[CSRanking] Favour members on concrete types over protocol members

This commit adds a new rule to `isDeclAsSpecializedAs` in order to favour a member on a concrete type over a protocol member. This rule is effectively an extension of the existing rule that prefers concrete type members over protocol extension members.

Author: hamishknight

lib/Sema/CSRanking.cpp

@@ -446,6 +446,18 @@ static bool isDeclAsSpecializedAs(TypeChecker &tc, DeclContext *dc,
         return inProtocolExtension2;
       }
 
+      // A concrete type member is always more specialised than a protocol
+      // member (bearing in mind that we have already handled the case where
+      // exactly one member is in a protocol extension). Only apply this rule in
+      // Swift 5 mode to better maintain source compatibility under Swift 4
+      // mode.
+      if (tc.Context.isSwiftVersionAtLeast(5)) {
+        auto *proto1 = dyn_cast<ProtocolDecl>(outerDC1);
+        auto *proto2 = dyn_cast<ProtocolDecl>(outerDC2);
+        if (proto1 != proto2)
+          return proto2;
+      }
+
       Type type1 = decl1->getInterfaceType();
       Type type2 = decl2->getInterfaceType();
 

test/Constraints/ranking.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-silgen %s -verify | %FileCheck %s
+// RUN: %target-swift-emit-silgen %s -verify -swift-version 5 | %FileCheck %s
 
 protocol P {
   var p: P { get set }
@@ -155,3 +155,116 @@ func testDerived(b: B) {
   f0(f1(b))
   // CHECK: end sil function '$S7ranking11testDerived1byAA1BC_tF'
 }
+
+protocol X {
+  var foo: Int { get }
+  var bar: Int { get }
+  func baz() -> Int
+  subscript(foo: String) -> Int { get }
+}
+
+class Y {
+  var foo: Int = 0
+  func baz() -> Int { return foo }
+  subscript(foo: String) -> Int { return 0 }
+}
+extension Y {
+  var bar: Int { return foo }
+}
+
+protocol Z : Y {
+  var foo: Int { get }
+  var bar: Int { get }
+  func baz() -> Int
+  subscript(foo: String) -> Int { get }
+}
+
+class GenericClass<T> {
+  var foo: T
+  init(_ foo: T) { self.foo = foo }
+  func baz() -> T { return foo }
+}
+extension GenericClass {
+  var bar: T { return foo }
+  subscript(foo: String) -> Int { return 0 }
+}
+
+// Make sure we favour the class implementation over the protocol requirement.
+
+// CHECK-LABEL: sil hidden @$S7ranking32testGenericPropertyProtocolClassyyxAA1YCRbzAA1XRzlF
+func testGenericPropertyProtocolClass<T : X & Y>(_ t: T) {
+  _ = t.foo   // CHECK: class_method {{%.*}} : $Y, #Y.foo!getter.1
+  _ = t.bar   // CHECK: function_ref @$S7ranking1YC3barSivg
+  _ = t.baz() // CHECK: class_method {{%.*}} : $Y, #Y.baz
+  _ = t[""]   // CHECK: class_method {{%.*}} : $Y, #Y.subscript!getter.1
+}
+
+// CHECK-LABEL: sil hidden @$S7ranking36testExistentialPropertyProtocolClassyyAA1X_AA1YCXcF
+func testExistentialPropertyProtocolClass(_ t: X & Y) {
+  _ = t.foo   // CHECK: class_method {{%.*}} : $Y, #Y.foo!getter.1
+  _ = t.bar   // CHECK: function_ref @$S7ranking1YC3barSivg
+  _ = t.baz() // CHECK: class_method {{%.*}} : $Y, #Y.baz
+  _ = t[""]   // CHECK: class_method {{%.*}} : $Y, #Y.subscript!getter.1
+}
+
+// CHECK-LABEL: sil hidden @$S7ranking46testGenericPropertySubclassConstrainedProtocolyyxAA1ZRzlF
+func testGenericPropertySubclassConstrainedProtocol<T : Z>(_ t: T) {
+  _ = t.foo   // CHECK: class_method {{%.*}} : $Y, #Y.foo!getter.1
+  _ = t.bar   // CHECK: function_ref @$S7ranking1YC3barSivg
+  _ = t.baz() // CHECK: class_method {{%.*}} : $Y, #Y.baz
+  _ = t[""]   // CHECK: class_method {{%.*}} : $Y, #Y.subscript!getter.1
+}
+
+// CHECK-LABEL: sil hidden @$S7ranking50testExistentialPropertySubclassConstrainedProtocolyyAA1Z_pF
+func testExistentialPropertySubclassConstrainedProtocol(_ t: Z) {
+  _ = t.foo   // CHECK: class_method {{%.*}} : $Y, #Y.foo!getter.1
+  _ = t.bar   // CHECK: function_ref @$S7ranking1YC3barSivg
+  _ = t.baz() // CHECK: class_method {{%.*}} : $Y, #Y.baz
+  _ = t[""]   // CHECK: class_method {{%.*}} : $Y, #Y.subscript!getter.1
+}
+
+// CHECK-LABEL: sil hidden @$S7ranking43testExistentialPropertyProtocolGenericClassyyAA1X_AA0fG0CySiGXcF
+func testExistentialPropertyProtocolGenericClass(_ t: GenericClass<Int> & X) {
+  _ = t.foo   // CHECK: class_method {{%.*}} : $GenericClass<Int>, #GenericClass.foo!getter.1
+  _ = t.bar   // CHECK: function_ref @$S7ranking12GenericClassC3barxvg
+  _ = t.baz() // CHECK: class_method {{%.*}} : $GenericClass<Int>, #GenericClass.baz
+  _ = t[""]   // CHECK: function_ref @$S7ranking12GenericClassCySiSScig
+}
+
+// CHECK-LABEL: sil hidden @$S7ranking43testExistentialPropertyProtocolGenericClassyyAA1X_AA0fG0CySSGXcF
+func testExistentialPropertyProtocolGenericClass(_ t: GenericClass<String> & X) {
+  _ = t.foo   // CHECK: class_method {{%.*}} : $GenericClass<String>, #GenericClass.foo!getter.1
+  _ = t.bar   // CHECK: function_ref @$S7ranking12GenericClassC3barxvg
+  _ = t.baz() // CHECK: class_method {{%.*}} : $GenericClass<String>, #GenericClass.baz
+  _ = t[""]   // CHECK: function_ref @$S7ranking12GenericClassCySiSScig
+}
+
+extension X where Self : Y {
+  // CHECK-LABEL: sil hidden @$S7ranking1XPA2A1YCRbzrlE32testGenericPropertyProtocolClassyyxF
+  func testGenericPropertyProtocolClass(_ x: Self) {
+    _ = self.foo   // CHECK: class_method {{%.*}} : $Y, #Y.foo!getter.1
+    _ = self.bar   // CHECK: function_ref @$S7ranking1YC3barSivg
+    _ = self.baz() // CHECK: class_method {{%.*}} : $Y, #Y.baz
+    _ = self[""]   // CHECK: class_method {{%.*}} : $Y, #Y.subscript!getter.1
+  }
+}
+
+extension X where Self : GenericClass<Int> {
+  // CHECK-LABEL: sil hidden @$S7ranking1XPA2A12GenericClassCySiGRbzrlE04testb16PropertyProtocolbC0yyxF
+  func testGenericPropertyProtocolGenericClass(_ x: Self) {
+    _ = self.foo   // CHECK: class_method {{%.*}} : $GenericClass<Int>, #GenericClass.foo!getter.1
+    _ = self.bar   // CHECK: function_ref @$S7ranking12GenericClassC3barxvg
+    _ = self.baz() // CHECK: class_method {{%.*}} : $GenericClass<Int>, #GenericClass.baz
+    _ = self[""]   // CHECK: function_ref @$S7ranking12GenericClassCySiSScig
+  }
+}
+
+extension X where Self : GenericClass<String> {
+  // CHECK-LABEL: sil hidden @$S7ranking1XPA2A12GenericClassCySSGRbzrlE04testb16PropertyProtocolbC0yyxF
+  func testGenericPropertyProtocolGenericClass(_ x: Self) {
+    _ = self.foo   // CHECK: class_method {{%.*}} : $GenericClass<String>, #GenericClass.foo!getter.1
+    _ = self.bar   // CHECK: function_ref @$S7ranking12GenericClassC3barxvg
+    _ = self.baz() // CHECK: class_method {{%.*}} : $GenericClass<String>, #GenericClass.baz
+    _ = self[""]   // CHECK: function_ref @$S7ranking12GenericClassCySiSScig
+  }
+}

