[5.9][ConstraintSystem] Fix a couple of issues related to generic specialization

include/swift/Sema/CSFix.h

@@ -454,6 +454,13 @@ enum class FixKind : uint8_t {
   /// Ignore the fact that member couldn't be referenced within init accessor
   /// because its name doesn't appear in 'initializes' or 'accesses' attributes.
   AllowInvalidMemberReferenceInInitAccessor,
+
+  /// Ignore an attempt to specialize non-generic type.
+  AllowConcreteTypeSpecialization,
+
+  /// Ignore situations when provided number of generic arguments didn't match
+  /// expected number of parameters.
+  IgnoreGenericSpecializationArityMismatch,
 };
 
 class ConstraintFix {
@@ -3647,6 +3654,69 @@ class AllowInvalidMemberReferenceInInitAccessor final : public ConstraintFix {
   }
 };
 
+class AllowConcreteTypeSpecialization final : public ConstraintFix {
+  Type ConcreteType;
+
+  AllowConcreteTypeSpecialization(ConstraintSystem &cs, Type concreteTy,
+                                  ConstraintLocator *locator)
+      : ConstraintFix(cs, FixKind::AllowConcreteTypeSpecialization, locator),
+        ConcreteType(concreteTy) {}
+
+public:
+  std::string getName() const override {
+    return "allow concrete type specialization";
+  }
+
+  bool diagnose(const Solution &solution, bool asNote = false) const override;
+
+  bool diagnoseForAmbiguity(CommonFixesArray commonFixes) const override {
+    return diagnose(*commonFixes.front().first);
+  }
+
+  static AllowConcreteTypeSpecialization *
+  create(ConstraintSystem &cs, Type concreteTy, ConstraintLocator *locator);
+
+  static bool classof(const ConstraintFix *fix) {
+    return fix->getKind() == FixKind::AllowConcreteTypeSpecialization;
+  }
+};
+
+class IgnoreGenericSpecializationArityMismatch final : public ConstraintFix {
+  ValueDecl *D;
+  unsigned NumParams;
+  unsigned NumArgs;
+  bool HasParameterPack;
+
+  IgnoreGenericSpecializationArityMismatch(ConstraintSystem &cs,
+                                           ValueDecl *decl, unsigned numParams,
+                                           unsigned numArgs,
+                                           bool hasParameterPack,
+                                           ConstraintLocator *locator)
+      : ConstraintFix(cs, FixKind::IgnoreGenericSpecializationArityMismatch,
+                      locator),
+        D(decl), NumParams(numParams), NumArgs(numArgs),
+        HasParameterPack(hasParameterPack) {}
+
+public:
+  std::string getName() const override {
+    return "ignore generic specialization mismatch";
+  }
+
+  bool diagnose(const Solution &solution, bool asNote = false) const override;
+
+  bool diagnoseForAmbiguity(CommonFixesArray commonFixes) const override {
+    return diagnose(*commonFixes.front().first);
+  }
+
+  static IgnoreGenericSpecializationArityMismatch *
+  create(ConstraintSystem &cs, ValueDecl *decl, unsigned numParams,
+         unsigned numArgs, bool hasParameterPack, ConstraintLocator *locator);
+
+  static bool classof(const ConstraintFix *fix) {
+    return fix->getKind() == FixKind::IgnoreGenericSpecializationArityMismatch;
+  }
+};
+
 } // end namespace constraints
 } // end namespace swift
 

lib/Sema/CSDiagnostics.cpp

@@ -9101,3 +9101,14 @@ bool InvalidMemberReferenceWithinInitAccessor::diagnoseAsError() {
   emitDiagnostic(diag::init_accessor_invalid_member_ref, MemberName);
   return true;
 }
+
+bool ConcreteTypeSpecialization::diagnoseAsError() {
+  emitDiagnostic(diag::not_a_generic_type, ConcreteType);
+  return true;
+}
+
+bool InvalidTypeSpecializationArity::diagnoseAsError() {
+  emitDiagnostic(diag::type_parameter_count_mismatch, D->getBaseIdentifier(),
+                 NumParams, NumArgs, NumArgs < NumParams, HasParameterPack);
+  return true;
+}

lib/Sema/CSDiagnostics.h

@@ -3036,6 +3036,50 @@ class InvalidMemberReferenceWithinInitAccessor final
   bool diagnoseAsError() override;
 };
 
