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every does not respect typeguard #36892

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deser opened this issue Feb 20, 2020 · 2 comments
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every does not respect typeguard #36892

deser opened this issue Feb 20, 2020 · 2 comments
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Design Limitation Constraints of the existing architecture prevent this from being fixed

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@deser
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deser commented Feb 20, 2020 •
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TypeScript Version: 3.7.5

Search Terms:
every, type guard

Code
https://www.typescriptlang.org/play/index.html#code/JYOwLgpgTgZghgYwgAgPrIN4FgBQz-LADOAcgK4C2ARtABQBucANmRAPwBcycIAngJRdGLFMWQhKNKLgC+AblwIA9iCJg0yALyZcBQqUnQuDZqy48BWgHzJhrWbkUq1hSBS2Z5T1eozIAHgA0yLzBAO7BABbIMh7AbtxEmAFcEtTQyAA+yGQgACYQMKAQeXIhqYZQWTn5hcWlyGEV6VXZuQVFICVlkc1S1e11XXkxCjjeLgAOSkTxwCoeANpBIeFRALoAdBD00Ly0qJvE5C38ugRsyLTYeHp3+EHn93qhT8-4EW-vkV8EMme3fBcQadbqOHDAGBXaazMDzED8ZJvJgQdT+fweGFzFSbfxjPTKVRKFGbJhKADmtHRAGpqfwxjJwcggA

See pic with issue below:
image

Expected behavior:
xx is number

Actual behavior:
xx is number | undefiend

Playground Link: https://www.typescriptlang.org/play/index.html#code/JYOwLgpgTgZghgYwgAgPrIN4FgBQz-LADOAcgK4C2ARtABQBucANmRAPwBcycIAngJRdGLFMWQhKNKLgC+AblwIA9iCJg0yALyZcBQqUnQuDZqy48BWgHzJhrWbkUq1hSBS2Z5T1eozIAHgA0yLzBAO7BABbIMh7AbtxEmAFcEtTQyAA+yGQgACYQMKAQeXIhqYZQWTn5hcWlyGEV6VXZuQVFICVlkc1S1e11XXkxCjjeLgAOSkTxwCoeANpBIeFRALoAdBD00Ly0qJvE5C38ugRsyLTYeHp3+EHn93qhT8-4EW-vkV8EMme3fBcQadbqOHDAGBXaazMDzED8ZJvJgQdT+fweGFzFSbfxjPTKVRKFGbJhKADmtHRAGpqfwxjJwcggA
@RyanCavanaugh RyanCavanaugh added the Design Limitation Constraints of the existing architecture prevent this from being fixed label Feb 20, 2020
@RyanCavanaugh
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Control flow analysis isn't capable of doing backwards reasoning like would be required to identify this as not undefined

@OliverJAsh
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Fixed by #38200?

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@OliverJAsh @deser @RyanCavanaugh