Pending QOI improvements, reinstate implicit bridging conversions.

Author: jopamer

lib/Sema/CSSimplify.cpp

@@ -1709,27 +1709,33 @@ ConstraintSystem::matchTypes(Type type1, Type type2, TypeMatchKind kind,
     // Bridging from a value type to an Objective-C class type.
     // FIXME: Banned for operator parameters, like user conversions are.
 
-    if (kind == TypeMatchKind::ExplicitConversion) {
 
-      if (type1->isPotentiallyBridgedValueType() &&
-          type1->getAnyNominal() 
-            != TC.Context.getImplicitlyUnwrappedOptionalDecl() &&
-          !(flags & TMF_ApplyingOperatorParameter)) {
-        
-        auto isBridgeableTargetType = type2->isBridgeableObjectType();
-        
-        // Allow bridged conversions to CVarArg through NSObject.
-        if (!isBridgeableTargetType && type2->isExistentialType()) {
-          if (auto nominalType = type2->getAs<NominalType>())
-            isBridgeableTargetType = nominalType->getDecl()->getName() ==
-                                        TC.Context.Id_CVarArg;
-        }
-        
-        if (isBridgeableTargetType && TC.getBridgedToObjC(DC, type1)) {
-          conversionsOrFixes.push_back(ConversionRestrictionKind::BridgeToObjC);
-        }
+    // NOTE: The plan for <rdar://problem/18311362> was to make such bridging
+    // conversions illegal except when explicitly converting with the 'as'
+    // operator. But using a String to subscript an [NSObject : AnyObject] is
+    // sufficiently common due to bridging that disallowing such conversions is
+    // not yet feasible, and a more targeted fix in the type checker is hard to
+    // justify.
+    if (type1->isPotentiallyBridgedValueType() &&
+        type1->getAnyNominal() 
+          != TC.Context.getImplicitlyUnwrappedOptionalDecl() &&
+        !(flags & TMF_ApplyingOperatorParameter)) {
+      
+      auto isBridgeableTargetType = type2->isBridgeableObjectType();
+      
+      // Allow bridged conversions to CVarArg through NSObject.
+      if (!isBridgeableTargetType && type2->isExistentialType()) {
+        if (auto nominalType = type2->getAs<NominalType>())
+          isBridgeableTargetType = nominalType->getDecl()->getName() ==
+                                      TC.Context.Id_CVarArg;
+      }
+      
+      if (isBridgeableTargetType && TC.getBridgedToObjC(DC, type1)) {
+        conversionsOrFixes.push_back(ConversionRestrictionKind::BridgeToObjC);
       }
+    }
 
+    if (kind == TypeMatchKind::ExplicitConversion) {
       // Bridging from an Objective-C class type to a value type.
       // Note that specifically require a class or class-constrained archetype
       // here, because archetypes cannot be bridged.

test/Constraints/bridging.swift

@@ -89,12 +89,12 @@ func ==(x: OtherClass, y: OtherClass) -> Bool { return true }
 
 // Basic bridging
 func bridgeToObjC(_ s: BridgedStruct) -> BridgedClass {
-  return s // expected-error{{cannot convert return expression of type 'BridgedStruct' to return type 'BridgedClass'}}
+  return s 
   return s as BridgedClass
 }
 
 func bridgeToAnyObject(_ s: BridgedStruct) -> AnyObject {
-  return s // expected-error{{return expression of type 'BridgedStruct' does not conform to 'AnyObject'}}
+  return s 
   return s as AnyObject
 }
 
@@ -112,10 +112,10 @@ func bridgeFromObjCDerived(_ s: BridgedClassSub) -> BridgedStruct {
 func arrayToNSArray() {
   var nsa: NSArray
 
-  nsa = [AnyObject]() // expected-error {{cannot assign value of type '[AnyObject]' to type 'NSArray'}}
-  nsa = [BridgedClass]() // expected-error {{cannot assign value of type '[BridgedClass]' to type 'NSArray'}}
-  nsa = [OtherClass]() // expected-error {{cannot assign value of type '[OtherClass]' to type 'NSArray'}}
-  nsa = [BridgedStruct]() // expected-error {{cannot assign value of type '[BridgedStruct]' to type 'NSArray'}}
+  nsa = [AnyObject]() 
+  nsa = [BridgedClass]()
+  nsa = [OtherClass]() 
+  nsa = [BridgedStruct]()
   nsa = [NotBridgedStruct]() // expected-error{{cannot assign value of type '[NotBridgedStruct]' to type 'NSArray'}}
 
   nsa = [AnyObject]() as NSArray
@@ -150,13 +150,13 @@ func dictionaryToNSDictionary() {
 
