Flush delayed bugs before codegen

compiler/rustc_errors/src/lib.rs

@@ -1133,6 +1133,12 @@ impl Handler {
         );
         std::mem::take(&mut self.inner.borrow_mut().fulfilled_expectations)
     }
+
+    pub fn flush_delayed(&self) {
+        let mut inner = self.inner.lock();
+        let bugs = std::mem::replace(&mut inner.delayed_span_bugs, Vec::new());
+        inner.flush_delayed(bugs, "no errors encountered even though `delay_span_bug` issued");
+    }
 }
 
 impl HandlerInner {

compiler/rustc_interface/src/queries.rs

@@ -246,6 +246,10 @@ impl<'tcx> Queries<'tcx> {
                 // Don't do code generation if there were any errors
                 self.session().compile_status()?;
 
+                // If we have any delayed bugs, for example because we created TyKind::Error earlier,
+                // it's likely that codegen will only cause more ICEs, obscuring the original problem
+                self.session().diagnostic().flush_delayed();
+
                 // Hook for UI tests.
                 Self::check_for_rustc_errors_attr(tcx);