lint: [move-only] Move cpp related lints to lint_cpp.rs

diff --git a/test/lint/test_runner/src/lint_cpp.rs b/test/lint/test_runner/src/lint_cpp.rs
new file mode 100644
index 00000000..250ebb46
--- /dev/null
+++ b/test/lint/test_runner/src/lint_cpp.rs
@@ -0,0 +1,180 @@
+// Copyright (c) The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://opensource.org/license/mit/.
+
+use std::process::Command;
+
+use crate::util::{check_output, get_pathspecs_default_excludes, git, LintResult};
+
+pub fn lint_includes_build_config() -> LintResult {
+    let config_path = "./cmake/bitcoin-build-config.h.in";
+    let defines_regex = format!(
+        r"^\s*(?!//).*({})",
+        check_output(Command::new("grep").args(["define", "--", config_path]))
+            .expect("grep failed")
+            .lines()
+            .map(|line| {
+                line.split_whitespace()
+                    .nth(1)
+                    .unwrap_or_else(|| panic!("Could not extract name in line: {line}"))
+            })
+            .collect::<Vec<_>>()
+            .join("|")
+    );
+    let print_affected_files = |mode: bool| {
+        // * mode==true: Print files which use the define, but lack the include
+        // * mode==false: Print files which lack the define, but use the include
+        let defines_files = check_output(
+            git()
+                .args([
+                    "grep",
+                    "--perl-regexp",
+                    if mode {
+                        "--files-with-matches"
+                    } else {
+                        "--files-without-match"
+                    },
+                    &defines_regex,
+                    "--",
+                    "*.cpp",
+                    "*.h",
+                ])
+                .args(get_pathspecs_default_excludes()),
+        )
+        .expect("grep failed");
+        git()
+            .args([
+                "grep",
+                if mode {
+                    "--files-without-match"
+                } else {
+                    "--files-with-matches"
+                },
+                if mode {
+                    "^#include <bitcoin-build-config.h> // IWYU pragma: keep$"
+                } else {
+                    "#include <bitcoin-build-config.h>" // Catch redundant includes with and without the IWYU pragma
+                },
+                "--",
+            ])
+            .args(defines_files.lines())
+            .status()
+            .expect("command error")
+            .success()
+    };
+    let missing = print_affected_files(true);
+    if missing {
+        return Err(format!(
+            r#"
+One or more files use a symbol declared in the bitcoin-build-config.h header. However, they are not
+including the header. This is problematic, because the header may or may not be indirectly
+included. If the indirect include were to be intentionally or accidentally removed, the build could
+still succeed, but silently be buggy. For example, a slower fallback algorithm could be picked,
+even though bitcoin-build-config.h indicates that a faster feature is available and should be used.
+
+If you are unsure which symbol is used, you can find it with this command:
+git grep --perl-regexp '{defines_regex}' -- file_name
+
+Make sure to include it with the IWYU pragma. Otherwise, IWYU may falsely instruct to remove the
+include again.
+
+#include <bitcoin-build-config.h> // IWYU pragma: keep
+            "#
+        )
+        .trim()
+        .to_string());
+    }
+    let redundant = print_affected_files(false);
+    if redundant {
+        return Err(r#"
+None of the files use a symbol declared in the bitcoin-build-config.h header. However, they are including
+the header. Consider removing the unused include.
+            "#
+        .to_string());
+    }
+    Ok(())
+}
+
+pub fn lint_std_filesystem() -> LintResult {
+    let found = git()
+        .args([
+            "grep",
+            "--line-number",
+            "std::filesystem",
+            "--",
+            "./src/",
+            ":(exclude)src/ipc/libmultiprocess/",
+            ":(exclude)src/util/fs.h",
+            ":(exclude)src/test/kernel/test_kernel.cpp",
+            ":(exclude)src/bitcoin-chainstate.cpp",
+        ])
+        .status()
+        .expect("command error")
+        .success();
+    if found {
+        Err(r#"
+Direct use of std::filesystem may be dangerous and buggy. Please include <util/fs.h> and use the
+fs:: namespace, which has unsafe filesystem functions marked as deleted.
