Sema: Suppress set accessor availability diagnostics in LoadExprs.

This fixes a regression from #72369.
The compiler now incorrectly diagnoses use of an unavailable setter in this
example:

```
func increaseBrightness(in window: UIWindow) {
  // warning: setter for 'screen' was deprecated in iOS 13.0
  window.screen.brightness = 1.0
}
```

While the setter is deprecated, it would not going to be called in the generated
code since `screen` is a reference type and there is no writeback through
the setter for `screen` after setting `brightness`.

Resolves rdar://129679658

Author: tshortli

lib/Sema/TypeCheckAvailability.cpp

@@ -3631,12 +3631,7 @@ class ExprAvailabilityWalker : public ASTWalker {
 
   /// Walk an inout expression, checking for availability.
   void walkInOutExpr(InOutExpr *E) {
-    // If there is a LoadExpr in the stack, then this InOutExpr is not actually
-    // indicative of any mutation so the access context should just be Getter.
-    auto accessContext = getEnclosingLoadExpr() ? MemberAccessContext::Getter
-                                                : MemberAccessContext::InOut;
-
-    walkInContext(E, E->getSubExpr(), accessContext);
+    walkInContext(E, E->getSubExpr(), MemberAccessContext::InOut);
   }
 
   bool shouldWalkIntoClosure(AbstractClosureExpr *closure) const {
@@ -3657,7 +3652,6 @@ class ExprAvailabilityWalker : public ASTWalker {
     return;
   }
 
-
   /// Walk the given expression in the member access context.
   void walkInContext(Expr *baseExpr, Expr *E,
                      MemberAccessContext AccessContext) {
@@ -3693,18 +3687,22 @@ class ExprAvailabilityWalker : public ASTWalker {
       break;
 
     case MemberAccessContext::Setter:
-      diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Set),
-                               ReferenceRange, ReferenceDC, std::nullopt);
+      if (!getEnclosingLoadExpr()) {
+        diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Set),
+                                 ReferenceRange, ReferenceDC, std::nullopt);
+      }
       break;
 
     case MemberAccessContext::InOut:
       diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Get),
                                ReferenceRange, ReferenceDC,
                                DeclAvailabilityFlag::ForInout);
 
-      diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Set),
-                               ReferenceRange, ReferenceDC,
-                               DeclAvailabilityFlag::ForInout);
+      if (!getEnclosingLoadExpr()) {
+        diagAccessorAvailability(D->getOpaqueAccessor(AccessorKind::Set),
+                                 ReferenceRange, ReferenceDC,
+                                 DeclAvailabilityFlag::ForInout);
+      }
       break;
     }
   }

test/Sema/availability_accessors.swift

@@ -72,14 +72,14 @@ struct BaseStruct<T: ValueProto> {
   var unavailableSetter: T {
     get { .defaultValue }
     @available(*, unavailable)
-    set { fatalError() } // expected-note 37 {{setter for 'unavailableSetter' has been explicitly marked unavailable here}}
+    set { fatalError() } // expected-note 27 {{setter for 'unavailableSetter' has been explicitly marked unavailable here}}
   }
 
   var unavailableGetterAndSetter: T {
     @available(*, unavailable)
     get { fatalError() } // expected-note 46 {{getter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
     @available(*, unavailable)
-    set { fatalError() } // expected-note 37 {{setter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
+    set { fatalError() } // expected-note 27 {{setter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
   }
 }
 
@@ -173,21 +173,15 @@ func testLValueAssignments_Class(_ someValue: ClassValue) {
   x.unavailableGetter[0].b = 1 // expected-error {{getter for 'unavailableGetter' is unavailable}}
 
   x.unavailableSetter = someValue // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  x.unavailableSetter.a = someValue.a // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  x.unavailableSetter[0] = someValue.a // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  x.unavailableSetter[0].b = 1 // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  x.unavailableSetter.a = someValue.a
+  x.unavailableSetter[0] = someValue.a
+  x.unavailableSetter[0].b = 1
 
