Merge pull request #27146 from xedin/dynamic-member-vs-contrained-ext

[CSRanking] Always rank key path dynamic member choices lower than no…

Author: xedin

lib/Sema/CSRanking.cpp

@@ -822,17 +822,27 @@ SolutionCompareResult ConstraintSystem::compareSolutions(
         continue;
       }
 
-      // Dynamic member lookup through a keypath is better than one using string
-      // because it carries more type information.
-      if (choice1.getKind() == OverloadChoiceKind::KeyPathDynamicMemberLookup &&
-          choice2.getKind() == OverloadChoiceKind::DynamicMemberLookup) {
-        score1 += weight;
+      if (choice1.getKind() == OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+        if (choice2.getKind() == OverloadChoiceKind::DynamicMemberLookup)
+          // Dynamic member lookup through a keypath is better than one using
+          // string because it carries more type information.
+          score1 += weight;
+        else
+          // Otherwise let's prefer non-dynamic declaration.
+          score2 += weight;
+
         continue;
       }
 
-      if (choice1.getKind() == OverloadChoiceKind::DynamicMemberLookup &&
-          choice2.getKind() == OverloadChoiceKind::KeyPathDynamicMemberLookup) {
-        score2 += weight;
+      if (choice2.getKind() == OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+        if (choice1.getKind() == OverloadChoiceKind::DynamicMemberLookup)
+          // Dynamic member lookup through a keypath is better than one using
+          // string because it carries more type information.
+          score2 += weight;
+        else
+          // Otherwise let's prefer non-dynamic declaration.
+          score1 += weight;
+
         continue;
       }
 

test/Constraints/keypath_dynamic_member_lookup.swift

@@ -367,3 +367,26 @@ func make_sure_delayed_keypath_dynamic_member_works() {
     }
   }
 }
+
+
+// SR-11465 - Ambiguity in expression which matches both dynamic member lookup and declaration from constrained extension
+
+@dynamicMemberLookup
+struct SR_11465<RawValue> {
+  var rawValue: RawValue
+
+  subscript<Subject>(dynamicMember keyPath: KeyPath<RawValue, Subject>) -> Subject {
+    rawValue[keyPath: keyPath]
+  }
+}
+
+extension SR_11465: Hashable, Equatable where RawValue: Hashable {
+  func hash(into hasher: inout Hasher) {
+    hasher.combine(self.rawValue)
+  }
+}
+
+func test_constrained_ext_vs_dynamic_member() {
+  // CHECK: function_ref @$s29keypath_dynamic_member_lookup8SR_11465VAASHRzlE9hashValueSivg
+  _ = SR_11465<Int>(rawValue: 1).hashValue // Ok, keep choice from constrained extension
+}