+            "#
+        .trim()
+        .to_string())
+    } else {
+        Ok(())
+    }
+}
+
+pub fn lint_rpc_assert() -> LintResult {
+    let found = git()
+        .args([
+            "grep",
+            "--line-number",
+            "--extended-regexp",
+            r"\<(A|a)ss(ume|ert)\(",
+            "--",
+            "src/rpc/",
+            "src/wallet/rpc*",
+            ":(exclude)src/rpc/server.cpp",
+            // src/rpc/server.cpp is excluded from this check since it's mostly meta-code.
+        ])
+        .status()
+        .expect("command error")
+        .success();
+    if found {
+        Err(r#"
+CHECK_NONFATAL(condition) or NONFATAL_UNREACHABLE should be used instead of assert for RPC code.
+
+Aborting the whole process is undesirable for RPC code. So nonfatal
+checks should be used over assert. See: src/util/check.h
+            "#
+        .trim()
+        .to_string())
+    } else {
+        Ok(())
+    }
+}
+
+pub fn lint_boost_assert() -> LintResult {
+    let found = git()
+        .args([
+            "grep",
+            "--line-number",
+            "--extended-regexp",
+            r"BOOST_ASSERT\(",
+            "--",
+            "*.cpp",
+            "*.h",
+        ])
+        .status()
+        .expect("command error")
+        .success();
+    if found {
+        Err(r#"
+BOOST_ASSERT must be replaced with Assert, BOOST_REQUIRE, or BOOST_CHECK to avoid an unnecessary
+include of the boost/assert.hpp dependency.
+            "#
+        .trim()
+        .to_string())
+    } else {
+        Ok(())
+    }
+}
diff --git a/test/lint/test_runner/src/main.rs b/test/lint/test_runner/src/main.rs
index 9adbe369..eddbff9d 100644
--- a/test/lint/test_runner/src/main.rs
+++ b/test/lint/test_runner/src/main.rs
@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or https://opensource.org/license/mit/.
 
+mod lint_cpp;
 mod lint_docs;
 mod lint_text_format;
 mod util;
@@ -11,6 +12,9 @@ use std::fs;
 use std::io::ErrorKind;
 use std::process::{Command, ExitCode};
 
+use lint_cpp::{
+    lint_boost_assert, lint_includes_build_config, lint_rpc_assert, lint_std_filesystem,
+};
 use lint_docs::{lint_doc_args, lint_doc_release_note_snippets, lint_markdown};
 use lint_text_format::{
     lint_commit_msg, lint_tabs_whitespace, lint_trailing_newline, lint_trailing_whitespace,
@@ -262,179 +266,6 @@ fn lint_py_lint() -> LintResult {
     }
 }
 
-fn lint_std_filesystem() -> LintResult {
-    let found = git()
-        .args([
-            "grep",
-            "--line-number",
-            "std::filesystem",
-            "--",
-            "./src/",
-            ":(exclude)src/ipc/libmultiprocess/",
-            ":(exclude)src/util/fs.h",
-            ":(exclude)src/test/kernel/test_kernel.cpp",
-            ":(exclude)src/bitcoin-chainstate.cpp",
-        ])
-        .status()
-        .expect("command error")
-        .success();
-    if found {
-        Err(r#"
-Direct use of std::filesystem may be dangerous and buggy. Please include <util/fs.h> and use the
-fs:: namespace, which has unsafe filesystem functions marked as deleted.
-            "#
-        .trim()
-        .to_string())
-    } else {
-        Ok(())
-    }
-}
-
-fn lint_rpc_assert() -> LintResult {
-    let found = git()
-        .args([
-            "grep",
-            "--line-number",
-            "--extended-regexp",
-            r"\<(A|a)ss(ume|ert)\(",
-            "--",
-            "src/rpc/",
-            "src/wallet/rpc*",
-            ":(exclude)src/rpc/server.cpp",
-            // src/rpc/server.cpp is excluded from this check since it's mostly meta-code.
