Mapped types assignable to objects with 'any' string index signature

Author: ahejlsberg

src/compiler/checker.ts

@@ -7730,8 +7730,11 @@ namespace ts {
                         }
                     }
                 }
-                else if (relation !== identityRelation && isEmptyObjectType(resolveStructuredTypeMembers(<ObjectType>target))) {
-                    return Ternary.True;
+                else if (relation !== identityRelation) {
+                    const resolved = resolveStructuredTypeMembers(<ObjectType>target);
+                    if (isEmptyObjectType(resolved) || resolved.stringIndexInfo && resolved.stringIndexInfo.type.flags & TypeFlags.Any) {
+                        return Ternary.True;
+                    }
                 }
                 return Ternary.False;
             }