+/// Diagnose attempts to specialize a concrete type or its alias:
+///
+/// \code
+/// struct Test {}
+/// typealias X = Test
+///
+/// _ = X<Int>() // error
+/// \endcode
+class ConcreteTypeSpecialization final : public FailureDiagnostic {
+  Type ConcreteType;
+
+public:
+  ConcreteTypeSpecialization(const Solution &solution, Type concreteTy,
+                             ConstraintLocator *locator)
+      : FailureDiagnostic(solution, locator),
+        ConcreteType(resolveType(concreteTy)) {}
+
+  bool diagnoseAsError() override;
+};
+
+/// Diagnose attempts to specialize with invalid number of generic arguments:
+///
+/// \code
+/// struct Test<T, U> {}
+///
+/// _ = Test<Int>() // error
+/// \endcode
+class InvalidTypeSpecializationArity final : public FailureDiagnostic {
+  ValueDecl *D;
+  unsigned NumParams;
+  unsigned NumArgs;
+  bool HasParameterPack;
+
+public:
+  InvalidTypeSpecializationArity(const Solution &solution, ValueDecl *decl,
+                                 unsigned numParams, unsigned numArgs,
+                                 bool hasParameterPack,
+                                 ConstraintLocator *locator)
+      : FailureDiagnostic(solution, locator), D(decl), NumParams(numParams),
+        NumArgs(numArgs), HasParameterPack(hasParameterPack) {}
+
+  bool diagnoseAsError() override;
+};
+
 } // end namespace constraints
 } // end namespace swift
 

lib/Sema/CSFix.cpp

@@ -2837,3 +2837,34 @@ AllowInvalidMemberReferenceInInitAccessor::create(ConstraintSystem &cs,
   return new (cs.getAllocator())
       AllowInvalidMemberReferenceInInitAccessor(cs, memberName, locator);
 }
+
+bool AllowConcreteTypeSpecialization::diagnose(const Solution &solution,
+                                               bool asNote) const {
+  ConcreteTypeSpecialization failure(solution, ConcreteType, getLocator());
+  return failure.diagnose(asNote);
+}
+
+AllowConcreteTypeSpecialization *
+AllowConcreteTypeSpecialization::create(ConstraintSystem &cs, Type concreteTy,
+                                        ConstraintLocator *locator) {
+  return new (cs.getAllocator())
+      AllowConcreteTypeSpecialization(cs, concreteTy, locator);
+}
+
+bool IgnoreGenericSpecializationArityMismatch::diagnose(
+    const Solution &solution, bool asNote) const {
+  InvalidTypeSpecializationArity failure(solution, D, NumParams, NumArgs,
+                                         HasParameterPack, getLocator());
+  return failure.diagnose(asNote);
+}
+
+IgnoreGenericSpecializationArityMismatch *
+IgnoreGenericSpecializationArityMismatch::create(ConstraintSystem &cs,
+                                                 ValueDecl *decl,
+                                                 unsigned numParams,
+                                                 unsigned numArgs,
+                                                 bool hasParameterPack,
+                                                 ConstraintLocator *locator) {
+  return new (cs.getAllocator()) IgnoreGenericSpecializationArityMismatch(
+      cs, decl, numParams, numArgs, hasParameterPack, locator);
+}

lib/Sema/CSSimplify.cpp

@@ -13598,21 +13598,41 @@ ConstraintSystem::simplifyExplicitGenericArgumentsConstraint(
     }
 
     decl = overloadChoice.getDecl();
+
     auto openedOverloadTypes = getOpenedTypes(overloadLocator);
     openedTypes.append(openedOverloadTypes.begin(), openedOverloadTypes.end());
   }
 
-  auto genericContext = decl->getAsGenericContext();
-  if (!genericContext)
+  std::function<GenericParamList *(ValueDecl *)> getGenericParams =
+      [&](ValueDecl *decl) -> GenericParamList * {
+    auto genericContext = decl->getAsGenericContext();
+    if (!genericContext)
+      return nullptr;
+
+    auto genericParams = genericContext->getGenericParams();
+    if (!genericParams) {
+      // If declaration is a non-generic typealias, let's point
+      // to the underlying generic declaration.
+      if (auto *TA = dyn_cast<TypeAliasDecl>(decl)) {
+        if (auto *UGT = TA->getUnderlyingType()->getAs<AnyGenericType>())
+          return getGenericParams(UGT->getDecl());
+      }
+    }
+
+    return genericParams;
+  };
+
+  if (!decl->getAsGenericContext())
     return SolutionKind::Error;
 
-  auto genericParams = genericContext->getGenericParams();
-  if (!genericParams || genericParams->size() == 0) {
+  auto genericParams = getGenericParams(decl);
+  if (!genericParams) {
     // FIXME: Record an error here that we're ignoring the parameters.
     return SolutionKind::Solved;
   }
 
   // Map the generic parameters we have over to their opened types.
+  bool hasParameterPack = false;
   SmallVector<Type, 2> openedGenericParams;
   auto genericParamDepth = genericParams->getParams()[0]->getDepth();
   for (const auto &openedType : openedTypes) {
@@ -13634,19 +13654,38 @@ ConstraintSystem::simplifyExplicitGenericArgumentsConstraint(
 
         auto *expansion = PackExpansionType::get(patternType, shapeType);
         openedGenericParams.push_back(expansion);
+        hasParameterPack = true;
       } else {
         openedGenericParams.push_back(Type(openedType.second));
       }
     }
   }
+
+  if (openedGenericParams.empty()) {
+    if (!shouldAttemptFixes())
+      return SolutionKind::Error;
+
+    return recordFix(AllowConcreteTypeSpecialization::create(
+               *this, type1, getConstraintLocator(locator)))
+               ? SolutionKind::Error
+               : SolutionKind::Solved;
+  }
+
   assert(openedGenericParams.size() == genericParams->size());
 
