[CS] A couple of fixes for implicit callAsFunction

include/swift/AST/TypeCheckRequests.h

@@ -1910,6 +1910,26 @@ class CallerSideDefaultArgExprRequest
   void cacheResult(Expr *expr) const;
 };
 
+/// Computes whether this is a type that supports being called through the
+/// implementation of a \c callAsFunction method.
+class IsCallableNominalTypeRequest
+    : public SimpleRequest<IsCallableNominalTypeRequest,
+                           bool(CanType, DeclContext *), CacheKind::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  // Evaluation.
+  llvm::Expected<bool> evaluate(Evaluator &evaluator, CanType ty,
+                                DeclContext *dc) const;
+
+public:
+  // Cached.
+  bool isCached() const { return true; }
+};
+
 // Allow AnyValue to compare two Type values, even though Type doesn't
 // support ==.
 template<>

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -88,6 +88,8 @@ SWIFT_REQUEST(TypeChecker, InterfaceTypeRequest,
               Type(ValueDecl *), SeparatelyCached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, IsAccessorTransparentRequest, bool(AccessorDecl *),
               SeparatelyCached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, IsCallableNominalTypeRequest,
+              bool(CanType, DeclContext *), Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, IsDynamicRequest, bool(ValueDecl *),
               SeparatelyCached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, IsFinalRequest, bool(ValueDecl *), SeparatelyCached,

include/swift/AST/Types.h

@@ -818,6 +818,11 @@ class alignas(1 << TypeAlignInBits) TypeBase {
             getAnyNominal());
   }
 
+  /// Checks whether this is a type that supports being called through the
+  /// implementation of a \c callAsFunction method. Note that this does not
+  /// check access control.
+  bool isCallableNominalType(DeclContext *dc);
+
   /// Retrieve the superclass of this type.
   ///
   /// \param useArchetypes Whether to use context archetypes for outer generic

lib/AST/Type.cpp

@@ -1480,6 +1480,21 @@ bool TypeBase::satisfiesClassConstraint() {
   return mayHaveSuperclass() || isObjCExistentialType();
 }
 
+bool TypeBase::isCallableNominalType(DeclContext *dc) {
+  // Don't allow callAsFunction to be used with dynamic lookup.
+  if (isAnyObject())
+    return false;
+
+  // If the type cannot have members, we're done.
+  if (!mayHaveMembers())
+    return false;
+
+  auto canTy = getCanonicalType();
+  auto &ctx = canTy->getASTContext();
+  return evaluateOrDefault(ctx.evaluator,
+                           IsCallableNominalTypeRequest{canTy, dc}, false);
+}
+
 Type TypeBase::getSuperclass(bool useArchetypes) {
   auto *nominalDecl = getAnyNominal();
   auto *classDecl = dyn_cast_or_null<ClassDecl>(nominalDecl);

lib/Sema/CSApply.cpp

@@ -6495,12 +6495,10 @@ static bool isValidDynamicCallableMethod(FuncDecl *method,
   return true;
 }
 
-// Resolve `callAsFunction` method applications.
-static Expr *finishApplyCallAsFunctionMethod(
+// Build a reference to a `callAsFunction` method.
+static Expr *buildCallAsFunctionMethodRef(
     ExprRewriter &rewriter, ApplyExpr *apply, SelectedOverload selected,
-    AnyFunctionType *openedMethodType,
     ConstraintLocatorBuilder applyFunctionLoc) {
-  auto &cs = rewriter.cs;
   auto *fn = apply->getFn();
   auto choice = selected.choice;
   // Create direct reference to `callAsFunction` method.
@@ -6512,21 +6510,7 @@ static Expr *finishApplyCallAsFunctionMethod(
   if (!declRef)
     return nullptr;
   declRef->setImplicit(apply->isImplicit());
-  apply->setFn(declRef);
-  // Coerce argument to input type of the `callAsFunction` method.
-  auto callee = rewriter.resolveConcreteDeclRef(choice.getDecl(),
-                                                applyFunctionLoc);
-  SmallVector<Identifier, 2> argLabelsScratch;
-  auto *arg = rewriter.coerceCallArguments(
-      apply->getArg(), openedMethodType, callee, apply,
-      apply->getArgumentLabels(argLabelsScratch), apply->hasTrailingClosure(),
-      applyFunctionLoc);
-  if (!arg)
-    return nullptr;
-  apply->setArg(arg);
-  cs.setType(apply, openedMethodType->getResult());
-  cs.cacheExprTypes(apply);
-  return apply;
+  return declRef;
 }
 
