diff --git a/.github/workflows/ci-post-merge.yml b/.github/workflows/ci-post-merge.yml
index 8d509d691..4231b4dc2 100644
--- a/.github/workflows/ci-post-merge.yml
+++ b/.github/workflows/ci-post-merge.yml
@@ -49,7 +49,7 @@ jobs:
           toolchain: ${{ matrix.version.version }}
 
       - name: Install just, cargo-hack, cargo-nextest, cargo-ci-cache-clean
-        uses: taiki-e/install-action@v2.33.22
+        uses: taiki-e/install-action@v2.34.0
         with:
           tool: just,cargo-hack,cargo-nextest,cargo-ci-cache-clean
 
@@ -80,7 +80,7 @@ jobs:
         uses: actions-rust-lang/setup-rust-toolchain@v1.8.0
 
       - name: Install cargo-hack
-        uses: taiki-e/install-action@v2.33.22
+        uses: taiki-e/install-action@v2.34.0
         with:
           tool: cargo-hack
 
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 56333e187..ed2930bc6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -54,13 +54,17 @@ jobs:
           echo 'OPENSSL_DIR=C:\Program Files\OpenSSL' >> $GITHUB_ENV
           echo "RUSTFLAGS=-C target-feature=+crt-static" >> $GITHUB_ENV
 
+      - name: Setup mold linker
+        if: matrix.target.os == 'ubuntu-latest'
+        uses: rui314/setup-mold@v1
+
       - name: Install Rust (${{ matrix.version.name }})
         uses: actions-rust-lang/setup-rust-toolchain@v1.8.0
         with:
           toolchain: ${{ matrix.version.version }}
 
       - name: Install just, cargo-hack, cargo-nextest, cargo-ci-cache-clean
-        uses: taiki-e/install-action@v2.33.22
+        uses: taiki-e/install-action@v2.34.0
         with:
           tool: just,cargo-hack,cargo-nextest,cargo-ci-cache-clean
 
@@ -109,7 +113,7 @@ jobs:
           toolchain: nightly
 
       - name: Install just
-        uses: taiki-e/install-action@v2.33.22
+        uses: taiki-e/install-action@v2.34.0
         with:
           tool: just
 
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 943f63223..da892bd7a 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -22,16 +22,16 @@ jobs:
         with:
           components: llvm-tools-preview
 
-      - name: Install cargo-llvm-cov
-        uses: taiki-e/install-action@v2.33.22
+      - name: Install just,cargo-llvm-cov
+        uses: taiki-e/install-action@v2.34.0
         with:
-          tool: cargo-llvm-cov
+          tool: just,cargo-llvm-cov
 
       - name: Generate code coverage
         run: cargo llvm-cov --workspace --all-features --codecov --output-path codecov.json
 
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v4.3.1
+        uses: codecov/codecov-action@v4.4.1
         with:
           files: codecov.json
           fail_ci_if_error: true
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 03b25ecda..d7a16ccb4 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -79,10 +79,10 @@ jobs:
       - name: Install Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1.8.0
         with:
-          toolchain: nightly-2024-04-26
+          toolchain: nightly-2024-06-07
 
       - name: Install cargo-public-api
-        uses: taiki-e/install-action@v2.33.22
+        uses: taiki-e/install-action@v2.34.0
         with:
           tool: cargo-public-api
 
diff --git a/.github/workflows/upload-doc.yml b/.github/workflows/upload-doc.yml
deleted file mode 100644
index 6352e44d2..000000000
--- a/.github/workflows/upload-doc.yml
+++ /dev/null
@@ -1,41 +0,0 @@
-name: Upload Documentation
-
-on:
-  push:
-    branches: [master]
-
-permissions:
-  contents: read
-
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
-
-jobs:
-  build:
-    permissions:
-      contents: write
-
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Install Rust
-        uses: actions-rust-lang/setup-rust-toolchain@v1.8.0
-        with:
-          toolchain: nightly
-
-      - name: Build Docs
-        run: cargo +nightly doc --no-deps --workspace --all-features
-        env:
-          RUSTDOCFLAGS: --cfg=docsrs
-
-      - name: Tweak HTML
-        run: echo '<meta http-equiv="refresh" content="0;url=actix_web/index.html">' > target/doc/index.html
-
-      - name: Deploy to GitHub Pages
-        uses: JamesIves/github-pages-deploy-action@v4.6.0
-        with:
-          folder: target/doc
-          single-commit: true
diff --git a/actix-web/CHANGES.md b/actix-web/CHANGES.md
index 993c7c596..e0390563c 100644
--- a/actix-web/CHANGES.md
+++ b/actix-web/CHANGES.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Added
+
+- Implement `From<Box<dyn ResponseError>>` for `Error`.
+
 ## 4.6.0
 
 ### Added
diff --git a/actix-web/src/app.rs b/actix-web/src/app.rs
index 1a3b79086..3d86d1f9b 100644
--- a/actix-web/src/app.rs
+++ b/actix-web/src/app.rs
@@ -112,8 +112,8 @@ where
     /// })
     /// ```
     #[doc(alias = "manage")]
-    pub fn app_data<U: 'static>(mut self, ext: U) -> Self {
-        self.extensions.insert(ext);
+    pub fn app_data<U: 'static>(mut self, data: U) -> Self {
+        self.extensions.insert(data);
         self
     }
 
diff --git a/actix-web/src/error/error.rs b/actix-web/src/error/error.rs
index 3a5a128f6..670a58a00 100644
--- a/actix-web/src/error/error.rs
+++ b/actix-web/src/error/error.rs
@@ -60,6 +60,12 @@ impl<T: ResponseError + 'static> From<T> for Error {
     }
 }
 
+impl From<Box<dyn ResponseError>> for Error {
+    fn from(value: Box<dyn ResponseError>) -> Self {
+        Error { cause: value }
+    }
+}
+
 impl From<Error> for Response<BoxBody> {
     fn from(err: Error) -> Response<BoxBody> {
         err.error_response().into()