Move error code explanation removal check into tidy

Author: GuillaumeGomez

src/ci/docker/host-x86_64/mingw-check-1/Dockerfile

@@ -39,7 +39,6 @@ RUN pip3 install --no-deps --no-cache-dir --require-hashes -r /tmp/reuse-require
 
 COPY host-x86_64/mingw-check-1/check-default-config-profiles.sh /scripts/
 COPY host-x86_64/mingw-check-1/validate-toolstate.sh /scripts/
-COPY host-x86_64/mingw-check-1/validate-error-codes.sh /scripts/
 
 # Check library crates on all tier 1 targets.
 # We disable optimized compiler built-ins because that requires a C toolchain for the target.
@@ -52,7 +51,6 @@ ENV SCRIPT \
            python3 ../x.py check --stage 1 --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu && \
            python3 ../x.py check --stage 1 --set build.optimized-compiler-builtins=false core alloc std --target=aarch64-unknown-linux-gnu,i686-pc-windows-msvc,i686-unknown-linux-gnu,x86_64-apple-darwin,x86_64-pc-windows-gnu,x86_64-pc-windows-msvc && \
            /scripts/validate-toolstate.sh && \
-           /scripts/validate-error-codes.sh && \
            reuse --include-submodules lint && \
            python3 ../x.py test collect-license-metadata && \
            # Runs checks to ensure that there are no issues in our JS code.

src/ci/docker/host-x86_64/mingw-check-1/validate-error-codes.sh

@@ -39,7 +39,6 @@ RUN pip3 install --no-deps --no-cache-dir --require-hashes -r /tmp/reuse-require
     && pip3 install virtualenv
 
 COPY host-x86_64/mingw-check-1/validate-toolstate.sh /scripts/
-COPY host-x86_64/mingw-check-1/validate-error-codes.sh /scripts/
 
 RUN bash -c 'npm install -g eslint@$(cat /tmp/eslint.version)'
 

src/ci/docker/host-x86_64/mingw-check-tidy/Dockerfile

@@ -43,9 +43,18 @@ macro_rules! verbose_print {
     };
 }
 
-pub fn check(root_path: &Path, search_paths: &[&Path], verbose: bool, bad: &mut bool) {
+pub fn check(
+    root_path: &Path,
+    search_paths: &[&Path],
+    verbose: bool,
+    ci_info: &crate::CiInfo,
+    bad: &mut bool,
+) {
     let mut errors = Vec::new();
 
+    // Check that no error code explanation was removed.
+    check_removed_error_code_explanation(ci_info, bad);
+
     // Stage 1: create list
     let error_codes = extract_error_codes(root_path, &mut errors);
     if verbose {
@@ -68,6 +77,27 @@ pub fn check(root_path: &Path, search_paths: &[&Path], verbose: bool, bad: &mut
     }
 }
 
+fn check_removed_error_code_explanation(ci_info: &crate::CiInfo, bad: &mut bool) {
+    let Some(base_commit) = &ci_info.base_commit else {
+        eprintln!("Skipping error code explanation removal check");
+        return;
+    };
+    let Some(diff) = crate::git_diff(base_commit, "--name-status") else {
+        *bad = true;
+        eprintln!("removed error code explanation tidy check: Failed to run git diff");
+        return;
+    };
+    if diff.lines().any(|line| {
+        line.starts_with('D') && line.contains("compiler/rustc_error_codes/src/error_codes/")
+    }) {
+        *bad = true;
+        eprintln!("tidy check error: Error code explanations should never be removed!");
+        eprintln!("Take a look at E0001 to see how to handle it.");
+        return;
+    }
+    println!("No error code explanation was removed!");
+}
+
 /// Stage 1: Parses a list of error codes from `error_codes.rs`.
 fn extract_error_codes(root_path: &Path, errors: &mut Vec<String>) -> Vec<String> {
     let path = root_path.join(Path::new(ERROR_CODES_PATH));

src/tools/tidy/src/error_codes.rs

@@ -117,7 +117,7 @@ fn main() {
         check!(unknown_revision, &tests_path);
 
         // Checks that only make sense for the compiler.
-        check!(error_codes, &root_path, &[&compiler_path, &librustdoc_path], verbose);
+        check!(error_codes, &root_path, &[&compiler_path, &librustdoc_path], verbose, &ci_info);
         check!(fluent_alphabetical, &compiler_path, bless);
         check!(fluent_period, &compiler_path);
         check!(target_policy, &root_path);