Fix primitive narrowing #8993
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Fix primitive narrowing #8993
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…ow-all-types"" This reverts commit fc3e040.
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| const enum Tag2 {} | ||
| declare function isNonBlank2(value: string) : value is (string & Tag2); |
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how is string & Tag2 structurally different from just string?
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Tag2 is a const enum (making the intersection nominal)
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I'll merge since Wesley's still waiting on commit privileges. |
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is this approved by @ahejlsberg, can i use it to build upon? |
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Yes, it turns out there's not much perf hit from this change. However, narrowing will not expand beyond this to methods. That's the performance cliff that @ahejlsberg was thinking of. |
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Fixes #7224.
Fixes #7441.
This is a re-submission of #7235 without the inversion of the type flag - meaning it simply adds all primitive types and intersection types to the narrowable types list.
@ahejlsberg @sandersn