fix miri-unleash delayed sanity checking

Author: RalfJung

src/librustc_interface/interface.rs

@@ -193,7 +193,7 @@ pub fn run_compiler_in_existing_thread_pool<R>(
 
     let r = {
         let _sess_abort_error = OnDrop(|| {
-            compiler.sess.diagnostic().print_error_count(registry);
+            compiler.sess.finish_diagnostics(registry);
         });
 
         f(&compiler)

src/librustc_mir/transform/check_consts/validation.rs

@@ -256,6 +256,8 @@ impl Validator<'mir, 'tcx> {
             // Use `def_span` to deduplicate all warnings for the same const.
             self.tcx.sess.span_warn(self.tcx.def_span(self.def_id), "skipping const checks");
             if let Some(feature) = O::feature_gate() {
+                // We'd like to use `delay_span_bug` here, but we cannot as that ICEs
+                // before codegen has the chance to emit errors.  So we use a custom system instead.
                 self.tcx.sess.miri_unleashed_feature(feature);
             }
             return;

src/librustc_session/session.rs

@@ -18,6 +18,7 @@ use rustc_data_structures::sync::{
 use rustc_errors::annotate_snippet_emitter_writer::AnnotateSnippetEmitterWriter;
 use rustc_errors::emitter::{Emitter, EmitterWriter, HumanReadableErrorType};
 use rustc_errors::json::JsonEmitter;
+use rustc_errors::registry::Registry;
 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId, ErrorReported};
 use rustc_span::edition::Edition;
 use rustc_span::source_map::{self, FileLoader, MultiSpan, RealFileLoader, SourceMap, Span};
@@ -193,10 +194,14 @@ impl From<&'static lint::Lint> for DiagnosticMessageId {
     }
 }
 
-impl Drop for Session {
-    fn drop(&mut self) {
+impl Session {
+    pub fn miri_unleashed_feature(&self, s: Symbol) {
+        self.miri_unleashed_features.lock().insert(s);
+    }
+
+    fn check_miri_unleashed_features(&self) {
         if !self.has_errors_or_delayed_span_bugs() {
-            let unleashed_features = self.miri_unleashed_features.get_mut();
+            let unleashed_features = self.miri_unleashed_features.lock();
             if !unleashed_features.is_empty() {
                 // Join the strings (itertools has it but libstd does not...)
                 let mut list = String::new();
@@ -207,20 +212,20 @@ impl Drop for Session {
                     write!(&mut list, "{}", feature).unwrap();
                 }
                 // We have skipped a feature gate, and not run into other errors... reject.
-                panic!(
+                self.err(&format!(
                     "`-Zunleash-the-miri-inside-of-you` may not be used to circumvent feature \
                     gates, except when testing error paths in the CTFE engine.\n\
                     The following feature flags are missing from this crate: {}",
                     list,
-                );
+                ));
             }
         }
     }
-}
 
-impl Session {
-    pub fn miri_unleashed_feature(&self, s: Symbol) {
-        self.miri_unleashed_features.lock().insert(s);
+    /// Invoked all the way at the end to finish off diagnostics printing.
+    pub fn finish_diagnostics(&self, registry: &Registry) {
+        self.check_miri_unleashed_features();
+        self.diagnostic().print_error_count(registry);
     }
 
     pub fn local_crate_disambiguator(&self) -> CrateDisambiguator {

src/test/ui/consts/miri_unleashed/const_refers_to_static.rs

@@ -1,8 +1,6 @@
 // build-fail
 // compile-flags: -Zunleash-the-miri-inside-of-you -Zdeduplicate-diagnostics
 #![allow(const_err)]
-#![feature(const_raw_ptr_deref)] // FIXME: cannot remove because then rustc thinks there is no error
-#![crate_type = "lib"]
 
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
@@ -26,7 +24,7 @@ static mut MUTABLE: u32 = 0;
 const READ_MUT: u32 = unsafe { MUTABLE };
 //~^ WARN skipping const checks
 
-pub fn main() {
+fn main() {
     MUTATE_INTERIOR_MUT;
     //~^ ERROR: erroneous constant used
     READ_INTERIOR_MUT;

src/test/ui/consts/miri_unleashed/const_refers_to_static.stderr

@@ -1,5 +1,5 @@
 warning: skipping const checks
-  --> $DIR/const_refers_to_static.rs:13:1
+  --> $DIR/const_refers_to_static.rs:11:1
    |
 LL | / const MUTATE_INTERIOR_MUT: usize = {
 LL | |
@@ -9,7 +9,7 @@ LL | | };
    | |__^
 
 warning: skipping const checks
-  --> $DIR/const_refers_to_static.rs:19:1
+  --> $DIR/const_refers_to_static.rs:17:1
    |
 LL | / const READ_INTERIOR_MUT: usize = {
 LL | |
@@ -19,25 +19,25 @@ LL | | };
    | |__^
 
 warning: skipping const checks
-  --> $DIR/const_refers_to_static.rs:26:1
+  --> $DIR/const_refers_to_static.rs:24:1
    |
 LL | const READ_MUT: u32 = unsafe { MUTABLE };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0080]: erroneous constant used
-  --> $DIR/const_refers_to_static.rs:30:5
+  --> $DIR/const_refers_to_static.rs:28:5
    |
 LL |     MUTATE_INTERIOR_MUT;
    |     ^^^^^^^^^^^^^^^^^^^ referenced constant has errors
 
 error[E0080]: erroneous constant used
-  --> $DIR/const_refers_to_static.rs:32:5
+  --> $DIR/const_refers_to_static.rs:30:5
    |
 LL |     READ_INTERIOR_MUT;
    |     ^^^^^^^^^^^^^^^^^ referenced constant has errors
 
 error[E0080]: erroneous constant used
-  --> $DIR/const_refers_to_static.rs:34:5
+  --> $DIR/const_refers_to_static.rs:32:5
    |
 LL |     READ_MUT;
    |     ^^^^^^^^ referenced constant has errors