Add type arguments support to singleton types

Previously, singleton type arguments could not be supported by RBS. This
adds support for them, enabling syntax like
`singleton(Array)[String, Integer]`.

Author: allcre

config.yml

@@ -573,8 +573,11 @@ nodes:
     fields:
       - name: name
         c_type: rbs_type_name
+      - name: args
+        c_type: rbs_node_list
     locations:
       - required: name
+      - optional: args
   - name: RBS::Types::Function
     rust_name: FunctionTypeNode
     expose_location: false

docs/syntax.md

@@ -3,17 +3,17 @@
 ## Types
 
 ```markdown
-_type_ ::= _class-name_ _type-arguments_                 (Class instance type)
-         | _interface-name_ _type-arguments_             (Interface type)
-         | _alias-name_ _type-arguments_                 (Alias type)
-         | `singleton(` _class-name_ `)`                 (Class singleton type)
-         | _literal_                                     (Literal type)
-         | _type_ `|` _type_                             (Union type)
-         | _type_ `&` _type_                             (Intersection type)
-         | _type_ `?`                                    (Optional type)
-         | `{` _record-name_ `:` _type_ `,` etc. `}`     (Record type)
-         | `[]` | `[` _type_ `,` etc. `]`                (Tuples)
-         | _type-variable_                               (Type variables)
+_type_ ::= _class-name_ _type-arguments_                     (Class instance type)
+         | _interface-name_ _type-arguments_                 (Interface type)
+         | _alias-name_ _type-arguments_                     (Alias type)
+         | `singleton(` _class-name_ `)` _type-arguments_    (Class singleton type)
+         | _literal_                                         (Literal type)
+         | _type_ `|` _type_                                 (Union type)
+         | _type_ `&` _type_                                 (Intersection type)
+         | _type_ `?`                                        (Optional type)
+         | `{` _record-name_ `:` _type_ `,` etc. `}`         (Record type)
+         | `[]` | `[` _type_ `,` etc. `]`                    (Tuples)
+         | _type-variable_                                   (Type variables)
          | `self`
          | `instance`
          | `class`
@@ -85,7 +85,8 @@ Class singleton type denotes _the type of a singleton object of a class_.
 