 // Resolve `@dynamicCallable` applications.
@@ -6768,12 +6752,19 @@ Expr *ExprRewriter::finishApply(ApplyExpr *apply, ConcreteDeclRef callee,
     auto methodType =
         simplifyType(selected->openedType)->getAs<AnyFunctionType>();
     if (method && methodType) {
-      if (method->isCallAsFunctionMethod())
-        return finishApplyCallAsFunctionMethod(
-            *this, apply, *selected, methodType, applyFunctionLoc);
-      if (methodType && isValidDynamicCallableMethod(method, methodType))
+      // Handle a call to a @dynamicCallable method.
+      if (isValidDynamicCallableMethod(method, methodType))
         return finishApplyDynamicCallable(
             apply, *selected, method, methodType, applyFunctionLoc);
+
+      // If this is an implicit call to a callAsFunction method, build the
+      // appropriate member reference.
+      if (method->isCallAsFunctionMethod()) {
+        fn = buildCallAsFunctionMethodRef(*this, apply, *selected,
+                                          applyFunctionLoc);
+        if (!fn)
+          return nullptr;
+      }
     }
   }
 

lib/Sema/CSDiag.cpp

@@ -2616,13 +2616,7 @@ bool FailureDiagnosis::visitApplyExpr(ApplyExpr *callExpr) {
     auto isDynamicCallable =
         CS.DynamicCallableCache[fnType->getCanonicalType()].isValid();
 
-    // Note: Consider caching `hasCallAsFunctionMethods` in `NominalTypeDecl`.
-    auto *nominal = fnType->getAnyNominal();
-    auto hasCallAsFunctionMethods = nominal &&
-      llvm::any_of(nominal->getMembers(), [](Decl *member) {
-          auto funcDecl = dyn_cast<FuncDecl>(member);
-          return funcDecl && funcDecl->isCallAsFunctionMethod();
-        });
+    auto hasCallAsFunctionMethods = fnType->isCallableNominalType(CS.DC);
 
     // Diagnose specific @dynamicCallable errors.
     if (isDynamicCallable) {

lib/Sema/CSSimplify.cpp

@@ -7334,20 +7334,16 @@ ConstraintSystem::simplifyApplicableFnConstraint(
   // Handle applications of types with `callAsFunction` methods.
   // Do this before stripping optional types below, when `shouldAttemptFixes()`
   // is true.
-  auto hasCallAsFunctionMethods =
-      desugar2->mayHaveMembers() &&
-      llvm::any_of(lookupMember(desugar2, DeclName(ctx.Id_callAsFunction)),
-                   [](LookupResultEntry entry) {
-                     return isa<FuncDecl>(entry.getValueDecl());
-                   });
-  if (hasCallAsFunctionMethods) {
+  if (desugar2->isCallableNominalType(DC)) {
     auto memberLoc = getConstraintLocator(
         outerLocator.withPathElement(ConstraintLocator::Member));
     // Add a `callAsFunction` member constraint, binding the member type to a
     // type variable.
     auto memberTy = createTypeVariable(memberLoc, /*options=*/0);
     // TODO: Revisit this if `static func callAsFunction` is to be supported.
     // Static member constraint requires `FunctionRefKind::DoubleApply`.
+    // TODO: Use a custom locator element to identify this member constraint
+    // instead of just pointing to the function expr.
     addValueMemberConstraint(origLValueType2, DeclName(ctx.Id_callAsFunction),
                              memberTy, DC, FunctionRefKind::SingleApply,
                              /*outerAlternatives*/ {}, locator);

