Merge pull request #73997 from hamishknight/implicit-self-fix-6.0

[6.0] [Sema] Preserve compatibility for `weak self` with `@_implicitSelfCapture`

Author: hamishknight

lib/Sema/MiscDiagnostics.cpp

@@ -2415,6 +2415,13 @@ static void diagnoseImplicitSelfUseInClosure(const Expr *E,
         return true;
       }
 
+      // Implicit self was also permitted for weak self captures in closures
+      // passed to @_implicitSelfCapture parameters in Swift 5.7.
+      if (auto *CE = dyn_cast<ClosureExpr>(ACE)) {
+        if (CE->allowsImplicitSelfCapture())
+          return true;
+      }
+
       // Invalid captures like `[weak self = somethingElse]`
       // were permitted in Swift 5.8, so we must only warn.
       if (!isSimpleSelfCapture(weakSelfDecl)) {

test/expr/closure/closures.swift

@@ -756,6 +756,8 @@ public class TestImplicitCaptureOfExplicitCaptureOfSelfInEscapingClosure {
     }
 }
 
+func takesEscapingWithAllowedImplicitSelf(@_implicitSelfCapture _ fn: @escaping () -> Void) {}
+
 public class TestImplicitSelfForWeakSelfCapture {
   static let staticOptional: TestImplicitSelfForWeakSelfCapture? = nil
   func method() { }
@@ -817,7 +819,13 @@ public class TestImplicitSelfForWeakSelfCapture {
         method()
       }
     }
-    
+
+    takesEscapingWithAllowedImplicitSelf { [weak self] in
+      method() // expected-warning {{call to method 'method' in closure requires explicit use of 'self' to make capture semantics explicit}}
+      guard let self = self else { return }
+      method()
+    }
+
     doVoidStuff { [weak self] in
       let `self`: TestImplicitSelfForWeakSelfCapture? = self ?? TestImplicitSelfForWeakSelfCapture.staticOptional
       guard let self = self else { return }
@@ -1743,4 +1751,4 @@ struct TestAsyncLetInStruct {
       async let _ = bar()
     }
   }
-}
+}

test/expr/closure/closures_swift6.swift

@@ -81,6 +81,8 @@ class C_56501 {
   }
 }
 
+func takesEscapingWithAllowedImplicitSelf(@_implicitSelfCapture _ fn: @escaping () -> Void) {}
+
 public final class TestImplicitSelfForWeakSelfCapture: Sendable {
   static let staticOptional: TestImplicitSelfForWeakSelfCapture? = .init()
   func method() { }
@@ -130,6 +132,12 @@ public final class TestImplicitSelfForWeakSelfCapture: Sendable {
       }
     }
 
+    takesEscapingWithAllowedImplicitSelf { [weak self] in
+      method() // expected-error {{explicit use of 'self' is required when 'self' is optional, to make control flow explicit}} expected-note {{reference 'self?.' explicitly}}
+      guard let self = self else { return }
+      method()
+    }
+
     doVoidStuff { [weak self] in
       doVoidStuff { // expected-note {{capture 'self' explicitly to enable implicit 'self' in this closure}}
         guard let self = self else { return }
@@ -796,4 +804,4 @@ struct TestInvalidSelfCaptureInStruct {
       self.method()
     }
   }
-}
+}