Type checking for default events

runtime/ast/composite.go

@@ -45,6 +45,10 @@ type CompositeLikeDeclaration interface {
 
 const ResourceDestructionDefaultEventName = "ResourceDestroyed"
 
+func IsResourceDestructionDefaultEvent(identifier string) bool {
+	return identifier == ResourceDestructionDefaultEventName
+}
+
 type CompositeDeclaration struct {
 	Members      *Members
 	DocString    string
@@ -284,7 +288,7 @@ func (d *CompositeDeclaration) ConformanceList() []*NominalType {
 
 func (d *CompositeDeclaration) IsResourceDestructionDefaultEvent() bool {
 	return d.CompositeKind == common.CompositeKindEvent &&
-		d.Identifier.Identifier == ResourceDestructionDefaultEventName
+		IsResourceDestructionDefaultEvent(d.Identifier.Identifier)
 }
 
 // FieldDeclarationFlags

runtime/parser/declaration.go

@@ -876,7 +876,7 @@ func parseEventDeclaration(
 	p.next()
 
 	// if this is a `ResourceDestroyed` event (i.e., a default event declaration), parse default arguments
-	parseDefaultArguments := identifier.Identifier == ast.ResourceDestructionDefaultEventName
+	parseDefaultArguments := ast.IsResourceDestructionDefaultEvent(identifier.Identifier)
 	parameterList, err := parseParameterList(p, parseDefaultArguments)
 	if err != nil {
 		return nil, err

runtime/sema/check_composite_declaration.go

@@ -267,6 +267,13 @@ func (checker *Checker) visitCompositeLikeDeclaration(declaration ast.CompositeL
 		)
 	}
 
+	if !compositeType.IsResourceType() && compositeType.DefaultDestroyEvent != nil {
+		checker.report(&DefaultDestroyEventInNonResourceError{
+			Kind:  declaration.DeclarationKind().Name(),
+			Range: ast.NewRangeFromPositioned(checker.memoryGauge, declaration),
+		})
+	}
+
 	// NOTE: visit entitlements, then interfaces, then composites
 	// DON'T use `nestedDeclarations`, because of non-deterministic order
 
@@ -283,6 +290,10 @@ func (checker *Checker) visitCompositeLikeDeclaration(declaration ast.CompositeL
 	}
 
 	for _, nestedComposite := range members.Composites() {
+		if compositeType.DefaultDestroyEvent != nil {
+			// we enforce elsewhere that each composite can have only one default destroy event
+			checker.checkDefaultDestroyEvent(compositeType.DefaultDestroyEvent, nestedComposite, compositeType, declaration)
+		}
 		ast.AcceptDeclaration[struct{}](nestedComposite, checker)
 	}
 
@@ -428,10 +439,23 @@ func (checker *Checker) declareNestedDeclarations(
 
 			firstNestedCompositeDeclaration := nestedCompositeDeclarations[0]
 
-			reportInvalidNesting(
-				firstNestedCompositeDeclaration.DeclarationKind(),
-				firstNestedCompositeDeclaration.Identifier,
-			)
+			// we want to permit this nesting under 2 conditions: the container is a resource declaration,
+			// and this nested declaration is a default destroy event
+
+			if firstNestedCompositeDeclaration.IsResourceDestructionDefaultEvent() {
+				if len(nestedCompositeDeclarations) > 1 {
+					firstNestedCompositeDeclaration = nestedCompositeDeclarations[1]
+					reportInvalidNesting(
+						firstNestedCompositeDeclaration.DeclarationKind(),
+						firstNestedCompositeDeclaration.Identifier,
+					)
+				}
+			} else {
+				reportInvalidNesting(
+					firstNestedCompositeDeclaration.DeclarationKind(),
+					firstNestedCompositeDeclaration.Identifier,
+				)
+			}
 
 		} else if len(nestedInterfaceDeclarations) > 0 {
 
@@ -819,6 +843,14 @@ func (checker *Checker) declareCompositeLikeMembersAndValue(
 			nestedCompositeDeclarationVariable :=
 				checker.valueActivations.Find(identifier.Identifier)
 