   // Match the opened generic parameters to the specialized arguments.
   auto specializedArgs = type2->castTo<PackType>()->getElementTypes();
   PackMatcher matcher(openedGenericParams, specializedArgs, getASTContext(),
                       isPackExpansionType);
-  if (matcher.match())
-    return SolutionKind::Error;
+  if (matcher.match()) {
+    if (!shouldAttemptFixes())
+      return SolutionKind::Error;
+
+    auto *fix = IgnoreGenericSpecializationArityMismatch::create(
+        *this, decl, openedGenericParams.size(), specializedArgs.size(),
+        hasParameterPack, getConstraintLocator(locator));
+    return recordFix(fix) ? SolutionKind::Error : SolutionKind::Solved;
+  }
 
   // Bind the opened generic parameters to the specialization arguments.
   for (const auto &pair : matcher.pairs) {
@@ -14746,7 +14785,9 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::MacroMissingPound:
   case FixKind::AllowGlobalActorMismatch:
   case FixKind::AllowAssociatedValueMismatch:
-  case FixKind::GenericArgumentsMismatch: {
+  case FixKind::GenericArgumentsMismatch:
+  case FixKind::AllowConcreteTypeSpecialization:
+  case FixKind::IgnoreGenericSpecializationArityMismatch: {
     return recordFix(fix) ? SolutionKind::Error : SolutionKind::Solved;
   }
   case FixKind::IgnoreInvalidASTNode: {

test/Macros/macro_and_typealias.swift

@@ -0,0 +1,56 @@
+// REQUIRES: swift_swift_parser, executable_test
+
+// RUN: %empty-directory(%t)
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/variadic_macros.swift -g -no-toolchain-stdlib-rpath
+// RUN: %target-typecheck-verify-swift -disable-availability-checking -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) -module-name MacroUser -DTEST_DIAGNOSTICS -swift-version 5
+
+@freestanding(expression) public macro Print<each Value>(_ value: repeat each Value) = #externalMacro(module: "MacroDefinition", type: "PrintMacro")
+@freestanding(expression) public macro OtherPrint<each Value>(_ value: repeat each Value) = #externalMacro(module: "MacroDefinition", type: "PrintMacro")
+@freestanding(expression) public macro ConcretePrint(_ value: Any) = #externalMacro(module: "MacroDefinition", type: "PrintMacro")
+@freestanding(expression) public macro MultiPrint(_ value: Any) = #externalMacro(module: "MacroDefinition", type: "PrintMacro")
+
+public struct Printer<Value> {
+  init(_: (Value) -> Void) {}
+}
+
+public struct MultiPrinter<T, U> {
+  // expected-note@-1 {{'T' declared as parameter to type 'MultiPrinter'}}
+  // expected-note@-2 {{'U' declared as parameter to type 'MultiPrinter'}}
+}
+
+typealias Print = Printer
+typealias OtherPrint<T> = Printer<T>
+typealias ConcretePrint = Printer<Any>
+typealias MultiPrint = MultiPrinter
+
+struct Test {
+  struct Object {
+    var prop: Int
+  }
+
+  func test() {
+    let _ = Print<Object> { // Ok
+      compute(root: $0, \.prop)
+    }
+
+    let _ = Print<Object, Int> {
+      // expected-error@-1 {{generic type 'Print' specialized with too many type parameters (got 2, but expected 1)}}
+    }
+
+    let _ = OtherPrint<Object> { // Ok
+      compute(root: $0, \.prop)
+    }
+
+    let _ = ConcretePrint<Object> { // expected-error {{cannot specialize non-generic type 'ConcretePrint' (aka 'Printer<Any>')}}
+      compute(root: $0, \.prop) // expected-error {{value of type 'Any' has no member 'prop'}}
+      // expected-note@-1 {{cast 'Any' to 'AnyObject' or use 'as!' to force downcast to a more specific type to access members}}
+    }
+
+    let _ = MultiPrint<Int>()
+    // expected-error@-1 {{generic type 'MultiPrint' specialized with too few type parameters (got 1, but expected 2)}}
+    // expected-error@-2 {{generic parameter 'T' could not be inferred}}
+    // expected-error@-3 {{generic parameter 'U' could not be inferred}}
+  }
+
+  func compute<R, V>(root: R, _: KeyPath<R, V>) {}
+}

test/Macros/macros_diagnostics.swift

@@ -96,8 +96,7 @@ macro genericDeclMacro<T: Numeric, U: Numeric>(_ x: T, _ y: U)
 // expected-note @-2 {{where 'U' = 'String'}}
 
 func testDiags(a: Int, b: Int) {
-  // FIXME: Bad diagnostic.
-  let s = #stringify<Int, Int>(a + b) // expected-error{{type of expression is ambiguous without a type annotation}}
+  let s = #stringify<Int, Int>(a + b) // expected-error{{generic type 'stringify' specialized with too many type parameters (got 2, but expected 1)}}
 
   _ = #stringify()
   // expected-error@-1{{missing argument for parameter #1 in macro expansion}}