 ```rbs
 singleton(String)
-singleton(::Hash)            # Class singleton type cannot be parametrized.
+singleton(::Hash)            # Class singleton type
+singleton(Array)[String]     # Class singleton type with type application
 ```
 
 ### Literal type

ext/rbs_extension/ast_translation.c

@@ -1229,10 +1229,12 @@ VALUE rbs_struct_to_ruby_value(rbs_translation_context_t ctx, rbs_node_t *instan
         VALUE h = rb_hash_new();
         VALUE location = rbs_location_range_to_ruby_location(ctx, node->base.location);
         rbs_loc *loc = rbs_check_location(location);
-        rbs_loc_legacy_alloc_children(loc, 1);
+        rbs_loc_legacy_alloc_children(loc, 2);
         rbs_loc_legacy_add_required_child(loc, rb_intern("name"), (rbs_loc_range) { .start = node->name_range.start_char, .end = node->name_range.end_char });
+        rbs_loc_legacy_add_optional_child(loc, rb_intern("args"), (rbs_loc_range) { .start = node->args_range.start_char, .end = node->args_range.end_char });
         rb_hash_aset(h, ID2SYM(rb_intern("location")), location);
         rb_hash_aset(h, ID2SYM(rb_intern("name")), rbs_struct_to_ruby_value(ctx, (rbs_node_t *) node->name)); // rbs_type_name
+        rb_hash_aset(h, ID2SYM(rb_intern("args")), rbs_node_list_to_ruby_array(ctx, node->args));
 
         return CLASS_NEW_INSTANCE(
             RBS_Types_ClassSingleton,

include/rbs/ast.h

@@ -772,8 +772,10 @@ typedef struct rbs_types_class_singleton {
     rbs_node_t base;
 
     struct rbs_type_name *name;
+    struct rbs_node_list *args;
 
     rbs_location_range name_range; /* Required */
+    rbs_location_range args_range; /* Optional */
 } rbs_types_class_singleton_t;
 
 typedef struct rbs_types_function {
@@ -947,7 +949,7 @@ rbs_types_bases_top_t *rbs_types_bases_top_new(rbs_allocator_t *allocator, rbs_l
 rbs_types_bases_void_t *rbs_types_bases_void_new(rbs_allocator_t *allocator, rbs_location_range location);
 rbs_types_block_t *rbs_types_block_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_node_t *type, bool required, rbs_node_t *self_type);
 rbs_types_class_instance_t *rbs_types_class_instance_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_type_name_t *name, rbs_node_list_t *args, rbs_location_range name_range);
-rbs_types_class_singleton_t *rbs_types_class_singleton_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_type_name_t *name, rbs_location_range name_range);
+rbs_types_class_singleton_t *rbs_types_class_singleton_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_type_name_t *name, rbs_node_list_t *args, rbs_location_range name_range);
 rbs_types_function_t *rbs_types_function_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_node_list_t *required_positionals, rbs_node_list_t *optional_positionals, rbs_node_t *rest_positionals, rbs_node_list_t *trailing_positionals, rbs_hash_t *required_keywords, rbs_hash_t *optional_keywords, rbs_node_t *rest_keywords, rbs_node_t *return_type);
 rbs_types_function_param_t *rbs_types_function_param_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_node_t *type, rbs_ast_symbol_t *name);
 rbs_types_interface_t *rbs_types_interface_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_type_name_t *name, rbs_node_list_t *args, rbs_location_range name_range);

lib/rbs/types.rb

@@ -199,58 +199,6 @@ def with_nonreturn_void?
       end
     end
 
-    class ClassSingleton
-      attr_reader :name
-      attr_reader :location
-
-      def initialize(name:, location:)
-        @name = name
-        @location = location
-      end
-
-      def ==(other)
-        other.is_a?(ClassSingleton) && other.name == name
-      end
-
-      alias eql? ==
-
-      def hash
-        self.class.hash ^ name.hash
-      end
-
-      include NoFreeVariables
-      include NoSubst
-
-      def to_json(state = nil)
-        { class: :class_singleton, name: name, location: location }.to_json(state)
-      end
-
-      def to_s(level = 0)
-        "singleton(#{name})"
-      end
-
-      include EmptyEachType
-
-      def map_type_name(&)
-        ClassSingleton.new(
-          name: yield(name, location, self),
-          location: location
-        )
-      end
-
-      def has_self_type?
-        false
-      end
-
-      def has_classish_type?
-        false
-      end
-
-      def with_nonreturn_void?
-        false
-      end
-    end
-
     module Application
       attr_reader :name
       attr_reader :args
@@ -309,6 +257,68 @@ def with_nonreturn_void?
       end
     end
 
+    class ClassSingleton
+      attr_reader :location
+
+      include Application
+
+      def initialize(name:, location:, args: [])
+        @name = name
+        @location = location
+        @args = args
+      end
+
+      def ==(other)
+        other.is_a?(ClassSingleton) && other.name == name && other.args == args
+      end
+
+      alias eql? ==
+
+      def hash
+        self.class.hash ^ name.hash ^ args.hash
+      end
+
+      def sub(s)
+        return self if s.empty?
+
+        self.class.new(name: name,
+                       args: args.map {|ty| ty.sub(s) },
+                       location: location)
+      end
+
+      def to_json(state = _ = nil)
+        { class: :class_singleton, name: name, args: args, location: location }.to_json(state)
+      end
+
+      def to_s(level = 0)
+        if args.empty?
+          "singleton(#{name})"
+        else
+          "singleton(#{name})[#{args.join(", ")}]"
+        end
+      end
+
+      def map_type_name(&block)
+        ClassSingleton.new(
+          name: yield(name, location, self),