+			if ast.IsResourceDestructionDefaultEvent(identifier.Identifier) {
+				// Find the default event's type declaration
+				defaultEventType :=
+					checker.typeActivations.Find(identifier.Identifier)
+				defaultEventComposite := defaultEventType.Type.(*CompositeType)
+				compositeType.DefaultDestroyEvent = defaultEventComposite
+			}
+
 			declarationMembers.Set(
 				nestedCompositeDeclarationVariable.Identifier,
 				&Member{
@@ -1963,6 +1995,122 @@ func (checker *Checker) enumMembersAndOrigins(
 	return
 }
 
+func (checker *Checker) checkDefaultDestroyParamExpressionKind(
+	arg ast.Expression,
+) {
+	switch arg := arg.(type) {
+	case *ast.StringExpression,
+		*ast.BoolExpression,
+		*ast.NilExpression,
+		*ast.IntegerExpression,
+		*ast.FixedPointExpression,
+		*ast.PathExpression:
+		break
+	case *ast.IdentifierExpression:
+		identifier := arg.Identifier.Identifier
+		// these are guaranteed to exist at time of destruction, so we allow them
+		if identifier == SelfIdentifier || identifier == BaseIdentifier {
+			break
+		}
+		// if it's an attachment, then it's also okay
+		if checker.typeActivations.Find(identifier) != nil {
+			break
+		}
+		checker.report(&DefaultDestroyInvalidArgumentError{
+			Range: ast.NewRangeFromPositioned(checker.memoryGauge, arg),
+		})
+	case *ast.MemberExpression:
+		checker.checkDefaultDestroyParamExpressionKind(arg.Expression)
+	case *ast.IndexExpression:
+		checker.checkDefaultDestroyParamExpressionKind(arg.TargetExpression)
+		checker.checkDefaultDestroyParamExpressionKind(arg.IndexingExpression)
+
+		// indexing expressions on arrays can fail, and must be disallowed, but
+		// indexing expressions on dicts, or composites (for attachments) will return `nil` and thus never fail
+		targetExprType := checker.Elaboration.IndexExpressionTypes(arg).IndexedType
+		// `nil` indicates that the index is a type-index (i.e. for an attachment access)
+		if targetExprType == nil {
+			return
+		}
+
+		switch targetExprType := targetExprType.(type) {
+		case *DictionaryType:
+			return
+		case *ReferenceType:
+			if _, isDictionaryType := targetExprType.Type.(*DictionaryType); isDictionaryType {
+				return
+			}
+		}
+
+		checker.report(&DefaultDestroyInvalidArgumentError{
+			Range: ast.NewRangeFromPositioned(checker.memoryGauge, arg),
+		})
+
+	default:
+		checker.report(&DefaultDestroyInvalidArgumentError{
+			Range: ast.NewRangeFromPositioned(checker.memoryGauge, arg),
+		})
+	}
+}
+
+func (checker *Checker) checkDefaultDestroyEventParam(
+	param Parameter,
+	index int,
+	constructorFunctionParameters []*ast.Parameter,
+	containerType ContainerType,
+	containerDeclaration ast.Declaration,
+) {
+	paramType := param.TypeAnnotation.Type
+	paramExpr := constructorFunctionParameters[index]
+	paramDefaultArgument := paramExpr.DefaultArgument
+
+	// make `self` and `base` available when checking default arguments so the fields of the composite are available
+	checker.declareSelfValue(containerType, containerDeclaration.DeclarationDocString())
+	if compositeContainer, isComposite := containerType.(*CompositeType); isComposite && compositeContainer.Kind == common.CompositeKindAttachment {
+		checker.declareBaseValue(
+			compositeContainer.baseType,
+			compositeContainer,
+			compositeContainer.baseTypeDocString)
+	}
+	param.DefaultArgument = checker.VisitExpression(paramDefaultArgument, paramType)
+
+	unwrappedParamType := UnwrapOptionalType(paramType)
+	// default events must have default arguments for all their parameters; this is enforced in the parser
+	// we want to check that these arguments are all either literals or field accesses, and have primitive types
+	if !IsSubType(unwrappedParamType, StringType) &&
+		!IsSubType(unwrappedParamType, NumberType) &&
+		!IsSubType(unwrappedParamType, TheAddressType) &&
+		!IsSubType(unwrappedParamType, PathType) &&
+		!IsSubType(unwrappedParamType, BoolType) {
+		checker.report(&DefaultDestroyInvalidParameterError{
+			ParamType: paramType,
+			Range:     ast.NewRangeFromPositioned(checker.memoryGauge, paramExpr),
+		})
+	}
+
+	checker.checkDefaultDestroyParamExpressionKind(paramDefaultArgument)
+}
+
+func (checker *Checker) checkDefaultDestroyEvent(
+	eventType *CompositeType,
+	eventDeclaration ast.CompositeLikeDeclaration,
+	containerType ContainerType,
+	containerDeclaration ast.Declaration,
+) {
+
+	// an event definition always has one "constructor" function in its declaration list
+	members := eventDeclaration.DeclarationMembers()
+	functions := members.Initializers()
+	constructorFunctionParameters := functions[0].FunctionDeclaration.ParameterList.Parameters
+
+	checker.enterValueScope()
+	defer checker.leaveValueScope(eventDeclaration.EndPosition, true)
+
+	for index, param := range eventType.ConstructorParameters {
+		checker.checkDefaultDestroyEventParam(param, index, constructorFunctionParameters, containerType, containerDeclaration)
+	}
+}
+
 func (checker *Checker) checkInitializers(
 	initializers []*ast.SpecialFunctionDeclaration,
 	fields []*ast.FieldDeclaration,

