Add a BuiltinGenericType base class.

Builtin.FixedArray was introduced as the first generic builtin type, with
special case handling in all the various recursive visitors. Introduce
a base class, and move the handling to that base class, so it is easier
to introduce other generic builtins in the future.

Author: jckarter

include/swift/AST/ASTContext.h

@@ -1609,6 +1609,10 @@ class ASTContext final {
     OutputBackend = std::move(OutBackend);
   }
 
+private:
+  friend class BuiltinGenericType;
+  GenericSignature &getCachedBuiltinGenericTypeSignature(TypeKind kind);
+
 private:
   friend Decl;
 

include/swift/AST/TypeDifferenceVisitor.h

@@ -134,13 +134,28 @@ class CanTypeDifferenceVisitor : public CanTypePairVisitor<Impl, bool> {
                                       CanBuiltinUnboundGenericType type2) {
     return asImpl().visitDifferentTypeStructure(type1, type2);
   }
-  
-  bool visitBuiltinFixedArrayType(CanBuiltinFixedArrayType type1,
-                                  CanBuiltinFixedArrayType type2) {
-    if (asImpl().visit(type1->getSize(), type2->getSize())) {
+
+  bool visitBuiltinGenericType(CanBuiltinGenericType type1,
+                               CanBuiltinGenericType type2) {
+    if (type1->getBuiltinTypeKind() != type2->getBuiltinTypeKind()) {
       return true;
     }
-    return asImpl().visit(type1->getElementType(), type2->getElementType());
+
+    auto subs1 = type1->getSubstitutions();
+    auto subs2 = type2->getSubstitutions();
+
+    for (unsigned i : indices(subs1.getReplacementTypes())) {
+      if (asImpl().visit(CanType(subs1.getReplacementTypes()[i]),
+                         CanType(subs2.getReplacementTypes()[i]))) {
+        return true;
+      }
+    }
+    for (unsigned i : indices(subs1.getConformances())) {
+      if (subs1.getConformances()[i] != subs2.getConformances()[i]) {
+        return true;
+      }
+    }
+    return false;
   }
 
   bool visitPackType(CanPackType type1, CanPackType type2) {

include/swift/AST/TypeMatcher.h

@@ -112,7 +112,7 @@ class TypeMatcher {
     TRIVIAL_CASE(BuiltinFloatType)
     TRIVIAL_CASE(BuiltinVectorType)
     TRIVIAL_CASE(BuiltinUnboundGenericType)
-    TRIVIAL_CASE(BuiltinFixedArrayType)
+    TRIVIAL_CASE(BuiltinGenericType)
     TRIVIAL_CASE(IntegerType)
 #define SINGLETON_TYPE(SHORT_ID, ID) TRIVIAL_CASE(ID##Type)
 #include "swift/AST/TypeNodes.def"

include/swift/AST/TypeNodes.def

@@ -141,7 +141,9 @@ ABSTRACT_TYPE(Builtin, Type)
   BUILTIN_CONCRETE_TYPE(BuiltinDefaultActorStorage, BuiltinType)
   BUILTIN_CONCRETE_TYPE(BuiltinNonDefaultDistributedActorStorage, BuiltinType)
   BUILTIN_CONCRETE_TYPE(BuiltinVector, BuiltinType)
-  BUILTIN_GENERIC_TYPE(BuiltinFixedArray, BuiltinType)
+  ABSTRACT_TYPE(BuiltinGeneric, BuiltinType)
+    BUILTIN_GENERIC_TYPE(BuiltinFixedArray, BuiltinGenericType)
+    TYPE_RANGE(BuiltinGeneric, BuiltinFixedArray, BuiltinFixedArray)
   BUILTIN_CONCRETE_TYPE(BuiltinUnboundGeneric, BuiltinType)
   BUILTIN_CONCRETE_TYPE(BuiltinImplicitActor, BuiltinType)
   TYPE_RANGE(Builtin, BuiltinInteger, BuiltinImplicitActor)

include/swift/AST/TypeTransform.h

@@ -21,6 +21,8 @@
 #include "swift/AST/GenericEnvironment.h"
 #include "swift/AST/SILLayout.h"
 #include "swift/AST/LifetimeDependence.h"
+#include "swift/AST/SubstitutionMap.h"
+#include "llvm/ADT/SmallVector.h"
 
 namespace swift {
 
@@ -117,29 +119,26 @@ case TypeKind::Id:
     case TypeKind::Integer:
       return t;
 
+    // BuiltinGenericType subclasses
     case TypeKind::BuiltinFixedArray: {
-      auto bfaTy = cast<BuiltinFixedArrayType>(base);
-      
-      Type transSize = doIt(bfaTy->getSize(),
-                            TypePosition::Invariant);
-      if (!transSize) {
-        return Type();
-      }
-      
-      Type transElement = doIt(bfaTy->getElementType(),
-                               TypePosition::Invariant);
-      if (!transElement) {
-        return Type();
-      }
-      
-      CanType canTransSize = transSize->getCanonicalType();
-      CanType canTransElement = transElement->getCanonicalType();
-      if (canTransSize != bfaTy->getSize()
-          || canTransElement != bfaTy->getElementType()) {
-        return BuiltinFixedArrayType::get(canTransSize, canTransElement);
+      auto bgaTy = cast<BuiltinGenericType>(base);
+
+      llvm::SmallVector<Type, 2> transReplacements;
+
+      for (auto t : bgaTy->getSubstitutions().getReplacementTypes()) {
+        Type transTy = doIt(t, TypePosition::Invariant);
+        if (!transTy) {
+          return Type();
+        }
+        transReplacements.push_back(transTy);
       }
-      
-      return bfaTy;
+
+      // TODO: translate conformances. No builtin types yet have conformance
+      // requirements in their generic signatures.
+      auto transSubs = SubstitutionMap::get(bgaTy->getGenericSignature(),
+                                            transReplacements,
+                                            ArrayRef<ProtocolConformanceRef>{});
+      return bgaTy->getWithSubstitutions(transSubs);
     }
 