+          args: args.map {|type| type.map_type_name(&block) },
+          location: location
+        )
+      end
+
+      def map_type(&block)
+        if block
+          ClassSingleton.new(
+            name: name,
+            args: args.map {|type| yield type },
+            location: location
+          )
+        else
+          enum_for :map_type
+        end
+      end
+    end
+
     class Interface
       attr_reader :location
 

lib/rbs/unit_test/type_assertions.rb

@@ -256,15 +256,17 @@ def method_defs(method)
         type, definition = target
 
         case type
-        when Types::ClassInstance
-          subst = RBS::Substitution.build(definition.type_params, type.args)
-          definition.methods[method].defs.map do |type_def|
-            type_def.update(
-              type: type_def.type.sub(subst)
-            )
+        when Types::ClassInstance, Types::ClassSingleton
+          if type.is_a?(Types::ClassSingleton) && type.args.empty?
+            definition.methods[method].defs
+          else
+            subst = RBS::Substitution.build(definition.type_params, type.args)
+            definition.methods[method].defs.map do |type_def|
+              type_def.update(
+                type: type_def.type.sub(subst)
+              )
+            end
           end
-        when Types::ClassSingleton
-          definition.methods[method].defs
         else
           raise
         end

sig/types.rbs

@@ -172,24 +172,23 @@ module RBS
     class ClassSingleton
       # singleton(::Foo)
       #           ^^^^^  => name
-      type loc = Location[:name, bot]
-
-      def initialize: (name: TypeName, location: loc?) -> void
+      type loc = Location[:name, :args]
 
-      attr_reader name: TypeName
+      def initialize: (name: TypeName, location: loc?, ?args: Array[t]) -> void
 
       attr_reader location: loc?
 
       include _TypeBase
-      include NoFreeVariables
-      include NoSubst
-      include EmptyEachType
+      include Application
 
       def ==: (untyped other) -> bool
 
       alias eql? ==
 
       def hash: () -> Integer
+              
+      def map_type: () { (t) -> t } -> ClassSingleton
+                  | () -> Enumerator[t, ClassSingleton]
     end
 
     module Application

src/ast.c

@@ -1303,7 +1303,7 @@ rbs_types_class_instance_t *rbs_types_class_instance_new(rbs_allocator_t *alloca
     return instance;
 }
 #line 140 "prism/templates/src/ast.c.erb"
-rbs_types_class_singleton_t *rbs_types_class_singleton_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_type_name_t *name, rbs_location_range name_range) {
+rbs_types_class_singleton_t *rbs_types_class_singleton_new(rbs_allocator_t *allocator, rbs_location_range location, rbs_type_name_t *name, rbs_node_list_t *args, rbs_location_range name_range) {
     rbs_types_class_singleton_t *instance = rbs_allocator_alloc(allocator, rbs_types_class_singleton_t);
 
     *instance = (rbs_types_class_singleton_t) {
@@ -1312,7 +1312,9 @@ rbs_types_class_singleton_t *rbs_types_class_singleton_new(rbs_allocator_t *allo
             .location = location,
         },
         .name = name,
+        .args = args,
         .name_range = name_range,
+        .args_range = RBS_LOCATION_NULL_RANGE,
     };
 
     return instance;

src/parser.c

@@ -1042,10 +1042,10 @@ static bool parse_instance_type(rbs_parser_t *parser, bool parse_alias, rbs_node
 }
 
 /*
-  singleton_type ::= {`singleton`} `(` type_name <`)`>
+  singleton_type ::= {`singleton`} `(` type_name <`)`> type_args?
 */
 NODISCARD
-static bool parse_singleton_type(rbs_parser_t *parser, rbs_types_class_singleton_t **singleton) {
+static bool parse_singleton_type(rbs_parser_t *parser, rbs_types_class_singleton_t **singleton, bool self_allowed, bool classish_allowed) {
     ASSERT_TOKEN(parser, kSINGLETON);
 
     rbs_range_t type_range;
@@ -1058,9 +1058,26 @@ static bool parse_singleton_type(rbs_parser_t *parser, rbs_types_class_singleton
     CHECK_PARSE(parse_type_name(parser, CLASS_NAME, &name_range, &type_name));
 
     ADVANCE_ASSERT(parser, pRPAREN);
+
+    rbs_node_list_t *types = rbs_node_list_new(ALLOCATOR());
+
+    rbs_location_range args_range = RBS_LOCATION_NULL_RANGE;
+    if (parser->next_token.type == pLBRACKET) {
+        rbs_parser_advance(parser);
+        args_range.start_byte = parser->current_token.range.start.byte_pos;
+        args_range.start_char = parser->current_token.range.start.char_pos;
+        CHECK_PARSE(parse_type_list(parser, pRBRACKET, types, true, self_allowed, classish_allowed));
+        ADVANCE_ASSERT(parser, pRBRACKET);
+        args_range.end_byte = parser->current_token.range.end.byte_pos;
+        args_range.end_char = parser->current_token.range.end.char_pos;
+    }
+
     type_range.end = parser->current_token.range.end;
+    rbs_location_range loc = RBS_RANGE_LEX2AST(type_range);
+
+    *singleton = rbs_types_class_singleton_new(ALLOCATOR(), loc, type_name, types, RBS_RANGE_LEX2AST(name_range));
+    (*singleton)->args_range = args_range;
 
-    *singleton = rbs_types_class_singleton_new(ALLOCATOR(), RBS_RANGE_LEX2AST(type_range), type_name, RBS_RANGE_LEX2AST(name_range));
     return true;
 }
 
@@ -1242,7 +1259,7 @@ static bool parse_simple(rbs_parser_t *parser, rbs_node_t **type, bool void_allo
     }
     case kSINGLETON: {
         rbs_types_class_singleton_t *singleton = NULL;
-        CHECK_PARSE(parse_singleton_type(parser, &singleton));
+        CHECK_PARSE(parse_singleton_type(parser, &singleton, self_allowed, classish_allowed));
         *type = (rbs_node_t *) singleton;
         return true;
     }