every does not respect typeguard

[deser]

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:

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]

Control flow analysis isn't capable of doing backwards reasoning like would be required to identify this as not undefined

[OliverJAsh]

Fixed by #38200?