{"action":"created","comment":{"url":"https://api.github.com/repos/dotnet/corefx/pulls/comments/34417780","id":34417780,"diff_hunk":"@@ -184,9 +184,12 @@ public override Iterator<TSource> Clone()\n \n             public override void Dispose()\n             {\n-                if (_enumerator is IDisposable) ((IDisposable)_enumerator).Dispose();\n-                _enumerator = null;\n-                base.Dispose();\n+                if (_enumerator != null)\n+                {\n+                    ((IDisposable)_enumerator).Dispose();\n+                    _enumerator = null;\n+                    base.Dispose();","path":"src/System.Linq/src/System/Linq/Enumerable.cs","position":null,"original_position":20,"commit_id":"94c7b0ca1c3e26bc8f450c726f79813a8e75defc","original_commit_id":"9b4c7855d1742182ffdedbf2591f3154d11ff6c3","user":{"login":"James-Ko","id":9159214,"avatar_url":"https://avatars.githubusercontent.com/u/9159214?v=3","gravatar_id":"","url":"https://api.github.com/users/James-Ko","html_url":"https://github.com/James-Ko","followers_url":"https://api.github.com/users/James-Ko/followers","following_url":"https://api.github.com/users/James-Ko/following{/other_user}","gists_url":"https://api.github.com/users/James-Ko/gists{/gist_id}","starred_url":"https://api.github.com/users/James-Ko/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/James-Ko/subscriptions","organizations_url":"https://api.github.com/users/James-Ko/orgs","repos_url":"https://api.github.com/users/James-Ko/repos","events_url":"https://api.github.com/users/James-Ko/events{/privacy}","received_events_url":"https://api.github.com/users/James-Ko/received_events","type":"User","site_admin":false},"body":"@stephentoub Fixed this in the latest commit; the cast is no longer there, and `base.Dispose()` has moved outside the block. I was keeping the cast before because I had seen it in other places throughout the BCL and there seem to be [a few](https://www.google.com/search?q=explicit+cast+to+idisposable) questions specifically about this, but I wasn't able to find any problems.","created_at":"2015-07-12T01:31:20Z","updated_at":"2015-07-12T01:31:20Z","html_url":"https://github.com/dotnet/corefx/pull/2318#discussion_r34417780","pull_request_url":"https://api.github.com/repos/dotnet/corefx/pulls/2318","_links":{"self":{"href":"https://api.github.com/repos/dotnet/corefx/pulls/comments/34417780"},"html":{"href":"https://github.com/dotnet/corefx/pull/2318#discussion_r34417780"},"pull_request":{"href":"https://api.github.com/repos/dotnet/corefx/pulls/2318"}}},"pull_request":{"url":"https://api.github.com/repos/dotnet/corefx/pulls/2318","id":39741714,"html_url":"https://github.com/dotnet/corefx/pull/2318","diff_url":"https://github.com/dotnet/corefx/pull/2318.diff","patch_url":"https://github.com/dotnet/corefx/pull/2318.patch","issue_url":"https://api.github.com/repos/dotnet/corefx/issues/2318","number":2318,"state":"open","locked":false,"title":"Many optimizations for System.Linq.Enumerable.","user":{"login":"James-Ko","id":9159214,"avatar_url":"https://avatars.githubusercontent.com/u/9159214?v=3","gravatar_id":"","url":"https://api.github.com/users/James-Ko","html_url":"https://github.com/James-Ko","followers_url":"https://api.github.com/users/James-Ko/followers","following_url":"https://api.github.com/users/James-Ko/following{/other_user}","gists_url":"https://api.github.com/users/James-Ko/gists{/gist_id}","starred_url":"https://api.github.com/users/James-Ko/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/James-Ko/subscriptions","organizations_url":"https://api.github.com/users/James-Ko/orgs","repos_url":"https://api.github.com/users/James-Ko/repos","events_url":"https://api.github.com/users/James-Ko/events{/privacy}","received_events_url":"https://api.github.com/users/James-Ko/received_events","type":"User","site_admin":false},"body":"Okay, so I was feeling slightly giddy and sat down for 5 hours to look at every method in `Enumerable.cs` to make every optimization I possibly could.