Fix bad printing of const-eval queries

src/librustc_middle/mir/interpret/mod.rs

@@ -143,6 +143,17 @@ pub struct GlobalId<'tcx> {
     pub promoted: Option<mir::Promoted>,
 }
 
+impl GlobalId<'tcx> {
+    pub fn display(self, tcx: TyCtxt<'tcx>) -> String {
+        let instance_name = tcx.def_path_str(self.instance.def.def_id());
+        if let Some(promoted) = self.promoted {
+            format!("{}::{:?}", instance_name, promoted)
+        } else {
+            instance_name
+        }
+    }
+}
+
 /// Input argument for `tcx.lit_to_const`.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, HashStable)]
 pub struct LitToConstInput<'tcx> {

src/librustc_middle/query/mod.rs

@@ -679,7 +679,7 @@ rustc_queries! {
             -> ConstEvalRawResult<'tcx> {
             desc { |tcx|
                 "const-evaluating `{}`",
-                tcx.def_path_str(key.value.instance.def.def_id())
+                key.value.display(tcx)
             }
         }
 
@@ -695,7 +695,7 @@ rustc_queries! {
             -> ConstEvalResult<'tcx> {
             desc { |tcx|
                 "const-evaluating + checking `{}`",
-                tcx.def_path_str(key.value.instance.def.def_id())
+                key.value.display(tcx)
             }
             cache_on_disk_if(_, opt_result) {
                 // Only store results without errors

src/test/ui/associated-const/defaults-cyclic-fail.stderr

@@ -32,7 +32,7 @@ note: ...which requires const-evaluating `Tr::B`...
 LL |     const B: u8 = Self::A;
    |     ^^^^^^^^^^^^^^^^^^^^^^
    = note: ...which again requires normalizing `<() as Tr>::A`, completing the cycle
-note: cycle used when const-evaluating `main`
+note: cycle used when const-evaluating `main::promoted[2]`
   --> $DIR/defaults-cyclic-fail.rs:14:1
    |
 LL | fn main() {

src/test/ui/consts/const-eval/const-eval-query-stack.rs

@@ -0,0 +1,20 @@
+// compile-flags: -Ztreat-err-as-bug
+// build-fail
+// failure-status: 101
+// normalize-stderr-test "\nerror: internal compiler error.*\n\n" -> ""
+// normalize-stderr-test "note:.*unexpectedly panicked.*\n\n" -> ""
+// normalize-stderr-test "note: we would appreciate a bug report.*\n\n" -> ""
+// normalize-stderr-test "note: compiler flags.*\n\n" -> ""
+// normalize-stderr-test "note: rustc.*running on.*\n\n" -> ""
+// normalize-stderr-test "thread.*panicked.*\n" -> ""
+// normalize-stderr-test "stack backtrace:\n" -> ""
+// normalize-stderr-test "  \d{1,}: .*\n" -> ""
+// normalize-stderr-test ".*note: Some details.*\n" -> ""
+
+#![allow(unconditional_panic)]
+
+fn main() {
+    let x: &'static i32 = &(1 / 0);
+    //~^ ERROR reaching this expression at runtime will panic or abort [const_err]
+    println!("x={}", x);
+}

src/test/ui/consts/const-eval/const-eval-query-stack.stderr

@@ -0,0 +1,18 @@
+error: reaching this expression at runtime will panic or abort
+  --> $DIR/const-eval-query-stack.rs:17:28
+   |
+LL |     let x: &'static i32 = &(1 / 0);
+   |                           -^^^^^^^
+   |                            |
+   |                            dividing by zero
+   |
+   = note: `#[deny(const_err)]` on by default
+
+query stack during panic:
+#0 [const_eval_raw] const-evaluating `main::promoted[1]`
+#1 [const_eval_validated] const-evaluating + checking `main::promoted[1]`
+#2 [const_eval_validated] const-evaluating + checking `main::promoted[1]`
+#3 [normalize_generic_arg_after_erasing_regions] normalizing `main::promoted[1]`
+#4 [optimized_mir] optimizing MIR for `main`
+#5 [collect_and_partition_mono_items] collect_and_partition_mono_items
+end of query stack