Sema: Ban shadowing generic parameters from outer scopes [5.9] #65430
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Contributor
slavapestov
commented
Apr 26, 2023
slavapestov
commented
- Description: Emit a warning (in -swift-version 5) or an error (in -swift-version 6) if you re-declare a generic parameter with the same name in a nested scope. Code like that is usually indicative of programmer error, and does not round-trip through module interface files since there is no source syntax to refer to an outer generic parameter. We've had to debug some weird issues which turned out to be caused by this.
- Risk: The new check might introduce a compiler crash or something, but it's a slightly generalized form of the old check (which prohibited re-declaring a generic parameter with the same name within a single scope only).
- Radar: rdar://problem/108385980
- Reviewed by: @xedin
Code like that is usually indicative of programmer error, and does not round-trip through module interface files since there is no source syntax to refer to an outer generic parameter. For source compatibility this is a warning, but becomes an error with -swift-version 6. Fixes rdar://problem/108385980 and swiftlang#62767.
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@swift-ci Please test |
hborla
approved these changes
Apr 26, 2023
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