codegen: add support for abstract classes

internal/codegen/codegen.go

@@ -368,6 +368,7 @@ func (g *generator) createGenClass(typeDef *winmd.TypeDef) (*genClass, error) {
 		ImplInterfaces:      implInterfaces,
 		ExclusiveInterfaces: exclusiveGenInterfaces,
 		HasEmptyConstructor: hasEmptyConstructor,
+		IsAbstract:          typeDef.Flags.Abstract(),
 	}, nil
 }
 
@@ -1155,6 +1156,12 @@ func (g *generator) Signature(typeDef *winmd.TypeDef) (string, error) {
 
 		return fmt.Sprintf(`delegate({%s})`, guid), nil
 	case typeDef.IsRuntimeClass():
+		// Static only classes carry the abstract flag.
+		// These cannot be instantiated so no signature needed.
+		if typeDef.Flags.Abstract() {
+			return "", nil
+		}
+
 		// runtime_class_signature => "rc(" runtime_class_name ";" default_interface ")"
 
 		// Runtime classes must specify the DefaultAttribute on exactly one of their InterfaceImpl rows.

internal/codegen/templates.go

@@ -67,6 +67,7 @@ type genClass struct {
 	ImplInterfaces      []*genInterface
 	ExclusiveInterfaces []*genInterface
 	HasEmptyConstructor bool
+	IsAbstract          bool
 }
 
 func (g *genClass) GetRequiredImports() []*genImport {

internal/codegen/templates/class.tmpl

@@ -1,3 +1,4 @@
+{{if not .IsAbstract}}
 const Signature{{.Name}} string = "{{.Signature}}"
 
 type {{.Name}} struct {
@@ -13,6 +14,7 @@ func New{{.Name}}() (*{{.Name}}, error) {
     return (*{{.Name}})(unsafe.Pointer(inspectable)), nil
 }
 {{end}}
+{{end}}
 
 {{$owner := .Name}}
 {{range .ImplInterfaces}}