go/types: mark completely imported packages as such

R=adonovan
CC=golang-dev
https://golang.org/cl/7103055

src/pkg/go/types/check.go

@@ -418,19 +418,7 @@ func check(ctxt *Context, fset *token.FileSet, files []*ast.File) (pkg *Package,
 	// resolve identifiers
 	imp := ctxt.Import
 	if imp == nil {
-		// wrap GcImport to import packages only once by default.
-		// TODO(gri) move this into resolve
-		imported := make(map[string]bool)
-		imp = func(imports map[string]*Package, path string) (*Package, error) {
-			if imported[path] && imports[path] != nil {
-				return imports[path], nil
-			}
-			pkg, err := GcImport(imports, path)
-			if err == nil {
-				imported[path] = true
-			}
-			return pkg, err
-		}
+		imp = GcImport
 	}
 	pkg, methods := check.resolve(imp)
 	check.pkg = pkg

src/pkg/go/types/gcimporter.go

@@ -77,10 +77,13 @@ func FindPkg(path, srcDir string) (filename, id string) {
 // adds the corresponding package object to the imports map indexed by id,
 // and returns the object.
 //
-// The imports map must contains all packages already imported, and no map
-// entry with id as the key must be present. The data reader position must
-// be the beginning of the export data section. The filename is only used
-// in error messages.
+// The imports map must contains all packages already imported. The data
+// reader position must be the beginning of the export data section. The
+// filename is only used in error messages.
+//
+// If imports[id] contains the completely imported package, that package
+// can be used directly, and there is no need to call this function (but
+// there is also no harm but for extra time used).
 //
 func GcImportData(imports map[string]*Package, filename, id string, data *bufio.Reader) (pkg *Package, err error) {
 	// support for gcParser error handling
@@ -118,12 +121,10 @@ func GcImport(imports map[string]*Package, path string) (pkg *Package, err error
 		return
 	}
 
-	// Note: imports[id] may already contain a partially imported package.
-	//       We must continue doing the full import here since we don't
-	//       know if something is missing.
-	// TODO: There's no need to re-import a package if we know that we
-	//       have done a full import before. At the moment we cannot
-	//       tell from the available information in this function alone.
+	// no need to re-import if the package was imported completely before
+	if pkg = imports[id]; pkg != nil && pkg.Complete {
+		return
+	}
 
 	// open file
 	f, err := os.Open(filename)
@@ -900,5 +901,8 @@ func (p *gcParser) parseExport() *Package {
 		p.errorf("expected no scanner errors, got %d", n)
 	}
 
+	// package was imported completely and without errors
+	pkg.Complete = true
+
 	return pkg
 }

src/pkg/go/types/objects.go

@@ -23,10 +23,11 @@ type Object interface {
 
 // A Package represents the contents (objects) of a Go package.
 type Package struct {
-	Name    string
-	Path    string              // import path, "" for current (non-imported) package
-	Scope   *Scope              // package-level scope
-	Imports map[string]*Package // map of import paths to imported packages
+	Name     string
+	Path     string              // import path, "" for current (non-imported) package
+	Scope    *Scope              // package-level scope
+	Imports  map[string]*Package // map of import paths to imported packages
+	Complete bool                // if set, this package was imported completely
 
 	spec *ast.ImportSpec
 }