From dd2f57bd4eacbb1acbf56299035ceb2191fe35be Mon Sep 17 00:00:00 2001
From: Soutaro Matsumoto <matsumoto@soutaro.com>
Date: Mon, 29 Aug 2022 20:56:02 +0900
Subject: [PATCH 1/2] Reduce Namespace/TypeName instantiation

---
 lib/rbs/namespace.rb          | 10 ++++++----
 lib/rbs/type_name_resolver.rb |  4 ++--
 sig/namespace.rbs             |  6 ++++++
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/lib/rbs/namespace.rb b/lib/rbs/namespace.rb
index d41496436..67b2ef3f9 100644
--- a/lib/rbs/namespace.rb
+++ b/lib/rbs/namespace.rb
@@ -10,11 +10,11 @@ def initialize(path:, absolute:)
     end
 
     def self.empty
-      new(path: [], absolute: false)
+      @empty ||= new(path: [], absolute: false)
     end
 
     def self.root
-      new(path: [], absolute: true)
+      @root ||= new(path: [], absolute: true)
     end
 
     def +(other)
@@ -30,8 +30,10 @@ def append(component)
     end
 
     def parent
-      raise "Parent with empty namespace" if empty?
-      self.class.new(path: path.take(path.size - 1), absolute: absolute?)
+      @parent ||= begin
+        raise "Parent with empty namespace" if empty?
+        self.class.new(path: path.take(path.size - 1), absolute: absolute?)
+      end
     end
 
     def absolute?
diff --git a/lib/rbs/type_name_resolver.rb b/lib/rbs/type_name_resolver.rb
index 87d1059ed..d32466c21 100644
--- a/lib/rbs/type_name_resolver.rb
+++ b/lib/rbs/type_name_resolver.rb
@@ -37,11 +37,11 @@ def resolve(type_name, context:)
 
       query = Query.new(type_name: type_name, context: context)
       try_cache(query) do
-        path_head, *path_tail = type_name.to_namespace.path
+        path_head, *path_tail = type_name.split
         raise unless path_head
 
         name_head = TypeName.new(name: path_head, namespace: Namespace.empty)
- 
+
         absolute_head = context.find do |namespace|
           # @type break: TypeName
           full_name = name_head.with_prefix(namespace)
diff --git a/sig/namespace.rbs b/sig/namespace.rbs
index fc505d7c6..3ab23affd 100644
--- a/sig/namespace.rbs
+++ b/sig/namespace.rbs
@@ -38,6 +38,12 @@ module RBS
 
     @absolute: bool
 
+    @parent: Namespace?
+
+    self.@root: Namespace?
+
+    self.@empty: Namespace?
+
     # Returns new _empty_ namespace.
     def self.empty: () -> Namespace
 

From 5f565df999a6c694114fd2503306d03ca128f61b Mon Sep 17 00:00:00 2001
From: Soutaro Matsumoto <matsumoto@soutaro.com>
Date: Fri, 2 Sep 2022 11:08:47 +0900
Subject: [PATCH 2/2] Reduce empty array/hash allocation

---
 lib/rbs/types.rb | 26 +++++++++++++++++++++-----
 sig/types.rbs    |  4 ++++
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/lib/rbs/types.rb b/lib/rbs/types.rb
index 1f5699344..ff3406a52 100644
--- a/lib/rbs/types.rb
+++ b/lib/rbs/types.rb
@@ -845,12 +845,12 @@ def free_variables(set = Set.new)
       def map_type(&block)
         if block
           Function.new(
-            required_positionals: required_positionals.map {|param| param.map_type(&block) },
-            optional_positionals: optional_positionals.map {|param| param.map_type(&block) },
+            required_positionals: amap(required_positionals) {|param| param.map_type(&block) },
+            optional_positionals: amap(optional_positionals) {|param| param.map_type(&block) },
             rest_positionals: rest_positionals&.yield_self {|param| param.map_type(&block) },
-            trailing_positionals: trailing_positionals.map {|param| param.map_type(&block) },
-            required_keywords: required_keywords.transform_values {|param| param.map_type(&block) },
-            optional_keywords: optional_keywords.transform_values {|param| param.map_type(&block) },
+            trailing_positionals: amap(trailing_positionals) {|param| param.map_type(&block) },
+            required_keywords: hmapv(required_keywords) {|param| param.map_type(&block) },
+            optional_keywords: hmapv(optional_keywords) {|param| param.map_type(&block) },
             rest_keywords: rest_keywords&.yield_self {|param| param.map_type(&block) },
             return_type: yield(return_type)
           )
@@ -859,6 +859,22 @@ def map_type(&block)
         end
       end
 
+      def amap(array, &block)
+        if array.empty?
+          _ = array
+        else
+          array.map(&block)
+        end
+      end
+
+      def hmapv(hash, &block)
+        if hash.empty?
+          _ = hash
+        else
+          hash.transform_values(&block)
+        end
+      end
+
       def map_type_name(&block)
         map_type do |type|
           type.map_type_name(&block)
diff --git a/sig/types.rbs b/sig/types.rbs
index 92f358c7b..7a565621e 100644
--- a/sig/types.rbs
+++ b/sig/types.rbs
@@ -404,6 +404,10 @@ module RBS
       def drop_tail: () -> [Param, Function]
 
       def has_keyword?: () -> bool
+
+      def amap: [A, B] (Array[A]) { (A) -> B } -> Array[B]
+
+      def hmapv: [X, Y, Z] (Hash[X, Y]) { (Y) -> Z } -> Hash[X, Z]
     end
 
     class Block