[SR-9425][Sema] Use derived conformance as witness when possible for == operator of raw representable enums

lib/Sema/TypeCheckProtocol.cpp

@@ -3833,6 +3833,30 @@ void ConformanceChecker::checkNonFinalClassWitness(ValueDecl *requirement,
   }
 }
 
+// If the given witness matches a generic RawRepresentable function conforming
+// with a given protocol e.g. `func == <T : RawRepresentable>(lhs: T, rhs: T) ->
+// Bool where T.RawValue : Equatable`
+static bool isRawRepresentableGenericFunction(
+    ASTContext &ctx, const ValueDecl *witness,
+    const NormalProtocolConformance *conformance) {
+  auto *fnDecl = dyn_cast<AbstractFunctionDecl>(witness);
+  if (!fnDecl || !fnDecl->isStdlibDecl())
+    return false;
+
+  return fnDecl->isGeneric() && fnDecl->getGenericParams()->size() == 1 &&
+         fnDecl->getGenericRequirements().size() == 2 &&
+         llvm::all_of(
+             fnDecl->getGenericRequirements(), [&](Requirement genericReq) {
+               if (genericReq.getKind() != RequirementKind::Conformance)
+                 return false;
+               return genericReq.getProtocolDecl() ==
+                          ctx.getProtocol(
+                              KnownProtocolKind::RawRepresentable) ||
+                      genericReq.getProtocolDecl() ==
+                          conformance->getProtocol();
+             });
+}
+
 ResolveWitnessResult
 ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
   assert(!isa<AssociatedTypeDecl>(requirement) && "Use resolveTypeWitnessVia*");
@@ -3881,6 +3905,16 @@ ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
   bool considerRenames =
       !canDerive && !requirement->getAttrs().hasAttribute<OptionalAttr>() &&
       !requirement->getAttrs().isUnavailable(getASTContext());
+
+  auto &ctx = getASTContext();
+  bool isEquatableConformance = Conformance->getProtocol() ==
+                                ctx.getProtocol(KnownProtocolKind::Equatable);
+
+  auto decl = Conformance->getDeclContext()->getSelfNominalTypeDecl();
+  auto *enumDecl = dyn_cast_or_null<EnumDecl>(decl);
+  bool isSwiftRawRepresentableEnum =
+      enumDecl && enumDecl->hasRawType() && !enumDecl->isObjC();
+
   if (findBestWitness(requirement,
                       considerRenames ? &ignoringNames : nullptr,
                       Conformance,
@@ -3889,6 +3923,17 @@ ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
     const auto &best = matches[bestIdx];
     auto witness = best.Witness;
 
+    if (canDerive && isSwiftRawRepresentableEnum && isEquatableConformance) {
+      // For swift enum types that can derive equatable conformance,
+      // if the best witness is default generic conditional conforming
+      // `func == <T : RawRepresentable>(lhs: T, rhs: T) -> Bool where
+      // T.RawValue : Equatable` let's return as missing and derive
+      // the conformance since it is possible.
+      if (isRawRepresentableGenericFunction(ctx, witness, Conformance)) {
+        return ResolveWitnessResult::Missing;
+      }
+    }
+
     // If the name didn't actually line up, complain.
     if (ignoringNames &&
         requirement->getName() != best.Witness->getName() &&

test/SILGen/enum_equatable_witness.swift

@@ -0,0 +1,70 @@
+// RUN: %target-swift-emit-silgen -module-name main %s -verify | %FileCheck %s
+// SR-9425
+enum MyState : String {
+    case closed = "closed"
+    case opened = "opened"
+}
+
+@inline(never)
+func check_state(_ state : MyState) -> Int {
+  // CHECK: function_ref @$s4main7MyStateO21__derived_enum_equalsySbAC_ACtFZ
+  return state == .opened ? 1 : 0
+}
+
+// generic-enum.swift
+enum GenericMyState<T> : String {
+  case closed
+  case opened
+}
+
+@inline(never)
+func check_generic_state(_ state : GenericMyState<Int>) -> Int {
+  // CHECK: function_ref @$s4main14GenericMyStateO21__derived_enum_equalsySbACyxG_AEtFZ
+  return state == .opened ? 1 : 0
+}
+
+// regular-enum.swift
+enum Regular {
+  case closed
+  case opened
+}
+
+@inline(never)
+func check_regular(_ state : Regular) -> Int {
+  // CHECK: function_ref @$s4main7RegularO21__derived_enum_equalsySbAC_ACtFZ
+  return state == .closed ? 1 : 0
+}
+
+// string-enum.swift
+enum Alphabet : String {
+  case A = "A", B = "B", C = "C", D = "D", E = "E", F = "F", G = "G", H = "H", I = "I", J = "J"
+}
+
+@inline(never)
+func check_alphabet(_ state : Alphabet) -> Int {
+  // CHECK: function_ref @$s4main8AlphabetO21__derived_enum_equalsySbAC_ACtFZ
+  return state == .E ? 1 : 0
+}
+
+@inline(never)
+func compareIt(_ state : Alphabet, _ rhs: Alphabet) -> Bool {
+  // CHECK: function_ref @$s4main8AlphabetO21__derived_enum_equalsySbAC_ACtFZ
+  return state == rhs
+}
+
+// int-enum.swift
+enum AlphabetInt : Int {
+  case A = 10, B = 100, C = 12, D = 456, E = 1, F = 3, G = 77, H = 2, I = 27, J = 42
+}
+
+@inline(never)
+func check_alphabet_int(_ state : AlphabetInt) -> Int {
+  // CHECK: function_ref @$s4main11AlphabetIntO21__derived_enum_equalsySbAC_ACtFZ
+  return state == .E ? 1 : 0
+}
+
+@inline(never)
+func compareIt(_ state : AlphabetInt, _ rhs: AlphabetInt) -> Bool {
+  // CHECK: function_ref @$s4main11AlphabetIntO21__derived_enum_equalsySbAC_ACtFZ
+  return state == rhs
+}

test/SILGen/opaque_ownership.swift

@@ -150,13 +150,33 @@ public struct Int64 : ExpressibleByIntegerLiteral, _ExpressibleByBuiltinIntegerL
   }
 }
 
