Sema: Diagnose availability of storage accessors for key paths.

Fixes the missing diagnostic about the availability of the setter of `x` in the
following example:

```
struct S {
  var x: Int {
    get { 0 }
    @available(*, unavailable) set {}
  }
}

var s = S()
s[keyPath: \.x] = 1
```

Resolves rdar://124977727

Author: tshortli

lib/Sema/TypeCheckAvailability.cpp

@@ -3557,6 +3557,7 @@ class ExprAvailabilityWalker : public ASTWalker {
   /// availability.
   void maybeDiagKeyPath(KeyPathExpr *KP) {
     auto flags = DeclAvailabilityFlags();
+    auto declContext = Where.getDeclContext();
     if (KP->isObjC())
       flags = DeclAvailabilityFlag::ForObjCKeyPath;
 
@@ -3566,7 +3567,10 @@ class ExprAvailabilityWalker : public ASTWalker {
       case KeyPathExpr::Component::Kind::Subscript: {
         auto decl = component.getDeclRef();
         auto loc = component.getLoc();
-        diagnoseDeclRefAvailability(decl, loc, nullptr, flags);
+        auto range = component.getSourceRange();
+        if (diagnoseDeclRefAvailability(decl, loc, nullptr, flags))
+          break;
+        maybeDiagStorageAccess(decl.getDecl(), range, declContext);
         break;
       }
 

test/Sema/availability_accessors.swift

@@ -34,21 +34,21 @@ struct BaseStruct {
 
   var unavailableGetter: Value {
     @available(*, unavailable)
-    get { fatalError() } // expected-note 24 {{getter for 'unavailableGetter' has been explicitly marked unavailable here}}
+    get { fatalError() } // expected-note 28 {{getter for 'unavailableGetter' has been explicitly marked unavailable here}}
     set {}
   }
 
   var unavailableSetter: Value {
     get { .defaultValue }
     @available(*, unavailable)
-    set { fatalError() } // expected-note 12 {{setter for 'unavailableSetter' has been explicitly marked unavailable here}}
+    set { fatalError() } // expected-note 16 {{setter for 'unavailableSetter' has been explicitly marked unavailable here}}
   }
 
   var unavailableGetterAndSetter: Value {
     @available(*, unavailable)
-    get { fatalError() } // expected-note 24 {{getter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
+    get { fatalError() } // expected-note 28 {{getter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
     @available(*, unavailable)
-    set { fatalError() } // expected-note 12 {{setter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
+    set { fatalError() } // expected-note 16 {{setter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
   }
 }
 
@@ -117,10 +117,10 @@ func testKeyPathLoads() {
   _ = a[keyPath: \.[takesIntInOut(&x.available.a.b)]]
   _ = a[keyPath: \.[takesIntInOut(&x.available[0].b)]]
 
-  _ = x[keyPath: \.unavailableGetter] // FIXME: missing diagnostic for getter
-  _ = x[keyPath: \.unavailableGetter.a] // FIXME: missing diagnostic for getter
-  _ = x[keyPath: \.unavailableGetter[0]] // FIXME: missing diagnostic for getter
-  _ = x[keyPath: \.unavailableGetter[0].b] // FIXME: missing diagnostic for getter
+  _ = x[keyPath: \.unavailableGetter] // expected-error {{getter for 'unavailableGetter' is unavailable}}
+  _ = x[keyPath: \.unavailableGetter.a] // expected-error {{getter for 'unavailableGetter' is unavailable}}
+  _ = x[keyPath: \.unavailableGetter[0]] // expected-error {{getter for 'unavailableGetter' is unavailable}}
+  _ = x[keyPath: \.unavailableGetter[0].b] // expected-error {{getter for 'unavailableGetter' is unavailable}}
   _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetter.a.b)]] // expected-error {{getter for 'unavailableGetter' is unavailable}}
   _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetter[0].b)]] // expected-error {{getter for 'unavailableGetter' is unavailable}}
 
@@ -131,10 +131,10 @@ func testKeyPathLoads() {
   _ = a[keyPath: \.[takesIntInOut(&x.unavailableSetter.a.b)]] // FIXME: missing diagnostic for setter
   _ = a[keyPath: \.[takesIntInOut(&x.unavailableSetter[0].b)]] // expected-error {{setter for 'unavailableSetter' is unavailable}}
 
-  _ = x[keyPath: \.unavailableGetterAndSetter] // FIXME: missing diagnostic for getter
-  _ = x[keyPath: \.unavailableGetterAndSetter.a] // FIXME: missing diagnostic for getter
-  _ = x[keyPath: \.unavailableGetterAndSetter[0]] // FIXME: missing diagnostic for getter
-  _ = x[keyPath: \.unavailableGetterAndSetter[0].b] // FIXME: missing diagnostic for getter
+  _ = 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}}
   _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter.a.b)]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} FIXME: missing diagnostic for setter
   _ = a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter[0].b)]] // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
 }
@@ -158,17 +158,17 @@ func testKeyPathAssignments() {
   a[keyPath: \.[takesIntInOut(&x.unavailableGetter.a.b)]] = 0 // expected-error {{getter for 'unavailableGetter' is unavailable}}
   a[keyPath: \.[takesIntInOut(&x.unavailableGetter[0].b)]] = 0 // expected-error {{getter for 'unavailableGetter' is unavailable}}
 
-  x[keyPath: \.unavailableSetter] = someValue
-  x[keyPath: \.unavailableSetter.a] = someValue.a // FIXME: missing diagnostic for setter
-  x[keyPath: \.unavailableSetter[0]] = someValue.a // FIXME: missing diagnostic for setter
-  x[keyPath: \.unavailableSetter[0].b] = 1 // FIXME: missing diagnostic for setter
+  x[keyPath: \.unavailableSetter] = someValue // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  x[keyPath: \.unavailableSetter.a] = someValue.a // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  x[keyPath: \.unavailableSetter[0]] = someValue.a // expected-error {{setter for 'unavailableSetter' is unavailable}}
+  x[keyPath: \.unavailableSetter[0].b] = 1 // expected-error {{setter for 'unavailableSetter' is unavailable}}
   a[keyPath: \.[takesIntInOut(&x.unavailableSetter.a.b)]] = 0 // FIXME: missing diagnostic for setter
   a[keyPath: \.[takesIntInOut(&x.unavailableSetter[0].b)]] = 0 // expected-error {{setter for 'unavailableSetter' is unavailable}}
 
-  x[keyPath: \.unavailableGetterAndSetter] = someValue
-  x[keyPath: \.unavailableGetterAndSetter.a] = someValue.a // FIXME: missing diagnostics for getter and setter
-  x[keyPath: \.unavailableGetterAndSetter[0]] = someValue.a // FIXME: missing diagnostics for getter and setter
-  x[keyPath: \.unavailableGetterAndSetter[0].b] = 1 // FIXME: missing diagnostics for getter and setter
+  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}}
+  x[keyPath: \.unavailableGetterAndSetter[0].b] = 1 // expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
   a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter.a.b)]] = 0 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} FIXME: missing diagnostic for setter
   a[keyPath: \.[takesIntInOut(&x.unavailableGetterAndSetter[0].b)]] = 0 // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
 }