runtime/sema/check_emit_statement.go

@@ -45,6 +45,15 @@ func (checker *Checker) VisitEmitStatement(statement *ast.EmitStatement) (_ stru
 		return
 	}
 
+	if ast.IsResourceDestructionDefaultEvent(compositeType.Identifier) {
+		checker.report(
+			&EmitDefaultDestroyEventError{
+				Range: ast.NewRangeFromPositioned(checker.memoryGauge, statement.InvocationExpression),
+			},
+		)
+		return
+	}
+
 	checker.Elaboration.SetEmitStatementEventType(statement, compositeType)
 
 	// Check that the emitted event is declared in the same location

runtime/sema/check_interface_declaration.go

@@ -134,6 +134,13 @@ func (checker *Checker) VisitInterfaceDeclaration(declaration *ast.InterfaceDecl
 		fieldPositionGetter,
 	)
 
+	if !interfaceType.IsResourceType() && interfaceType.DefaultDestroyEvent != nil {
+		checker.report(&DefaultDestroyEventInNonResourceError{
+			Kind:  declaration.DeclarationKind().Name(),
+			Range: ast.NewRangeFromPositioned(checker.memoryGauge, declaration),
+		})
+	}
+
 	// NOTE: visit entitlements, then interfaces, then composites
 	// DON'T use `nestedDeclarations`, because of non-deterministic order
 
@@ -151,6 +158,9 @@ func (checker *Checker) VisitInterfaceDeclaration(declaration *ast.InterfaceDecl
 		if nestedComposite.Kind() == common.CompositeKindEvent {
 			checker.visitCompositeLikeDeclaration(nestedComposite)
 		}
+		if interfaceType.DefaultDestroyEvent != nil {
+			checker.checkDefaultDestroyEvent(interfaceType.DefaultDestroyEvent, nestedComposite, interfaceType, declaration)
+		}
 	}
 
 	return
@@ -432,7 +442,15 @@ func (checker *Checker) declareInterfaceMembersAndValue(declaration *ast.Interfa
 
 		for _, nestedCompositeDeclaration := range declaration.Members.Composites() {
 			if nestedCompositeDeclaration.Kind() == common.CompositeKindEvent {
-				checker.declareNestedEvent(nestedCompositeDeclaration, eventMembers, interfaceType)
+				if nestedCompositeDeclaration.IsResourceDestructionDefaultEvent() {
+					// Find the value declaration
+					nestedEvent :=
+						checker.typeActivations.Find(nestedCompositeDeclaration.Identifier.Identifier)
+					defaultEventComposite := nestedEvent.Type.(*CompositeType)
+					interfaceType.DefaultDestroyEvent = defaultEventComposite
+				} else {
+					checker.declareNestedEvent(nestedCompositeDeclaration, eventMembers, interfaceType)
+				}
 			}
 		}
 	})()