   x.unavailableGetterAndSetter = someValue // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  x.unavailableGetterAndSetter.a = someValue.a // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
+  x.unavailableGetterAndSetter.a = someValue.a // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
   // FIXME: missing diagnostic for getter
-  // FIXME: spurious unavailable setter error
-  x.unavailableGetterAndSetter[0] = someValue.a // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  x.unavailableGetterAndSetter[0].b = 1 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
+  x.unavailableGetterAndSetter[0] = someValue.a
+  x.unavailableGetterAndSetter[0].b = 1 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
 }
 
 func testKeyPathLoads_Struct() {
@@ -245,17 +239,15 @@ func testKeyPathLoads_Class() {
   _ = x[keyPath: \.unavailableSetter.a]
   _ = x[keyPath: \.unavailableSetter[0]]
   _ = x[keyPath: \.unavailableSetter[0].b]
-  _ = a[keyPath: \.[takesIntInOut(&x.unavailableSetter.a.b)]] // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  _ = a[keyPath: \.[takesIntInOut(&x.unavailableSetter[0].b)]] // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  _ = a[keyPath: \.[takesIntInOut(&x.unavailableSetter.a.b)]]
+  _ = a[keyPath: \.[takesIntInOut(&x.unavailableSetter[0].b)]]
 
   _ = x[keyPath: \.unavailableGetterAndSetter] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
   _ = x[keyPath: \.unavailableGetterAndSetter.a] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
   _ = x[keyPath: \.unavailableGetterAndSetter[0]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
   _ = x[keyPath: \.unavailableGetterAndSetter[0].b] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter.a.b)]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter[0].b)]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
+  _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter.a.b)]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
+  _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter[0].b)]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
 }
 
 func testKeyPathAssignments_Struct(_ someValue: StructValue) {
@@ -318,20 +310,16 @@ func testKeyPathAssignments_Class(_ someValue: ClassValue) {
   x[keyPath: \.unavailableSetter[0]] = someValue.a // expected-error {{setter for 'unavailableSetter' is unavailable}}
   // FIXME: spurious unavailable setter error
   x[keyPath: \.unavailableSetter[0].b] = 1 // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  a[keyPath: \.[takesIntInOut(&x.unavailableSetter.a.b)]] = 0 // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  a[keyPath: \.[takesIntInOut(&x.unavailableSetter[0].b)]] = 0 // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  a[keyPath: \.[takesIntInOut(&x.unavailableSetter.a.b)]] = 0
+  a[keyPath: \.[takesIntInOut(&x.unavailableSetter[0].b)]] = 0
 
   x[keyPath: \.unavailableGetterAndSetter] = someValue // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
   x[keyPath: \.unavailableGetterAndSetter.a] = someValue.a // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
   x[keyPath: \.unavailableGetterAndSetter[0]] = someValue.a // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
   // FIXME: spurious unavailable setter error
   x[keyPath: \.unavailableGetterAndSetter[0].b] = 1 // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter.a.b)]] = 0 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter[0].b)]] = 0 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
+  a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter.a.b)]] = 0 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
+  a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter[0].b)]] = 0 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
 }
 
 func testMutatingStructMember() {
@@ -405,20 +393,14 @@ func testPassAsInOutParameter_Class() {
   takesInOut(&x.unavailableGetter[0].b) // expected-error {{getter for 'unavailableGetter' is unavailable}}
 
   takesInOut(&x.unavailableSetter) // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  takesInOut(&x.unavailableSetter.a) // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  takesInOut(&x.unavailableSetter[0]) // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  takesInOut(&x.unavailableSetter[0].b) // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  takesInOut(&x.unavailableSetter.a)
+  takesInOut(&x.unavailableSetter[0])
+  takesInOut(&x.unavailableSetter[0].b)
 
   takesInOut(&x.unavailableGetterAndSetter) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  takesInOut(&x.unavailableGetterAndSetter.a) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  takesInOut(&x.unavailableGetterAndSetter[0]) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: spurious unavailable setter error
-  takesInOut(&x.unavailableGetterAndSetter[0].b) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
+  takesInOut(&x.unavailableGetterAndSetter.a) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
+  takesInOut(&x.unavailableGetterAndSetter[0]) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
+  takesInOut(&x.unavailableGetterAndSetter[0].b) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
 }
 
 var global = BaseStruct<StructValue>()