test/Constraints/rdar39401774.swift

@@ -1,16 +1,16 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -swift-version 5
 
 class A<T> {
-  var foo: Int? { return 42 }      // expected-note {{found this candidate}}
-  func baz() -> T { fatalError() } // expected-note {{found this candidate}}
-  func fiz() -> Int { return 42 }  // expected-note {{found this candidate}}
+  var foo: Int? { return 42 }
+  func baz() -> T { fatalError() }
+  func fiz() -> Int { return 42 }
 }
 
 protocol P1 {
   associatedtype T
-  var foo: Int? { get } // expected-note {{found this candidate}}
-  func baz() -> T       // expected-note {{found this candidate}}
-  func fiz() -> Int     // expected-note {{found this candidate}}
+  var foo: Int? { get }
+  func baz() -> T
+  func fiz() -> Int
 }
 
 protocol P2 : P1 {
@@ -19,8 +19,9 @@ protocol P2 : P1 {
 
 extension P2 where Self: A<Int> {
   var bar: Int? {
-    guard let foo = foo else { return 0 } // expected-error {{ambiguous use of 'foo'}}
-    let _ = baz() // expected-error {{ambiguous use of 'baz()'}}
-    return fiz()  // expected-error {{ambiguous use of 'fiz()'}}
+    guard let foo = foo else { return 0 }
+    _ = foo
+    let _ = baz()
+    return fiz()  
   }
 }