go.tools/go/types: support for fake imports of package "C"

Also:
- cleaner method set printing
- disable debug mode internally (50% faster)

R=adonovan, bradfitz
CC=golang-dev
https://golang.org/cl/12578043

go/types/api.go

@@ -29,16 +29,15 @@ import (
 	"code.google.com/p/go.tools/go/exact"
 )
 
-// Check type-checks a package and returns the resulting package object,
-// or a nil package and the first error. The package is specified by a
-// list of *ast.Files and corresponding file set, and the import path
-// the package is identified with. The clean path must not be empty or
-// dot (".").
+// Check type-checks a package and returns the resulting complete package
+// object, or a nil package and the first error. The package is specified
+// by a list of *ast.Files and corresponding file set, and the import path
+// the package is identified with. The clean path must not be empty or dot (".").
 //
 // For more control over type-checking and results, use Config.Check.
 func Check(path string, fset *token.FileSet, files []*ast.File) (*Package, error) {
 	var conf Config
-	pkg, err := conf.check(path, fset, files, nil)
+	pkg, err := conf.Check(path, fset, files, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -52,6 +51,12 @@ type Config struct {
 	// type-checked.
 	IgnoreFuncBodies bool
 
+	// If FakeImportC is set, `import "C"` (for packages requiring Cgo)
+	// and expressions with qualified identifiers referrring to package
+	// C are silently ignored.
+	// Caution: Effects may be unpredictable - do not use casually!
+	FakeImportC bool
+
 	// If Error != nil, it is called with each error found
 	// during type checking. The error strings of errors with
 	// detailed position information are formatted as follows:
@@ -125,12 +130,20 @@ type Info struct {
 	Selections map[*ast.SelectorExpr]*Selection
 }
 
-// Check type-checks a package and returns the resulting package object, the first
-// error if any, and if info != nil, additional type information. The package is
-// specified by a list of *ast.Files and corresponding file set, and the import
-// path the package is identified with. The clean path must not be empty or dot (".").
+// Check type-checks a package and returns the resulting package object,
+// the first error if any, and if info != nil, additional type information.
+// The package is marked as complete if no errors occurred, otherwise it is
+// incomplete.
+//
+// The package is specified by a list of *ast.Files and corresponding file
+// set, and the import path the package is identified with. The clean path
+// must not be empty or dot (".").
 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
-	return conf.check(path, fset, files, info)
+	pkg, err := conf.check(path, fset, files, info)
+	if err == nil {
+		pkg.complete = true
+	}
+	return pkg, err
 }
 
 // IsAssignableTo reports whether a value of type V

go/types/call.go

@@ -173,12 +173,12 @@ func (check *checker) selector(x *operand, e *ast.SelectorExpr) {
 			check.recordObject(ident, pkg)
 			exp := pkg.scope.Lookup(sel)
 			if exp == nil {
-				check.errorf(e.Pos(), "%s not declared by package %s", sel, ident)
+				if !pkg.fake {
+					check.errorf(e.Pos(), "%s not declared by package %s", sel, ident)
+				}
 				goto Error
-			} else if !exp.IsExported() {
-				// gcimported package scopes contain non-exported
-				// objects such as types used in partially exported
-				// objects - do not accept them
+			}
+			if !exp.IsExported() {
 				check.errorf(e.Pos(), "%s not exported by package %s", sel, ident)
 				goto Error
 			}

go/types/check.go

@@ -17,7 +17,7 @@ import (
 
 // debugging/development support
 const (
-	debug = true  // leave on during development
+	debug = false // leave on during development
 	trace = false // turn on for detailed type resolution traces
 )
 

go/types/gcimporter.go

@@ -370,7 +370,7 @@ func (p *gcParser) getPkg(id, name string) *Package {
 	}
 	pkg := p.imports[id]
 	if pkg == nil && name != "" {
-		pkg = NewPackage(token.NoPos, id, name, NewScope(nil), nil, false)
+		pkg = NewPackage(token.NoPos, id, name, NewScope(nil), nil)
 		p.imports[id] = pkg
 	}
 	return pkg
@@ -985,7 +985,7 @@ func (p *gcParser) parseExport() *Package {
 	}
 
 	// package was imported completely and without errors
-	pkg.complete = true
+	pkg.MarkComplete()
 
 	return pkg
 }

go/types/methodset.go

@@ -28,8 +28,7 @@ func (s *MethodSet) String() string {
 	var buf bytes.Buffer
 	fmt.Fprintln(&buf, "MethodSet {")
 	for _, f := range s.list {
-		m := f.obj.(*Func)
-		fmt.Fprintf(&buf, "\t%s -> %s\n", m.Id(), m)
+		fmt.Fprintln(&buf, f)
 	}
 	fmt.Fprintln(&buf, "}")
 	return buf.String()

go/types/objects.go

@@ -122,16 +122,24 @@ func (obj *object) sameId(pkg *Package, name string) bool {
 }
 