+public struct Int : _ExpressibleByBuiltinIntegerLiteral, ExpressibleByIntegerLiteral, Equatable {
+  var _value: Builtin.Int64
+  public init() {
+    self = 0
+  }
+  public typealias IntegerLiteralType = Int
+  public init(_builtinIntegerLiteral x: _MaxBuiltinIntegerType) {
+    _value = Builtin.s_to_s_checked_trunc_IntLiteral_Int64(x).0
+  }
+
+  public init(integerLiteral value: Int) {
+    self = value
+  }
+
+  public static func ==(_ lhs: Int, rhs: Int) -> Bool {
+    return Bool(Builtin.cmp_eq_Int64(lhs._value, rhs._value))
+  }
+}
+
 // Test ownership of multi-case Enum values in the context of to @in thunks.
 // ---
 // CHECK-LABEL: sil shared [transparent] [serialized] [thunk] [ossa] @$ss17FloatingPointSignOSQsSQ2eeoiySbx_xtFZTW :
 // CHECK: bb0(%0 : $FloatingPointSign, %1 : $FloatingPointSign, %2 : $@thick FloatingPointSign.Type):
-// CHECK:   %3 = function_ref @$ss2eeoiySbx_xtSYRzSQ8RawValueRpzlF : $@convention(thin) <τ_0_0 where τ_0_0 : RawRepresentable, τ_0_0.RawValue : Equatable> (@in_guaranteed τ_0_0, @in_guaranteed τ_0_0) -> Bool
-// CHECK:   %4 = apply %3<FloatingPointSign>(%0, %1) : $@convention(thin) <τ_0_0 where τ_0_0 : RawRepresentable, τ_0_0.RawValue : Equatable> (@in_guaranteed τ_0_0, @in_guaranteed τ_0_0) -> Bool
-// CHECK:   return %4 : $Bool
+// CHECK:   %3 = metatype $@thin FloatingPointSign.Type // user: %5
+// CHECK:   %4 = function_ref @$ss17FloatingPointSignO21__derived_enum_equalsySbAB_ABtFZ : $@convention(method) (FloatingPointSign, FloatingPointSign, @thin FloatingPointSign.Type) -> Bool // user: %5
+// CHECK:   %5 = apply %4(%0, %1, %3) : $@convention(method) (FloatingPointSign, FloatingPointSign, @thin FloatingPointSign.Type) -> Bool // user: %6
+// CHECK:   return %5 : $Bool
 // CHECK-LABEL: } // end sil function '$ss17FloatingPointSignOSQsSQ2eeoiySbx_xtFZTW'
 public enum FloatingPointSign: Int64 {
   /// The sign for a positive value.

test/api-digester/Outputs/cake-abi.json

@@ -541,6 +541,37 @@
           "moduleName": "cake",
           "fixedbinaryorder": 0
         },
+        {
+          "kind": "Function",
+          "name": "__derived_enum_equals",
+          "printedName": "__derived_enum_equals(_:_:)",
+          "children": [
+            {
+              "kind": "TypeNominal",
+              "name": "Bool",
+              "printedName": "Swift.Bool",
+              "usr": "s:Sb"
+            },
+            {
+              "kind": "TypeNominal",
+              "name": "Number",
+              "printedName": "cake.Number",
+              "usr": "s:4cake6NumberO"
+            },
+            {
+              "kind": "TypeNominal",
+              "name": "Number",
+              "printedName": "cake.Number",
+              "usr": "s:4cake6NumberO"
+            }
+          ],
+          "declKind": "Func",
+          "usr": "s:4cake6NumberO21__derived_enum_equalsySbAC_ACtFZ",
+          "moduleName": "cake",
+          "static": true,
+          "implicit": true,
+          "funcSelfKind": "NonMutating"
+        },
         {
           "kind": "Constructor",
           "name": "init",

test/api-digester/Outputs/cake.json

@@ -544,6 +544,37 @@
           "usr": "s:4cake6NumberO3oneyA2CmF",
           "moduleName": "cake"
         },
+        {
+          "kind": "Function",
+          "name": "__derived_enum_equals",
+          "printedName": "__derived_enum_equals(_:_:)",
+          "children": [
+            {
+              "kind": "TypeNominal",
+              "name": "Bool",
+              "printedName": "Swift.Bool",
+              "usr": "s:Sb"
+            },
+            {
+              "kind": "TypeNominal",
+              "name": "Number",
+              "printedName": "cake.Number",
+              "usr": "s:4cake6NumberO"
+            },
+            {
+              "kind": "TypeNominal",
+              "name": "Number",
+              "printedName": "cake.Number",
+              "usr": "s:4cake6NumberO"
+            }
+          ],
+          "declKind": "Func",
+          "usr": "s:4cake6NumberO21__derived_enum_equalsySbAC_ACtFZ",
+          "moduleName": "cake",
+          "static": true,
+          "implicit": true,
+          "funcSelfKind": "NonMutating"
+        },
         {
           "kind": "Constructor",
           "name": "init",