   var nsd: NSDictionary
 
-  nsd = [NSObject : AnyObject]() // expected-error {{cannot assign value of type '[NSObject : AnyObject]' to type 'NSDictionary'}}
+  nsd = [NSObject : AnyObject]()
   nsd = [NSObject : AnyObject]() as NSDictionary
-  nsd = [NSObject : BridgedClass]() // expected-error {{cannot assign value of type '[NSObject : BridgedClass]' to type 'NSDictionary'}}
+  nsd = [NSObject : BridgedClass]()
   nsd = [NSObject : BridgedClass]() as NSDictionary
-  nsd = [NSObject : OtherClass]() // expected-error {{cannot assign value of type '[NSObject : OtherClass]' to type 'NSDictionary'}}
+  nsd = [NSObject : OtherClass]()
   nsd = [NSObject : OtherClass]() as NSDictionary
-  nsd = [NSObject : BridgedStruct]() // expected-error {{cannot assign value of type '[NSObject : BridgedStruct]' to type 'NSDictionary'}}
+  nsd = [NSObject : BridgedStruct]()
   nsd = [NSObject : BridgedStruct]() as NSDictionary
   nsd = [NSObject : NotBridgedStruct]() // expected-error{{cannot assign value of type '[NSObject : NotBridgedStruct]' to type 'NSDictionary'}}
   nsd = [NSObject : NotBridgedStruct]() as NSDictionary // expected-error{{cannot convert value of type '[NSObject : NotBridgedStruct]' to type 'NSDictionary' in coercion}}
@@ -166,18 +166,18 @@ func dictionaryToNSDictionary() {
   nsd = [NSObject : BridgedStruct?]()  // expected-error{{cannot assign value of type '[NSObject : BridgedStruct?]' to type 'NSDictionary'}}
   nsd = [NSObject : BridgedStruct?]() as NSDictionary //expected-error{{cannot convert value of type '[NSObject : BridgedStruct?]' to type 'NSDictionary' in coercion}}
 
-  nsd = [BridgedClass : AnyObject]() // expected-error {{cannot assign value of type '[BridgedClass : AnyObject]' to type 'NSDictionary'}}
+  nsd = [BridgedClass : AnyObject]()
   nsd = [BridgedClass : AnyObject]() as NSDictionary
-  nsd = [OtherClass : AnyObject]() // expected-error {{cannot assign value of type '[OtherClass : AnyObject]' to type 'NSDictionary'}}
+  nsd = [OtherClass : AnyObject]()
   nsd = [OtherClass : AnyObject]() as NSDictionary
-  nsd = [BridgedStruct : AnyObject]() // expected-error {{cannot assign value of type '[BridgedStruct : AnyObject]' to type 'NSDictionary'}}
+  nsd = [BridgedStruct : AnyObject]()
   nsd = [BridgedStruct : AnyObject]() as NSDictionary
   nsd = [NotBridgedStruct : AnyObject]()  // expected-error{{cannot assign value of type '[NotBridgedStruct : AnyObject]' to type 'NSDictionary'}}
   nsd = [NotBridgedStruct : AnyObject]() as NSDictionary  // expected-error{{cannot convert value of type '[NotBridgedStruct : AnyObject]' to type 'NSDictionary' in coercion}}
 
   // <rdar://problem/17134986>
   var bcOpt: BridgedClass?
-  nsd = [BridgedStruct() : bcOpt] // expected-error{{value of type 'BridgedStruct' does not conform to expected dictionary key type 'NSCopying'}}
+  nsd = [BridgedStruct() : bcOpt] // expected-error{{value of optional type 'BridgedClass?' not unwrapped; did you mean to use '!' or '?'?}}
   bcOpt = nil
   _ = nsd
 }
@@ -233,7 +233,7 @@ func rdar19695671() {
 // This failed at one point while fixing rdar://problem/19600325.
 func getArrayOfAnyObject(_: AnyObject) -> [AnyObject] { return [] }
 func testCallback(_ f: (AnyObject) -> AnyObject?) {}
-testCallback { return getArrayOfAnyObject($0) } // expected-error {{cannot convert value of type '[AnyObject]' to closure result type 'AnyObject?'}}
+testCallback { return getArrayOfAnyObject($0) }
 
 // <rdar://problem/19724719> Type checker thinks "(optionalNSString ?? nonoptionalNSString) as String" is a forced cast
 func rdar19724719(_ f: (String) -> (), s1: NSString?, s2: NSString) {
@@ -292,10 +292,10 @@ func rdar19836341(_ ns: NSString?, vns: NSString?) {
 
 // <rdar://problem/20029786> Swift compiler sometimes suggests changing "as!" to "as?!"
 func rdar20029786(_ ns: NSString?) {
-  var s: String = ns ?? "str" as String as String // expected-error{{cannot convert value of type 'NSString?' to expected argument type 'String?'}}
-  var s2 = ns ?? "str" as String as String // expected-error {{binary operator '??' cannot be applied to operands of type 'NSString?' and 'String'}} expected-note{{}}
+  var s: String = ns ?? "str" as String as String // expected-error{{'NSString' is not implicitly convertible to 'String'; did you mean to use 'as' to explicitly convert?}}
+  var s2 = ns ?? "str" as String as String
 
-  let s3: NSString? = "str" as String? // expected-error {{cannot convert value of type 'String?' to specified type 'NSString?'}}
+  let s3: NSString? = "str" as String?
 
   var s4: String = ns ?? "str" // expected-error{{'NSString' is not implicitly convertible to 'String'; did you mean to use 'as' to explicitly convert?}}{{20-20=(}}{{31-31=) as String}}
   var s5: String = (ns ?? "str") as String // fixed version