Sema: Handle ArchetypeType and DynamicSelfType in determineBestChoicesInContext()

This fixes a regression introduced in https://github.com/swiftlang/swift/pull/82574.

The test case demonstrates the issue: we would incorrectly choose the base class
overload of == if one of the parameters was an archetype or dynamic Self.

Fixes rdar://156454697.

lib/Sema/CSOptimizer.cpp

@@ -1159,6 +1159,16 @@ static void determineBestChoicesInContext(
         });
       }
 
+      if (auto *selfType = candidateType->getAs<DynamicSelfType>()) {
+        candidateType = selfType->getSelfType();
+      }
+
+      if (auto *archetypeType = candidateType->getAs<ArchetypeType>()) {
+        candidateType = archetypeType->getSuperclass();
+        if (!candidateType)
+          return false;
+      }
+
       auto *subclassDecl = candidateType->getClassOrBoundGenericClass();
       auto *superclassDecl = superclassType->getClassOrBoundGenericClass();
 

test/Constraints/subclass_shadows_operator_equals.swift

@@ -0,0 +1,74 @@
+// RUN: %target-swift-emit-silgen %s | %FileCheck %s
+
+// rdar://156454697
+
+// The appearance of DynamicSelfType as an argument type to ==
+// would lead us to choose the Base.== overload, which is less
+// "specific" than Derived.==. There was a similar bug with
+// archetypes.
+//
+// This is a SILGen test, to check the overload choice.
+
+public class Base: Equatable {
+    public static func ==(lhs: Base, rhs: Base) -> Bool {
+        return false
+    }
+}
+
+public class Derived: Base {
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2f1SbyF : $@convention(method) (@guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func f1() -> Bool {
+        return self == self
+    }
+
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2f2SbyF : $@convention(method) (@guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func f2() -> Bool {
+        let c = self as! Self
+        return self == c
+    }
+
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2f3SbyF : $@convention(method) (@guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func f3() -> Bool {
+        let c = self as! Self
+        return c == self
+    }
+
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2f4SbyF : $@convention(method) (@guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func f4() -> Bool {
+        let c = self as! Self
+        return c == c
+    }
+
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2g1ySbxACRbzlF : $@convention(method) <T where T : Derived> (@guaranteed T, @guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func g1<T: Derived>(_ c: T) -> Bool {
+        return self == c
+    }
+
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2g2ySbxACRbzlF : $@convention(method) <T where T : Derived> (@guaranteed T, @guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func g2<T: Derived>(_ c: T) -> Bool {
+        return c == self
+    }
+
+    // CHECK-LABEL: sil [ossa] @$s32subclass_shadows_operator_equals7DerivedC2g3ySbxACRbzlF : $@convention(method) <T where T : Derived> (@guaranteed T, @guaranteed Derived) -> Bool {
+    // CHECK: function_ref @$s32subclass_shadows_operator_equals7DerivedC2eeoiySbAC_ACtFZ : $@convention(method) (@guaranteed Derived, @guaranteed Derived, @thick Derived.Type) -> Bool
+    // CHECK: return
+    public func g3<T: Derived>(_ c: T) -> Bool {
+        return c == c
+    }
+
+    public static func ==(lhs: Derived, rhs: Derived) -> Bool {
+        return false
+    }
+}