Run CI with "4.0.0-preview2"

Author: soutaro

.github/workflows/c-check.yml

@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "3.4"
+          ruby-version: "4.0.0-preview2"
           bundler-cache: none
       - name: Set working directory as safe
         run: git config --global --add safe.directory $(pwd)

.github/workflows/ruby.yml

@@ -13,24 +13,24 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.2', '3.3', '3.4', head]
+        ruby: ['3.3', '3.4', '4.0.0-preview2', head]
         rubyopt: [""]
         job:
           - test
         include:
           - ruby: head
             job: stdlib_test rubocop
-          - ruby: "3.4"
+          - ruby: "4.0.0-preview2"
             job: stdlib_test
-          - ruby: "3.4"
+          - ruby: "4.0.0-preview2"
             job: test
             rubyopt: "--enable-frozen-string-literal"
-          - ruby: "3.4"
+          - ruby: "4.0.0-preview2"
             job: stdlib_test
             rubyopt: "--enable-frozen-string-literal"
-          - ruby: "3.4"
+          - ruby: "4.0.0-preview2"
             job: rubocop validate test_doc build test_generate_stdlib raap
-          - ruby: "3.4"
+          - ruby: "4.0.0-preview2"
             job: typecheck_test
     env:
       RANDOMIZE_STDLIB_TEST_ORDER: "true"
@@ -74,7 +74,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.4', head]
+        ruby: ['4.0.0-preview2', head]
     steps:
       - uses: actions/checkout@v6
       - name: Install dependencies

.github/workflows/windows.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.2', '3.3', ucrt, mswin]
+        ruby: ['3.4', '4.0.0-preview2', ucrt, mswin]
     steps:
       - uses: actions/checkout@v6
       - name: load ruby