MIR printing: print the path of uneval'd const; refer to promoteds in a consistent way

2 files changed, 17 insertions, 4 deletions

diff --git a/compiler/rustc_middle/src/mir/consts.rs b/compiler/rustc_middle/src/mir/consts.rs
index 9731d86fb17..5feee3c3ba1 100644
--- a/compiler/rustc_middle/src/mir/consts.rs
+++ b/compiler/rustc_middle/src/mir/consts.rs
@@ -7,6 +7,7 @@ use rustc_target::abi::{HasDataLayout, Size};
 
 use crate::mir::interpret::{alloc_range, AllocId, ConstAllocation, ErrorHandled, Scalar};
 use crate::mir::{pretty_print_const_value, Promoted};
+use crate::ty::print::with_no_trimmed_paths;
 use crate::ty::GenericArgsRef;
 use crate::ty::ScalarInt;
 use crate::ty::{self, print::pretty_print_const, Ty, TyCtxt};
@@ -489,9 +490,18 @@ impl<'tcx> Display for Const<'tcx> {
             Const::Ty(c) => pretty_print_const(c, fmt, true),
             Const::Val(val, ty) => pretty_print_const_value(val, ty, fmt),
             // FIXME(valtrees): Correctly print mir constants.
-            Const::Unevaluated(..) => {
-                fmt.write_str("_")?;
-                Ok(())
+            Const::Unevaluated(c, _ty) => {
+                ty::tls::with(move |tcx| {
+                    let c = tcx.lift(c).unwrap();
+                    // Matches `GlobalId` printing.
+                    let instance =
+                        with_no_trimmed_paths!(tcx.def_path_str_with_args(c.def, c.args));
+                    write!(fmt, "{instance}")?;
+                    if let Some(promoted) = c.promoted {
+                        write!(fmt, "::{promoted:?}")?;
+                    }
+                    Ok(())
+                })
             }
         }
     }
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 18069547a7e..090b84ff08f 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -496,7 +496,7 @@ fn write_mir_sig(tcx: TyCtxt<'_>, body: &Body<'_>, w: &mut dyn io::Write) -> io:
         _ => tcx.is_closure_like(def_id),
     };
     match (kind, body.source.promoted) {
-        (_, Some(i)) => write!(w, "{i:?} in ")?,
+        (_, Some(_)) => write!(w, "const ")?, // promoteds are the closest to consts
         (DefKind::Const | DefKind::AssocConst, _) => write!(w, "const ")?,
         (DefKind::Static(hir::Mutability::Not), _) => write!(w, "static ")?,
         (DefKind::Static(hir::Mutability::Mut), _) => write!(w, "static mut ")?,
@@ -509,6 +509,9 @@ fn write_mir_sig(tcx: TyCtxt<'_>, body: &Body<'_>, w: &mut dyn io::Write) -> io:
         // see notes on #41697 elsewhere
         write!(w, "{}", tcx.def_path_str(def_id))?
     }
+    if let Some(p) = body.source.promoted {
+        write!(w, "::{p:?}")?;
+    }
 
     if body.source.promoted.is_none() && is_function {
         write!(w, "(")?;