     case TypeKind::PrimaryArchetype:

include/swift/AST/Types.h

@@ -1780,25 +1780,63 @@ class BuiltinUnboundGenericType : public BuiltinType {
 };
 DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinUnboundGenericType, BuiltinType)
 
+/// BuiltinGenericType - Base class for builtins that are parameterized by
+/// a generic signature.
+class BuiltinGenericType : public BuiltinType {
+protected:
+
+  BuiltinGenericType(TypeKind kind, ASTContext &context,
+                     RecursiveTypeProperties properties)
+    : BuiltinType(kind, context, properties)
+  {}
+
+  /// The substitution map is cached here once requested.
+  mutable std::optional<SubstitutionMap> CachedSubstitutionMap = std::nullopt;
+  
+public:  
+  static bool classof(const TypeBase *T) {
+    return T->getKind() >= TypeKind::First_BuiltinGenericType
+      && T->getKind() <= TypeKind::Last_BuiltinGenericType;
+  }
+
+  // Get the generic signature describing the parameterization of types of
+  // this class.
+  GenericSignature getGenericSignature() const;
+
+  // Get the substitution map for this particular type.
+  SubstitutionMap getSubstitutions() const;
+
+  // Produce another type of the same class but with different arguments.
+  CanTypeWrapper<BuiltinGenericType>
+  getWithSubstitutions(SubstitutionMap newSubs) const;
+};
+DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinGenericType, BuiltinType)
+
 /// BuiltinFixedArrayType - The builtin type representing N values stored
 /// inline contiguously.
 ///
 /// All elements of a value of this type must be fully initialized any time the
 /// value may be copied, moved, or destroyed.
-class BuiltinFixedArrayType : public BuiltinType, public llvm::FoldingSetNode {
+class BuiltinFixedArrayType : public BuiltinGenericType,
+                              public llvm::FoldingSetNode {
   friend class ASTContext;
 
   CanType Size;
   CanType ElementType;
 
   BuiltinFixedArrayType(CanType Size, CanType ElementType,
                         RecursiveTypeProperties properties)
-    : BuiltinType(TypeKind::BuiltinFixedArray, ElementType->getASTContext(),
-                  properties),
+    : BuiltinGenericType(TypeKind::BuiltinFixedArray,
+                         ElementType->getASTContext(),
+                         properties),
         Size(Size),
         ElementType(ElementType)
   {}
 
+  friend BuiltinGenericType;
+  /// Get the generic arguments as a substitution map.
+  SubstitutionMap buildSubstitutions() const;
+  
 public:
   /// Arrays with more elements than this are always treated as in-memory values.
   ///
@@ -1826,7 +1864,7 @@ class BuiltinFixedArrayType : public BuiltinType, public llvm::FoldingSetNode {
 
   /// Get the element type.
   CanType getElementType() const { return ElementType; }
-  
+
   void Profile(llvm::FoldingSetNodeID &ID) const {
     Profile(ID, getSize(), getElementType());
   }
@@ -1836,7 +1874,7 @@ class BuiltinFixedArrayType : public BuiltinType, public llvm::FoldingSetNode {
     ID.AddPointer(ElementType.getPointer());
   }
 };
-DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinFixedArrayType, BuiltinType)
+DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinFixedArrayType, BuiltinGenericType)
 
 /// BuiltinRawPointerType - The builtin raw (and dangling) pointer type.  This
 /// pointer is completely unmanaged and is equivalent to i8* in LLVM IR.

lib/AST/ASTContext.cpp

@@ -533,6 +533,13 @@ struct ASTContext::Implementation {
   /// Local and closure discriminators per context.
   llvm::DenseMap<const DeclContext *, unsigned> NextDiscriminator;
 
+  /// Cached generic signatures for generic builtin types.
+  static const unsigned NumBuiltinGenericTypes
+    = unsigned(TypeKind::Last_BuiltinGenericType)
+        - unsigned(TypeKind::First_BuiltinGenericType) + 1;
+  std::array<GenericSignature, NumBuiltinGenericTypes>
+  BuiltinGenericTypeSignatures = {};
+
   /// Structure that captures data that is segregated into different
   /// arenas.
   struct Arena {
@@ -7309,3 +7316,13 @@ AvailabilityDomain ASTContext::getTargetAvailabilityDomain() const {
   // Fall back to the universal domain for triples without a platform.
   return AvailabilityDomain::forUniversal();
 }
+
+GenericSignature &
+ASTContext::getCachedBuiltinGenericTypeSignature(TypeKind kind) {
+  ASSERT(kind >= TypeKind::First_BuiltinGenericType
+         && kind <= TypeKind::Last_BuiltinGenericType
+         && "not a builtin generic type kind");
+
+  return getImpl().BuiltinGenericTypeSignatures
+    [unsigned(kind) - unsigned(TypeKind::First_BuiltinGenericType)];
+}