runtime/sema/errors.go

@@ -2490,6 +2490,23 @@ func (e *EmitNonEventError) Error() string {
 	)
 }
 
+// EmitDefaultDestroyEventError
+
+type EmitDefaultDestroyEventError struct {
+	ast.Range
+}
+
+var _ SemanticError = &EmitDefaultDestroyEventError{}
+var _ errors.UserError = &EmitDefaultDestroyEventError{}
+
+func (*EmitDefaultDestroyEventError) isSemanticError() {}
+
+func (*EmitDefaultDestroyEventError) IsUserError() {}
+
+func (e *EmitDefaultDestroyEventError) Error() string {
+	return "default destruction events may not be explicitly emitted"
+}
+
 // EmitImportedEventError
 
 type EmitImportedEventError struct {
@@ -4657,6 +4674,62 @@ func (e *InvalidAttachmentEntitlementError) EndPosition(common.MemoryGauge) ast.
 	return e.Pos
 }
 
+// DefaultDestroyEventInNonResourceError
+
+type DefaultDestroyEventInNonResourceError struct {
+	Kind string
+	ast.Range
+}
+
+var _ SemanticError = &DefaultDestroyEventInNonResourceError{}
+var _ errors.UserError = &DefaultDestroyEventInNonResourceError{}
+
+func (*DefaultDestroyEventInNonResourceError) isSemanticError() {}
+
+func (*DefaultDestroyEventInNonResourceError) IsUserError() {}
+
+func (e *DefaultDestroyEventInNonResourceError) Error() string {
+	return fmt.Sprintf(
+		"cannot declare default destruction event in %s",
+		e.Kind,
+	)
+}
+
+// DefaultDestroyInvalidArgumentError
+
+type DefaultDestroyInvalidArgumentError struct {
+	ast.Range
+}
+
+var _ SemanticError = &DefaultDestroyInvalidArgumentError{}
+var _ errors.UserError = &DefaultDestroyInvalidArgumentError{}
+
+func (*DefaultDestroyInvalidArgumentError) isSemanticError() {}
+
+func (*DefaultDestroyInvalidArgumentError) IsUserError() {}
+
+func (e *DefaultDestroyInvalidArgumentError) Error() string {
+	return "default destroy event arguments must be literals, member access expressions on `self` or `base`, indexed access expressions on dictionaries, or attachment accesses"
+}
+
+// DefaultDestroyInvalidArgumentError
+
+type DefaultDestroyInvalidParameterError struct {
+	ParamType Type
+	ast.Range
+}
+
+var _ SemanticError = &DefaultDestroyInvalidParameterError{}
+var _ errors.UserError = &DefaultDestroyInvalidParameterError{}
+
+func (*DefaultDestroyInvalidParameterError) isSemanticError() {}
+
+func (*DefaultDestroyInvalidParameterError) IsUserError() {}
+
+func (e *DefaultDestroyInvalidParameterError) Error() string {
+	return fmt.Sprintf("`%s` is not a valid parameter type for a default destroy event", e.ParamType.QualifiedString())
+}
+
 // InvalidTypeParameterizedNonNativeFunctionError
 
 type InvalidTypeParameterizedNonNativeFunctionError struct {

runtime/sema/type.go

@@ -2954,9 +2954,10 @@ func formatParameter(spaces bool, label, identifier, typeAnnotation string) stri
 }
 
 type Parameter struct {
-	TypeAnnotation TypeAnnotation
-	Label          string
-	Identifier     string
+	TypeAnnotation  TypeAnnotation
+	DefaultArgument Type
+	Label           string
+	Identifier      string
 }
 
 func (p Parameter) String() string {
@@ -4296,6 +4297,8 @@ type CompositeType struct {
 	RequiredEntitlements        *EntitlementOrderedSet
 	AttachmentEntitlementAccess *EntitlementMapAccess
 
+	DefaultDestroyEvent *CompositeType
+
 	cachedIdentifiers *struct {
 		TypeID              TypeID
 		QualifiedIdentifier string
@@ -5152,6 +5155,8 @@ type InterfaceType struct {
 	effectiveInterfaceConformances   []Conformance
 	effectiveInterfaceConformanceSet *InterfaceSet
 	supportedEntitlements            *EntitlementOrderedSet
+
+	DefaultDestroyEvent *CompositeType
 }
 
 var _ Type = &InterfaceType{}