Add -Zerror-metrics=PATH to save diagnostic metadata to disk

.gitignore

@@ -19,6 +19,7 @@ Session.vim
 *.iml
 .vscode
 .project
+.vim/
 .favorites.json
 .settings/
 .vs/

compiler/rustc_driver_impl/src/lib.rs

@@ -51,7 +51,8 @@ use rustc_metadata::creader::MetadataLoader;
 use rustc_metadata::locator;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_session::config::{
-    nightly_options, ErrorOutputType, Input, OutFileName, OutputType, CG_OPTIONS, Z_OPTIONS,
+    nightly_options, ErrorOutputType, Input, OutFileName, OutputType, UnstableOptions, CG_OPTIONS,
+    Z_OPTIONS,
 };
 use rustc_session::getopts::{self, Matches};
 use rustc_session::lint::{Lint, LintId};
@@ -301,6 +302,8 @@ fn run_compiler(
     let Some(matches) = handle_options(&default_early_dcx, &args) else { return Ok(()) };
 
     let sopts = config::build_session_options(&mut default_early_dcx, &matches);
+    // fully initialize ice path static once unstable options are available as context
+    let _ = ice_path_with_config(Some(&sopts.unstable_opts));
 
     if let Some(ref code) = matches.opt_str("explain") {
         handle_explain(&default_early_dcx, diagnostics_registry(), code, sopts.color);
@@ -1307,15 +1310,14 @@ pub fn catch_with_exit_code(f: impl FnOnce() -> interface::Result<()>) -> i32 {
 static ICE_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
 
 fn ice_path() -> &'static Option<PathBuf> {
+    ice_path_with_config(None)
+}
+
+fn ice_path_with_config(config: Option<&UnstableOptions>) -> &'static Option<PathBuf> {
     ICE_PATH.get_or_init(|| {
         if !rustc_feature::UnstableFeatures::from_environment(None).is_nightly_build() {
             return None;
         }
-        if let Some(s) = std::env::var_os("RUST_BACKTRACE")
-            && s == "0"
-        {
-            return None;
-        }
         let mut path = match std::env::var_os("RUSTC_ICE") {
             Some(s) => {
                 if s == "0" {
@@ -1324,7 +1326,10 @@ fn ice_path() -> &'static Option<PathBuf> {
                 }
                 PathBuf::from(s)
             }
-            None => std::env::current_dir().unwrap_or_default(),
+            None => config
+                .and_then(|unstable_opts| unstable_opts.error_metrics.to_owned())
+                .or_else(|| std::env::current_dir().ok())
+                .unwrap_or_default(),
         };
         let now: OffsetDateTime = SystemTime::now().into();
         let file_now = now

compiler/rustc_session/src/options.rs

@@ -1714,6 +1714,8 @@ options! {
         "emit the bc module with thin LTO info (default: yes)"),
     enforce_type_length_limit: bool = (false, parse_bool, [TRACKED],
         "enforce the type length limit when monomorphizing instances in codegen"),
+    error_metrics: Option<PathBuf> = (None, parse_opt_pathbuf, [UNTRACKED],
+        "stores metrics about the errors being emitted by rustc to disk"),
     export_executable_symbols: bool = (false, parse_bool, [TRACKED],
         "export symbols from executables, as if they were dynamic libraries"),
     external_clangrt: bool = (false, parse_bool, [UNTRACKED],