gob: clean up getTypeInfo (address a TODO)

also fix a caching bug.

R=rsc
CC=golang-dev
https://golang.org/cl/4261049

src/pkg/gob/type.go

@@ -638,41 +638,34 @@ var typeInfoMap = make(map[reflect.Type]*typeInfo) // protected by typeLock
 
 // typeLock must be held.
 func getTypeInfo(ut *userTypeInfo) (*typeInfo, os.Error) {
-
+	rt := ut.base
 	if ut.isGobEncoder {
-		// TODO: clean up this code - too much duplication.
-		info, ok := typeInfoMap[ut.user]
+		// We want the user type, not the base type.
+		rt = ut.user
+	}
+	info, ok := typeInfoMap[rt]
 	if ok {
 		return info, nil
 	}
-		// We want the user type, not the base type.
-		userType, err := getType(ut.user.Name(), ut, ut.user)
+	info = new(typeInfo)
+	gt, err := getBaseType(rt.Name(), rt)
 	if err != nil {
 		return nil, err
 	}
-		info = new(typeInfo)
-		gt, err := getBaseType(ut.base.Name(), ut.base)
+	info.id = gt.id()
+
+	if ut.isGobEncoder {
+		userType, err := getType(rt.Name(), ut, rt)
 		if err != nil {
 			return nil, err
 		}
-		info.id = gt.id()
 		info.wire = &wireType{GobEncoderT: userType.id().gobType().(*gobEncoderType)}
 		typeInfoMap[ut.user] = info
 		return info, nil
 	}
 
-	base := ut.base
-	info, ok := typeInfoMap[base]
-	if !ok {
-		info = new(typeInfo)
-		name := base.Name()
-		gt, err := getBaseType(name, base)
-		if err != nil {
-			return nil, err
-		}
-		info.id = gt.id()
 	t := info.id.gobType()
-		switch typ := base.(type) {
+	switch typ := rt.(type) {
 	case *reflect.ArrayType:
 		info.wire = &wireType{ArrayT: t.(*arrayType)}
 	case *reflect.MapType:
@@ -685,8 +678,7 @@ func getTypeInfo(ut *userTypeInfo) (*typeInfo, os.Error) {
 	case *reflect.StructType:
 		info.wire = &wireType{StructT: t.(*structType)}
 	}
-		typeInfoMap[base] = info
-	}
+	typeInfoMap[rt] = info
 	return info, nil
 }