go/internal/gcimporter: add a test case for issue 51219

Based on CL 387814, construct a reproducer for issue 51219 using
x/tools/go/internal/gcimporter.

Confirmed that this fails without the fix in CL 392475.

Additionally, this CL includes some minor cleanup:
 - no need to take two passes in testExportSrc, as
   IExportVersionGenerics and IExportVersionGo1_18 are the same
 - remove skips that are no longer needed.

Fixes golang/go#51219

Change-Id: Ia76fe9038aab7a2b9efc8429dc211b03adbb5560
Reviewed-on: https://go-review.googlesource.com/c/tools/+/392734
Trust: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

go/internal/gcimporter/iexport_go118_test.go

@@ -9,6 +9,7 @@ package gcimporter_test
 
 import (
 	"bytes"
+	"fmt"
 	"go/ast"
 	"go/importer"
 	"go/parser"
@@ -71,39 +72,27 @@ func testExportSrc(t *testing.T, src []byte) {
 		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
 	}
 
-	// Test at both stages of the 1.18 export data format change.
-	tests := []struct {
-		name    string
-		version int
-	}{
-		{"legacy generics", gcimporter.IExportVersionGenerics},
-		{"go1.18", gcimporter.IExportVersionGo1_18},
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "g.go", src, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conf := types.Config{
+		Importer: importer.Default(),
+	}
+	pkg, err := conf.Check("", fset, []*ast.File{f}, nil)
+	if err != nil {
+		t.Fatal(err)
 	}
 
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			fset := token.NewFileSet()
-			f, err := parser.ParseFile(fset, "g.go", src, 0)
-			if err != nil {
-				t.Fatal(err)
-			}
-			conf := types.Config{
-				Importer: importer.Default(),
-			}
-			pkg, err := conf.Check("", fset, []*ast.File{f}, nil)
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			// export
-			data, err := iexport(fset, test.version, pkg)
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			testPkgData(t, fset, test.version, pkg, data)
-		})
+	// export
+	version := gcimporter.IExportVersion
+	data, err := iexport(fset, version, pkg)
+	if err != nil {
+		t.Fatal(err)
 	}
+
+	testPkgData(t, fset, version, pkg, data)
 }
 
 func TestImportTypeparamTests(t *testing.T) {
@@ -118,21 +107,13 @@ func TestImportTypeparamTests(t *testing.T) {
 		t.Skip("unified export data format is currently unsupported")
 	}
 
-	skip := map[string]string{
-		"issue48424.go": "go/types support missing", // TODO: need to implement this if #48424 is accepted
-	}
-
 	for _, entry := range list {
 		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".go") {
 			// For now, only consider standalone go files.
 			continue
 		}
 
 		t.Run(entry.Name(), func(t *testing.T) {
-			if reason, ok := skip[entry.Name()]; ok {
-				t.Skip(reason)
-			}
-
 			filename := filepath.Join(rootDir, entry.Name())
 			src, err := os.ReadFile(filename)
 			if err != nil {
@@ -150,3 +131,124 @@ func TestImportTypeparamTests(t *testing.T) {
 		})
 	}
 }
+
+func TestRecursiveExport_Issue51219(t *testing.T) {
+	const srca = `
+package a
+
+type Interaction[DataT InteractionDataConstraint] struct {
+}
+
+type InteractionDataConstraint interface {
+	[]byte |
+		UserCommandInteractionData
+}
+
+type UserCommandInteractionData struct {
+	resolvedInteractionWithOptions
+}
+
+type resolvedInteractionWithOptions struct {
+	Resolved Resolved
+}
+
+type Resolved struct {
+	Users ResolvedData[User]
+}
+
+type ResolvedData[T ResolvedDataConstraint] map[uint64]T
+
+type ResolvedDataConstraint interface {
+	User | Message
+}
+
+type User struct{}
+
+type Message struct {
+	Interaction *Interaction[[]byte]
+}
+`
+
+	const srcb = `
+package b
+
+import (
+	"a"
+)
+
+// InteractionRequest is an incoming request Interaction
+type InteractionRequest[T a.InteractionDataConstraint] struct {
+	a.Interaction[T]
+}
+`
+
+	const srcp = `
+package p
+
+import (
+	"b"
+)
+
+// ResponseWriterMock mocks corde's ResponseWriter interface
+type ResponseWriterMock struct {
+	x b.InteractionRequest[[]byte]
+}
+`
+
+	importer := &testImporter{
+		src: map[string][]byte{
+			"a": []byte(srca),
+			"b": []byte(srcb),
+			"p": []byte(srcp),
+		},
+		pkgs: make(map[string]*types.Package),
+	}
+	_, err := importer.Import("p")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// testImporter is a helper to test chains of imports using export data.
+type testImporter struct {
+	src  map[string][]byte         // original source
+	pkgs map[string]*types.Package // memoized imported packages
+}
+
+func (t *testImporter) Import(path string) (*types.Package, error) {
+	if pkg, ok := t.pkgs[path]; ok {
+		return pkg, nil
+	}
+	src, ok := t.src[path]
+	if !ok {
+		return nil, fmt.Errorf("unknown path %v", path)
+	}
+
+	// Type-check, but don't return this package directly.
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, path+".go", src, 0)
+	if err != nil {
+		return nil, err
+	}
+	conf := types.Config{
+		Importer: t,
+	}
+	pkg, err := conf.Check(path, fset, []*ast.File{f}, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// Export and import to get the package imported from export data.
+	exportdata, err := iexport(fset, gcimporter.IExportVersion, pkg)
+	if err != nil {
+		return nil, err
+	}
+	imports := make(map[string]*types.Package)
+	fset2 := token.NewFileSet()
+	_, pkg2, err := gcimporter.IImportData(fset2, imports, exportdata, pkg.Path())
+	if err != nil {
+		return nil, err
+	}
+	t.pkgs[path] = pkg2
+	return pkg2, nil
+}