Sema: A LoadExpr enclosing a call does not affect the arguments.

Fixes missing setter availability diagnostics in some edge cases.

Author: tshortli

lib/Sema/TypeCheckAvailability.cpp

@@ -3524,13 +3524,19 @@ class ExprAvailabilityWalker : public ASTWalker {
     return call;
   }
 
-  /// Walks up to the first enclosing LoadExpr and returns it.
+  /// Walks up from a potential member reference to the first LoadExpr that would
+  /// make the member reference an r-value instead of an l-value.
   const LoadExpr *getEnclosingLoadExpr() const {
     assert(!ExprStack.empty() && "must be called while visiting an expression");
     ArrayRef<const Expr *> stack = ExprStack;
     stack = stack.drop_back();
 
     for (auto expr : llvm::reverse(stack)) {
+      // Do not search past the first enclosing ApplyExpr. Any enclosing
+      // LoadExpr from this point only applies to the result of the call.
+      if (auto applyExpr = dyn_cast<ApplyExpr>(expr))
+        return nullptr;
+
       if (auto loadExpr = dyn_cast<LoadExpr>(expr))
         return loadExpr;
     }

test/Sema/availability_accessors.swift

@@ -72,14 +72,14 @@ struct BaseStruct<T: ValueProto> {
   var unavailableSetter: T {
     get { .defaultValue }
     @available(*, unavailable)
-    set { fatalError() } // expected-note 36 {{setter for 'unavailableSetter' has been explicitly marked unavailable here}}
+    set { fatalError() } // expected-note 37 {{setter for 'unavailableSetter' has been explicitly marked unavailable here}}
   }
 
   var unavailableGetterAndSetter: T {
     @available(*, unavailable)
     get { fatalError() } // expected-note 62 {{getter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
     @available(*, unavailable)
-    set { fatalError() } // expected-note 36 {{setter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
+    set { fatalError() } // expected-note 37 {{setter for 'unavailableGetterAndSetter' has been explicitly marked unavailable here}}
   }
 }
 
@@ -461,8 +461,7 @@ func testDiscardedApplyOfFuncWithInOutParam_Class() {
   _ = takesInOut(&x.unavailableGetter[0].b).magnitude // expected-error {{getter for 'unavailableGetter' is unavailable}}
 
   _ = takesInOut(&x.unavailableSetter) // expected-error {{setter for 'unavailableSetter' is unavailable}}
-  // FIXME: missing diagnostic for setter
-  _ = takesInOut(&x.unavailableSetter).a
+  _ = takesInOut(&x.unavailableSetter).a // expected-error {{setter for 'unavailableSetter' is unavailable}}
   _ = takesInOut(&x.unavailableSetter.a)
   _ = takesInOut(&x.unavailableSetter.a).b
   _ = takesInOut(&x.unavailableSetter[0])
@@ -471,8 +470,7 @@ func testDiscardedApplyOfFuncWithInOutParam_Class() {
   _ = takesInOut(&x.unavailableSetter[0].b).magnitude
 
   _ = takesInOut(&x.unavailableGetterAndSetter) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}} expected-error {{setter for 'unavailableGetterAndSetter' is unavailable}}
-  // FIXME: missing diagnostic for setter
-  _ = takesInOut(&x.unavailableGetterAndSetter).a // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
+  _ = takesInOut(&x.unavailableGetterAndSetter).a // 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.a).b // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}
   _ = takesInOut(&x.unavailableGetterAndSetter[0]) // expected-error {{getter for 'unavailableGetterAndSetter' is unavailable}}