Revert "Allow a witness's noescape parameter to match a requirement's escaping parameter"

This reverts commit 44e230b.

Author: gottesmm

lib/Sema/TypeCheckProtocol.cpp

@@ -138,17 +138,6 @@ static std::tuple<Type, Type, OptionalAdjustmentKind>
 getTypesToCompare(ValueDecl *reqt, Type reqtType, bool reqtTypeIsIUO,
                   Type witnessType, bool witnessTypeIsIUO,
                   VarianceKind variance) {
-  // If the witness type is noescape but the requirement type is not,
-  // adjust the witness type to be escaping. This permits a limited form of
-  // covariance.
-  bool reqNoescapeToEscaping = false;
-  (void)adjustInferredAssociatedType(reqtType, reqNoescapeToEscaping);
-  bool witnessNoescapeToEscaping = false;
-  Type adjustedWitnessType =
-    adjustInferredAssociatedType(witnessType, witnessNoescapeToEscaping);
-  if (witnessNoescapeToEscaping && !reqNoescapeToEscaping)
-    witnessType = adjustedWitnessType;
-
   // For @objc protocols, deal with differences in the optionality.
   // FIXME: It probably makes sense to extend this to non-@objc
   // protocols as well, but this requires more testing.
@@ -163,7 +152,8 @@ getTypesToCompare(ValueDecl *reqt, Type reqtType, bool reqtTypeIsIUO,
     reqtType = reqtValueType;
   }
   bool witnessIsOptional = false;
-  if (Type witnessValueType = witnessType->getOptionalObjectType()) {
+  if (Type witnessValueType =
+      witnessType->getOptionalObjectType()) {
     witnessIsOptional = true;
     witnessType = witnessValueType;
   }

lib/Sema/TypeCheckProtocol.h

@@ -852,13 +852,6 @@ RequirementMatch matchWitness(TypeChecker &tc,
 AssociatedTypeDecl *getReferencedAssocTypeOfProtocol(Type type,
                                                      ProtocolDecl *proto);
 
-/// Perform any necessary adjustments to the inferred associated type to
-/// make it suitable for later use.
-///
-/// \param noescapeToEscaping Will be set \c true if this operation performed
-/// the noescape-to-escaping adjustment.
-Type adjustInferredAssociatedType(Type type, bool &noescapeToEscaping);
-
 }
 
 #endif // SWIFT_SEMA_PROTOCOL_H

lib/Sema/TypeCheckProtocolInference.cpp

@@ -607,11 +607,13 @@ AssociatedTypeInference::inferTypeWitnessesViaAssociatedType(
   return result;
 }
 
-Type swift::adjustInferredAssociatedType(Type type, bool &noescapeToEscaping) {
+/// Perform any necessary adjustments to the inferred associated type to
+/// make it suitable for later use.
+static Type adjustInferredAssociatedType(Type type) {
   // If we have an optional type, adjust its wrapped type.
   if (auto optionalObjectType = type->getOptionalObjectType()) {
     auto newOptionalObjectType =
-      adjustInferredAssociatedType(optionalObjectType, noescapeToEscaping);
+      adjustInferredAssociatedType(optionalObjectType);
     if (newOptionalObjectType.getPointer() == optionalObjectType.getPointer())
       return type;
 
@@ -621,11 +623,14 @@ Type swift::adjustInferredAssociatedType(Type type, bool &noescapeToEscaping) {
   // If we have a noescape function type, make it escaping.
   if (auto funcType = type->getAs<FunctionType>()) {
     if (funcType->isNoEscape()) {
-      noescapeToEscaping = true;
       return FunctionType::get(funcType->getParams(), funcType->getResult(),
                                funcType->getExtInfo().withNoEscape(false));
     }
   }
+
+  // We can only infer materializable types.
+  if (!type->isMaterializable()) return nullptr;
+
   return type;
 }
 
@@ -684,11 +689,8 @@ AssociatedTypeInference::inferTypeWitnessesViaValueWitness(ValueDecl *req,
       if (secondType->hasError())
         return true;
 
-      // Adjust the type to a type that can be written explicitly.
-      bool noescapeToEscaping = false;
-      Type inferredType =
-        adjustInferredAssociatedType(secondType, noescapeToEscaping);
-      if (!inferredType->isMaterializable())
+      Type inferredType = adjustInferredAssociatedType(secondType);
+      if (!inferredType)
         return true;
 
       auto proto = Conformance->getProtocol();

test/SILGen/witnesses.swift

@@ -510,16 +510,3 @@ class CrashableBase {
 // CHECK-NEXT: return [[RESULT]] : $()
 
 class GenericCrashable<T> : CrashableBase, Crashable {}
-
-// rdar://problem/35297911: allow witness with a noescape parameter to
-// match a requirement with an escaping paameter.
-protocol EscapingReq {
-  func f(_: @escaping (Int) -> Int)
-}
-
-// CHECK-LABEL: sil private [transparent] [thunk] @$S9witnesses18EscapingCovarianceVAA0B3ReqA2aDP1fyyS2icFTW : $@convention(witness_method: EscapingReq) (@owned @callee_guaranteed (Int) -> Int, @in_guaranteed EscapingCovariance) -> ()
-// CHECK-NOT: return
-// CHECK: convert_escape_to_noescape %0
-struct EscapingCovariance: EscapingReq {
-  func f(_: (Int) -> Int) { }
-}

test/decl/protocol/conforms/associated_type.swift

@@ -38,6 +38,8 @@ protocol P1 {
   associatedtype A
 
   func f(_: A)
+  // expected-note@-1 {{protocol requires function 'f' with type '(X1c.A) -> ()' (aka '((Int) -> Int) -> ()'); do you want to add a stub?}}
+  // expected-note@-2 {{protocol requires function 'f' with type '((Int) -> Int) -> ()'; do you want to add a stub?}}
 }
 
 struct X1a : P1 {
@@ -50,24 +52,12 @@ struct X1b : P1 {
   func f(_: @escaping (Int) -> Int) { }
 }
 
-struct X1c : P1 {
+struct X1c : P1 { // expected-error{{type 'X1c' does not conform to protocol 'P1'}}
   typealias A = (Int) -> Int
 
-  func f(_: (Int) -> Int) { }
+  func f(_: (Int) -> Int) { } // expected-note{{candidate has non-matching type '((Int) -> Int) -> ()'}}
 }
 
-struct X1d : P1 {
-  func f(_: (Int) -> Int) { }
-}
-
-protocol P2 {
-  func f(_: (Int) -> Int) // expected-note{{protocol requires function 'f' with type '((Int) -> Int) -> ()'; do you want to add a stub?}}
-}
-
-struct X2a : P2 {
-  func f(_: (Int) -> Int) { }
-}
-
-struct X2b : P2 { // expected-error{{type 'X2b' does not conform to protocol 'P2'}}
-  func f(_: @escaping (Int) -> Int) { } // expected-note{{candidate has non-matching type '(@escaping (Int) -> Int) -> ()'}}
+struct X1d : P1 { // expected-error{{type 'X1d' does not conform to protocol 'P1'}}
+  func f(_: (Int) -> Int) { } // expected-note{{candidate has non-matching type '((Int) -> Int) -> ()' [with A = (Int) -> Int]}}
 }