Fix excess property check with empty target object type

Author: ahejlsberg

src/compiler/checker.ts

@@ -8328,8 +8328,11 @@ namespace ts {
                 !t.numberIndexInfo;
         }
 
-        function isEmptyObjectType(type: Type) {
-            return type.flags & TypeFlags.Object && isEmptyResolvedType(resolveStructuredTypeMembers(<ObjectType>type));
+        function isEmptyObjectType(type: Type): boolean {
+            return type.flags & TypeFlags.Object ? isEmptyResolvedType(resolveStructuredTypeMembers(<ObjectType>type)) :
+                type.flags & TypeFlags.Union ? forEach((<UnionType>type).types, isEmptyObjectType) :
+                type.flags & TypeFlags.Intersection ? !forEach((<UnionType>type).types, t => !isEmptyObjectType(t)) :
+                false;
         }
 
         function isEnumTypeRelatedTo(source: EnumType, target: EnumType, errorReporter?: ErrorReporter) {
@@ -8645,14 +8648,8 @@ namespace ts {
             function isKnownProperty(type: Type, name: string, isComparingJsxAttributes: boolean): boolean {
                 if (type.flags & TypeFlags.Object) {
                     const resolved = resolveStructuredTypeMembers(<ObjectType>type);
-                    if ((relation === assignableRelation || relation === comparableRelation) &&
-                        (type === globalObjectType || (!isComparingJsxAttributes && isEmptyObjectType(resolved)))) {
-                        return true;
-                    }
-                    else if (resolved.stringIndexInfo || (resolved.numberIndexInfo && isNumericLiteralName(name))) {
-                        return true;
-                    }
-                    else if (getPropertyOfType(type, name) || (isComparingJsxAttributes && !isUnhyphenatedJsxName(name))) {
+                    if (resolved.stringIndexInfo || resolved.numberIndexInfo && isNumericLiteralName(name) ||
+                        getPropertyOfType(type, name) || isComparingJsxAttributes && !isUnhyphenatedJsxName(name)) {
                         // For JSXAttributes, if the attribute has a hyphenated name, consider that the attribute to be known.
                         return true;
                     }
@@ -8670,6 +8667,10 @@ namespace ts {
             function hasExcessProperties(source: FreshObjectLiteralType, target: Type, reportErrors: boolean): boolean {
                 if (maybeTypeOfKind(target, TypeFlags.Object) && !(getObjectFlags(target) & ObjectFlags.ObjectLiteralPatternWithComputedProperties)) {
                     const isComparingJsxAttributes = !!(source.flags & TypeFlags.JsxAttributes);
+                    if ((relation === assignableRelation || relation === comparableRelation) &&
+                        (target === globalObjectType || (!isComparingJsxAttributes && isEmptyObjectType(target)))) {
+                        return false;
+                    }
                     for (const prop of getPropertiesOfObjectType(source)) {
                         if (!isKnownProperty(target, prop.name, isComparingJsxAttributes)) {
                             if (reportErrors) {