Fix type errors

Gemfile.lock

@@ -12,7 +12,7 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (7.2.2.1)
+    activesupport (8.0.1)
       base64
       benchmark (>= 0.3)
       bigdecimal
@@ -24,18 +24,19 @@ GEM
       minitest (>= 5.1)
       securerandom (>= 0.3)
       tzinfo (~> 2.0, >= 2.0.5)
+      uri (>= 0.13.1)
     ast (2.4.2)
     base64 (0.2.0)
     benchmark (0.4.0)
-    bigdecimal (3.1.8)
+    bigdecimal (3.1.9)
     concurrent-ruby (1.3.4)
     connection_pool (2.4.1)
-    csv (3.3.0)
+    csv (3.3.2)
     diff-lcs (1.5.1)
     drb (2.2.1)
     ffi (1.17.1)
     ffi (1.17.1-x86_64-linux-gnu)
-    fileutils (1.7.2)
+    fileutils (1.7.3)
     i18n (1.14.6)
       concurrent-ruby (~> 1.0)
     json (2.9.1)
@@ -48,7 +49,7 @@ GEM
     minitest (5.25.4)
     net-http (0.6.0)
       uri
-    parser (3.3.5.0)
+    parser (3.3.6.0)
       ast (~> 2.4.1)
       racc
     racc (1.8.1)
@@ -75,7 +76,7 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
     rspec-support (3.13.1)
-    securerandom (0.4.0)
+    securerandom (0.4.1)
     singleton (0.3.0)
     steep (1.9.3)
       activesupport (>= 5.1)
@@ -93,7 +94,7 @@ GEM
       strscan (>= 1.0.0)
       terminal-table (>= 2, < 4)
       uri (>= 0.12.0)
-    strscan (3.1.0)
+    strscan (3.1.2)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
     tzinfo (2.0.6)

lib/fetch/headers.rb

@@ -35,7 +35,7 @@ def keys
     end
 
     def set(key, value)
-      @data[key.to_s.downcase] = [value]
+      @data[key.to_s.downcase] = [value.to_s]
     end
 
     def values

lib/fetch/multi_map.rb

@@ -41,8 +41,8 @@ def values
       @entries.map(&:last)
     end
 
-    def each(&)
-      @entries.each(&)
+    def each(&block)
+      block ? @entries.each(&block) : @entries.each
     end
 
     private

sig/fetch/client.rbs

@@ -2,6 +2,8 @@ module Fetch
   class Client
     include Singleton
 
+    def self.instance: () -> Client
+
     def fetch: (
       string,
       method: String | Symbol,

sig/fetch/connection_pool.rbs

@@ -1,5 +1,7 @@
 module Fetch
   class ConnectionPool
+    @connections: Hash[String, [Net::HTTP, Time]]
+
     def initialize: () -> void
     def with_connection: [T] (URI::HTTP) { (Net::HTTP) -> T } -> T
 

sig/fetch/headers.rbs

@@ -2,6 +2,8 @@ module Fetch
   class Headers
     include Enumerable[[String, String]]
 
+    @data: Hash[String, Array[String]]
+
     def initialize: (_Each[[_ToS, _ToS]]) -> void
     def append: (_ToS, _ToS) -> void
     def delete: (_ToS) -> void

sig/fetch/multi_map.rbs

@@ -1,7 +1,9 @@
 module Fetch
-  class MultiMap[KIN, KOUT, VIN, VOUT]
+  class MultiMap[KIN, KOUT < Comparable, VIN, VOUT]
     include Enumerable[[KOUT, VOUT]]
 
+    @entries: Array[[KOUT, VOUT]]
+
     def initialize: () -> void
     def append: (KIN, VIN) -> void
     def delete: (KIN) -> void