lib/Sema/ConstraintSystem.cpp

@@ -478,17 +478,29 @@ ConstraintSystem::getCalleeLocator(ConstraintLocator *locator,
   if (lookThroughApply) {
     if (auto *applyExpr = dyn_cast<ApplyExpr>(anchor)) {
       auto *fnExpr = applyExpr->getFn();
+
+      // FIXME: We should probably assert that we don't get a type variable
+      // here to make sure we only retrieve callee locators for resolved calls,
+      // ensuring that callee locators don't change after binding a type.
+      // Unfortunately CSDiag currently calls into getCalleeLocator, so all bets
+      // are off. Once we remove that legacy diagnostic logic, we should be able
+      // to assert here.
+      auto fnTy = getFixedTypeRecursive(getType(fnExpr), /*wantRValue*/ true);
+
       // For an apply of a metatype, we have a short-form constructor. Unlike
       // other locators to callees, these are anchored on the apply expression
       // rather than the function expr.
-      auto fnTy = getFixedTypeRecursive(getType(fnExpr), /*wantRValue*/ true);
       if (fnTy->is<AnyMetatypeType>()) {
         auto *fnLocator =
             getConstraintLocator(applyExpr, ConstraintLocator::ApplyFunction);
         return getConstraintLocator(fnLocator,
                                     ConstraintLocator::ConstructorMember);
       }
 
+      // Handle an apply of a nominal type which supports callAsFunction.
+      if (fnTy->isCallableNominalType(DC))
+        return getConstraintLocator(anchor, ConstraintLocator::ApplyFunction);
+
       // Otherwise fall through and look for locators anchored on the function
       // expr. For CallExprs, this can look through things like parens and
       // optional chaining.

lib/Sema/TypeCheckConstraints.cpp

@@ -36,6 +36,7 @@
 #include "swift/AST/ProtocolConformance.h"
 #include "swift/AST/SubstitutionMap.h"
 #include "swift/AST/TypeCheckerDebugConsumer.h"
+#include "swift/AST/TypeCheckRequests.h"
 #include "swift/Basic/Statistic.h"
 #include "swift/Parse/Confusables.h"
 #include "swift/Parse/Lexer.h"
@@ -4569,3 +4570,22 @@ ForcedCheckedCastExpr *swift::findForcedDowncast(ASTContext &ctx, Expr *expr) {
 
   return nullptr;
 }
+
+llvm::Expected<bool>
+IsCallableNominalTypeRequest::evaluate(Evaluator &evaluator, CanType ty,
+                                       DeclContext *dc) const {
+  auto options = defaultMemberLookupOptions;
+  options |= NameLookupFlags::IgnoreAccessControl;
+  if (isa<AbstractFunctionDecl>(dc))
+    options |= NameLookupFlags::KnownPrivate;
+
+  // Look for a callAsFunction method.
+  auto &ctx = ty->getASTContext();
+  auto results =
+      TypeChecker::lookupMember(dc, ty, ctx.Id_callAsFunction, options);
+  return llvm::any_of(results, [](LookupResultEntry entry) -> bool {
+    if (auto *fd = dyn_cast<FuncDecl>(entry.getValueDecl()))
+      return fd->isCallAsFunctionMethod();
+    return false;
+  });
+}

test/Constraints/dynamic_lookup.swift

@@ -398,3 +398,13 @@ class HasMethodWithDefault {
 func testAnyObjectWithDefault(_ x: AnyObject) {
   x.hasDefaultParam()
 }
+
+// SR-11829: Don't perform dynamic lookup for callAsFunction.
+class ClassWithObjcCallAsFunction {
+  @objc func callAsFunction() {}
+}
+
+func testCallAsFunctionAnyObject(_ x: AnyObject) {
+  x() // expected-error {{cannot call value of non-function type 'AnyObject'}}
+  x.callAsFunction() // Okay.
+}

test/SILGen/default_arguments.swift

@@ -408,3 +408,26 @@ func genericMagic<T : ExpressibleByStringLiteral>(x: T = #file) -> T {
 }
 