\r\n\r\nHere's a summary of the changes:\r\n\r\n - `WhereEnumerableIterator<TSource>` and `WhereSelectEnumerableIterator<TSource>` no longer check if `IEnumerator<T>` implements `IDisposable` (it does)\r\n - `SkipWhileIterator`: remove redundant checks on `yielding`\r\n - `RangeIterator` has been optimized to avoid double adding\r\n - Avoid null checks on `int?` and `long?` and etc. before calling `GetValueOrDefault()` (you **can** call a method on `null` if it's a nullable)\r\n - Optimize every single `Min` and `Max` call:\r\n  - No more first-time loop checking.\r\n  - Nullables like `int?` and `long?` avoid many null-checks after \"scrolling forward\" to the first non-null element in the collection.\r\n  - `float?` and `double?` avoid another null-check with a trick using `GetValueOrDefault()`\r\n\r\nEnjoy!","created_at":"2015-07-11T07:05:41Z","updated_at":"2015-07-12T01:31:20Z","closed_at":null,"merged_at":null,"merge_commit_sha":"872d70d267500b77b42d858cfdf6191be98aae81","assignee":null,"milestone":null,"commits_url":"https://api.github.com/repos/dotnet/corefx/pulls/2318/commits","review_comments_url":"https://api.github.com/repos/dotnet/corefx/pulls/2318/comments","review_comment_url":"https://api.github.com/repos/dotnet/corefx/pulls/comments{/number}","comments_url":"https://api.github.com/repos/dotnet/corefx/issues/2318/comments","statuses_url":"https://api.github.com/repos/dotnet/corefx/statuses/94c7b0ca1c3e26bc8f450c726f79813a8e75defc","head":{"label":"James-Ko:patch-2","ref":"patch-2","sha":"94c7b0ca1c3e26bc8f450c726f79813a8e75defc","user":{"login":"James-Ko","id":9159214,"avatar_url":"https://avatars.githubusercontent.com/u/9159214?v=3","gravatar_id":"","url":"https://api.github.com/users/James-Ko","html_url":"https://github.com/James-Ko","followers_url":"https://api.github.com/users/James-Ko/followers","following_url":"https://api.github.com/users/James-Ko/following{/other_user}","gists_url":"https://api.github.com/users/James-Ko/gists{/gist_id}","starred_url":"https://api.github.com/users/James-Ko/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/James-Ko/subscriptions","organizations_url":"https://api.github.com/users/James-Ko/orgs","repos_url":"https://api.github.com/users/James-Ko/repos","events_url":"https://api.github.com/users/James-Ko/events{/privacy}","received_events_url":"https://api.github.com/users/James-Ko/received_events","type":"User","site_admin":false},"repo":{"id":37746383,"name":"corefx","full_name":"James-Ko/corefx","owner":{"login":"James-Ko","id":9159214,"avatar_url":"https://avatars.githubusercontent.com/u/9159214?v=3","gravatar_id":"","url":"https://api.github.com/users/James-Ko","html_url":"https://github.com/James-Ko","followers_url":"https://api.github.com/users/James-Ko/followers","following_url":"https://api.github.com/users/James-Ko/following{/other_user}","gists_url":"https://api.github.com/users/James-Ko/gists{/gist_id}","starred_url":"https://api.github.com/users/James-Ko/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/James-Ko/subscriptions","organizations_url":"https://api.github.com/users/James-Ko/orgs","repos_url":"https://api.github.com/users/James-Ko/repos","events_url":"https://api.github.com/users/James-Ko/events{/privacy}","received_events_url":"https://api.github.com/users/James-Ko/received_events","type":"User","site_admin":false},"private":false,"html_url":"https://github.com/James-Ko/corefx","description":"This repo contains the .NET Core foundational libraries, called CoreFX. 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