[dev.typeparams] cmd/compile/internal/types2: review of hilbert_test.go

[dev.typeparams] cmd/compile/internal/types2: review of hilbert_test.go

Primary differences:
1) syntax package is used instead of the go/* packages
2) parseSrc is a helper function that is used
   in place of parser.parseFile.
3) defaultImporter is a helper function providing
   access to an importer.

f=hilbert_test.go; diff $f ../../../../go/types/$f
5c5
< package types2_test
---
> package types_test
9d8
< 	"cmd/compile/internal/syntax"
11a11,14
> 	"go/ast"
> 	"go/importer"
> 	"go/parser"
> 	"go/token"
15c18
< 	. "cmd/compile/internal/types2"
---
> 	. "go/types"
32,33c35,36
< 	// TODO(gri) get rid of []bytes to string conversion below
< 	f, err := parseSrc("hilbert.go", string(src))
---
> 	fset := token.NewFileSet()
> 	f, err := parser.ParseFile(fset, "hilbert.go", src, 0)
40,41c43,44
< 	conf := Config{Importer: defaultImporter()}
< 	_, err = conf.Check(f.PkgName.Value, []*syntax.File{f}, nil)
---
> 	conf := Config{Importer: importer.Default()}
> 	_, err = conf.Check(f.Name.Name, fset, []*ast.File{f}, nil)

Change-Id: I65851725a3b6ac35b87177f90b788c469a54a986
Reviewed-on: https://go-review.googlesource.com/c/go/+/265679
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>