 let _: String = genericMagic()
+
+// SR-11778
+struct CallableWithDefault {
+  func callAsFunction(x: Int = 4) {}
+  func callAsFunction(y: Int, z: String = #function) {}
+}
+
+// CHECK-LABEL: sil hidden [ossa] @$s17default_arguments23testCallableWithDefaultyyAA0deF0VF : $@convention(thin) (CallableWithDefault) -> ()
+func testCallableWithDefault(_ x: CallableWithDefault) {
+  // CHECK: [[DEF_FN:%[0-9]+]] = function_ref @$s17default_arguments19CallableWithDefaultV14callAsFunction1xySi_tFfA_ : $@convention(thin) () -> Int
+  // CHECK: [[DEF:%[0-9]+]] = apply [[DEF_FN]]() : $@convention(thin) () -> Int
+  // CHECK: [[CALL_AS_FN:%[0-9]+]] = function_ref @$s17default_arguments19CallableWithDefaultV14callAsFunction1xySi_tF : $@convention(method) (Int, CallableWithDefault) -> ()
+  // CHECK: apply [[CALL_AS_FN]]([[DEF]], {{%[0-9]+}})
+  x()
+
+  // CHECK: [[RAW_I:%[0-9]+]] = integer_literal $Builtin.IntLiteral, 5
+  // CHECK: [[I:%[0-9]+]] = apply {{%[0-9]+}}([[RAW_I]], {{%[0-9]+}}) : $@convention(method) (Builtin.IntLiteral, @thin Int.Type) -> Int
+  // CHECK: [[RAW_STR:%[0-9]+]] = string_literal utf8 "testCallableWithDefault(_:)"
+  // CHECK: [[STR:%[0-9]+]] = apply {{%[0-9]+}}([[RAW_STR]], {{%[0-9]+}}, {{%[0-9]+}}, {{%[0-9]+}}) : $@convention(method) (Builtin.RawPointer, Builtin.Word, Builtin.Int1, @thin String.Type) -> @owned String
+  // CHECK: [[CALL_AS_FN:%[0-9]+]] = function_ref @$s17default_arguments19CallableWithDefaultV14callAsFunction1y1zySi_SStF : $@convention(method) (Int, @guaranteed String, CallableWithDefault) -> ()
+  // CHECK: apply [[CALL_AS_FN]]([[I]], [[STR]], {{%[0-9]+}})
+  x(y: 5)
+}

test/Sema/call_as_function_generic.swift

@@ -41,3 +41,19 @@ let genericString = GenericType<[String]>(collection: ["Hello", "world", "!"])
 _ = genericString("Hello")
 let genericInt = GenericType<Set<Int>>(collection: [1, 2, 3])
 _ = genericInt(initialValue: 1)
+
+// SR-11386
+class C<T> {}
+protocol P1 {}
+extension C where T : P1 { // expected-note {{where 'T' = 'Int'}}
+  func callAsFunction(t: T) {}
+}
+
+struct S0 : P1 {}
+
+func testCallAsFunctionWithWhereClause(_ c1: C<Int>, _ c2: C<S0>, _ s0: S0) {
+  c1(42) // expected-error {{referencing instance method 'callAsFunction(t:)' on 'C' requires that 'Int' conform to 'P1'}}
+  // expected-error@-1 {{missing argument label 't:' in call}}
+
+  c2(t: s0) // Okay.
+}

test/Sema/call_as_function_simple.swift

@@ -192,3 +192,39 @@ func testIUO(a: SimpleCallable!, b: MultipleArgsCallable!, c: Extended!,
   _ = try? h()
   _ = try? h { throw DummyError() }
 }
+
+// SR-11778
+struct DoubleANumber {
+  func callAsFunction(_ x: Int, completion: (Int) -> Void = { _ in }) {
+    completion(x + x)
+  }
+}
+
+func testDefaults(_ x: DoubleANumber) {
+  x(5)
+  x(5, completion: { _ in })
+}
+
+// SR-11881
+struct IUOCallable {
+  static var callable: IUOCallable { IUOCallable() }
+  func callAsFunction(_ x: Int) -> IUOCallable! { nil }
+}
+
+func testIUOCallAsFunction(_ x: IUOCallable) {
+  let _: IUOCallable = x(5)
+  let _: IUOCallable? = x(5)
+  let _ = x(5)
+
+  let _: IUOCallable = .callable(5)
+  let _: IUOCallable? = .callable(5)
+}
+
+// Test access control.
+struct PrivateCallable {
+  private func callAsFunction(_ x: Int) {} // expected-note {{'callAsFunction' declared here}}
+}
+
+func testAccessControl(_ x: PrivateCallable) {
+  x(5) // expected-error {{'callAsFunction' is inaccessible due to 'private' protection level}}
+}