Sema: Fix conditional downcasts from Swift types to CF types [4.0]

lib/Sema/CSApply.cpp

@@ -5816,6 +5816,8 @@ Expr *ExprRewriter::buildCollectionUpcastExpr(Expr *expr, Type toType,
 
 Expr *ExprRewriter::buildObjCBridgeExpr(Expr *expr, Type toType,
                                         ConstraintLocatorBuilder locator) {
+  auto &tc = cs.getTypeChecker();
+
   Type fromType = cs.getType(expr);
 
   // Bridged collection casts always succeed, so we treat them as
@@ -5838,6 +5840,20 @@ Expr *ExprRewriter::buildObjCBridgeExpr(Expr *expr, Type toType,
     if (!objcExpr)
       return nullptr;
 
+    // We might have a coercion of a Swift type to a CF type toll-free
+    // bridged to Objective-C.
+    //
+    // FIXME: Ideally we would instead have already recorded a restriction
+    // when solving the constraint, and we wouldn't need to duplicate this
+    // part of coerceToType() here.
+    if (auto foreignClass = toType->getClassOrBoundGenericClass()) {
+      if (foreignClass->getForeignClassKind() ==
+            ClassDecl::ForeignKind::CFType) {
+        return cs.cacheType(
+          new (tc.Context) ForeignObjectConversionExpr(objcExpr, toType));
+      }
+    }
+
     return coerceToType(objcExpr, toType, locator);
   }
 

test/Inputs/clang-importer-sdk/usr/include/CoreFoundation.h

@@ -14,6 +14,10 @@ typedef struct __attribute__((objc_bridge(NSString))) __CFString const *CFString
 typedef struct __CFTree *CFTreeRef;
 typedef const struct __attribute__((objc_bridge(CFURL))) __CFURL * CFURLRef;
 
+typedef struct __attribute__((objc_bridge(NSDictionary))) __CFDictionary const *CFDictionaryRef;
+typedef struct __attribute__((objc_bridge(NSArray))) __CFArray const *CFArrayRef;
+typedef struct __attribute__((objc_bridge(NSSet))) __CFSet const *CFSetRef;
+
 typedef CFTypeRef CFAliasForTypeRef;
 
 

test/expr/cast/cf.swift

@@ -80,3 +80,25 @@ func testCFConvWithIUO(_ x: CFString!, y: NSString!) {
   acceptNSString(x)
   acceptCFString(y)
 }
+
+func testBridgedCFDowncast(array: [Any], dictionary: [AnyHashable : Any], set: Set<AnyHashable>) {
+  let cfArray = array as CFArray
+  let cfDictionary = dictionary as CFDictionary
+  let cfSet = set as CFSet
+
+  _ = array as? CFArray // expected-warning {{conditional cast from '[Any]' to 'CFArray' always succeeds}}
+  _ = dictionary as? CFDictionary // expected-warning {{conditional cast from '[AnyHashable : Any]' to 'CFDictionary' always succeeds}}
+  _ = set as? CFSet // expected-warning {{conditional cast from 'Set<AnyHashable>' to 'CFSet' always succeeds}}
+
+  _ = array as! CFArray // expected-warning {{forced cast from '[Any]' to 'CFArray' always succeeds}}
+  _ = dictionary as! CFDictionary // expected-warning {{forced cast from '[AnyHashable : Any]' to 'CFDictionary' always succeeds}}
+  _ = set as! CFSet // expected-warning {{forced cast from 'Set<AnyHashable>' to 'CFSet' always succeeds}}
+
+  _ = cfArray as! [Any]
+  _ = cfDictionary as! [AnyHashable : Any]
+  _ = cfSet as! Set<AnyHashable>
+
+  _ = cfArray as? [Any]
+  _ = cfDictionary as? [AnyHashable : Any]
+  _ = cfSet as? Set<AnyHashable>
+}