internal/gcimporter: remove test of unsupported "goroot" iimport

This CL eliminates the "goroot" flavor of
TestIExportDataTypeParameterizedAliases, leaving just
the "tools" flavor, and simplifies accordingly.

The logic of the goroot version assumed that importer.Default()
could read what gcexportdata.Write would write... except that
that comments correctly stated the assumption was false.

Updates golang/go#68898

Change-Id: Ifded4ed2cc2103de32ac869731176a49877d10e0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/620036
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: adonovan

internal/gcimporter/iexport_test.go

@@ -11,12 +11,10 @@ import (
 	"fmt"
 	"go/ast"
 	"go/constant"
-	"go/importer"
 	"go/parser"
 	"go/token"
 	"go/types"
 	"math/big"
-	"os"
 	"path/filepath"
 	"reflect"
 	"strings"
@@ -461,76 +459,38 @@ type Chained = C[Named] // B[Named, A[Named]] = B[Named, *Named] = []*Named
 		t.Fatal(err)
 	}
 
-	testcases := map[string]func(t *testing.T) *types.Package{
-		// Read the result of IExportData through x/tools/internal/gcimporter.IImportData.
-		"tools": func(t *testing.T) *types.Package {
-			// export
-			exportdata, err := iexport(fset1, gcimporter.IExportVersion, pkg1)
-			if err != nil {
-				t.Fatal(err)
-			}
+	// Read the result of IExportData through x/tools/internal/gcimporter.IImportData.
+	// export
+	exportdata, err := iexport(fset1, gcimporter.IExportVersion, pkg1)
+	if err != nil {
+		t.Fatal(err)
+	}
 
-			// import
-			imports := make(map[string]*types.Package)
-			fset2 := token.NewFileSet()
-			_, pkg2, err := gcimporter.IImportData(fset2, imports, exportdata, pkg1.Path())
-			if err != nil {
-				t.Fatalf("IImportData(%s): %v", pkg1.Path(), err)
-			}
-			return pkg2
-		},
-		// Read the result of IExportData through $GOROOT/src/internal/gcimporter.IImportData.
-		//
-		// This test fakes creating an old go object file in indexed format.
-		// This means that it can be loaded by go/importer or go/types.
-		// This step is not supported, but it does give test coverage for stdlib.
-		"goroot": func(t *testing.T) *types.Package {
-			testenv.NeedsGo1Point(t, 24) // requires >= 1.24 go/importer.
-
-			// Write indexed export data file contents.
-			//
-			// TODO(taking): Slightly unclear to what extent this step should be supported by go/importer.
-			var buf bytes.Buffer
-			buf.WriteString("go object \n$$B\n") // object file header
-			if err := gcexportdata.Write(&buf, fset1, pkg1); err != nil {
-				t.Fatal(err)
-			}
+	// import
+	imports := make(map[string]*types.Package)
+	fset2 := token.NewFileSet()
+	_, pkg2, err := gcimporter.IImportData(fset2, imports, exportdata, pkg1.Path())
+	if err != nil {
+		t.Fatalf("IImportData(%s): %v", pkg1.Path(), err)
+	}
 
-			// Write export data to temporary file
-			out := t.TempDir()
-			name := filepath.Join(out, "pkg.out")
-			if err := os.WriteFile(name+".a", buf.Bytes(), 0644); err != nil {
-				t.Fatal(err)
-			}
-			pkg2, err := importer.Default().Import(name)
-			if err != nil {
-				t.Fatal(err)
-			}
-			return pkg2
-		},
-	}
-
-	for name, importer := range testcases {
-		t.Run(name, func(t *testing.T) {
-			pkg := importer(t)
-			for name, want := range map[string]string{
-				"A":       "type pkg.A[T any] = *T",
-				"B":       "type pkg.B[R any, S *R] = []S",
-				"C":       "type pkg.C[U any] = pkg.B[U, pkg.A[U]]",
-				"Named":   "type pkg.Named int",
-				"Chained": "type pkg.Chained = pkg.C[pkg.Named]",
-			} {
-				obj := pkg.Scope().Lookup(name)
-				if obj == nil {
-					t.Errorf("failed to find %q in package %s", name, pkg)
-					continue
-				}
+	pkg := pkg2
+	for name, want := range map[string]string{
+		"A":       "type pkg.A[T any] = *T",
+		"B":       "type pkg.B[R any, S *R] = []S",
+		"C":       "type pkg.C[U any] = pkg.B[U, pkg.A[U]]",
+		"Named":   "type pkg.Named int",
+		"Chained": "type pkg.Chained = pkg.C[pkg.Named]",
+	} {
+		obj := pkg.Scope().Lookup(name)
+		if obj == nil {
+			t.Errorf("failed to find %q in package %s", name, pkg)
+			continue
+		}
 
-				got := strings.ReplaceAll(obj.String(), pkg.Path(), "pkg")
-				if got != want {
-					t.Errorf("(%q).String()=%q. wanted %q", name, got, want)
-				}
-			}
-		})
+		got := strings.ReplaceAll(obj.String(), pkg.Path(), "pkg")
+		if got != want {
+			t.Errorf("(%q).String()=%q. wanted %q", name, got, want)
+		}
 	}
 }