var/folders/rv/899xlzw506q0tx02w9c57x9w0000gn/T/TestNewResolveReferences200602618/fake/v1alpha1
    resolver_test.go:343: NewResolveReferences(): -want, +got
          (
          	"""
          	... // 182 identical lines
          	
          		rsp, err = r.Resolve(ctx, reference.ResolutionRequest{
        - 			CurrentValue: reference.FromPtrValue(mg.Spec.ForProvider.CustomConfiguration),
        + 			CurrentValue: mg.Spec.ForProvider.CustomConfiguration,
          			Extract:      Configuration(),
          			Reference:    mg.Spec.ForProvider.CustomConfigurationRef,
          	... // 7 identical lines
          			return errors.Wrap(err, "mg.Spec.ForProvider.CustomConfiguration")
          		}
        - 		mg.Spec.ForProvider.CustomConfiguration = reference.ToPtrValue(rsp.ResolvedValue)
        + 		mg.Spec.ForProvider.CustomConfiguration = rsp.ResolvedValue
          		mg.Spec.ForProvider.CustomConfigurationRef = rsp.ResolvedReference
          	
          	... // 19 identical lines
          	"""
          )
--- FAIL: TestNewResolveReferences (0.15s)

My understanding is that there's a behavior change for Go's type checker:
If you give a try to the following program:

• With Go 1.23, it reports Field type: *types.Pointer.
• With Go 1.24, it reports: Field type: *types.Basic.
  This observation coupled with our reference processing logic here explains the broken test with Go 1.24. With Go 1.23, because the unknown type is represented with a *types.Pointer, the test, in its current shape, succeeds because the spec.forProvider.customConfiguration is actually a *Configuration, where Configuration is an unknown type. With Go 1.24, we cannot deduce it's actually a pointer.

There's an easy fix that I've tried for the failing test (with Go 1.24):

const (
	source = `
package v1alpha1

type Configuration struct {}

type ModelParameters struct {
...

, i.e., adding a definition for the Configuration type in the source file used in the test. However, I'm hesitant to propose that fix because I'm not sure if all referenced types are always in scope of the type checker when this tool runs. In other words, if all type definitions are not always in scope when generating references, we could be making the test pass but people will observe failures. Then we would need to actually fix how we process references.

How can we reproduce it?

Bump the module's Go version to 1.24 and run the tests in internal/method/resolver_test.go.

What environment did it happen in?

Crossplane version: