Move is-container check to the type itself

runtime/interpreter/interpreter_expression.go

@@ -245,10 +245,8 @@ func (interpreter *Interpreter) memberExpressionGetterSetter(memberExpression *a
 // e.g.2: Given T?, this returns (&T)?
 func (interpreter *Interpreter) getReferenceValue(value Value, semaType sema.Type) Value {
 	switch value.(type) {
-	case NilValue:
+	case NilValue, ReferenceValue:
 		// Reference to a nil, should return a nil.
-		return value
-	case ReferenceValue:
 		// If the value is already a reference then return the same reference.
 		return value
 	}

runtime/sema/account_capability_controller.cdc

@@ -1,4 +1,4 @@
-access(all) struct AccountCapabilityController {
+access(all) struct AccountCapabilityController: MemberAccessible {
 
     /// An arbitrary "tag" for the controller.
     /// For example, it could be used to describe the purpose of the capability.

runtime/sema/anyresource_type.go

@@ -30,6 +30,7 @@ var AnyResourceType = &SimpleType{
 	Equatable:  false,
 	Comparable: false,
 	// The actual returnability of a value is checked at run-time
-	Exportable: true,
-	Importable: false,
+	Exportable:       true,
+	Importable:       false,
+	MemberAccessible: true,
 }

runtime/sema/anystruct_type.go

@@ -31,7 +31,8 @@ var AnyStructType = &SimpleType{
 	Comparable: false,
 	Exportable: true,
 	// The actual importability is checked at runtime
-	Importable: true,
+	Importable:       true,
+	MemberAccessible: true,
 }
 
 var AnyStructTypeAnnotation = NewTypeAnnotation(AnyStructType)

runtime/sema/authaccount.cdc

@@ -1,5 +1,5 @@
 
-access(all) struct AuthAccount {
+access(all) struct AuthAccount: MemberAccessible {
 
     /// The address of the account.
     access(all) let address: Address

runtime/sema/block.cdc

@@ -1,5 +1,5 @@
 
-access(all) struct Block {
+access(all) struct Block: MemberAccessible {
 
     /// The height of the block.
     ///

runtime/sema/check_member_expression.go

@@ -112,7 +112,7 @@ func shouldReturnReference(parentType, memberType Type) bool {
 		return false
 	}
 
-	return isContainerType(memberType)
+	return memberType.IsMemberAccessible()
 }
 
 func isReferenceType(typ Type) bool {
@@ -121,23 +121,6 @@ func isReferenceType(typ Type) bool {
 	return isReference
 }
 
-func isContainerType(typ Type) bool {
-	switch typ := typ.(type) {
-	case *CompositeType,
-		*DictionaryType,
-		ArrayType:
-		return true
-	case *OptionalType:
-		return isContainerType(typ.Type)
-	default:
-		switch typ {
-		case AnyStructType, AnyResourceType:
-			return true
-		}
-		return false
-	}
-}
-
 func (checker *Checker) visitMember(expression *ast.MemberExpression) (accessedType Type, resultingType Type, member *Member, isOptional bool) {
 	memberInfo, ok := checker.Elaboration.MemberExpressionMemberInfo(expression)
 	if ok {

runtime/sema/deployedcontract.cdc

@@ -1,5 +1,5 @@
 
-access(all) struct DeployedContract {
+access(all) struct DeployedContract: MemberAccessible {
     /// The address of the account where the contract is deployed at.
     access(all) let address: Address
 

runtime/sema/gen/main.go

@@ -151,6 +151,7 @@ type typeDecl struct {
 	exportable         bool
 	comparable         bool
 	importable         bool
+	memberAccessible   bool
 	memberDeclarations []ast.Declaration
 	nestedTypes        []*typeDecl
 }
@@ -423,6 +424,15 @@ func (g *generator) VisitCompositeDeclaration(decl *ast.CompositeDeclaration) (_
 
 		case "Importable":
 			typeDecl.importable = true
+
+		case "MemberAccessible":
+			if !canGenerateSimpleType {
+				panic(fmt.Errorf(
+					"composite types cannot be explicitly marked as member accessible: %s",
+					g.currentTypeID(),
+				))
+			}
+			typeDecl.memberAccessible = true
 		}
 	}
 
@@ -1158,6 +1168,7 @@ func simpleTypeLiteral(ty *typeDecl) dst.Expr {
 		goKeyValue("Comparable", goBoolLit(ty.comparable)),
 		goKeyValue("Exportable", goBoolLit(ty.exportable)),
 		goKeyValue("Importable", goBoolLit(ty.importable)),
+		goKeyValue("MemberAccessible", goBoolLit(ty.memberAccessible)),
 	}
 
 	return &dst.UnaryExpr{

runtime/sema/simple_type.go

@@ -50,6 +50,7 @@ type SimpleType struct {
 	Comparable          bool
 	Storable            bool
 	IsResource          bool
+	MemberAccessible    bool
 }
 
 var _ Type = &SimpleType{}
@@ -106,6 +107,10 @@ func (t *SimpleType) IsImportable(_ map[*Member]bool) bool {
 	return t.Importable
 }
 
+func (t *SimpleType) IsMemberAccessible() bool {
+	return t.MemberAccessible
+}
+
 func (*SimpleType) TypeAnnotationState() TypeAnnotationState {
 	return TypeAnnotationStateValid
 }

runtime/sema/storage_capability_controller.cdc

@@ -1,4 +1,4 @@
-access(all) struct StorageCapabilityController {
+access(all) struct StorageCapabilityController: MemberAccessible {
 
     /// An arbitrary "tag" for the controller.
     /// For example, it could be used to describe the purpose of the capability.