[5.0] Don't fix access of an 'open' decl in a 'public' extension #22216
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Don't fix access of an 'open' override in a 'public' extension rdar://problem/47557376&28493971 (cherry picked from commit de93ba0)
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@swift-ci Please test |
AnnaZaks
approved these changes
Jan 29, 2019
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Explanation: This is reasonable to diagnose with a warning, but dropping the 'open' down to 'public' isn't the right fix, because it might have been an override or satisfying a protocol requirement. In that case, the declaration would have to get moved to another extension instead, or the extension has to not set a default access level.
This turned out to be a source compat issue because the same logic that emits the fix-it also updates the access of the member, which then resulted in "must be as accessible as the declaration it overrides" in the same build. It's not immediately clear what caused this to work in 4.2 but result in an error in 5.0; probably something's just being validated in a different order than it was before. The change makes sense either way.
Stepping back, it's weird that a warning would change how the compiler saw the code, and while we could check for 'override' explicitly, we can't know if the member might be satisfying a protocol requirement. Better to just not guess at the right answer here.
Scope: Affects members of extensions with a greater level of access than the extension's default.
Issue: rdar://problem/47557376&28493971
Risk: Low. We're choosing not to emit a fix-it (basically no risk), making sure we emit another diagnostic (for something that would never work), and not changing the AST from what the user wrote (a behavior change, but one that matches different source the user could have written).
Testing: Updated/added compiler regression tests, passed source compatibility suite.
Reviewed by: @brentdax, @dingobye