-        ])
-        .status()
-        .expect("command error")
-        .success();
-    if found {
-        Err(r#"
-CHECK_NONFATAL(condition) or NONFATAL_UNREACHABLE should be used instead of assert for RPC code.
-
-Aborting the whole process is undesirable for RPC code. So nonfatal
-checks should be used over assert. See: src/util/check.h
-            "#
-        .trim()
-        .to_string())
-    } else {
-        Ok(())
-    }
-}
-
-fn lint_boost_assert() -> LintResult {
-    let found = git()
-        .args([
-            "grep",
-            "--line-number",
-            "--extended-regexp",
-            r"BOOST_ASSERT\(",
-            "--",
-            "*.cpp",
-            "*.h",
-        ])
-        .status()
-        .expect("command error")
-        .success();
-    if found {
-        Err(r#"
-BOOST_ASSERT must be replaced with Assert, BOOST_REQUIRE, or BOOST_CHECK to avoid an unnecessary
-include of the boost/assert.hpp dependency.
-            "#
-        .trim()
-        .to_string())
-    } else {
-        Ok(())
-    }
-}
-
-fn lint_includes_build_config() -> LintResult {
-    let config_path = "./cmake/bitcoin-build-config.h.in";
-    let defines_regex = format!(
-        r"^\s*(?!//).*({})",
-        check_output(Command::new("grep").args(["define", "--", config_path]))
-            .expect("grep failed")
-            .lines()
-            .map(|line| {
-                line.split_whitespace()
-                    .nth(1)
-                    .unwrap_or_else(|| panic!("Could not extract name in line: {line}"))
-            })
-            .collect::<Vec<_>>()
-            .join("|")
-    );
-    let print_affected_files = |mode: bool| {
-        // * mode==true: Print files which use the define, but lack the include
-        // * mode==false: Print files which lack the define, but use the include
-        let defines_files = check_output(
-            git()
-                .args([
-                    "grep",
-                    "--perl-regexp",
-                    if mode {
-                        "--files-with-matches"
-                    } else {
-                        "--files-without-match"
-                    },
-                    &defines_regex,
-                    "--",
-                    "*.cpp",
-                    "*.h",
-                ])
-                .args(get_pathspecs_default_excludes()),
-        )
-        .expect("grep failed");
-        git()
-            .args([
-                "grep",
-                if mode {
-                    "--files-without-match"
-                } else {
-                    "--files-with-matches"
-                },
-                if mode {
-                    "^#include <bitcoin-build-config.h> // IWYU pragma: keep$"
-                } else {
-                    "#include <bitcoin-build-config.h>" // Catch redundant includes with and without the IWYU pragma
-                },
-                "--",
-            ])
-            .args(defines_files.lines())
-            .status()
-            .expect("command error")
-            .success()
-    };
-    let missing = print_affected_files(true);
-    if missing {
-        return Err(format!(
-            r#"
-One or more files use a symbol declared in the bitcoin-build-config.h header. However, they are not
-including the header. This is problematic, because the header may or may not be indirectly
-included. If the indirect include were to be intentionally or accidentally removed, the build could
-still succeed, but silently be buggy. For example, a slower fallback algorithm could be picked,
-even though bitcoin-build-config.h indicates that a faster feature is available and should be used.
-
-If you are unsure which symbol is used, you can find it with this command:
-git grep --perl-regexp '{defines_regex}' -- file_name
-
-Make sure to include it with the IWYU pragma. Otherwise, IWYU may falsely instruct to remove the
-include again.
-
-#include <bitcoin-build-config.h> // IWYU pragma: keep
-            "#
-        )
-        .trim()
-        .to_string());
-    }
-    let redundant = print_affected_files(false);
-    if redundant {
-        return Err(r#"
-None of the files use a symbol declared in the bitcoin-build-config.h header. However, they are including
-the header. Consider removing the unused include.
-            "#
-        .to_string());
-    }
-    Ok(())
-}
-
 fn run_all_python_linters() -> LintResult {
     let mut good = true;
     let lint_dir = get_git_root().join("test/lint");