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Suppose you have an exhaustive switch statement which matches all the cases of
a Swift enum defined in a different module named `External`:
```
import External
var e: External.SomeEnum = //...
switch e {
case .a: break
}
```
If `External` is compiled with library evolution and `SomeEnum` is not frozen,
then the compiler will warn:
```
warning: switch covers known cases, but 'SomeEnum' may have additional unknown values
```
You add an `@unknown default` to the switch to resolve this warning. Now
suppose in another build configuration, `External` is built _without_ library
evolution. The compiler will complain about the unreachability of the default
case:
```
warning: Default will never be executed
```
These contradictory compiler diagnostics encourage the developer to change the
code in a way that will cause a diagnostic in the other configuration.
Developers should have the tools to address all warning diagnostics in a
reasonable fashion and this is a case where the compiler makes that especially
difficult. Given that writing `@unknown default` instead of `default` is a very
intentional action that would be the result of addressing the library evolution
configuration, it seems reasonable to suppress the `Default will never be
executed` diagnostic.
212 lines
5.4 KiB
Swift
212 lines
5.4 KiB
Swift
// RUN: %target-typecheck-verify-swift -swift-version 5 -enable-library-evolution -enable-nonfrozen-enum-exhaustivity-diagnostics -debugger-support
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// RUN: %target-typecheck-verify-swift -swift-version 5 -enable-library-evolution -enable-nonfrozen-enum-exhaustivity-diagnostics -playground
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public enum NonExhaustive {
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case a, b
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}
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public enum NonExhaustivePayload {
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case a(Int), b(Bool)
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}
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// Inlineable code is considered "outside" the module and must include a default
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// case.
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@inlinable
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public func testNonExhaustive(_ value: NonExhaustive, _ payload: NonExhaustivePayload, flag: Bool) {
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switch value { // expected-error {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b'}} {{none}} expected-note {{handle unknown values using "@unknown default"}} {{none}}
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case .a: break
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}
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switch value { // no-warning
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case .a: break
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case .b: break
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}
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switch value {
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case .a: break
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case .b: break
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default: break // no-warning
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}
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switch value {
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case .a: break
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case .b: break
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@unknown case _: break // no-warning
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}
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switch value { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b'}} {{none}}
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case .a: break
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@unknown case _: break
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}
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switch value { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.a'}} {{none}} expected-note {{add missing case: '.b'}} {{none}}
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@unknown case _: break
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}
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switch value {
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case _: break
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@unknown case _: break
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}
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// Test being part of other spaces.
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switch value as Optional { // no-warning
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case .a?: break
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case .b?: break
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case nil: break
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}
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switch value as Optional {
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case _?: break
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case nil: break
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} // no-warning
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switch (value, flag) { // no-warning
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case (.a, _): break
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case (.b, false): break
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case (_, true): break
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}
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switch (flag, value) { // no-warning
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case (_, .a): break
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case (false, .b): break
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case (true, _): break
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}
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// Test payloaded enums.
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switch payload { // expected-error {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(_)'}} {{none}} expected-note {{handle unknown values using "@unknown default"}} {{none}}
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case .a: break
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}
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switch payload { // no-warning
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case .a: break
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case .b: break
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}
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switch payload {
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case .a: break
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case .b: break
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default: break // no-warning
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}
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switch payload {
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case .a: break
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case .b: break
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@unknown case _: break // no-warning
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}
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switch payload { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(_)'}} {{none}}
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case .a: break
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@unknown case _: break
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}
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switch payload { // expected-error {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(true)'}} {{none}} expected-note {{handle unknown values using "@unknown default"}} {{none}}
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case .a: break
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case .b(false): break
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}
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switch payload { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(true)'}} {{none}}
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case .a: break
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case .b(false): break
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@unknown case _: break
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}
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}
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public func testNonExhaustiveWithinModule(_ value: NonExhaustive, _ payload: NonExhaustivePayload, flag: Bool) {
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switch value { // expected-error {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b'}}
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case .a: break
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}
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switch value { // no-warning
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case .a: break
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case .b: break
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}
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switch value {
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case .a: break
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case .b: break
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default: break // no-warning
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}
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switch value {
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case .a: break
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case .b: break
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@unknown case _: break // no-warning
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}
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switch value { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b'}} {{none}}
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case .a: break
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@unknown case _: break
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}
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switch value { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.a'}} {{none}} expected-note {{add missing case: '.b'}} {{none}}
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@unknown case _: break
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}
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switch value {
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case _: break
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@unknown case _: break
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}
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// Test being part of other spaces.
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switch value as Optional { // no-warning
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case .a?: break
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case .b?: break
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case nil: break
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}
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switch value as Optional {
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case _?: break
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case nil: break
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} // no-warning
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switch (value, flag) { // no-warning
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case (.a, _): break
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case (.b, false): break
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case (_, true): break
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}
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switch (flag, value) { // no-warning
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case (_, .a): break
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case (false, .b): break
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case (true, _): break
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}
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// Test payloaded enums.
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switch payload { // expected-error {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(_)'}} {{none}}
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case .a: break
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}
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switch payload { // no-warning
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case .a: break
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case .b: break
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}
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switch payload {
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case .a: break
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case .b: break
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default: break // no-warning
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}
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switch payload {
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case .a: break
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case .b: break
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@unknown case _: break // no-warning
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}
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switch payload { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(_)'}} {{none}}
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case .a: break
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@unknown case _: break
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}
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switch payload { // expected-error {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(true)'}} {{none}}
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case .a: break
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case .b(false): break
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}
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switch payload { // expected-warning {{switch must be exhaustive}} {{none}} expected-note {{add missing case: '.b(true)'}} {{none}}
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case .a: break
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case .b(false): break
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@unknown case _: break
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}
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}
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