Give a message with a span on validation error

Author: scottmcm

compiler/rustc_mir_transform/src/validate.rs

@@ -119,14 +119,16 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
     #[track_caller]
     fn fail(&self, location: Location, msg: impl AsRef<str>) {
         // We might see broken MIR when other errors have already occurred.
-        assert!(
-            self.tcx.dcx().has_errors().is_some(),
-            "broken MIR in {:?} ({}) at {:?}:\n{}",
-            self.body.source.instance,
-            self.when,
-            location,
-            msg.as_ref(),
-        );
+        if self.tcx.dcx().has_errors().is_none() {
+            span_bug!(
+                self.body.span,
+                "broken MIR in {:?} ({}) at {:?}:\n{}",
+                self.body.source.instance,
+                self.when,
+                location,
+                msg.as_ref(),
+            );
+        }
     }
 
     fn check_edge(&mut self, location: Location, bb: BasicBlock, edge_kind: EdgeKind) {

src/tools/miri/tests/panic/mir-validation.stderr

@@ -1,11 +1,20 @@
+error: internal compiler error: compiler/rustc_mir_transform/src/validate.rs:LL:CC: broken MIR in Item(DefId) (after phase change to runtime-optimized) at bb0[1]:
+                                place (*(_2.0: *mut i32)) has deref as a later projection (it is only permitted as the first projection)
+  --> tests/panic/mir-validation.rs:LL:CC
+   |
+LL | / pub fn main() {
+LL | |     mir! {
+LL | |         let x: i32;
+LL | |         let tuple: (*mut i32,);
+...  |
+LL | | }
+   | |_^
+
 
 thread 'rustc' panicked at compiler/rustc_mir_transform/src/validate.rs:LL:CC:
-broken MIR in Item(DefId) (after phase change to runtime-optimized) at bb0[1]:
-place (*(_2.0: *mut i32)) has deref as a later projection (it is only permitted as the first projection)
+Box<dyn Any>
 stack backtrace:
 
-error: the compiler unexpectedly panicked. this is a bug.
-
 
 
 
@@ -20,3 +29,5 @@ LL |     extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 
+error: aborting due to 1 previous error
+

tests/ui/mir/validate/critical-edge.rs

@@ -12,6 +12,8 @@ use core::intrinsics::mir::*;
 #[custom_mir(dialect = "runtime", phase = "optimized")]
 #[inline(always)]
 pub fn f(a: u32) -> u32 {
+//~^ ERROR broken MIR in Item
+//~| ERROR encountered critical edge in `Call` terminator
     mir! {
         {
             match a {
@@ -29,5 +31,3 @@ pub fn f(a: u32) -> u32 {
         }
     }
 }
-
-//~? RAW encountered critical edge in `Call` terminator