Merge pull request #13253 from DougGregor/se-0143-remove-assertions

[SE-0143] Eliminate assertions blocking the use of conditional conformances

Author: DougGregor

lib/Sema/CSApply.cpp

@@ -161,8 +161,6 @@ static DeclTy *findNamedWitnessImpl(
     if (!conformance)
       return nullptr;
   }
-  assert(conformance->getConditionalRequirements().empty() &&
-         "unhandled conditional conformance");
 
   // For a type with dependent conformance, just return the requirement from
   // the protocol. There are no protocol conformance tables.
@@ -6608,8 +6606,6 @@ Expr *ExprRewriter::convertLiteral(Expr *literal,
   auto conformance = tc.conformsToProtocol(type, protocol, cs.DC,
                                            ConformanceCheckFlags::InExpression);
   assert(conformance && "must conform to literal protocol");
-  assert(conformance->getConditionalRequirements().empty() &&
-         "unexpected conditional requirements");
 
   // Figure out the (non-builtin) argument type if there is one.
   Type argType;
@@ -6752,8 +6748,6 @@ Expr *ExprRewriter::convertLiteralInPlace(Expr *literal,
   auto conformance = tc.conformsToProtocol(type, protocol, cs.DC,
                                            ConformanceCheckFlags::InExpression);
   assert(conformance && "must conform to literal protocol");
-  assert(conformance->getConditionalRequirements().empty() &&
-         "unexpected conditional requirements");
 
   // Dig out the literal type and perform a builtin literal conversion to it.
   if (!literalType.empty()) {

lib/Sema/TypeCheckDecl.cpp

@@ -3002,13 +3002,7 @@ static void checkEnumRawValues(TypeChecker &TC, EnumDecl *ED) {
     // primitive literal protocols.
     auto conformsToProtocol = [&](KnownProtocolKind protoKind) {
         ProtocolDecl *proto = TC.getProtocol(ED->getLoc(), protoKind);
-        auto conformance =
-            TC.conformsToProtocol(rawTy, proto, ED->getDeclContext(), None);
-        if (conformance)
-          assert(conformance->getConditionalRequirements().empty() &&
-                 "conditionally conforming to literal protocol not currently "
-                 "supported");
-        return conformance;
+        return TC.conformsToProtocol(rawTy, proto, ED->getDeclContext(), None);
     };
 
     static auto otherLiteralProtocolKinds = {

lib/Sema/TypeCheckProtocol.cpp

@@ -6209,9 +6209,6 @@ void TypeChecker::useBridgedNSErrorConformances(DeclContext *dc, Type type) {
                      (ConformanceCheckFlags::SuppressDependencyTracking|
                       ConformanceCheckFlags::Used));
   if (conformance && conformance->isConcrete()) {
-    assert(conformance->getConditionalRequirements().empty() &&
-           "cannot conform condtionally to _ErrorCodeProtocol");
-
     if (Type errorType = ProtocolConformanceRef::getTypeWitnessByName(
           type, *conformance, Context.Id_ErrorType, this)) {
       (void)conformsToProtocol(errorType, bridgedStoredNSError, dc,

lib/Sema/TypeCheckStmt.cpp

@@ -670,9 +670,6 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
                             sequence->getLoc());
     if (!genConformance)
       return nullptr;
-    assert(
-        genConformance->getConditionalRequirements().empty() &&
-        "conditionally conforming to IteratorProtocol not currently supported");
 
     Type elementTy = TC.getWitnessType(generatorTy, generatorProto,
                                        *genConformance, TC.Context.Id_Element,

test/Constraints/array_literal.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -enable-experimental-conditional-conformances
 
 struct IntList : ExpressibleByArrayLiteral {
   typealias Element = Int
@@ -322,3 +322,21 @@ let routerFruit = Company(
 //        accident.
 let SR3786a: [Int] = [1, 2, 3]
 let SR3786aa = [SR3786a.reversed(), SR3786a]
+
+// Conditional conformance
+protocol P { }
+
+struct PArray<T> { }
+
+extension PArray : ExpressibleByArrayLiteral where T: P {
+  typealias ArrayLiteralElement = T
+
+  init(arrayLiteral elements: T...) { }
+}
+
+extension Int: P { }
+
+func testConditional(i: Int, s: String) {
+  let _: PArray<Int> = [i, i, i]
+  let _: PArray<String> = [s, s, s] // expected-error{{contextual type 'PArray<String>' cannot be used with array literal}}
+}

test/stmt/foreach.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -enable-experimental-conditional-conformances
 
 // Bad containers and ranges
 struct BadContainer1 {
@@ -178,3 +178,42 @@ func testExistentialSequence(s: Sequence) { // expected-error {{protocol 'Sequen
     _ = x
   }
 }
+
+// Conditional conformance to Sequence and IteratorProtocol.
+protocol P { }
+
+struct RepeatedSequence<T> {
+  var value: T
+  var count: Int
+}
+
+struct RepeatedIterator<T> {
+  var value: T
+  var count: Int
+}
+
+extension RepeatedIterator: IteratorProtocol where T: P {
+  typealias Element = T
+
+  mutating func next() -> T? {
+    if count == 0 { return nil }
+    count = count - 1
+    return value
+  }
+}
+
+extension RepeatedSequence: Sequence where T: P {
+  typealias Element = T
+  typealias Iterator = RepeatedIterator<T>
+  typealias SubSequence = AnySequence<T>
+
+  func makeIterator() -> RepeatedIterator<T> {
+    return Iterator(value: value, count: count)
+  }
+}
+
+extension Int : P { }
+
+func testRepeated(ri: RepeatedSequence<Int>) {
+  for x in ri { _ = x }
+}