 // A Package represents the contents (objects) of a Go package.
+//
+// A package is complete if all its package scope objects are present.
+// Incomplete packages may arise via imports where the exported data
+// contains only partial information about transitively imported and
+// re-exported packages; or as a result of type-checking a package
+// that contains errors.
+//
 type Package struct {
 	object
 	path     string              // import path, "" for current (non-imported) package
 	scope    *Scope              // imported objects
 	imports  map[string]*Package // map of import paths to imported packages
-	complete bool                // if set, this package was imported completely
+	complete bool                // if set, this package is complete
+	fake     bool                // if set, this package is fake (internal use only)
 }
 
-func NewPackage(pos token.Pos, path, name string, scope *Scope, imports map[string]*Package, complete bool) *Package {
-	obj := &Package{object{nil, pos, nil, name, Typ[Invalid]}, path, scope, imports, complete}
+func NewPackage(pos token.Pos, path, name string, scope *Scope, imports map[string]*Package) *Package {
+	obj := &Package{object{nil, pos, nil, name, Typ[Invalid]}, path, scope, imports, false, false}
 	obj.pkg = obj
 	return obj
 }
@@ -142,6 +150,9 @@ func (obj *Package) Scope() *Scope                { return obj.scope }
 func (obj *Package) Imports() map[string]*Package { return obj.imports }
 func (obj *Package) Complete() bool               { return obj.complete }
 
+// MarkComplete marks a package as complete.
+func (obj *Package) MarkComplete() { obj.complete = true }
+
 // A Const represents a declared constant.
 type Const struct {
 	object

go/types/resolver.go

@@ -165,14 +165,22 @@ func (check *checker) resolveFiles(files []*ast.File) {
 				for iota, spec := range d.Specs {
 					switch s := spec.(type) {
 					case *ast.ImportSpec:
+						var imp *Package
 						path, _ := strconv.Unquote(s.Path.Value)
-						imp, err := importer(pkg.imports, path)
-						if imp == nil && err == nil {
-							err = errors.New("Config.Import returned nil")
-						}
-						if err != nil {
-							check.errorf(s.Path.Pos(), "could not import %s (%s)", path, err)
-							continue
+						if path == "C" && check.conf.FakeImportC {
+							// TODO(gri) shouldn't create a new one each time
+							imp = NewPackage(token.NoPos, "C", "C", NewScope(nil), nil)
+							imp.fake = true
+						} else {
+							var err error
+							imp, err = importer(pkg.imports, path)
+							if imp == nil && err == nil {
+								err = errors.New("Config.Import returned nil but no error")
+							}
+							if err != nil {
+								check.errorf(s.Path.Pos(), "could not import %s (%s)", path, err)
+								continue
+							}
 						}
 
 						// local name overrides imported package name
@@ -185,7 +193,9 @@ func (check *checker) resolveFiles(files []*ast.File) {
 							}
 						}
 
-						imp2 := NewPackage(s.Pos(), path, name, imp.scope, nil, imp.complete)
+						imp2 := NewPackage(s.Pos(), path, name, imp.scope, nil)
+						imp2.complete = imp.complete
+						imp2.fake = imp.fake
 						if s.Name != nil {
 							check.recordObject(s.Name, imp2)
 						} else {

go/types/universe.go

@@ -87,7 +87,8 @@ var predeclaredFunctions = [...]*Builtin{
 
 func init() {
 	Universe = NewScope(nil)
-	Unsafe = NewPackage(token.NoPos, "unsafe", "unsafe", NewScope(Universe), nil, true)
+	Unsafe = NewPackage(token.NoPos, "unsafe", "unsafe", NewScope(Universe), nil)
+	Unsafe.complete = true
 
 	// predeclared types
 	for _, t := range Typ {

ssa/interp/reflect.go

@@ -24,7 +24,7 @@ type opaqueType struct {
 func (t *opaqueType) String() string { return t.name }
 
 // A bogus "reflect" type-checker package.  Shared across interpreters.
-var reflectTypesPackage = types.NewPackage(token.NoPos, "reflect", "reflect", nil, nil, true)
+var reflectTypesPackage = types.NewPackage(token.NoPos, "reflect", "reflect", nil, nil)
 
 // rtype is the concrete type the interpreter uses to implement the
 // reflect.Type interface.  Since its type is opaque to the target