Error on syntactically impossible ===s to undefined #60433
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Error message is just a placeholder so I can run top800
typescript-bot
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Author: Team
For Uncommitted Bug
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@typescript-bot test it |
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@RyanCavanaugh Here are the results of running the user tests with tsc comparing Something interesting changed - please have a look. Details
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Hey @RyanCavanaugh, the results of running the DT tests are ready. Everything looks the same! |
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@RyanCavanaugh Here they are:
tscComparison Report - baseline..pr
System info unknown
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Developer Information: |
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@typescript-bot test top800 |
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@RyanCavanaugh Here are the results of running the top 400 repos with tsc comparing Something interesting changed - please have a look. Details
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Webpack had two instances of this (both of which had lint suppressions which were applied in a routine dep upgrade) if (!this._redirectTo !== undefined) {javascript-obfuscator had public static isNode (object: Object & { type?: string }): object is ESTree.Node {
return object && !object.type !== undefined;
}Everything else was some variant of There was also a false positive, #60439 |
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@RyanCavanaugh Here are the results of running the top 800 repos with tsc comparing Something interesting changed - please have a look. Details
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Both <Div dashed={typeof props.llm === undefined}> {typeof modelOptions.apiKey !== undefined && |
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update: gotcha, you're saying they're bugs in this PR, which i agree with :-) |
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aha, you are of course correct :-) |
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Does this PR seem likely to land? |
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I recommend just adding a lint rule; not sure if we'll try to land this or not. Last time we added checks like this there were a lot of people responding with "But I wrote that [non-working] code on purpose" so I have slightly less appetite for pushing on this right now. |
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Can you add this case? |
Thanks for the response. I sympathize. We get that kind of pushback from our users, also. On the other hand, it seems like all but one of the cases found in your testing are actually broken code. That one false positive was due to a different bug in TSC, which you've now fixed. Do you expect there to be cases where doing |
I wonder about the reason behind this because a type error is also a code "not working". Why we will check something as a type error and other cases don't? |
| @@ -110,6 +116,8 @@ comparisonOperatorWithIdenticalPrimitiveType.ts(43,24): error TS18050: The value | |||
| var rf5 = e != e; | |||
| var rf6 = null != null; | |||
| var rf7 = undefined != undefined; | |||
| ~~~~~~~~~ | |||
| !!! error TS2870: This binary expression is never nullish. Are you missing parentheses? | |||
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Why would we get this error here? Surely undefined is always nullish?
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i mean, when it's not ES5, or not the global scope, it could be any value, but presumably TS is ignoring that possibility :-)
Not a fully-correct implementation yet. Error message is just a placeholder so I can run top800 and see who's comparing what to
undefined